research about dogs

Dogs: History, evolution and behavior of our best friends

Dogs and humans have been companions for thousands of years.

When were dogs domesticated?

• Do dogs see color?

Can dogs feel emotions?

How smart are dogs, how do dogs help people, additional resources.

It hardly seems like a dainty teacup poodle and a wrinkly Neapolitan mastiff could belong to the same species, much less the same subspecies. But both are Canis lupus familiaris , the beloved domestic dog.

A member of the family Canidae — along with wolves, foxes, coyotes and jackals — dogs have been human companions for at least 14,000 years (and possibly much longer than that). Much about how dogs and humans became inseparable remains a mystery, but research finds that the bond is very real. As many pet owners may already attest, there is evidence that dogs understand human distress and want to help their owners when they're sad.

Despite the diversity of domestic dogs, these animals share an evolutionary history and behavioral traits.

The closest living relative to modern dogs is the gray wolf ( Canis lupus ). The ancestor of modern dogs and the ancestor of modern wolves probably split at some point in the late Pleistocene , the last ice age. Genetic studies put different dates on this split. One 2014 study based on the mutation rates found that the schism happened between 9,000 and 34,000 years ago, and that the wolf population dogs split from later went extinct . Another genetic study from 2017 put the window between 20,000 and 40,000 years ago.

The oldest fossil that scientists agree came from a dog, rather than a wolf, comes from a site in Germany called Bonn-Oberkassel and dates back about 14,200 years . But archaeologists have found fossil specimens that might be domesticated dogs dating back more than 30,000 years . It's difficult to confidently identify a Pleistocene fossil fragment as being from either a dog or a wolf, and because dogs and wolves interbred even after they diverged genetically, genomic studies are complicated. Researchers also debate whether dog domestication happened once or at multiple sites around the world.

"We don't know where in the world it happened," Anders Bergström, a postdoctoral fellow in ancient genomics at the Francis Crick Institute in London, told Live Science in 2022 . "We don't know what human group was involved, and we don't know whether it happened once or multiple times."  

It is clear that humankind's bond with dogs goes way back. The 14,200-year-old dog from Bonn-Oberkassel was buried with two humans and had been nursed through several episodes of canine distemper before it died. In a 12,000-year-old cemetery in Israel, a woman was found buried with her hand on a small wolf or dog puppy . A Stone Age dog from what is now Sweden was buried with a human companion about 8,400 years ago, researchers reported in 2020.

What are dog breeds?

In the time since domestication, humans have shaped dogs like clay: Sometimes it seems like the only things different dog breeds have in common are four legs and a tail. The American Kennel Club (AKC) currently recognizes 200 breeds , and that list doesn't even begin to touch the diversity of hybrid breeds (Labradoodles, anyone?) and uncategorizable mutts (often the best kind).

The AKC isn't the final arbiter of what makes a dog breed. According to the organization, there are some 400 dog breeds registered around the world. AKC registration just means there are enough of a certain breed in the United States and enough interest from owners in documenting a breeding history and a "breed standard," which is a description of the ideal characteristics of a breed.

Picking dogs with certain traits and breeding to maximize those traits has led to dogs specialized for many different tasks. Labrador retrievers, for example — which often top the lists of most popular breeds in the United States — have webbed toes and a two-layered coat that is resistant to water. These are traits left over from the breed's original role of retrieving downed ducks for duck hunters. According to the AKC , Labradors were bred from the St. John's dog, a water-loving breed used in early Newfoundland fisheries to retrieve nets and lines.

The sausage-like dachshund, on the other hand, is a poor swimmer but a keen hunter. It was bred for its narrow body and digging acumen, all the better for burrowing into badger dens and killing the occupants, according to the AKC .

Though most official modern breeds date back to the Victorian era, a 2010 paper did find divergence between some breeds indicating that they emerged 500 or more years ago. These breeds were the basenji, Afghan hound, Samoyed, saluki, Canaan dog, New Guinea singing dog, dingo (a wild canine), chow chow, Chinese shar-pei, Akita, Alaskan malamute, Siberian husky and American Eskimo dog.

Do dogs see color? (And other dog senses)

Dogs can see yellow and green hues , but they can't distinguish red from green ​​— a similar situation to humans who are red-green color-blind. However, dogs may be more sensitive to ultraviolet light than humans are, according to 2014 research , in which case they would be better at sensing a wider ranges of blues than people are.

Dog vision is almost three times blurrier than human vision, according to a 2017 study . In that research, whippets, pugs and Shetland sheepdogs were trained with treats to distinguish lines that were different distances from one another. These lines were then used to give the dogs a visual test, not unlike the alphabet chart a human might see during a visit to the eye doctor. Dogs had about 20/50 vision, the study found, meaning that something a human could see clearly at a distance of 50 feet (15 meters), a dog could see clearly at 20 feet (6 m). Dogs, however, do see better than people in dim light, according to the Merck Manual for Veterinary Medicine , and can see movement better, too. One special feature that magnifies light to a dog's eye is the tapetum lucidum, a reflective layer that also gives dogs their characteristic eyeshine at night.

Hearing and smell are where dogs really shine. According to the Merck Manual, dogs hear about four times better than humans do. Incredibly, their sense of smell is a whopping thousand to ten thousand times better than ours. The olfactory center of a dog's brain is 40 times the size of the olfactory center in a human's brain. Because dogs can distinguish between smells with great sensitivity, they have been trained to sniff out human diseases: researchers discovered in the early 2000s that dogs can sniff out signs of early stage cancers , and in 2021 scientists found that dogs could identify COVID-19 in the scent of urine samples, Live Science previously reported.

Humans and dogs really do understand each other. A 2014 study found that emotional processing regions of dogs' brains respond to human emotional sounds , like laughing and crying, in the same way as these regions respond to dog emotional sounds, like whining or yipping. Humans, too, process dog emotional sounds in the same way they process human emotional sounds.

But what emotions do dogs feel? And what do they understand about others' emotions?

It's pretty clear that dogs experience basic emotions, like pleasure, sadness, anxiety and fear, said Julia Meyers-Manor, a psychologist at Ripon College in Wisconsin who studies animal emotions. Meyers-Manor led a 2018 study that found that dogs showed stress in response to their owners' crying noises and that dogs were more likely to attempt to comfort or help a crying owner compared with a laughing owner. Follow-up research that has not yet been published suggests that dogs attempt to comfort upset strangers, too, though not as readily as they comfort their owners, Meyers-Manor told Live Science.

"There's quite a bit of consistency in brain areas that process emotions across mammal species," she said. Dogs are social animals, so it's not surprising that they'd respond to the emotions of others. It is interesting, however, that dogs respond to emotions across species, she said. It's possible that crying is similar enough among species to elicit a response no matter what animal is crying and what animal is listening, she said. It's also possible that, because dogs have co-evolved with humans for so long, they're particularly good at interpreting human emotion. More research comparing different species' reactions is needed to clear up these questions, Meyers-Manor said.

Despite these similarities, one thing is certain: Your dog probably doesn't feel guilt when it digs up the flower beds and knocks over the trash. Though many dog owners take the pitiful, droopy-eyed look a dog gives when it senses trouble to mean that their dogs know exactly what they did wrong, a 2009 study found that the guilty look is simply a way to stay out of trouble. In that study, dogs were put into situations where they were framed for doing something wrong, like eating a forbidden treat. Even when the dogs had not eaten the treat, they looked guilty when their owners thought they had and scolded them.

In other words, the expression that humans interpret as guilt is nothing of the sort. It's just a reaction to a scolding human. "They've just learned, make this expression when there's a big mess in the house and owners won't kill you," Meyers-Manor said.

Dogs are pretty smart, though not "exceptional," according to a 2018 study in the journal Learning & Behavior . The study compared dogs with other carnivores, with other social hunters, and with other domesticated animals, looking at definitions of intelligence that covered sensory cognition, physical cognition, spatial cognition, social cognition and self-awareness. These comparisons focused on other species for which intelligence studies had been conducted, which mainly included wolves, hyenas, African wild dogs, cats , bottlenose dolphins, chimpanzees , horses and pigeons.

On the whole, the researchers concluded, dogs have sensory abilities similar to those of other hunting carnivores. They're pretty bad at solving problems involving objects, such as pulling a string to get at a treat attached to the other end. Spatial cognition, which involves understanding places and navigation, was harder to compare, the researchers found, but there did not seem to be any evidence that dogs were standouts compared with other hunters. Dogs were impressive at using other animals' behavior to cue their own and did beat out many other similar animals at social learning, though dolphins and chimps might be better at imitation. Finally, unlike dolphins and chimpanzees, dogs don't show many signs of self-awareness, or the ability to project themselves mentally into the past or future by remembering events like a story or planning for future events.

Dog smarts are about what would be expected from a domesticated social carnivore and hunter, the researchers concluded in their paper. Dogs are socially savvy, paying attention to cues from other dogs and from humans, their evolutionary co-pilots. They have sensory abilities and spatial smarts sufficient to navigate the environment of a pack hunter. But they aren't as good at things that don't matter as much to their survival, such as figuring out how objects work or making detailed plans for the future.

Humans and dogs have been working together for a long time. Though the earliest history of dogs is shrouded in mystery, there are hints that humans may have used dogs to help with hunts as long as 14,000 years ago, according to a 2019 study in the Journal of Anthropological Archaeology . In Saudi Arabia, rock art estimated to be about 8,000 years old shows humans hunting with dogs on leashes, killing ibex and gazelles, ScienceAlert reported .

— Why is chocolate bad for dogs?

— Are cats or dogs smarter?

— Dogs know when humans are lying to them  

Today, dogs still help hunters stalk quarry large and small. Labrador retrievers continue to be used to hunt ducks, while sprinters such as the Pharaoh hound are excellent at catching prey such as rabbits.

Dogs are also used by police and the military, often to sniff out drugs or explosives, to perform search and rescue operations, and to bite and hold suspects. According to the AKC , police dogs are usually breeds that have been bred to be highly trainable, including German shepherds, Labrador retrievers, and bloodhounds.

Modern dogs also play a huge role as service dogs, therapy dogs and emotional support animals. Guide Dogs or Seeing Eye Dogs help people with vision loss navigate obstacles. Therapy dogs are used to support and calm people with autism, post-traumatic stress disorder, anxiety and other conditions. There are even squads of good-natured dogs roaming airports (with their handlers, of course), calming nervous travelers with snuggles.

Check out the Humane Society of America for more on pet dog behavior and welfare. The American Kennel Club is an exhaustive reference on dog breeds, health, and training. For a deep and detailed dive into what scientists know (and don't) about how dogs were domesticated and came to the Americas, read the 2021 paper " Dog domestication and the dual dispersal of people and dogs into the Americas ," which is freely available.

Originally published on Live Science.

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz. 

Why do dogs sniff each other's butts?

Genetic quirk in 25% of Labrador retrievers can lead to overeating, obesity

Earth-size planet found orbiting nearby star that will outlive the sun by 100 billion years

Most Popular

• 2 Black hole singularities defy physics. New research could finally do away with them.
• 3 Snake Island: The isle writhing with vipers where only Brazilian military and scientists are allowed
• 4 Newfound 'glitch' in Einstein's relativity could rewrite the rules of the universe, study suggests
• 5 James Webb telescope spots 2 monster black holes merging at the dawn of time, challenging our understanding of the universe
• 2 Does the Milky Way orbit anything?
• 3 'More Neanderthal than human': How your health may depend on DNA from our long-lost ancestors
• 4 The mystery of the disappearing Neanderthal Y chromosome
• 5 Scientists discover bizarre region around black holes that proves Einstein right yet again

clock This article was published more than  2 years ago

Thinking about how dogs think

Back in 2002, when Alexandra Horowitz was working toward her PhD at the University of California at San Diego, she believed that dogs were a worthy thing to study. But her dissertation committee, which favored apes and monkeys, needed convincing.

“They were primate people,” she said. “They all studied nonhuman primates or human primates, and that’s where it was thought that the interesting cognitive work was going to happen. Trying to show them that there would be something interesting with dogs — that was a challenge.”

Oh, how things can change in just two decades, especially in a nation that includes about 90 million dogs among its residents — everything from beloved pets to working dogs doing all kinds of tasks, from sniffing out drugs in airports to assisting blind people with crossing a street. Today, Horowitz is a senior research fellow at Barnard College in New York City, where her specialty is dog cognition: understanding how dogs think, including the mental processes that go into tasks such as learning, problem-solving and communication. Dog cognition is now a widely respected field, a growing specialty branch of the more general animal-cognition research that has existed since the early 20th century.

“This field, and animal cognition, really, is all within our lifetimes,” Horowitz said. “It’s not as if nobody ever looked at dogs, but they weren’t looking at their minds.”

Looking at dogs’ minds, so far, has revealed quite a few insights. The Canine Cognition Center at Yale University, using a game where humans offer dogs pointing and looking cues to spot where treats are hidden, showed that dogs can follow our thinking even without verbal commands. The Max Planck Institute for Evolutionary Anthropology in Germany figured out that dogs are smart about getting what they want — they will eat forbidden food more frequently if humans can’t see them. Researchers from Austria, Israel and Britain determined that seeing a caregiver, versus a stranger, activated dogs’ brain regions of emotion and attachment much as it does in the human mother-child bond. Other European researchers showed that negative-reinforcement training (like jerking on a leash) causes lingering emotional changes and makes the dog less optimistic overall.

Read more stories of dogs, humans and the relationship they share

Some dog owners hear about this type of research and think: “They did a whole study to figure out that my dog looks where I point? I could have told you that.” But the studies aren’t just about what a dog is doing. They’re indicating areas to research so that we can better understand why and how the dog is doing it — in other words, what’s happening inside the dog’s mind.

“Maybe they’re not looking at your finger at all. Maybe they’re paying attention to your face and not to your hand,” said Federico Rossano, whose team at the University of California at San Diego is trying to determine whether dogs can translate their thoughts into words that humans can understand through a language device. “A lot of this becomes interesting in terms of how you can train them better.”

An evolving area of research

Right now, with no organizing body in the field, it’s hard to say exactly how many people are doing dog-cognition research. You can count on two hands the number of dedicated university spaces led by professors with graduate students and funding grants. When the leaders from those places get together once a year, it’s usually at someone’s home.

But researchers at universities doing studies on dogs? There are now many dozens of those, and there’s no lack of students wanting to at least dabble in the work.

“The thing that gets my students all abuzz is that people always want to know whether their dog loves them back,” said Ellen Furlong, associate professor of psychology at Illinois Wesleyan University and leader of its Dog Scientists Group.

Every semester, on the first day, she asks students if their dogs are happy. It’s her way of helping them understand why the study of dog cognition is important.

“They’re always kind of offended — ‘O f course my dog is happy. I love my dog,’ ” she said. “But then you dig a little bit and push them and say: ‘Your dog’s life is different from your life. You get to decide when your dog gets to eat and play and go outside. You decide everything about your dog’s life, but your dog isn’t human. They have different wants and needs than you do.’ They have a semester-long assignment where they have to consider how their work on cognition can help to design some enrichment activities to improve the dogs’ lives.”

The topics that dog-cognition researchers focus on today often are chosen based on personal interests. While Furlong is most curious about ethics, welfare and how humans can meet dogs’ psychological needs, Horowitz is focusing her research on what dogs understand through smell. At the Duke Canine Cognition Center in North Carolina, Brian Hare is trying to determine — when a dog is still a puppy — whether the way a dog thinks might make her a good candidate for different jobs as an adult.

“We’re saying, ‘Here are some cognitive abilities that are critical for training for these jobs,’ ” Hare said. “It’s a little bit like talking about personality, but we’re talking about your cognitive personality, in a way. Maybe you have a really good memory for space, or maybe you’re good at understanding human gestures. The question is whether we can identify some of these dogs really early, in the first two to three months of life, who will do well in these programs.”

How the research is done

One example of dog cognition research with a potential training application is a study that Horowitz did on nose work — an activity that lets dogs use their natural abilities with scents to find everything from a treat hidden under a cone to marijuana in somebody’s suitcase.

Horowitz and her team showed the dogs three buckets and taught them that one of the buckets always had a treat under it, and one did not. Then she measured how quickly the dogs went to the “ambiguous bucket” in the middle.

The dogs then attended nose-work classes. These types of advanced classes are widely available at the same types of schools that teach basic obedience. In the nose-work classes, dogs are encouraged and trained to use their noses to search for and find treats or favorite toys that are hidden under boxes or cones, inside suitcases or in other places.

After a few weeks of nose-work classes, Horowitz repeated the bucket test.

“What we found was the dogs in the nose-work class got faster at approaching ambiguous stimulus,” she said, adding that the results suggest that for some dogs, taking nose-work classes could help them feel more optimistic. “The group that had nose work changed their behavior afterward, so I have to say it’s something about the nose work. I don’t know exactly what it was, but if the effect is profound and we keep seeing it, we would go in and try to see what it was that made it useful for the subjects.”

Hare is widely credited with having jump-started America’s dog-cognition research field. In the late 1990s as an undergraduate, he was doing research with chimpanzees when he realized they couldn’t do something that his dogs could do: follow a human’s pointing gesture to find food. Chimpanzees are the closest animal relatives humans have, and dogs could do something they couldn’t. Researchers suddenly wanted to know why dogs could understand something that chimpanzees could not.

In his most recent study , published in July, Hare and his team looked at the difference between wolf and dog pups. There had been some debate in the dog-cognition field about where dogs’ unusual abilities to cooperate with humans originate — whether those abilities are biological or taught. So the team gave a battery of temperament and cognition tests to dog and wolf puppies that were 5 weeks to 18 weeks old. The pups of both species were given the chance to approach familiar and unfamiliar humans to retrieve food; to follow a human’s pointing gesture to find food; to make eye contact with humans, and more. The team found that even at such a young age, the dog pups were more attracted to humans, read the human gestures more skillfully, and made more eye contact with humans than the wolf pups did.

The conclusion? The way that humans domesticated dogs actually altered the dogs’ developmental pathways, meaning their abilities to cooperate with us today are biological — a research result that is likely to have many practical implications.

“It’s highly inheritable, and it’s potentially manipulatable through breeding,” Hare said, adding that dogs might be bred to specialize in certain types of thinking. The finding opens up the idea of studying dogs in ways that could make deep-pocketed entities like the U.S. government want to fund more dog-cognition research, Hare said.

By way of example, he talked about dogs he has worked with for the U.S. Marine Corps, compared with dogs he has worked with for Canine Companions for Independence in California. The Marines needed dogs in places like Afghanistan to help sniff out incendiary devices, while the companions agency needed dogs that were good at helping people with disabilities.

Just looking at both types of purpose-bred dogs, most people would think they’re the same — to the naked eye, they all look like Labrador retrievers, and on paper, they would all be considered Labrador retrievers. But behaviorally and cognitively, because of their breeding for specific program purposes, Hare said, they were different in many ways.

Hare devised a test that could tell them apart in two or three minutes. It’s a test that’s intentionally impossible for the dog to solve — what Star Trek fans would recognize as the Kobayashi Maru. In Hare’s version, the dog was at first able to get a reward from inside a container whose lid was loosely secured and easy to dislodge; then, the reward was placed inside the same container with the lid locked and unable to be opened. Just as Starfleet was trying to figure out what a captain’s character would lead him to do in a no-win situation, Hare’s team was watching whether the dog kept trying to solve the test indefinitely, or looked to a human for help.

“What we found is that the dogs that ask for help are fantastic at the assistance-dog training, and the dogs that persevere and try to solve the problem no matter what are ideal for the detector training,” Hare said. “It’s not testing to see which dog is smart or dumb. What we’ve been able to show is that some of these measures tell you what jobs these dogs would be good at.”

What comes next in the field of dog-cognition research is probably a bit more of everything. Some researchers are following their interests, while others are following the research grants. Those grants can come from a wide array of sources, including the government trying to help soldiers with post-traumatic stress disorder, shelters trying to rehome animals and neuroscience institutes looking for insights across species.

“It’s a really exciting moment,” Hare said. “I think we can continue on with individual researchers pursuing fun, interesting things — the students and the universities love it — but most successful academic endeavors have two parts. Being intellectual is wonderful, but that kind of research tends to struggle with funding. Academic endeavors with practical application tend to be incredibly well funded, and then the field grows.

“If you can have both of those things, then it will grow, and it will grow phenomenally,” he added. “If it’s just, ‘We’re going to do this because people love dogs,’ that’ll be fun, but it will stay small like it is now.”

Research in a Nutshell

What’s in a Name? Effect of Breed Perceptions & Labeling on Attractiveness, Adoptions & Length of Stay for Pit-Bull-Type Dogs

Comparison of behavioural tendencies between “dangerous dogs” and other domestic dog breeds–Evolutionary context and practical implications

Dog behavior and animal shelters, no better than flipping a coin: reconsidering canine behavior evaluations in animal shelters, what is the evidence for reliability and validity of behavior evaluations for shelter dogs a prequel to “no better than flipping a coin.”, saving normal: a new look at behavioral incompatibilities and dog relinquishment to shelters.

Never miss any important news. Subscribe to the Canine Behavior Science and Policy Newsletter.

Top Research Categories

Visual breed identification.

Comparison of visual and DNA breed identification of dogs and inter-observer reliability

This study examined both inter-rater reliability between experienced canine professionals and validity of visual breed identifications compared to DNA profiles—both were very low.

A canine identity crisis: Genetic breed heritage testing of shelter dogs

Visual Breed Identification: A Literature Review

Rethinking dog breed identification in veterinary practice

Breed-specific policies.

Looking for safety in all the wrong places: India’s new ban on 23 dog breeds cannot succeed

Thankfully, banning dogs of certain breeds is increasingly rare. But when this choice is made, as with the recent national BSL legislation in India, we

Eighth Circuit Court Fails to Protect Dog Owners’ Rights

Red herrings and just plain lies: Insurance companies vs. dog loving families

“What kind of dog is that?” Asking the wrong question and answering it badly

Breed-specific legislation is myth-based and ineffective according to the american veterinary society of animal behavior (avsab), talking with canine behavior scientists, additional research.

Dog Bite-Related Fatalities: A Literature Review

Enrichment centered on human interaction moderates fear-induced aggression and increases positive expectancy in fearful shelter dogs

Differences in Trait Impulsivity Indicate Diversification of Dog Breeds into Working and Show Lines

Associations between domestic-dog morphology and behaviour scores in the dog mentality assessment

Dog behavior co-varies with height, bodyweight and skull shape

Efficacy of drug detection by fully-trained police dogs varies by breed, training level, type of drug and search environment

Performance of Pugs, German Shepherds, and Greyhounds (Canis lupus familiaris) on an odor-discrimination task

Accurate & Reliable Source For Understanding Canine-Related Behavior Science

National Canine Research Council is a non-profit canine behavior science and policy think tank that focuses on the relationship between dogs and people. Our mission is to underwrite, conduct and disseminate academically rigorous research that studies dogs in the context of human society.

• Empirically-verified data
• Research that embodies the principle that dogs must be considered in relation to humans
• Removing barriers to safe and humane pet ownership
• Leading experts in the field

Canine Behavior Research & Policy eNewsletter

© 2016-2020 National Canine Research Council, LLC.  Trade/service marks are the property of National Canine Research Council.  All rights reserved.

Domestic dog

What is a domestic dog.

The term “domestic dog” refers to any of several hundred breeds of dog in the world today. While these animals vary drastically in appearance, every dog—from the Chihuahua to the Great Dane—is a member of the same species, Canis familiaris . This separates domestic dogs from wild canines , such as coyotes, foxes, and wolves.

Domestic dogs are mostly kept as pets, though many breeds are capable of surviving on their own, whether it’s in a forest or on city streets. A third of all households worldwide have a dog, according to a 2016 consumer insights study . This makes the domestic dog the most popular pet on the planet.

Evolutionary origins

All dogs descend from a species of wolf, but not the gray wolf ( Canis lupus ), like many people assume. In fact, DNA evidence suggests that the now-extinct wolf ancestor to modern dogs was Eurasian . However, scientists are still working to understand exactly what species gave rise to dogs.   

When dogs broke off from their wild ancestors is also a matter of mystery, but genetics suggest that it occurred between 15,000 and 30,000 years ago.

While it’s impossible to say exactly how a wild wolf species became a domesticated dog, most scientists believe the process happened gradually as wolves became more comfortable with humans. Perhaps wolves started down this path simply by eating human scraps. Many generations later, humans might have encouraged wolves to stay near by actively feeding them. Later still, those wolves may have been welcomed into the human home and eventually bred to encourage certain traits. All of this is thought to have unfolded over thousands of years.

Today, many of the dogs you know and love are the product of selective breeding between individuals with desirable traits, either physical or behavioral. For instance, around 9,500 years ago , ancient peoples began breeding dogs that were best able to survive and work in the cold. These dogs would become the family of sled dogs—including breeds such as huskies and malamutes—that remains relatively unchanged today.

Similarly, humans bred German shepherds for their ability to herd livestock, Labrador retrievers to help collect ducks and other game felled by hunters, and sausage-shaped Dachshunds for their ability to rush down a burrow after a badger . Many more breeds were created to fill other human needs, such as home protection and vermin control.  

Certain breeds have also been created to make dogs more desirable as companions. For instance, the labradoodle, which combines the traits of a Labrador retriever and a poodle, was invented as an attempt to create a hypoallergenic guide dog .

Modern working dogs

While people rely less on dogs for daily tasks than they did in the past, there are still many modern jobs for pooches.

Because the domestic dog’s sense of smell is between 10,000 and 100,000 better than our own, canines now assist law enforcement by sniffing out drugs, explosives, and even electronics . They can also help conservationists find and protect endangered species using their super-powered schnozzes.

They assist search and rescue teams in the wake of natural disasters or reports of people lost in the outdoors. Dogs trained to warn of hidden explosives and enemies serve as allies in military operations . Other dogs assist police looking for jail escapees or the bodies of murder victims. Some partner instead with customs officials searching for contraband, from drugs to elephant ivory . Still others lead the way tracking down poachers , patrolling cargo ships for rats that might escape at distant harbors, or exposing forest insect pests in shipments of wood from abroad.

Similarly, dogs can sniff out early signs of Parkinson’s disease, diabetes, several types of cancer , oncoming epileptic seizures , and antibiotic-resistant bacteria . They guide deaf and blind people, and they help people with autism and post-traumatic stress disorder manage with anxiety.

Living with dogs

Most dogs are a mix of breeds—in 2015, one study estimated that only 5 percent of dogs in shelters are purebred. Just as dogs come in all sizes, shapes, and colors, these animals also come in a spectrum of temperaments. A bulldog might look fierce but be cuddly as a kitten, whereas a cute cocker spaniel might nip at your finger without thinking twice.

This is why animal handling expert Jack Hanna recommends teaching children to always exercise caution around a dog they do not know. For instance, he says kids should ask for permission from the dog’s owner before trying to pet or play with the animal. Offering an outstretched hand also allows the dog to familiarize itself with a new person before reaching behind its head where it can’t see what you’re doing, which might make a dog nervous or scared. Finally, never allow children to put their faces near the dog’s muzzle.

“I don’t care what kind of dog it is,” Hanna told National Geographic . “The owner may say, ‘Well, this dog’s never bit anyone before.’ But that’s not the point. The point is it can happen.”

Of course, when dogs are cared for properly and treated with respect, they can be incredibly loving, playful, and intelligent companions. What’s more, by understanding where dogs come from, pet owners might learn to appreciate their canines even more.

After all, the yipping and tail-wagging your dog performs when you grab a bag of treats are carry-overs from when its ancestors needed to communicate with other members of its social group. Chasing sticks and balls may be linked to the pursuit of prey, while digging at the carpet or a dog bed echoes how a wild canid would prepare its sleeping area. And each time Fido stops to sniff a fire hydrant on your walk, it’s analyzing the pheromones left behind by another dog’s urine.

We take these behaviors for granted because dogs have become “man’s best friend.” But deep inside every pit bull and Pomeranian, there lie hints of the past.  

Editor's note: Bringing a dog into your household is a major responsibility. More than 1.6 million dogs ended up in shelters in 2020. Learn how to keep your dog happy and healthy with the National Geographic book Complete Guide To Pet Health, Behavior, and Happiness .

• Environment
• Perpetual Planet

History & Culture

• History & Culture
• History Magazine
• Mind, Body, Wonder
• Terms of Use
• Privacy Policy
• Your US State Privacy Rights
• Children's Online Privacy Policy
• Interest-Based Ads
• About Nielsen Measurement
• Do Not Sell or Share My Personal Information
• Nat Geo Home
• Attend a Live Event
• Book a Trip
• Inspire Your Kids
• Shop Nat Geo
• Visit the D.C. Museum
• Learn About Our Impact
• Support Our Mission
• Advertise With Us
• Customer Service
• Renew Subscription
• Manage Your Subscription
• Work at Nat Geo
• Sign Up for Our Newsletters
• Contribute to Protect the Planet

Copyright © 1996-2015 National Geographic Society Copyright © 2015-2024 National Geographic Partners, LLC. All rights reserved

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• 28 April 2022

Massive study of pet dogs shows breed does not predict behaviour

• Freda Kreier

You can also search for this author in PubMed   Google Scholar

Dog enthusiasts have long assumed that a dog’s breed shapes its temperament. But a sweeping study comparing the behaviour and ancestry of more than 18,000 dogs finds that although ancestry does affect behaviour, breed has much less to do with a dog’s personality than is generally supposed 1 .

Access options

Access Nature and 54 other Nature Portfolio journals

Get Nature+, our best-value online-access subscription

24,99 € / 30 days

cancel any time

Subscribe to this journal

Receive 51 print issues and online access

185,98 € per year

only 3,65 € per issue

Rent or buy this article

Prices vary by article type

Prices may be subject to local taxes which are calculated during checkout

doi: https://doi.org/10.1038/d41586-022-01193-1

Morrill, K., et al. Science 376 , eabk0639 (2022).

Google Scholar  

Download references

Reprints and permissions

Related Articles

• Animal behaviour

Parental-care puzzle in mice solved by thinking outside the brain

News & Views 15 MAY 24

These parrots go on killing sprees over real-estate shortages

Research Highlight 10 MAY 24

Puppy-dog eyes in wild canines sparks rethink on dog evolution

News 05 MAY 24

Pig-organ transplants: what three human recipients have taught scientists

News 17 MAY 24

The rise of baobab trees in Madagascar

Article 15 MAY 24

Powerful ‘nanopore’ DNA sequencing method tackles proteins too

Technology Feature 08 MAY 24

Senior Postdoctoral Research Fellow

Senior Postdoctoral Research Fellow required to lead exciting projects in Cancer Cell Cycle Biology and Cancer Epigenetics.

Melbourne University, Melbourne (AU)

University of Melbourne & Peter MacCallum Cancer Centre

Overseas Talent, Embarking on a New Journey Together at Tianjin University

We cordially invite outstanding young individuals from overseas to apply for the Excellent Young Scientists Fund Program (Overseas).

Tianjin, China

Tianjin University (TJU)

Chair Professor Positions in the School of Pharmaceutical Science and Technology

SPST seeks top Faculty scholars in Pharmaceutical Sciences.

Chair Professor Positions in the School of Precision Instruments and Optoelectronic Engineering

We are committed to accomplishing the mission of achieving a world-top-class engineering school.

Chair Professor Positions in the School of Mechanical Engineering

Aims to cultivate top talents, train a top-ranking faculty team, construct first-class disciplines and foster a favorable academic environment.

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Read our Dog Testing FAQ

Our new Dog FAQ page provides answers to the most frequently asked questions about dogs in research.

Dogs ( Canis familiaris ) belong to the family Canidae and are thought to be one of the first domesticated animals. They have been used in research for more than a century, however, they are currently very rarely used in animal research in Great Britain, only being used in 0.24% of experimental procedures in 2019 (latest published figures).

They are medium-sized mammals that can grow from 15 to 100 cm and weigh from 1.5 to 75 kg, depending on the type of dog. Dogs are carnivores but can thrive on a well-designed suitably processed omnivorous diet in the domestic situation.

Why are dogs used in research?

In the UK, dogs are primarily used to find out how new drugs act within a whole, living body and whether new medicines are safe enough to test in humans. They predict this safety very well, with  up to 96% accuracy .

This is done to satisfy safety regulations which came about after the drug Thalidomide maimed and killed children while they were still in the womb. It is known as toxicology testing, but normally seeks to confirm the absence of toxic effects.

The tests can tell us lots of sorts of information all at once, like the safety if a drug across lots of different internal organs, how the drug travels around the body and other information that helps us to design much safer human trials.

Dogs are also used to test the safety and efficacy of veterinary medicines, and also in nutrition studies to ensure that pet dogs eat healthily, particularly when they are prescribed specialist diets by their vets.

Although animal and nonanimal methods are used alongside each other, there are currently no alternatives to using dogs. They nevertheless have special protections under UK law. For instance, they cannot be used if another animal species could be used.

There is a project that hopes to create a  ‘virtual dog’  that could significantly reduce the number of dogs needed by using computers to mine historical dog data. It is being run by the UK’s national centre for  developing animal replacements, the NC3Rs , but is of international interest.

What types of research are dogs used in?

The physiological similarities between humans and dogs mean that they are useful in various types of research. Their genome has been sequenced and because of our genetic similarities, they are often used in genetic studies.

Dogs are primarily used in regulatory research, also known as toxicology or safety testing. This type of research is required by law to test the safety and effectiveness of potential new medicines and medical devices before they are given to human volunteers during clinical trials. Dogs are also used to test the safety and efficacy of veterinary medicines, and also in nutrition studies to ensure that pet dogs eat healthily, particularly when they are prescribed specialist diets by their vets.

A smaller number of dogs are also used in translational research (also called applied research) to help us learn about human and animal diseases so that we can develop treatments. Examples of translational diseases can be found below.

Dogs are also used to study Duchenne muscular dystrophy (DMD), which is the most common type of muscular dystrophy. It is another condition that can affect both humans and dogs. Because dogs can naturally have this condition, they can be studied to show how the condition progresses. This very useful model for DMD has helped scientists work on better genetic tests and treatments for the condition.  

An early use of dogs in research was in the search for a treatment for diabetes, which resulted in the discovery of insulin. This discovery in the 1920s, which won researchers a Nobel prize, now allows people with diabetes to live long lives. In the past, people with diabetes would die soon after developing the condition.

How are the dogs looked after?

The use of animals in research is highly regulated, an important part of that regulation is ensuring the animals are housed and cared for correctly. Laboratory dogs are housed in enclosures that can isolate individual dogs for treatment but usually opened up for dogs to interact. Dogs’ need to socialise is well considered, so the dogs are housed in small groups most of the time. The facilities usually also have space to run around for exercise and you can usually find dogs interacting with each other, environmental enrichments, and the animal technicians.

https://www.nc3rs.org.uk/3rs-resources/housing-and-husbandry/housing-and-husbandry-dogs

You can see this in this film about dogs in research.

https://www.nationalgeographic.com/animals/mammals/d/domestic-dog/

https://www.britannica.com/animal/dog/Breed-specific-behaviour#ref15478

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5070630/#:~:text=Dogs%20have%20approximately%20the%20same,similar%20to%20human%20than%20mouse

http://www.animalresearch.info/en/designing-research/research-animals/dog/

Dogs in drug safety prediction:  https://pubmed.ncbi.nlm.nih.gov/28893587/

Virtual dog:  https://nc3rs.org.uk/news/ps16m-awarded-develop-virtual-second-species

Featured news

A decade of openness on animal research

Bird flu in cows: is it a human problem?

Openness, a powerful tool to support science

Subscribe to our newsletter.

Get the latest articles and news from Understanding Animal Research in your email inbox every month. For more information, please see our  privacy policy .

• Cheap and Budget Friendly Recipes
• Health Related Illness Diets
• Homemade Treat Recipes
• Homemade Dog Treats for Health Issues
• Seasonal Recipes
• Can Dogs Eat…
• Dog Diseases & Conditions
• Dog Symptoms
• Dog Grooming
• Caring For Seniors
• Dog Loss & Grieving
• Dog Reproductive Health
• Treatments and Home Remedies
• Dry Dog Food
• Wet Dog Food
• Best Dog Products
• Dog Accessories
• Dog Health Products
• CBD for Dogs
• Toy Dog Breeds
• Working Dog Breeds
• Terrier Dog Breeds
• Sporting Dog Breeds
• Non-Sporting Dog Breeds
• Mixed Breeds
• Hound Dog Breeds
• Livestock and Herding Dog Breeds

20 Most Fascinating Scientific Studies on Dogs

W e all know that dogs are amazing , but do you know just how amazing they really are? Scientists have been carrying out many different studies on dogs over the years, and they have discovered numerous fascinating and truly unbelievable things about them. The  best scientific studies on dogs have proven many things about the species and their connection to humans.

Science is proving that dogs are very beneficial to our physical and mental well-being. I mean, we don't call them “man's best friend” for nothing, right? Studies have been done on the effects of dogs on humans, including children, and how they benefit us both mentally and physically .

Most of us probably don't spend a whole lot of time reading up on different canine studies done over the years. Today I'd like to share a few of the best scientific studies on dogs with you, because I think you'll be surprised at some of the findings.

Best Scientific Studies on Dogs

1. pets keep us fit.

Dog owners are much fitter because they own a dog, which makes sense if you think about it. You have to walk your dog daily to keep him happy and fit, and so you too become fitter.

A study that included 2,000 adults discovered that those who regularly walked their dog were less likely to be obese, compared with those who didn’t have a dog to walk. Older walkers can benefit too, as in another study it was found that walkers aged between 71 and 82 could walk longer and indeed faster than non dog walkers.

Read more about the study:  https://www.ncbi.nlm.nih.gov/pubmed/16459211

2. Dogs can prevent allergies and help boost your immune system

Studies have discovered that living with a dog, especially when you’re young, will prevent you from having allergies when you’re older. By having a dog, your immune system is boosted and the pet will also lower your risk of suffering from asthma and also eczema. Your immune system doesn’t need long with a dog to be boosted either – just a short amount of time is enough.

One of the best scientific studies on dogs showed that just patting a dog for 18 minutes increased saliva and raised immunoglobulin A (IgA) levels in the saliva. These raised levels mean that you have a very strong immune system.

3. Dogs reduce stress

Studies have found that owning a dog can greatly reduce your stress levels. When you have contact with a dog your stress response is lowered, and this lowers stress hormones like cortisol and your heart rate is lowered too.

Dogs can also help to lower anxiety and fear and will help to increase feelings of calmness. A study found that elderly people who walked their dogs every day had an enhanced heart rate, which is a sign of low stress levels.

Read more about the study:  https://www.mja.com.au/journal/2006/184/2/effect-dog-walking-autonomic-nervous-activity-senior-citizens

4. Dogs make you more social

Studies have found that dogs make us more social, as when we walk our dogs we are out and about meeting and greeting different people. They act as icebreakers and people are far more likely to talk to you if you have a dog. One study discovered that people in wheelchairs who are with dogs received more smiles from others.

Read more about the study: https://www.health.harvard.edu/blog/pets-can-help-their-humans-create-friendships-find-social-support-201505067981

5. Dogs prevent heart attacks and strokes

Some of the best scientific studies on dogs relating to heart health have discovered that dogs can dramatically reduce your chances of having a heart attack or stroke. Dog owners have a decrease in blood pressure compared to non dog owners. Dog owners also have a reduction in cholesterol levels and also triglyceride levels.

If you have high levels of these then your chances of having a heart attack or stroke is high. Studies also found that if you have already had a heart attack or stroke you will recover faster if you have a dog.

Read more about the study:       https://www.ahajournals.org/doi/full/10.1161/CIR.0b013e31829201e1

6. Dogs keep depression away

Dogs make us laugh and they make us smile, when we are with our dogs we are happier. Studies have discovered that dogs really do keep depression away.

Our dogs love us unconditionally and they need us in order to stay healthy and strong. Studies show that when we’re around dogs we feel more positive about things.

Read more about the study:  https://habri.org/depression

7. Dogs keep children healthy

When children grow up with a family dog around them, they are much stronger and have stronger immune systems which will reduce the chance of them having allergies. A study carried out in 2010 showed that if you are around a dog during the first year of life you are far less likely to develop chronic skin conditions.

Read more about the study: https://www.sciencedaily.com/releases/2010/09/100930093229.htm

8. Dogs help children develop

When a child grows up with a dog, there are many emotional benefits as well, and the best scientific studies on dogs have proven that. The child will have someone to talk to and spend time with.

Children can express themselves better when they have a dog around them. Children also learn responsibility when they have a dog. Studies have discovered that children with autism and AHDH also benefit greatly from dog ownership.

Read more about the study: https://www.ncbi.nlm.nih.gov/pubmed/25308197

9. Dogs help older people

Many studies have shown that an elderly person is much happier when they have a dog to look after. The dog is a great source of comfort to them and offers companionship. A dog will help to keep an elderly person connected and will greatly boost their vitality. Dogs will help to reduce the feelings of loneliness that elderly people can have.

Read more about the study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3351901/

10. Dogs help Alzheimer’s patients

Studies have revealed that dogs really can help those suffering from Alzheimer’s disease. They show that dogs reduce behavioral issues amongst dementia patients by greatly boosting their moods. These studies also found that a patient’s nutritional intake is increased when around a dog.

Read more about the study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4248608/

11. Dogs help against PTSD

Several studies have discovered that those suffering from PTSD are benefited greatly by the love of a dog. A dog boosts oxytocin levels in the body and can be a great help against the flashbacks that come with PTSD.

People suffering from PTSD can have angry outbursts and emotional numbness, but when around a dog this is greatly reduced. There are now many programs that team up those suffering with PTSD with dogs.

Read more about the study:  https://www.mnn.com/family/pets/stories/nature-loving-pets-help-veteran-overcome-ptsd

12. Dogs can help you fight cancer

Dogs can help people suffering from cancer, and some of the best scientific studies on dogs are showing that canines ease the loneliness and depression that people with cancer can suffer from. Dogs encourage people to eat and keep up with their cancer treatment. Dogs really do try and help people recover from cancer. Canine companions benefit both adults and children that are fighting cancer.

Read more about the study:  https://www.eurekalert.org/pub_releases/2015-01/tmsh-cts011315.php

13. Dogs reduce pain

Studies show that dogs can greatly reduce our pain and just 10-15 minutes with a dog is all it takes for pain to be reduced. Dogs also help improve your mood and can help with fatigue that comes with pain.

One study showed that people who had joint replacement surgery needed 28% less medication, thanks to being around a dog.

Read more about the study: https://www.sciencedaily.com/releases/2014/08/140807180314.htm

14. Dogs make you more attractive

Believe it or not, some of the best scientific studies on dogs show that people who own a canine are more attractive than non dog owners. They also show that women are more attracted to dog owners than non dog owners. So, if you’re out to impress, a dog will work wonders.

Read more about the study: https://www.slate.com/articles/health_and_science/science/2014/02/

15. Dogs help to strengthen bonds

Studies show that those who have a strong bond with their dog also have greater bonds with other people. One study involved 500 people aged between 18 and 26 and discovered that the ones that owned dogs had a closer bond with others.

Read more about the study:  https://www.huffingtonpost.com/2014/02/03/pet-social-connectedness-young-adult_n_4703790.html

16. Dogs can detect cancer

A few of the best scientific studies on dogs have revealed that some dogs can literally sniff out cancer and could save your life. One dog named Marnie who is an eight year old black Labrador sniffed out cancer 91% of the time just by sniffing breath.

Marnie also showed that she can detect colorectal cancer 97% of the time by sniffing stools.

Read more about the study:  https://abcnews.go.com/Health/CancerPreventionAndTreatment/dog-detects-colorectal-cancer-standard-screening-test/story?id=12805641

17. Dogs can detect food that you’re allergic to

Your dog knows exactly what you’re allergic to studies can reveal, and can smell just the hint of peanut butter. Peanut detecting dogs really can help to save the lives for those with peanut allergies.

Read more about the study:  https://www.livescience.com/35463-seven-surprising-health-benefits-dog-ownership-110209.html

18. Dogs make us happy

A study in 2009 showed that our oxytocin levels were dramatically raised when we are in contact with a dog.

The study found that those who looked into a dog’s eye the longest had the highest readings of oxytoxin. No wonder we’re always happy when we’re with our best firends.

Read more about the study:  https://www.ncbi.nlm.nih.gov/pubmed/19124024

19. Dogs bring out the caretaker in us

It has been found that just by looking at a dog’s face they can bring out the caretaker in us. Their large eyes, floppy ears and cute features make us feel that we have to take good care of them. We have the same reaction when we’re around infants.

Read more about the study:  https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0058248

20. Dogs boost self esteem

When you have the responsibility of caring for your dog you feel so much better about yourself. You have someone to care for who loves you unconditionally and you have to do your very best for them.

When you have a dog to care for your whole outlook on life changes and you get to meet and greet new people as you’re walking your dog, resulting in higher self esteem.

Read more about the study:  https://psycnet.apa.org/psycinfo/2011-13783-001/

LATEST FEATURES

4 Tips & Tricks for Navigating Peak Flea and Tick Season

Can I Afford A Dog?

How to Get Rid of a Dog: The Right Way

Why Are Dogs So Loyal?

Why Do Pets Make Us Happy?

Dog Names Starting With Z

How Many Dogs Are Too Many?

Can Dogs Get Sick From Humans?

Dandie Dinmont Terrier Breed Profile

Dog Names Starting With Y

• Terms of Use
• Privacy Policy
• No AI Clause

May 6, 2024

Puppy-Dog Eyes in Wild Canines Spark Rethink on Dog Evolution

The eyebrows of the African wild dog have scientists wondering whether other canine species besides domestic dogs can make the irresistible “puppy-dog eyes” expression

By Gillian Dohrn & Nature magazine

A pack of African wild dogs ( Lycaon pictus ) warily approaches a remote camera near banks of Moremi River in Botswana.

Paul Souders/Getty Images

“Puppy-dog eyes didn’t just evolve for us, in domestic dogs,” says comparative anatomist Heather Smith. Her team’s work has thrown a 2019 finding that the muscles in dogs’ eyebrows evolved to communicate with humans in the doghouse by showing that African wild dogs also have the muscles to make the infamous pleading expression. The study was published on 10 April in The Anatomical Record .

Now, one of the researchers who described the evolution of puppy-dog eyebrow muscles is considering what the African dog discovery means for canine evolution. “It opens a door to thinking about where dogs come from, and what they are,” says Anne Burrows, a biological anthropologist at the Duquesne University in Pittsburgh, Pennsylvania, and author of the earlier paper.

Evolution of canine eyebrows

On supporting science journalism.

If you're enjoying this article, consider supporting our award-winning journalism by subscribing . By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

The 2019 study garnered headlines around the world when it found that the two muscles responsible for creating the sad–sweet puppy-dog stare are pronounced in several domestic breeds ( Canis familiaris ), but almost absent in wolves ( Canis lupus ).

If the social dynamic between humans and dogs drove eyebrow evolution, Smith wondered whether the highly social African wild dog might also have expressive brows.

African wild dogs ( Lycaon pictus ) are native to sub-Saharan Africa. Between 1997 and 2012, their numbers dropped by half in some areas. With only 8,000 or so remaining in the wild, studying them is difficult but crucial for conservation efforts.

Smith, who is based at Midwestern University in Glendale, Arizona, and her colleagues dissected a recently deceased African wild dog from Phoenix Zoo. They found that both the levator anguli oculi medalis (LAOM) and the retractor anguli oculi lateralis (RAOL) muscles, credited with creating the puppy-dog expression, were similar in size to those of domestic dog breeds.

“We could see distinct fibres that are very prominent, very robust,” says Smith. Although the researchers only looked at one African wild dog, Smith says it’s unlikely that such a large and well-developed muscle would be present in one animal and not others.

A communication strategy

The team proposes that the gregarious African wild dogs evolved these muscles to communicate with each other. They use a range of vocal cues to organize hunts and share resources, but until now, non-vocal strategies haven’t been studied.

Burrows speculates that more dog species might have muscles for facial expression than the researchers realized when they compared wolves and domestic dogs. “I wonder if these muscles have been around for a really long time and wolves are the ones that lost them.”

Muhammad Spocter, an anatomist at Des Moines University in West Des Moines, Iowa, says the study is exciting, but cautions against making assumptions about wild dog behaviour based on their physical structure. “Just because the anatomy is there, is it being used?” says Spocter. “And how is it being used?”

This article is reproduced with permission and was first published on May 5, 2024 .

• DIGITAL MAGAZINE

MOST POPULAR

10 awesome dog facts!

Get the lowdown on these adorable animals….

Ready to learn some paw- some dog facts? Then you’re in the right place! Join National Geographic Kids as we get the lowdown on our fur -tastic friends…

1. Dogs are the most popular pet on the planet!

A third of ALL households around the world have a dog. These playful, friendly, loyal animals make great companions , but they can also be fierce and tough protectors , or intelligent helpers .

2. They evolved from a now-extinct species of wolf.

Dogs were the first animal domesticated (tamed) by humans, over 20,000 years ago! As they evolved from wolves , their skulls, teeth and paws shrank , and they became more docile and obedient .

FUN FACT! Evidence from fossils suggests that five types of dog had evolved by the Bronze Age , around 4500BC. These were mastiffs , wolf-type dogs, dogs similar to greyhounds, pointing dogs and herding dogs. Bow wow!

3. They can learn over 100 words and gestures!

Dogs are thought to be as smart as two-year-old children (and much easier to train!), so many owners teach them commands and tricks .

4. Dog noses are at least 40x more sensitive than ours!

These clever canines have an incredible sense of smell – allowing them to follow scent trails days after they were left. Amazingly, bloodhounds ‘ sense of smell is so spot on that it can be used as evidence in court!

FUN FACT! Dogs also have fantastic hearing! They can detect high-pitched noises and spot sounds from much further away than humans can.

5. Many work as assistance dogs, helping humans!

Many dogs are trained to work as guide dogs , helping blind people get around safely. Others are assistance dogs , who keep their owners calm and safe , while some brave hounds are search and rescue dogs , who help human rescuers save people from danger.

WEIRD BUT TRUE! Some working dogs are trained to use their super senses to sniff out explosives and illegal goods , or alert humans to potentially dangerous health issues . Wow!

6. They only sweat from their paws, and have to cool down by panting.

The sweat is much oilier than humans’, and it contains lots of chemicals that only other dogs can detect. Weirdly, it also makes many dog paws smell of cheesy crisps !

7. They can be right or left-pawed!

Like humans, most dogs have a dominant hand – or in their case, paw! To figure out which one it is, you can conduct a simple science experiment …

Watch a dog moving from standing still to walking forwards. Do they start walking with their left leg, or their right? Watch several times, noting down the starting leg each time, and see if there’s a pattern . Many dogs will often lead with the same leg – their dominant one!

8. The Ancient Egyptians saw dogs as god-like !

Ancient breeds like the Saluki lived in the lavish palaces of Egyptian royalty ! The pampered pooches had their own servants , were decked out in jewelled collars , and ate only the finest meats .

WEIRD BUT TRUE! Dead rulers were often buried with their doggy pals, as they believed the hounds would protect them from harm in the afterlife.

9. Dogs use body language to express their feelings.

From their ears to their eyebrows , shoulders , and tail , dogs often use signals and smells , rather than sound , to communicate! Their posture makes a big difference, too.

Next time you see a dog interacting with a person or other dog, pay close attention. Are they shrinking themselves down small, or standing up big and tall? What do you think they’re trying to say ?

10. Owning a dog is a BIG responsibility!

Just like humans, dogs have feelings and needs , and they have to be taken care of properly. They need regular walking , healthy food , a clean, cosy place to sleep and lots and lots of love and affection ! Make sure you and your family think carefully before you get a dog (or any pet!) to make sure you have the time and means to take one on.

What did you think of our awesome dog facts? Let us know by leaving a comment, below!

Leave a comment.

Your comment will be checked and approved shortly.

WELL DONE, YOUR COMMENT HAS BEEN ADDED!

GREAT READ THANKS

I love dogs I think there amazing animals!

Thanks for the cool magazine NatGeoKids! They’re the best!!!

This is so amazing. I love Dogs

i am a big fan of dogs

I love dogs, they are the coolest living thing on earth

pretty good it does tell a lot of good facts about dog's and i like the pitcher's and time put in it! And i think other kids might like it like me!

My favirote fact is the trick to see what there domnante paw is defently going to try it with my dog.

When my dog is curious or hears something his ears always go up and forward.

CUSTOMIZE YOUR AVATAR

More like general animals.

10 hopping fun rabbit facts!

Hedgehog Facts!

10 terrific tiger facts!

Rhino facts!

Sign up to our newsletter

Get uplifting news, exclusive offers, inspiring stories and activities to help you and your family explore and learn delivered straight to your inbox.

You will receive our UK newsletter. Change region

WHERE DO YOU LIVE?

COUNTRY * Australia Ireland New Zealand United Kingdom Other

By entering your email address you agree to our Terms of Use and Privacy Policy and will receive emails from us about news, offers, activities and partner offers.

You're all signed up! Back to subscription site

Type whatever you want to search

More Results

You’re leaving natgeokids.com to visit another website!

Ask a parent or guardian to check it out first and remember to stay safe online.

You're leaving our kids' pages to visit a page for grown-ups!

Be sure to check if your parent or guardian is okay with this first.

• Reference Manager
• Simple TEXT file

People also looked at

Perspective article, the new era of canine science: reshaping our relationships with dogs.

• 1 School of Anthropology, University of Arizona, Tucson, AZ, United States
• 2 College of Veterinary Medicine, University of Arizona, Tucson, AZ, United States
• 3 Cognitive Science, University of Arizona, Tucson, AZ, United States
• 4 California State Polytechnic University, Pomona, CA, United States
• 5 Department of Psychology, Western Carolina University, Cullowhee, NC, United States
• 6 Center for Urban Resilience, Loyola Marymount University, Los Angeles, CA, United States
• 7 Animal Welfare Science Centre, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Melbourne, VIC, Australia

Canine science is rapidly maturing into an interdisciplinary and highly impactful field with great potential for both basic and translational research. The articles in this Frontiers Research Topic, Our Canine Connection: The History, Benefits and Future of Human-Dog Interactions , arise from two meetings sponsored by the Wallis Annenberg PetSpace Leadership Institute, which convened experts from diverse areas of canine science to assess the state of the field and challenges and opportunities for its future. In this final Perspective paper, we identify a set of overarching themes that will be critical for a productive and sustainable future in canine science. We explore the roles of dog welfare, science communication, and research funding, with an emphasis on developing approaches that benefit people and dogs, alike.

Dogs have played important roles in the lives of humans for millennia ( 1 , 2 ). However, throughout much of scientific history they have been dismissed as an artificial species with little to contribute to our understanding of the natural world, or our place within it. During the last two decades, this sentiment has changed dramatically; canine science is rapidly maturing into an established, impactful, and highly interdisciplinary field ( Figure 1 ). Canine scientists, who previously occupied relatively marginalized roles in academic research, are increasingly being hired at major research universities, and centers devoted to the study of dogs and their interactions with humans are proliferating around the world. The factors underlying dogs' newfound popularity in science are diverse and include (1) increased interest in understanding dog origins, behavior, and cognition; (2) diversification in our approaches to research with non-human animals; (3) recognition of dogs' value as a unique biological model with relevance for humans; and (4) growth in research on the nature and consequences of dog-human interactions, in their myriad forms, from working dog performance to displaced canines living in shelters.

Figure 1 . Canine science is an interdisciplinary field with connections to other traditional and emerging areas of research. The specific fields shown overlap in ways not depicted here and are not an exhaustive list of disciplines contributing to canine science. Rather, they are included as examples of the diversity of scholarship in canine science.

This Perspective represents the final article in a collection of manuscripts arising from two workshops sponsored by the Wallis Annenberg PetSpace Leadership Institute. Leadership Fellows from around the world gathered in 2017 and 2020 to discuss the state of research and future directions in canine science. The individual articles in this collection provide a detailed treatment of key topics discussed at these events. In this final article, we identify a set of overarching challenges that emerge from this work and identify priorities and opportunities for the future of canine science.

The rise of canine science has benefited substantially from public interest and participation in the research process. Unlike many research studies, which unfold quietly in the ivory towers of research universities, the new era of canine science is intentionally public facing. The dogs being studied are not laboratory animals, bred and housed for research purposes, but rather are companions living in private homes, or assisting humans in capacities ranging from assistance for people with disabilities, to medical and explosives detection. Campus-based research laboratories have opened their doors to members of the public who bring their dogs to participate in problem-solving tasks, social interactions, and sometimes even non-invasive neuroimaging studies. Increasingly, dog owners themselves play a significant role in the scientific process, serving as community scientists who contribute to the systematic gathering of data from the convenience of their homes.

This new research model in conjunction with emerging technologies, makes canine science a highly visible field that engages public stakeholders in unprecedented ways. From a scientific perspective, society has become the new laboratory, and in doing so, has facilitated research with dogs of a scope and scale that was heretofore unthinkable. As tens of thousands of dogs contribute to research on topics ranging from cognition and genetics ( 3 , 4 ) to aging and human loneliness ( 5 ), canine science is entering the realm of “big data” and eclipsing many traditional research approaches. Importantly, these advances are occurring simultaneously across diverse fields of science, creating powerful new opportunities for consilience that will make canine science even more valuable in the years ahead. However, maturing this model toward a sustainable future that serves its diverse stakeholders—who include scientists, research funders, members of the public, and dogs themselves—will require careful navigation of key challenges related to dog welfare, science communication, and financial support ( Figure 2 ).

Figure 2 . Visual summary of the key issues identified in this Perspective . A sustainable future in canine science will require (1) research approaches that prioritize and monitor the welfare of dogs, (2) improved science communication to avoid incorrect reporting of study results, and to translate research findings to meaningful change in practices relating to dogs, and (3) availability of research funding that is not tied exclusively to studying the possible benefits of dogs for humans.

Dog Welfare

Globally, animal welfare has been linked to the public acceptability that underpins sustainable animal interactions and partnerships ( 6 ). Where human-animal interactions have failed to meet community expectations, practices and in some case entire industries, have been disrupted or ceased. Recent examples include whaling for profit and greyhound racing ( 6 , 7 ). Science is not exempt from this necessity to meet with public expectations and the new era of canine science must place canine welfare at the forefront. Considering dogs as individuals and co-workers, rather than tools for work or subjects, reflects a community moral and ethical paradigm shift that is currently underway. Reimagining our relationship with domestic dogs in research will also help inform our treatment of other animals. In this way, studies of dogs and our interactions with them can serve as a pioneering new model for many areas of science.

As scientists advocate for the revision of community and industry practices with dogs in light of new evidence, we must apply the same criteria to the conduct of our research. This includes adjusting canine research and training methods to acknowledge the sentience of dogs, and the importance of the affective experience for dogs in both research and community settings ( 8 – 11 ). The discipline of animal welfare science has progressed rapidly over the last two decades, and we have many animal-based, welfare-outcome measures available to us ( 6 , 11 ). Ensuring the well-being of the dogs we study will be as critical to ongoing social license to operate (i.e., community approval) for canine science as it is for working dog interests ( 12 ). Being transparent about the issues of animal consent and vulnerability, as well as offering animals agency with regard to their participation in science are valuable suggestions offered within this special issue. We encourage our colleagues to not just consider this paradigm shift, but to effect it through prioritizing and representing the dog's perspective and welfare in their research.

Although increasingly, researchers may include a single or limited set of canine stress measures in studies exploring dogs' potential benefits to humans, this approach alone does not fill the need for studies that prioritize an understanding of canine welfare as their central focus. Canine welfare should be considered not just as an emergent population-level measure ( 13 ) but rather with respect to the way in which it is experienced: from the perspectives of individual dogs. Commonly used statistical methods from human research, such as group-based trajectory analysis ( 14 ) may offer proven techniques that allow meaningful reporting on populations while reflecting the nuance of shared, sub-group patterns. Such approaches will better reflect individual differences, for example variations in canine personality, social support and relationship styles, as well as other significant factors. One impediment to robust measurement of animal welfare in canine science has been limited funding.

We believe that all granting bodies who fund exploration of the possible benefits to people from dogs should also fund and require the canine perspective to be robustly monitored and reported. Impediments to this work arise not from lack of researcher interest or access to dogs, but rather from challenges to securing funding that is independent from a focus on human health outcomes, or other tangible outcomes of work that dogs perform. To be able to optimize canine welfare, there is an urgent need for increased funding specifically to study the welfare of dogs, in all their diversity. The new era of canine science will identify what dogs need to thrive, propelling us toward a mutually sustainable partnership between people and dogs.

Communication

One area that has not received much attention in relation to canine science is the way in which research findings are communicated outside the empirical literature. Fueled by media reports, interest in canine science and the impact of dogs on human health and well-being has grown substantially in the last 10 years. A survey by the Human-Animal Bond Research Institute found that 71% of pet owners were aware of studies demonstrating that pets improve mental and physical health. Some of these claims are justified. For example, many studies have found that interacting with therapy dogs reduces stress and anxiety and increases positive emotional states in a variety of settings including hospitals, schools and nursing homes ( 15 , 16 ). In other cases, high public expectations about the healing power of pets are not matched by the results of empirical studies. For instance, while the Human-Animal Bond Research Institute survey found that 86% of pet owners believe pets relieve depression, the majority of studies on pet-ownership and depression do not support these conclusions ( 17 ).

Because so many people have extensive personal experiences with dogs, investigators face unique challenges in sharing research results with the public. In their hearts, dog owners believe that their canine companions make them feel less depressed, or that dogs feel guilty when they've eliminated indoors or explored the kitchen garbage—even though research might suggest otherwise. In addition, when it comes to animal companions, people much prefer to read a news article in which visits with a therapy dog improved the well-being of a child undergoing chemotherapy than an article about a randomized clinical trial which found no differences between the well-being of children in a therapy dog group and a control group ( 18 ). Nor is there likely to be much press coverage devoted to methodological issues such as small effect sizes and inappropriate attributions of causality to the results of correlational studies.

Canine scientists and scholars of human-animal interactions (anthrozoologists) are fortunate that the public is intrinsically interested in our research. We feel that it is critical for investigators to make efforts to communicate the findings of important studies to the public. We caution however, that researchers should not overstate the implications of their findings in press releases and conversations with journalists, despite frequent pressure to do so. These distortions could have a negative impact on misleading the public and misrepresenting the actual findings, a problem that is particularly acute in canine science where well-intentioned pet owners may eagerly adopt practices based on media coverage of scientific studies. The now-established discipline of science communication offers guidance for how best to engage with community and research stakeholders in meaningful ways.

Traditionally, science communication has relied on the knowledge deficit model of communication ( 19 ). Directionally one-way, the deficit model operates on the assumption that ignorance is the reason for a lack of community support and application of scientific evidence. Examples where practices have not been updated in response to research findings include dog training methodology ( 9 ) and breeding selection for extreme body types, such as brachycephaly in pugs and bulldogs, even though the health and welfare impacts are scientifically well understood ( 20 ). Scientists who share their research results thinking that knowledge disseminated—to “educate” the public—is enough to result in different dog care decisions, industry practices or legislation, will generally find this to be ineffective ( 21 ). This is because the deficit model overlooks the underlying beliefs, existing attitudes and motivations for current practices. We now recognize that the deficit model is not the most effective way to communicate, engage stakeholders and effect change ( 22 , 23 ).

Further exploration of the effect of targeted and intentional science communication, informed by human behavior change research, will improve the translation of canine science to meaningful outcomes for dogs and people alike ( 12 ). This is important, as many studies in canine science have applied aims designed to inform global policies and the creation of best practices ( 24 , 25 ). Applied research from the livestock and farming sector suggests that coordinating human behavior change strategies from social and psychological sciences can influence beliefs and attitudes to motivate changes in the ways people behave toward animals, resulting in improved animal welfare ( 26 – 28 ). In the era of attention economics, where scientists are competing for public attention alongside other diverse media, it is vital that the communication of our work is honest, relevant, and effective, to ensure that our field stays on the radar of key stakeholders, funding bodies and change agents.

A third key challenge in the future of canine science concerns research funding and a careful balancing of the priorities of scientists and funding agencies. In the last decade, canine science has received considerable support from the pet care sector, as well as human health and defense agencies [e.g., ( 29 )]. Fine and Andersen ( 30 ) stress that although funding is still a challenge in human-animal interaction research, there are now more options to be found. In 2008, the Waltham Petcare Science Institute initiated a public-private partnership with the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Over the past decade, this partnership has provided funding for research aimed at measuring the impact of specific Animal-assisted interventions. Since 2014, the Human Animal Bond Research Institute has funded a total of 35 academic research grants investigating the health outcomes of pet ownership and/or human-animal interaction, both for the people and non-human animals involved. Despite clear benefits for enabling research, there remains a limited group of agencies responsible for funding this work. This has potential to constrain the range of topics being studied. In addition, scientists may feel compelled to support the agendas of industry groups, such as those in the pet sector, who often encourage research that will demonstrate the benefits of pets and human-animal interactions.

These constraints were recognized by Wallis Annenberg PetSpace in 2017 when they envisioned their Leadership Institute Program with a mission to promote interdisciplinary scholarship and convene meetings to accelerate research and policy development ( https://www.annenbergpetspace.org/about/leadership ). This model for engagement inspired the organization to offer two invited retreats (2017, 2020) for a total of 33 experts in the field that provided opportunities for open ended and frank discussion about the nature of human-animal interaction research, and the maturing field of canine science. By providing the space and financial support, plus the opportunity to work together and publish, Annenberg PetSpace provided a way to both illuminate current limitations, and to identify priorities for the future, free of constraints from outside interest groups. These intellectual salons have no specific agenda other than to consider the future of the field and what kinds of questions need to be asked based on what we already know. The results of these two retreats include 14 published refereed papers, plus a suite of collaborations that might otherwise not have happened. We hope that these fellowships and retreats continue and inspire others to support similar initiatives so that scholars across multiple disciplines have the opportunity to experience the transformational exchanges that occur during these programs. The new era of canine science will require diverse funding that is not limited to how dogs can benefit humans, from health, safety and economic perspectives. This change will enable researchers the freedom to further our understanding of dogs and their needs for optimized welfare. In turn, this will allow us to identify how dogs and people can thrive together.

Looking Ahead

We hope that the publications emerging from these retreats will reach a diverse community of stakeholders, including students, early career researchers, animal welfare and advocacy groups, legislators and policy makers, philanthropies, and traditional agency funders. The goal of these papers is to spark imagination for projects not yet engaged and to help set the agenda for future research that can enhance our understanding of human-dog interactions and identify paths to ensure a future of symbiotic relationships between these species.

The vision of this collective group of scholars includes the goal of establishing studies with dogs as a sustainable and broad-reaching research focus. Although dogs provide many advantages as a “model species” —including their phenotypic diversity, and shared environments and evolutionary history with humans—a research model centered around dogs has many additional benefits. Dogs provide a rich, interactive and sentient model with deep implications for the way scientists approach animal research, and animal welfare. Dogs also increase the accessibility of research, both literally, due to their ubiquity and opportunities for large-scale public participation in research ( 31 , 32 ), and figuratively, through a body of work with appeal to the broader public.

The field of canine science has much in common with a similar emerging science, that of urban ecology. Humans are historically at the core of the subject material, but non-human elements are often the focus of the study. As such, the work is always culturally embedded, relevant to a variety of stakeholders, and ultimately expected to improve quality of life. The urban ecologists coined a term Use-Inspired Research ( 33 ) from modifying the existing idea of Pasteur's Quadrant which organizes research questions across the axes of fundamental understanding and considerations of use ( 34 ). Both canine research and urban ecology seek fundamental understanding, but also expect to directly apply the knowledge gained to improve outcomes for their subjects and stakeholders.

By including the public in canine science we not only increase the quantity of the data that we can gather, we serve as ambassadors for a new model of responsible animal research. The result increases the value of human-animal interaction research and creates opportunities for the next generation of interdisciplinary scientists. The goal of this collection has been both to highlight specific recent advances in canine science as well as to identify emerging and overarching issues that will shape the future of this field. The multidisciplinary nature of our work with dogs allows scientists to contribute to a robust research agenda, enhancing our understanding of canines and their impact on society. Ultimately, the nexus of our discoveries should have profound effects on reshaping and enriching our relationships with dogs.

Data Availability Statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.

Author Contributions

All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.

We thank Wallis Annenberg PetSpace for supporting the open-access publishing fees associated with this manuscript.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

1. Serpell JA. Commensalism or cross-species adoption? A critical review of theories of wolf domestication. Front Vet Sci . (2021) 8:662370. doi: 10.3389/fvets.2021.662370

PubMed Abstract | CrossRef Full Text | Google Scholar

2. Wynne C. The indispensable dog. Front Vet Sci. (2021).

3. Chen F, Zimmermann M, Hekman JP, Lord KA, Logan B, Russenberger J, et al. Advancing genetic selection and behavioral genomics of working dogs through collaborative science. Front Vet Sci. (2021).

Google Scholar

4. Gnanadesikan GE, Hare B, Snyder-Mackler N, MacLean EL. Estimating the heritability of cognitive traits across dog breeds reveals highly heritable inhibitory control and communication factors. Anim Cogn . (2020) 23:953–64. doi: 10.1007/s10071-020-01400-4

5. McCune S, Promislow D. Healthy, active aging for people and dogs. Front Vet Sci . (2021). doi: 10.3389/fvets.2021.655191

6. Broom DM. International Animal Welfare Perspectives, Including Whaling and Inhumane Seal Killing as a Wto Public Morality Issue. In: Animal Law and Welfare-International Perspectives . New York, NY: Springer (2016). p. 45–61.

7. Markwell K, Firth T, Hing N. Blood on the race track: an analysis of ethical concerns regarding animal-based gambling. Ann Leisure Res. (2017) 20:594–609. doi: 10.1080/11745398.2016.1251326

CrossRef Full Text | Google Scholar

8. Cobb M, Lill A, Bennett P. Not all dogs are equal: Perception of canine welfare varies with context. Anim Welfare. (2020) 29:27–35. doi: 10.7120/09627286.29.1.027

9. Hall NJ, Johnston AM, Bray EE, Otto CM, MacLean EL, Udell MA. Working dog training for the 21st century. Front Vet Sci. (2021).

10. Horowitz A. Considering the “dog” in dog-human interaction. Front Vet Sci . (2021). doi: 10.3389/fvets.2021.642821

11. Mellor DJ, Beausoleil NJ, Littlewood KE, McLean AN, McGreevy PD, Jones B, et al. The 2020 five domains model: including human–animal interactions in assessments of animal welfare. Animals. (2020) 10:1870. doi: 10.3390/ani10101870

12. Cobb ML, Otto CM, Fine AH. The animal welfare science of working dogs: current perspectives on recent advances and future directions. Front Vet Sci. (2021).

13. Richter SH, Hintze S. From the individual to the population–and back again? Emphasising the role of the individual in animal welfare science. Appl Anim Behav Sci. (2019) 212:1–8. doi: 10.1016/j.applanim.2018.12.012

14. Nagin DS, Odgers CL. Group-based trajectory modeling in clinical research. Ann Rev Clin Psychol. (2010) 6:109–38. doi: 10.1146/annurev.clinpsy.121208.131413

15. Barker SB, Gee NR. Canine-assisted interventions in hospitals: Best practices for maximizing human and canine safety. Front Vet Sci . (2021) 8:615730. doi: 10.3389/fvets.2021.615730

16. Gee NR, Rodriguez KE, Fine AH, Trammell JP. Dogs supporting human health and wellbeing: a biopsychosocial approach. Front Vet Sci . (2021) 8:630465. doi: 10.3389/fvets.2021.630465

17. Rodriguez KE, Herzog H, Gee NR. Variability in human-animal interaction research. Front Vet Sci . (2021) 7:619600. doi: 10.3389/fvets.2020.619600

18. McCullough A, Ruehrdanz A, Jenkins MA, Gilmer MJ, Olson J, Pawar A, et al. Measuring the effects of an animal-assisted intervention for pediatric oncology patients and their parents: a multisite randomized controlled trial. J Pediatr Oncol Nurs. (2018) 35:159–77. doi: 10.1177/1043454217748586

19. Simis MJ, Madden H, Cacciatore MA, Yeo SK. The lure of rationality: why does the deficit model persist in science communication? Public Understand Sci. (2016) 25:400–14. doi: 10.1177/0963662516629749

20. Packer RM, O'Neill DG, Fletcher F, Farnworth MJ. Great expectations, inconvenient truths, and the paradoxes of the dog-owner relationship for owners of brachycephalic dogs. PLoS ONE. (2019) 14:e0219918. doi: 10.1371/journal.pone.0219918

21. Seethaler S, Evans JH, Gere C, Rajagopalan RM. Science, values, and science communication: competencies for pushing beyond the deficit model. Sci Commun. (2019) 41:378–88. doi: 10.1177/1075547019847484

22. Philpotts I, Dillon J, Rooney N. Improving the welfare of companion dogs—is owner education the solution? Animals. (2019) 9:662. doi: 10.3390/ani9090662

23. Westgarth C, Christley RM, Marvin G, Perkins E. The responsible dog owner: the construction of responsibility. Anthrozoös. (2019) 32:631–46. doi: 10.1080/08927936.2019.1645506

24. Bray EE, Otto CM, Udell MA, Hall NJ, Johnston AM, MacLean EL. Enhancing the selection and performance of working dogs. Front Vet Sci . (2021) 8:644431. doi: 10.3389/fvets.2021.644431

25. Feldman S, Fine AH, Melfi L. Research, practice, science public policy: How they fit together in the context of aai. In: Fine AH, editor. Handbook on Animal Assisted Therapy. 5th ed. San Diego, CA: Elsevier/Academic Press (2019). p. 417–24.

26. Coleman G, Hemsworth PH. Training to improve stockperson beliefs and behaviour towards livestock enhances welfare and productivity. Rev Sci Tech. (2014) 33:131–7. doi: 10.20506/rst.33.1.2257

27. Fernandes J, Blache D, Maloney SK, Martin GB, Venus B, Walker FR, et al. Addressing animal welfare through collaborative stakeholder networks. Agriculture. (2019) 9:132. doi: 10.3390/agriculture9060132

28. Vigors B. Reducing the consumer attitude–behaviour gap in animal welfare: the potential role of ‘nudges’. Animals. (2018) 8:232. doi: 10.3390/ani8120232

29. McCune S, McCardle P, Griffin JA, Esposito L, Hurley K, Bures R, et al. Human-animal interaction (hai) research: a decade of progress. Front Vet Sci. (2020) 7:44. doi: 10.3389/fvets.2020.00044

30. Fine AH, Andersen SJ. A commentary on the contemporary issues confronting animal assisted and equine assisted interactions. J Equine Vet Sci. (2021) 103436. doi: 10.1016/j.jevs.2021.103436

31. Kaeberlein M, Creevy KE, Promislow DE. The dog aging project: Translational geroscience in companion animals. Mamm Genome. (2016) 27:279–88. doi: 10.1007/s00335-016-9638-7

32. Stewart L, MacLean EL, Ivy D, Woods V, Cohen E, Rodriguez K, et al. Citizen science as a new tool in dog cognition research. PLoS ONE. (2015) 10:e0135176. doi: 10.1371/journal.pone.0135176

33. Grove JM, Childers DL, Galvin M, Hines S, Muñoz-Erickson T, Svendsen ES. Linking science and decision making to promote an ecology for the city: practices and opportunities. Ecosyst Health Sustain. (2016) 2:e01239. doi: 10.1002/ehs2.1239

34. Stokes DE. Pasteur's Quadrant: Basic Science and Technological Innovation . Washington, DC: Brookings Institution Press (2011).

Keywords: canine science, dog, animal welfare, human-animal interaction, science communication, funding, sustainability

Citation: MacLean EL, Fine A, Herzog H, Strauss E and Cobb ML (2021) The New Era of Canine Science: Reshaping Our Relationships With Dogs. Front. Vet. Sci. 8:675782. doi: 10.3389/fvets.2021.675782

Received: 03 March 2021; Accepted: 11 June 2021; Published: 15 July 2021.

Reviewed by:

Copyright © 2021 MacLean, Fine, Herzog, Strauss and Cobb. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Evan L. MacLean, evanmaclean@arizona.edu

This article is part of the Research Topic

Our Canine Connection: The History, Benefits and Future of Human-Dog Interactions

To Optimize Guide-Dog Robots, First Listen to the Visually Impaired

Guide-dog users and trainers can provide insight into features that make robotic helpers useful in the real world.

What features does a robotic guide dog need? Ask the blind, say researchers behind an  award-winning paper led by University of Massachusetts Amherst computer scientists and involving The University of Texas at Austin’s Joydeep Biswas. 

The study, which identified how to develop robot guide dogs with insights from guide dog users and trainers, won a Best Paper Award at CHI 2024: Conference on Human Factors in Computing Systems (CHI), the leading venue for human-computer interaction research. 

Guide dogs enable remarkable autonomy and mobility for their handlers. However, only a fraction of people with visual impairments have one of these companions. The barriers include the scarcity of trained dogs, cost (which is $40,000 for training alone), allergies and other physical limitations that preclude caring for a dog. 

Robots have the potential to step in where canines can’t and address a truly gaping need— if designers can get the features right. 

“This paper really takes a user-first perspective to developing guide-dog robots: by starting out with a thorough analysis of interviews and observation sessions with dog guide handlers and trainers,” said Biswas, an associate professor of computer science.

The research team worked with 23 visually impaired dog-guide handlers and five trainers. Through thematic analysis, they distilled the current limitations of canine guide dogs and the traits handlers are looking for in an effective guide with considerations to make for future robotic guide dogs.

“We’re not the first ones to develop guide-dog robots,” said  Donghyun Kim , assistant professor in the UMass Amherst Manning College of Information and Computer Science (CICS) and one of the corresponding authors of the paper. “There are 40 years of study there, and none of these robots are actually used by end users. We tried to tackle that problem first so that, before we develop the technology, we understand how they use the animal guide dog and what technology they are waiting for.”

Nuanced themes came from the interviews, such as the delicate balance between robot autonomy and human control – all issues important to understanding how to develop robots deployable in the real world. In other examples, researchers learned about the importance of extended battery life for ensuring the robots would meet real-world needs for visually impaired commuters and providing clarity about the importance of guidance to follow the street (as a sidewalk does) versus always heading in the same direction.

Biswas brought to the project experience in creating artificial intelligence algorithms that allow robots to navigate through unstructured environments. Biswas is involved in a project that studies  how robots in close proximity with people in public interact , including on the campus of UT Austin, the university that declared this year to be the Year of AI .

Other researchers who contributed to the paper were  Hochul Hwang and Ivan Lee , of UMass Amherst;  Hee Tae Jung of Indiana University; and  Nicholas Giudice , of the University of Maine.

Adapted from a post by University of Massachusetts Amherst .

• Share on Facebook
• Share on LinkedIn
• Show and hide the URL copier tool.
• Share via email
• Computer Science
• Machine Learning, Data and AI

Artificial Intelligence Trained to Draw Inspiration From Images, Not Copy Them

May 17, 2024 • by Karen Davidson

Department of Computer Science

Transforming Human-Robot Interaction Through Mood-Inducing Music

May 5, 2024 • by Trinity Erales

Celebrating the 2024 College of Natural Sciences Dean’s Honored Graduates

May 3, 2024 • by Esther Robards-Forbes

share this!

May 15, 2024

This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

peer-reviewed publication

trusted source

New research addresses alleged benefits of a vegan diet for dogs

by University of Liverpool

Associations between feeding dogs a vegan diet and owner perceptions of their health are likely to be minimal, according to a new study by the University of Liverpool. The work is published in the journal PLOS ONE .

Scientists at the University reinvestigated data that had been used to claim that a nutritionally-sound vegan diet is "the heathiest and least hazardous dietary choice for dogs ." The findings from this new analysis do not support those earlier claims, with associations between owner perceptions of dog health and feeding a vegan diet instead being minimal.

The previous research , published in April 2022, utilized an online survey of dog owners to gather information about them, their dogs and the type of food they fed to them. Owners were also asked to recall details of their dogs' veterinary care (e.g. number of veterinary visits, use of medication , etc.) and to give an overall opinion about their dogs' health. The results of this original study implied that dogs fed either a raw meat or vegan diet appeared to fare better than those fed a conventional diet.

However, the new analysis by researchers at the University of Liverpool offers further insights.

Alex German, Professor of Small Animal Medicine, said, "On first reading this paper in 2022, it was evident that the study exclusively relied upon owner survey data and had an observational design, meaning that the associations between diet type and dog health could only suggest a possible correlation and not causality.

"In other words, it was not accurate to conclude that 'Nutritionally-sound vegan diets are the healthiest and least hazardous choices for owners to feed their pet dogs.' Further, the statistical analyses used did not explore the effect of possible confounding from other variables, such as the age and breed of the dogs and owner variables including age, gender, education and diet."

The researchers conducted further statistical analyses on the original study dataset, utilizing different modeling techniques to investigate one outcome variable from the original study, owner opinions of dog health. They tested the effects of owner and dog diet, as well as other owner and dog variables, while some models also included veterinary care variables.

Owner opinions of dog health were most strongly associated with the age of the dog, with other variables (such as owner age, owner education, and breed size) also featuring. Model fit was improved when veterinary care variables were included. However, in all best-fit models (with or without the veterinary care variables), the association between owner opinions of health and feeding vegan dog food was minimal.

Commenting on these findings, Richard Barrett-Jolley, Professor of Neuropharmacology, said, "We know how seriously owners take their pet's health. By revisiting and further interrogating these data, we have been able to draw more nuanced insights. Crucially, we cannot draw a firm conclusion as to what diet type is actually best for dogs; this was never possible given the nature of the original dataset and study design . However, we can conclude that variables other than dog diet are more strongly associated with owner opinions about the health of their dog."

The new study underwent a rigorous peer review process, and as per journal policy, the senior author of the original paper acted as a reviewer. Details of the review process as well as statistical analyses and the statistical code used are published alongside the paper.

Journal information: PLoS ONE

Provided by University of Liverpool

Explore further

Feedback to editors

Blue Origin flies thrill seekers to space, including oldest astronaut

14 hours ago

Composition of gut microbiota could influence decision-making

May 18, 2024

Researchers realize multiphoton electron emission with non-classical light

Saturday Citations: Mediterranean diet racks up more points; persistent quantum coherence; vegan dogs

Physicists propose path to faster, more flexible robots

Scientists develop new geochemical 'fingerprint' to trace contaminants in fertilizer

May 17, 2024

Study reveals how a sugar-sensing protein acts as a 'machine' to switch plant growth—and oil production—on and off

Researchers develop world's smallest quantum light detector on a silicon chip

How heat waves are affecting Arctic phytoplankton

Horse remains show Pagan-Christian trade networks supplied horses from overseas for the last horse sacrifices in Europe

Relevant physicsforums posts, what was the original purpose of the chainsaw.

2 hours ago

DNA-maternity test - could you see other relationship than mother?

8 hours ago

And Now, here comes COVID-19 version BA.2, BA.4, BA.5,...

Is it usual for vaccine injection site to hurt again during infection.

May 16, 2024

A Brief Biography of Dr Virgina Apgar, creator of the baby APGAR test

May 12, 2024

Who chooses official designations for individual dolphins, such as FB15, F153, F286?

May 9, 2024

More from Biology and Medical

Related Stories

Vegan diets for dogs may be linked with better health, and could be less hazardous, than meat-based diets

Apr 13, 2022

New research highlights aging dog health care needs

Apr 15, 2024

Dogs with more active owners may get more exercise

Aug 24, 2022

Study dispels myth that purebred dogs are more prone to health problems

Apr 30, 2024

Dogs and their owners share a risk of developing diabetes

Dec 10, 2020

'Just old age' or is your dog experiencing a serious clinical issue?

Mar 29, 2023

Recommended for you

Furry thieves are running loose in a Maine forest, research shows

Major declines reported in South Korean big cat trade

New research shows the true cost of reproduction across the animal kingdom

Study shows plants restrict use of corrective 'Tipp-Ex proteins'

Sea otter study finds tool use allows access to larger prey, reduces tooth damage

Let us know if there is a problem with our content.

Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form . For general feedback, use the public comments section below (please adhere to guidelines ).

Please select the most appropriate category to facilitate processing of your request

Thank you for taking time to provide your feedback to the editors.

Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.

E-mail the story

Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Phys.org in any form.

Newsletter sign up

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.

More information Privacy policy

Donate and enjoy an ad-free experience

We keep our content available to everyone. Consider supporting Science X's mission by getting a premium account.

E-mail newsletter

This is how inbred purebred dogs have become…

By Alexandra Horowitz Graphics by Sara Chodosh and Taylor Maggiacomo

Dr. Horowitz is a cognitive scientist who studies dogs.

Sex with your sibling is called incest and is illegal in almost all 50 states. Sex with your sibling or other close relations, if you are a dog, is called inbreeding, and inbreeding is part of the practice of pure-breeding dogs.

Breeders are not typically mating siblings, though it is not prohibited by the American Kennel Club and is not unheard-of. Any mating within a closed gene pool of candidates will do, as far as breeders are concerned. But according to research published by a team from the University of California, Davis, and Wisdom Health Genetics in Finland, purebred dogs have, on average, a “coefficient of inbreeding” of 0.25, the same number you get when two siblings have a child. This number indicates the probability that two individuals will share two alleles from a common ancestor, like a parent or grandparent. And this number — 0.25 — is a problem.

The results of pure-breeding, on display starting this Saturday at the Westminster Kennel Club Dog Show in New York, are profound. The radical morphological diversity of dog breeds today — from four-pound Malteses, white-haired and small-faced, to 170-pound Great Danes, large of body and of presence — is due to selective breeding.

So, too, are the consequences: the occurrence of several hundred health disorders related to genetics or to adherence to the standards set by breed groups that have emerged since dog pure-breeding took off in the 19th century. These include changes to anatomy so drastic that they affect reproduction (the bulldog’s head is so big that the overwhelming majority cannot be birthed naturally), respiration (the pug’s small skull leads to a constellation of abnormalities that make breathing difficult) and recreation (the German shepherd and other large-breed dogs are prone to debilitating hip dysplasia).

German shepherds used to have straight backs

A German shepherd in 1958.

Erich Andres/United Archives, via Getty Images

Modern shepherds have more pronounced slopes

A German shepherd at the 2013 Westminster Kennel Club Dog Show.

Fred R. Conrad/The New York Times

The U.C. Davis research, led by Danika Bannasch, a veterinary geneticist, also found that the more inbred a breed was, the more inherited disease the breed had. (Remember the number they found, 0.25? Healthy rates of genetic similarity occur with a coefficient of inbreeding below 0.05.) This finding aligns with what anyone who has taken biology already knows: When you limit the breeding population, the frequency of potentially unhealthy mutations increases, as deleterious but recessive alleles become prominent.

When we breed to a type, genetic diversity is lost. Now we have dozens of small- and large-scale studies showing the inevitable results of inbreeding with dogs: smaller litter sizes, fewer surviving newborns and even decreasing life spans. A large 2019 study found, controlling for size, that purebred dogs lived over a year less than mixed-breed dogs did. As a society, in other words, we’re trading a year of their lives for the ability to choose their shape, size and color.

More inbred dogs tend to have more health issues

Morbidity is a measure of suffering from disease, shown here as the number of non-routine vet visits for each breed, per 10,000 dog years, as observed by an insurance company.

Parents are cousins

Half siblings

↑ Morbidity

2,500 non-routine vet visits

Inbreeding →

Irish Wolfhound

Mixed breed

Dogs are living examples of a paradox — the paradox of our human impulses. I know no dog people who want their dogs to live a year less than they would, statistically speaking, if they were mutts. But I know lots of people who want to purchase a purebred dog. Why is this? I think it comes down to our psychological tendencies, on one hand, and consumer mind-set, on the other.

Psychologically, we love anecdotal data and are easily persuaded by single data points. As a researcher on dog cognition for the past 20 years, I have seen this demonstrated in reaction to published and replicated research when our experiences seem to belie the results. When I describe research that finds that the guilty look of dogs is a response to their owners’ behavior, not a reflection of their understanding of their own misbehavior, the most common reaction I receive is: But my dog looks guilty only when he is guilty.

Pugs used to have more prominent snouts

A pug in 1915.

Imagno/Getty Images

Modern pugs have smushed, round faces

A pug at the 2013 Westminster Kennel Club Dog Show.

There are plenty of individual examples of long-lived purebred dogs — several of the oldest living dogs on record, north of 20 years, are purebred — so we hold on to those anecdotes, like a smoker to cigarettes because a grandmother lived until 102 clutching her Marlboros. Also contributing to our paradoxical behavior is our love for buying things, even (sometimes especially) living things. Societally, we treat dogs as commercial products, although each dog purchaser is hoping the dog will become a member of the family, not shelved with our other household objects for display.

In an era when you can get groceries and a new computer delivered to your home in an hour, I am surprised that we can’t buy puppies on Amazon (yet). But we can head online, scrolling through websites and collecting recommendations from other dog purchasers. We start to imagine the kind of dog we would like, with features we can choose. The American Kennel Club and the dog breed clubs within it are happy to tell you about the features you can expect in your new dog — friendly, good with kids, trainable. The possibility of a reliable dog product is more fun to believe in than the scholarly research that clearly demonstrates that breed type is a poor predictor of behavior. The illusion of certainty mesmerizes us.

Chow chows were smaller, with fewer wrinkles

A chow in 1930.

Fox Photos/Getty Images

Modern chows are slightly larger, with more fluffy fur

A chow at the 2013 Westminster Kennel Club Dog Show.

The deluge of evidence showing both the ubiquity of inbreeding and its detrimental results is a chance for reflection. While science is steadily producing more details about exactly how inbreeding is deforming the species we claim to love, there is nothing fundamentally new here: We have known for years about the poor results for dogs. What the evidence may now be showing us, though, is the poor result for us: We are a species that is willfully damaging dogs.

This result is born not just of our obsession with breeds or our willingness to overlook the damage of inbreeding but also of our thinking about dogs as objects to be molded to our desires. We are drawn to the infantile look of big-eyed, flat-faced dogs, and as a result, we inadvertently created dogs whose eyes ulcerate and whose noses and tracheas are small and often nearly blocked. We are drawn to dogs with distinctive coats (Dalmatian: spotted; Rhodesian Ridgeback: with a characteristic line down the spine), the genes for which also lead to disorders (Dalmatian: deafness; Ridgeback: dermoid sinus, a neural tube defect).

Bull terriers had more typical snout bridges

A bull terrier in 1949.

Modern bull terriers have more football-shaped heads

A bull terrier at the 2013 Westminster Kennel Club Dog Show.

As a species, we are so attached to the idea that we should be able to buy a dog who looks however we like — flat of face or fancy of coat — that we are willing to overlook the consequences for the species, for the breeds and often for the very sweet, exuberant pup we add to our families.

We have a chance to redeem ourselves. Right now, the American Kennel Club has no constraints on inbreeding (even as it encourages breeders to remember that “crippling or fatal” hereditary diseases may result). But I am not counting on the American Kennel Club. Instead, we could make outcrosses — the introduction of different genetic material to breeds — the norm. Research looking at dog genotypes and phenotypes has found several putative genes associated with longevity in dogs. What if we pursued robust health, instead of breed standards based on appearance, by investigating and working with those genes? If we loosen our grip on the idea that dogs are consumer objects to be designed and from whom we can demand certain behaviors, we will have a chance to meet dogs again on their own terms.

Methodology

The position of each dog breed in the inbreeding chart is an approximation. Within each breed, the inbreeding coefficient for a given dog will vary.

Dogs Are Not Here for Our Convenience

Spaying and neutering puppies shouldn’t be standard policy — and it isn’t automatically the “responsible” choice either.

By Alexandra Horowitz

My Year of Being Very Online About Dogs

The world of dog training has fractured dramatically across ideological differences. It turns out no one is safe from the culture wars — not even your Shih Tzu.

By Alicia P.Q. Wittmeyer and Mark Peckmezian

Things People Say to Their Dogs

Our running commentary tells us a lot about who we are — and who we think animals are.

An earlier version of this article misstated the name of a terrier breed. It is the soft-coated wheaten terrier, not the Irish terrier.

• Share full article

Advertisement

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Animals (Basel)

The Effectiveness of Dog Population Management: A Systematic Review

Lauren m. smith.

1 Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK; ku.ca.sdeel@imslsb (L.M.S.); [email protected] (R.J.Q.)

Sabine Hartmann

2 VIER PFOTEN International, 1150 Vienna, Austria; [email protected] (S.H.); [email protected] (A.M.M.)

Alexandru M. Munteanu

Paolo dalla villa.

3 Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise “G. Caporale”, 64100 Teramo, Italy; [email protected]

Rupert J. Quinnell

Lisa m. collins, associated data, simple summary.

Domestic dogs are abundant worldwide—as owned pets, unowned strays, and feral animals. High numbers of free-roaming dogs can be a concern because of the risks they pose to public health, animal welfare, and wildlife. Using a systematic review process, we investigated what the research published to date can tell us about the effectiveness of different dog population management methods. We found that management methods for dog populations have been researched in multiple countries worldwide, using a wide range of indicators to assess method effectiveness. We outline the results and suggest improvements to help guide future dog population management policy.

The worldwide population of domestic dogs is estimated at approximately 700 million, with around 75% classified as “free-roaming”. Where free-roaming dogs exist in high densities, there are significant implications for public health, animal welfare, and wildlife. Approaches to manage dog populations include culling, fertility control, and sheltering. Understanding the effectiveness of each of these interventions is important in guiding future dog population management. We present the results of a systematic review of published studies investigating dog population management, to assess: (1) where and when studies were carried out; (2) what population management methods were used; and (3) what was the effect of the method. We evaluated the reporting quality of the published studies for strength of evidence assessment. The systematic review resulted in a corpus of 39 papers from 15 countries, reporting a wide disparity of approaches and measures of effect. We synthesised the management methods and reported effects. Fertility control was most investigated and had the greatest reported effect on dog population size. Reporting quality was low for power calculations (11%), sample size calculations (11%), and the use of control populations (17%). We provide recommendations for future studies to use common metrics and improve reporting quality, study design, and modelling approaches in order to allow better assessment of the true impact of dog population management.

1. Introduction

1.1. the dog population.

Dogs ( Canis familiaris ) have a global distribution and an estimated total population size of around 700 million [ 1 ]. Dogs have one of two ownership states—either they are owned or they are unowned. The owned population is dependent upon humans for food, water, and shelter and may have one or more owner (e.g., “community dogs”). The owned dog population includes both dogs that are restricted in their movement to a limited area (e.g., within a fenced yard or under human supervision on walks), and those that are free to roam unrestricted, without human supervision [ 2 ]. Unowned dogs (often referred to as stray) do not have an owner but may still depend upon humans directly or indirectly for resources such as food, water, and shelter [ 2 ]. Similar to owned dogs, the unowned population’s movements may be restricted or unrestricted—dogs housed in shelters have restricted movement, but street-dwelling dogs have unrestricted movement. Unrestricted dogs are particularly important as the lack of restriction allows them to roam freely, to mate, and to reproduce. This group is commonly referred to as the free-roaming dog population and includes unrestricted owned and unrestricted unowned dogs [ 3 ].

Approximately 75% of dogs across the world fit into this free-roaming dog category [ 1 ]. Free-roaming dog abundance varies greatly between countries, relating to the habitat type (urban/rural) and human population (e.g., density and cultural/social factors) [ 2 ]. Although dog densities vary globally, they can exist in high numbers. For example, densities as high as 719 dogs km -2 have been estimated in Maharashtra in India [ 4 ]. Where free-roaming dogs exist in high densities, they can be considered an issue in terms of public health (e.g., transmission of rabies and other zoonotic pathogens) [ 5 , 6 , 7 ], the environment (e.g., threatening the survival of wildlife) [ 8 , 9 , 10 ], and the animals’ welfare state [ 2 , 11 , 12 , 13 ]. Population management therefore typically focusses on free-roaming dogs [ 14 ] to control the population size and—depending on the approach taken—to improve dog health and welfare and mitigate against public health and environmental problems [ 15 , 16 ].

1.2. Reasons for Managing Free-Roaming Dog Populations

1.2.1. the impact of free-roaming dogs on public health.

Free-roaming dogs are associated with the transmission of a number of zoonotic pathogens [ 17 , 18 , 19 , 20 , 21 ], dog bite injuries [ 22 , 23 , 24 ], and road traffic accidents [ 2 , 25 ]. Dogs are responsible for transmitting over 300 zoonoses to humans [ 26 , 27 ]. They are perhaps best known for the role they play in the spread and maintenance of the rabies virus [ 28 ]. This virus is responsible for an estimated 60,000 human deaths per year amounting to an annual economic cost of 8.6 billion US dollars [ 29 ]. Dogs are a primary reservoir host of this virus and account for 99% of human-rabies transmissions [ 28 ]. Other notable zoonoses include Leishmania infantum , the causative agent of zoonotic visceral leishmaniasis [ 30 ]; Echinococcus spp. ( E. granulosus and E. multilocularis ) [ 31 ], which causes echinococcosis; and Toxocara canis, which causes toxocariasis [ 32 ].

1.2.2. The Impact of Free-Roaming Dogs on Wild and Domestic Animals

Free-roaming dogs can compromise the conservation of wild animals through a combination of pathogen pollution (i.e., the spread of pathogens to naive hosts) [ 8 , 33 , 34 ], predation [ 35 ], competition [ 36 ], and hybridisation [ 9 , 37 , 38 ]. It is estimated that dogs have played a role in the extinction of 11 vertebrate species and threaten the survival of at least 188 more species [ 10 ]. In addition to the negative consequences that canine pathogens have on human health, these pathogens can have an important impact on the conservation of endangered species. For example, rabies spread by domestic dogs can threaten Ethiopian wolf ( Canis simensis ) [ 8 ] and African wild dog ( Lycaon pictus ) [ 33 ] populations. The taxonomic relatedness of the domestic dog to other canids, such as dingoes ( Canis lupus dingo ) and wolves ( Canis lupus ssp.), is also of concern when dogs are free-roaming. Inter-species breeding can result in hybridisation and threaten species survival [ 9 , 37 , 39 ]. In addition, dogs have been responsible for the reduction of other species through predation and competition [ 1 , 40 , 41 ]. For example, predation by dogs resulted in the decrease of mountain gazelle ( Gazella gazella gazella ) in Israel [ 42 ], puda ( Puda puda ) in Chile [ 43 ], and kiwi ( Apteryx australis mantelli ) in New Zealand [ 44 ].

Domestic dogs can also be responsible for the killing of livestock [ 45 , 46 , 47 , 48 , 49 ]; in particular, small-and medium-bodied livestock such as sheep, goats, and donkeys [ 45 , 46 , 47 , 48 , 49 ]. The loss of livestock contributes to substantial economic losses [ 45 ]. For example, in the USA, this amounts to over $620 million US dollars annually [ 48 ]. The financial consequences can be particularly problematic in areas of low-income communities [ 45 ]. Additionally, the loss of livestock can increase human–wildlife conflict, as predation by dogs is often mistaken for that of other species, such as wolves [ 45 , 46 , 49 ] or snow leopards [ 45 ]. This can hinder local support for conservation programs.

1.2.3. Health and Welfare of Free-Roaming Dogs

Free-roaming dogs can often experience poor health and welfare conditions. In particular, unowned free-roaming dogs may have an inadequate diet and a high prevalence of starvation and dehydration [ 2 , 13 ]. For example, in India, around 49% of free-roaming dogs have an emaciated body condition [ 50 ]. Unowned free-roaming dogs can still be dependent on humans for resources, either directly through feeding or indirectly through the provision of food in human waste [ 51 ]. The high prevalence of emaciated body condition state in free-roaming dogs that occurs in some areas may be due to poor quantity or quality of food resources and a high disease burden [ 50 , 52 ]. Free-roaming dogs, particularly those that are unowned, lack veterinary care (such as vaccination or antiparasitics) and are therefore more susceptible to disease. High prevalence of skin conditions and ectoparasites have been reported in several populations [ 50 , 53 ]. Canine transmissible venereal tumour disease is also a welfare concern in free-roaming dog populations, with the prevalence estimated at around 1% in dog populations in Africa, Asia, South America, and Central America [ 54 ], although the prevalence has been estimated to be as high as 15% in female dogs in some free-roaming populations [ 55 ]. Additional health and welfare risks to free-roaming dogs include injury caused by road traffic accidents, abusive treatment by locals [ 3 ], and inhumane methods of removal (e.g., poisoning, electrocution, drowning, or carbon monoxide poisoning [ 56 ]).

1.3. Methods of Managing Dog Populations

1.3.1. responsible groups and motivations for dog population management.

Different groups (e.g., researchers, animal welfare organisations, or government agencies) are often responsible for setting up dog population management programs [ 15 ]. They manage the population in three main ways: culling, long-term sheltering, and fertility control of free-roaming dogs [ 14 , 15 ]. In addition, programs may include a focus on public education of responsible ownership and taxation of dog ownership. Different countries, as well as different regions within a country, may vary in their objectives for carrying out dog population management programs [ 14 , 15 ], such as: reducing the number of free-roaming dogs; increasing awareness of responsible ownership practices; or improving the health of the free-roaming dog population. These objectives may be underpinned by: dog-centric motives, such as improving dog health and welfare; human-centric motives, such as the control of zoonotic disease [ 14 ] and reduced prevalence of dog bite injuries; and wildlife-centric motives, such as reducing the risk to the conservation of other species.

1.3.2. Culling

Historically, culling has been the primary method used to reduce numbers of free-roaming dogs [ 57 ]. Culling is the episodic removal and killing of individuals for the purpose of population reduction. The World Health Organisation published guidelines in 1990 discouraging the use of culling and recommending alternative methods (e.g., registration and identification, vaccination, public education, and sterilisation) [ 58 ]. Despite these recommendations, many countries continue to use culling as a primary method of population control [ 15 ]. Injectable barbiturates are more commonly used in high- and upper-middle-income countries [ 15 ], whereas poisoning and shooting are often used in lower-middle- and low-income countries [ 15 ]. National law in some countries (e.g., Bulgaria [ 59 ], Italy [ 60 ], and Kosovo [ 61 ])) prohibits the killing of dogs for the purpose of population control.

1.3.3. Sheltering

In some countries, sheltering free-roaming dogs is the most common method of dog population control. Similar to culling, sheltering aims to reduce the free-roaming dog population size by removal of dogs. Ultimately, sheltered dogs may be: (i) euthanised; (ii) adopted; or (iii) permanently stay in the shelter. Shelters are commonplace globally and may be government-run (public shelters), privately-run, or operated by NGOs. The numbers of dogs coming into the shelter are often greater than the number of dogs going out, for example to be rehomed [ 62 , 63 , 64 ]. This results in either lifelong stays in the shelter or euthanasia [ 62 , 63 , 64 ]. As national law in some countries prohibits euthanasia of healthy animals, this can lead to long-term sheltering and overcrowding [ 65 ]. Moreover, the use of shelters to house dogs is costly and, as such, more commonly employed in high- and upper-middle-income countries [ 15 ]. Due to the expense, this method may be unsuitable in lower-middle- and low-income countries [ 15 ].

1.3.4. Fertility Control

Fertility control can be achieved through surgical or chemical sterilisation or contraception [ 66 ]. Surgical sterilisation through the catch-neuter-release (CNR) of free-roaming dogs is the predominant method of fertility control. This method involves collecting free-roaming dogs and carrying out spay or castration surgery in either a fixed-location or mobile clinic. CNR has been carried out in several countries and states, for example in Italy [ 67 ], India [ 68 , 69 , 70 ], Bangladesh [ 71 ], Sri Lanka [ 72 ], and Brazil [ 73 ]. Surgical sterilisation is generally more socially acceptable than culling. However, in some locations, there can be conflict between locals and the groups/agencies conducting CNR, as some owned free-roaming dogs are caught and neutered against their owner’s wishes [ 74 ]. In some communities, owners are against the surgical sterilisation of dogs due to their religious beliefs or the misunderstanding that neutering causes undesired behavioural changes [ 75 , 76 ]. In addition, CNR has associated expense, as it requires skilled staff, clinical facilities, and medicines.

1.4. Study Aims

We conducted a systematic review to synthesise the existing evidence of the effectiveness of different dog population management methods. In this review, we describe: (1) where and when the impact of dog population management has been assessed; (2) what management methods have been used; and (3) what effect the management method had on: (i) the dog population size; (ii) dog health and welfare; (iii) public health risk; (iv) public attitude; and (v) risk to wildlife populations. The effectiveness of dog population management depends upon the management intensity (coverage and length of management); therefore, we reported the effects in relation to these criteria wherever possible. In addition, we evaluated the reporting quality of the relevant published studies to allow weighting of evidence for future decision-making.

2. Materials and Methods

2.1. search strategy.

We conducted an initial literature search in February 2017, using the following search engines: Web of Science; ProQuest (Applied Social Sciences Index & Abstracts, PAIS Index, Sociological Abstracts, and Worldwide Political Science Abstracts); LILACS; and Google Scholar (results from Google Scholar were limited to the first 50 pages, due to the high volume of returned literature and lack of relevancy). The search used key words relating to dog population management ( Table S1 ). We carried out a second search using the same search engines, keywords, and eligibility requirements in January 2019 to include any papers published in the interim period.

2.2. Eligibility Requirements

A single corpus of all returned literature was compiled across the searches and cleaned of any duplications prior to filtering. Entries were filtered in three stages, based on the relevance to the study aims. These stages involved assessing the paper’s: (1) title; (2) abstract; and (3) full text. At each stage, papers were included or excluded depending on their match to the following inclusion criteria: (i) one of the primary aims of the literature was to assess, describe, investigate, or compare the impact of unowned free-roaming dog population management, in terms of dog population demographics, dog health and welfare, public attitude, or public health risk; (ii) the study design was observational, intervention or modelling; and (iii) was primary literature. Papers were excluded from the review if: (i) they were not a primary research source; (ii) their study design was systematic review, meta-analysis, lab intervention, or case report; or (iii) they assessed, described, or compared only owned dogs that were not free-roaming (i.e., restricted, owned dogs). This was assessed at Stage (1) (title stage) depending on whether the title included the key words ( Table S1 ) indicating that the paper met the inclusion criteria. At Stages (2) (abstract) and (3) (full text), this was assessed by whether the text met the above-stated inclusion and exclusion criteria. Studies in all languages were considered, although searches were conducted with keywords in English only. There was no restriction on date of publication.

Papers that passed through all three filtering stages were included for review and are referred to as the final corpus. At Stages (1) and (2) of the filtering process, a second reviewer assessed 3% of the papers (Stage (1) = 150 of 4629 papers and Stage (2) = 30 of 923 papers) to check the level of inter-rater inclusion/exclusion agreement. Any papers that were disagreed upon were disputed and a decision reached jointly by both reviewers (details in the Supplementary Materials ).

To increase the possibility of capturing all relevant papers, references from papers in the final corpus were screened using the above three-stage filtering process. All references that matched the above inclusion/exclusion criteria were included in the final corpus.

2.3. Information Extraction

The following information was extracted from the final corpus: (i) year of publication, country of study, and its economic status (defined by The World Bank 2019 country income classification [ 77 ]); (ii) study impact category (dog health and welfare, dog demographics, public attitude, public health, or wildlife), and dog population management method (culling, sheltering, fertility control, or a combination of methods); and (iii) methods, measurements, and study reporting quality. Reporting quality was assessed based on guidelines from Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [ 78 ] and Animals in Research: Reporting In Vivo Experiments (ARRIVE) [ 79 ]. For the final corpus, we assessed quality based on: study design, reporting of aims/hypotheses, appropriate study outcome (as defined by [ 16 ]), and definition of study population. Study populations were classified into: (i) unowned, free-roaming; (ii) owned, free-roaming; (iii) unowned, restricted; (iv) owned restricted; (v) undefined (i.e., the paper did not report which population was under investigation); or a combination of the five categories.

2.4. Evaluating Study Design and Reporting Quality

Where appropriate for the study design, we assessed the study and reporting quality based on: the presence/absence of a power calculation, presence/absence of a sample size calculation, inclusion of a control population, accounting for inter-observer reliability, and reporting of baseline characteristics.

3.1. Year of Publishing, Country of Study and Economic Status

The systematic review resulted in an initial (pre-filtered) corpus of 4863 papers, which we reduced following the three-stage filtering process to 36 papers ( Figure 1 ). To ensure key papers were not missed, the references of included papers were reviewed using the same inclusion/exclusion criteria. This resulted in three additional papers and a final corpus of 39 papers. The final corpus comprised 36 peer-reviewed papers and three theses (two Masters of Science and one Masters of Veterinary Medicine). The papers were published between 1977 and 2018, with 82% published between 2008 and 2018.

Number of papers included and excluded at each stage of the systematic review process. Grey boxes indicate the number excluded at each stage and the green box indicates the number of papers included in the final corpus.

Most of the studies were carried out or used data from locations within a single country (87%). These were located in 15 different countries across Africa (3%), Asia (39%), Central America (3%), Europe (18%), North America (10%), and South America (15%), in countries that were high income (27%), upper-middle income (38%), lower-middle income (32%), and low income (3%). A high proportion of the studies was conducted in India (26%) ( Table S2 ). Three studies used data from multiple countries (8%) and two studies did not specify a country (5%).

3.2. Dog Population Management Methods and Impacts

3.2.1. dog population management methods.

The management methods studied in the final corpus included: fertility control through neutering and immunocontraceptives (13 papers, 33%); culling (indiscriminate culling and culling of infected dogs: (7 papers, 18%)); sheltering (2 papers, 5%); and taxation (1 paper, 3%) ( Table 1 ). Combinations of methods were also studied: fertility control and sheltering (9 papers, 23%); fertility control and culling (6 papers, 15%); and fertility control and movement restriction (1 paper, 3%) ( Table 2 ). Of the papers that involved fertility control, 79% (23 of 29 papers) controlled the fertility of both male and female dogs ( Table 3 and Table 4 ). Eight papers (21%) directly compared different methods of management: three compared fertility control and culling (8%); three compared fertility control and sheltering (8%); one compared fertility control and movement restriction (3%); and one compared different taxation methods (3%).

Impact categories and indicators of effect used in the final corpus to evaluate the effects of management methods. Study design is indicated with either O/I indicating an observational or intervention study, or M for a modelling study. Following the indication of study design is the number of papers (denoted = n , where n is the number of papers) adopting this design to test this combination of dog population management method, indicator, and measured impact, followed by the reference details for the relevant papers.

All final corpus papers by management factors (method and intensity), study design factors, and reporting quality. Management intensity is reported in terms of coverage and length. Length is reported as years of: (i) mgmt. = management (indicating the study and management method took place at the same time) or (ii) study (indicating the study took place after management began). NA = not applicable for the study design.

Results from papers in the final corpus (excluding modelling studies) of the effects of methods of dog population management on the indicators of impact and impact categories. ↑ indicates an increasing effect, ↓ a decreasing effect and n.e. no effect; combinations of different symbols indicate where evidence is conflicting. Where p -values were reported, this is included (e.g., p < 0.05), NR = p -value was not reported, NS = p -value not significant. NA = not applicable for the study design. The size of effect is extracted from papers and reported in terms of the years of: (i) mgmt. = management (indicating the study and management method took place at the same time) or (ii) study (indicating the study took place after management began). Where fertility control is included in the dog population management method, (M&F) indicates fertility control was applied to both males and females, (F) indicates only female fertility was controlled. Supporting evidence is provided in references.

a Contradictory result within paper, contacted author to confirm correct results. b Estimated by approximating numbers from figures in paper. c Alpha value for pairwise post-hoc adjusted to 0.005 to control for multiple comparisons.

Results from only modelling papers from the final corpus of the effects of methods of dog population management on the indicators of impact and impact categories. ↑ indicates an increasing effect, ↓ a decreasing effect, and n.e. no effect; combinations of different symbols indicate where evidence is conflicting. The size of effect is extracted from papers and reported in terms of the years of modelling simulation. Supporting evidence is provided in references.

* Estimated by approximating numbers from figures in paper.

3.2.2. Impact Category and Indicators of Effect

Dog population management methods were investigated in terms of the impact they have on: dog health and welfare (6 papers, 15%); dog demographics (13 papers, 33%); public attitude to free-roaming populations (3 papers, 8%); public health (16 papers, 41%); and risk to wildlife populations (1 paper, 3%) ( Table S3 ). To evaluate these impacts, the final corpus reported 19 different indicators of effect.

The majority of these were different indicators of dog health and welfare, and public health risk, and relatively few different indicators were used to assess dog demographics and public attitude. Considering all the reported indicators, studies used dog population size most frequently to evaluate impact (19 papers, 49%). Considering all management methods and indicators, studies most often evaluated the effect of fertility control and sheltering using dog population size as an indicator (8 papers, 21%).

3.3. Quality Evaluation

We assessed the quality of the intervention and observational studies in the final corpus. We split our measures into two categories: those that applied to all papers (including study design, reporting of aims/hypotheses, appropriate outcome studied, and definition of study population), and those that applied to papers depending on their study design (inclusion of power calculation, sample size calculation, control population, inter-observer reliability, and reporting of baseline characteristics).

3.3.1. Study Design and Study Populations

In the final corpus, 33 papers used only one study design and six papers used two different study designs within the paper ( Table 2 ). Papers in the final corpus used observational (i.e., observing dog population management, but not imposing the intervention themselves) (18 papers, 46%), intervention (1 paper, 3%), modelling (14 papers, 36%), a combination of observational study designs (3 papers, 8%), and a combination of observational and modelling study designs (3 papers, 8%). Of the observational study designs, seven papers used a retrospective cohort (33%), six papers used a longitudinal cross-sectional (29%), nine papers used a single time point cross-sectional approach (38%), two papers combined prospective cohort and retrospective cohort (10%), and one paper combined a single time point cross-sectional and retrospective cohort study design (5%). Papers reported various combinations of dog populations, including: free-roaming owned, free-roaming unowned, restricted owned, and shelter dogs ( Table 2 ). Of the various combinations, 36 papers (92%) investigated both free-roaming unowned and free-roaming owned dogs. Twenty-six of these papers (72%) grouped this population as one (e.g., the free-roaming dog population) and did not distinguish between owned and unowned dogs ( Table S4 ). Two papers did not define their study population (5%).

3.3.2. Study Reporting Quality Indicators

All papers in the final corpus reported their aims, with the majority aiming to understand the impact of dog population management as a primary objective and others describing methods of dog population estimation, model development, and guideline development. All papers in the final corpus used an appropriate outcome to measure the effect of dog population management (as defined by Hiby et al. (2017) [ 16 ]). In the observational/intervention studies, 35% of papers did not report the management coverage and 9% did not report the length of management ( Table 2 ). In general, study quality was low in the observational/intervention papers. Only one study used replication (4%), only six studies investigated different groups (26%) and only four included a control population (17%). Reporting was low for both power calculations (11%) (i.e., a calculation to determine statistical power: the probability of correctly rejecting the null hypothesis) and sample size calculations (11%) (i.e., a calculation to determine the minimum sample size required to answer the study question). However, where appropriate, the reporting of inter-observer reliability (71%) and baseline characteristics was high (80%). Table S5 outlines the results of the reporting quality indicators. Reporting quality (RQ) scores are reported in Table 2 .

3.4. Effects of Management Methods on Impact Categories—Observational and Intervention Studies

The effects of the different methods of dog population management in observational and intervention studies are summarised in Table 3 .

3.4.1. Dog Health and Welfare

The impacts of fertility control alone, sheltering alone, and combined fertility control and sheltering were investigated on dog health and welfare in observational studies. No papers in the final corpus investigated the effect of culling or taxation on dog health and welfare.

Fertility control significantly increased body condition score in two of three papers. This was achieved when fertility control was implemented at an unreported coverage level over two years of management ([ 50 ] 100% RQ) and when an 80% coverage was applied to the female free-roaming dog population over both seven and 17 years of management ([ 70 ] 25% RQ). Fertility control was associated with reduced prevalence of injuries ([ 70 ] 25% RQ: 80% female coverage over seven and 17 years) and had few associated post-operative complications (between 5% and 7%, depending on the length of observation) ([ 82 ] 40% RQ). Yoak et al. (2014) ([ 70 ] 25% RQ) reported that fertility control (at an unreported coverage level over two years of management) had varying effects on the prevalence of pathogens, depending on the type of pathogen. This paper compared the prevalence of various pathogens between areas where varying levels of fertility control had been applied. Whilst fertility control significantly decreased viruses and most bacteria, it significantly increased the prevalence of ectoparasites (e.g., Rhipicephalus sanguineus ) and Brucella canis over the two years of management. Similarly, Totton et al. (2011) ([ 50 ] 100% RQ; unreported management coverage over two years of management) found that neutered dogs were 1.7 times more likely to have a visible skin condition compared to intact dogs.

One study investigated the impact of sheltering on the post-adoptive welfare of previously free-roaming dogs. This study found no significant differences in the prevalence of behavioural problems following adoption, using the behavioural indicators “destructiveness”, “hyperattachment to owner”, “fearfulness”, “aggressiveness”, and “excessive barking” ([ 80 ] 0% RQ).

One paper in the final corpus investigated the impact of combined fertility control and sheltering on dog health and welfare. Radisavljevic et al. (2017) ([ 81 ] 0% RQ) reported that neutering, transport, and housing in a new environment did not have a significant effect on physiological stress measures ( Table 3 ).

3.4.2. Dog Population Demographics

The effects of fertility control and combined fertility control and sheltering on dog population demographics were explored through observational studies. All applied fertility control to both male and female dogs at various intensities (see Table 3 ) and all reported a reduction in dog population size. Totton et al. (2010) ([ 69 ] 20% RQ) described different results between their study areas. These study areas had various levels of fertility control coverage. In three of their five study areas, they observed a decline in the dog population size ( p < 0.05) (at 62%, 66%, and 67% coverage), in one they found a decreasing trend ( p > 0.05), and in one study area they saw no effect of fertility control (87% coverage). Although different results were reported for the impact of fertility control and sheltering, one study reported a significant decrease in population size by 34% when fertility control and sheltering was applied at 43% over nine months of management ([ 93 ] 20% RQ). It is important to note that this is a particularly short period of management and these initial results may be the immediate effects of sheltering, rather than fertility control.

3.4.3. Public Attitude

The effect of fertility control alone and fertility control and sheltering on public attitude was explored in two papers. Costa et al. (2017) ([ 97 ] 80% RQ) reported no effect of fertility control on the public perception towards the effectiveness of different dog population management methods after three years of fertility control at an unspecified level of coverage. Public attitude, in this study, was quantified using a questionnaire with both open and closed questions. Boey (2017) ([ 94 ] 20% RQ) described a positive improvement of public attitude towards the presence of free-roaming dogs after fertility control and sheltering campaigns at an unspecified level of coverage and length. This was measured using qualitative data collected in interviews and discussion groups.

3.4.4. Public Health Risk

The effects of culling, fertility control, sheltering, combined fertility control and culling, and combined fertility control and sheltering on public health risk were explored in observational and intervention studies. Two papers in the final corpus investigated the effect of culling on public health risk. Both reported that culling decreased the prevalence of visceral leishmaniasis in dogs over short-term periods, but did not have a significant effect over long-term periods (at an unreported level of coverage over two years of management ([ 106 ] 50% RQ), and 8% coverage over 14 months of management ([ 105 ] 20% RQ). One study found that culling significantly decreased the prevalence of visceral leishmaniasis in children (decrease in incidence from 12 cases per 1000 people per year to 2 cases per 1000 people per year, at an unreported coverage level over four years of management) ([ 106 ]; 50% RQ). Papers were in agreement that fertility control can reduce public health risk, at the investigated management intensities (see Table 3 ). Fertility control of 65% of females over an unspecified length of management was associated with a significant reduction in human bite cases (a decrease of five bites per month) ([ 99 ] 50% RQ). Sheltering at an unspecified level of coverage over 11 years of management was associated with a reduction in Echinococcus granulosus prevalence in humans, livestock, and dogs, but significance was not reported ([ 5 ] 0% RQ). The combination of fertility control and culling on public health risk was explored in three observational studies. All studies reported a reduction in Echinococcus granulosus prevalence in dogs and in livestock at the reported management intensities (see Table 3 ), but did not report significant effects. There was no effect of this management method at an unspecified level of coverage on the number of people operated on for Echinococcus granulosus cysts over eight years of management ([ 103 ] 20% RQ). Combined fertility control and sheltering at various management intensities was associated with a decrease in public health risk. Schurer et al. (2015) ([ 93 ] 20% RQ) reported a decrease of 43% of dog parasite prevalence after nine months of population management intervention at 43% fertility control and 33% sheltering coverage.

3.5. Effects of Management Methods on Impact Categories—Modelling Studies

The effects of the different methods of dog population management in modelling studies are presented in Table 4 . The effects of methods that are directly compared within the final corpus papers are summarised in Table 5 .

Summary of methods directly compared within papers. All papers included in the final corpus directly comparing different methods of dog population management used a modelling study design.

3.5.1. Dog Population Demographics

The effects of culling, fertility control, sheltering, taxation, and combined fertility control and movement restriction on dog population demographics were investigated through modelling studies. All used dog population size as an indicator of effect. Three modelling studies investigated the effect of culling on dog population demographics. All reported that culling decreased dog population size at the intensity modelled (see Table 4 for management coverage and length). Yoak et al.’s (2016) [ 85 ] agent-based model simulated that culling would decrease population size by 13% over 20 years [ 85 ] at current capture rates, although the intensity required to achieve this reduction is not reported. All papers reported that fertility control reduced population size at the intensity modelled. The effect varied from a minimum decrease in population size of 14% over 20 years to 78% over 20 years, depending on the neutering coverage [ 89 ]. Sheltering at the modelled intensity had little or no effect on dog population size (population decrease of 3% in 10 years [ 90 ]), or no effect [ 87 , 90 ]). One paper in the final corpus [ 92 ] reported that taxation of dog buyers at various intensities decreased the free-roaming dog population size. Three papers [ 87 , 89 , 96 ] explored the effect of combined movement restriction and sheltering at various modelled intensities, all reported synergistic effects but this varied from a 5% population decrease in 30 years [ 96 ] to a 73% decrease in 20 years [ 89 ].

When sheltering was directly compared to fertility control, fertility control was more effective at reducing population size [ 87 , 90 ]. For example, Hogasen et al. (2013) [ 90 ] modelled that an increase in fertility control by 20–40% per year reduced the free-roaming dog population size by 34%, compared to only a 3% reduction where sheltering was increased by 10% each year. In studies that directly compared the effects of culling to fertility control on dog population size, culling was less effective at reducing the population size. Yoak et al. (2016) [ 85 ] reported that fertility control decreased population size by 75%, compared to approximately only 13% with culling when using model simulations with the same capture probability and intensity of intervention.

3.5.2. Public Health Risk

The effects of culling and fertility control on public health risk were investigated in modelling studies. All papers reported that, at various modelled intensities, culling decreased dog rabies prevalence (decreasing trend [ 100 , 101 , 102 ]) and rabies basic reproductive number (R0) (decreasing trend [ 91 , 107 , 108 ]). Fertility control at the modelled intensities also decreased public health risk. Fitzpatrick et al. (2016) [ 98 ] reported a reduction in the number of human rabies cases, estimating a 92% decrease in five years of model simulation when an intervention coverage between 25% and 50% was modelled. Carroll et al. (2010) [ 100 ] reported that fertility control decreased the prevalence of dog rabies. The modelled intensity of fertility control required to eradicate rabies varied from maintaining 100% coverage for one month to maintaining 25% coverage for over two years. Carroll et al. (2010) [ 100 ] directly compared culling to fertility control and reported culling to be just as effective at reducing dog rabies prevalence at the modelled intensities. However, when combined with rabies vaccination, fertility control was more effective than culling at eradicating dog rabies [ 100 ].

3.5.3. Wildlife

One modelling study investigated the effect of fertility control on disease risk to wild animal populations. Using an agent-based model, Belsare et al. (2015) [ 109 ] reported that fertility control (at unspecified intensities) reduced the risk to the Indian fox ( Vulpes bengalensis ) population, using the number of canine distemper spill over events as an indicator.

4. Discussion

4.1. limitations in assessing dog population management.

This systematic review synthesises research papers investigating different dog population management methods. We determined: (1) where and when the impact of dog population management has been described in the published literature; (2) what methods were assessed and at what intensity (coverage and length of management); and (3) what effects were reported. Furthermore, we evaluated the reporting quality of the studies. Papers in the final corpus suggest that most dog population management methods were associated with some effect on the impact of interest, and mostly in a favourable direction (such as decreasing public health risk or dog population size). The interpretation of these results and assessment of the effectiveness of dog population management methods is limited due to the following reasons:

• Few studies used a study design that would allow causation to be determined (such as intervention or certain observational studies), and many lacked an appropriate number of treatment and control groups ( Table S5 ) and replication ( Table 3 ). This therefore makes it challenging to distinguish between changes to a population that are caused by the management method, to incidental changes caused by other factors (e.g., reduction in population numbers over a few years caused by environmental or human related factors in the study area).
• Multiple indicators are used to assess the impact of dog population management ( Table 1 ). It is therefore difficult to compare the effect of the same population management method across different studies, and even more challenging to compare different methods across studies. This makes it difficult to carry out a formal synthesis of results, such as a meta-analysis, to report the combined evidence. For example, we found that different papers reporting on the evaluation of different management methods did not use the same measurement of dog health and welfare. In this example, it does not make substantive sense to compare whether an increase in normal body condition scores of 13% (with fertility control) indicates a greater impact on dog health and welfare compared to a decrease in leukocyte counts by 4 (×109 cell/L) (when fertility control and sheltering are combined). This therefore makes it difficult to directly compare effects between methods.
• Studies often investigated combinations of population management methods, such as fertility control and sheltering, and fertility control and culling. It is difficult to assess the impact of dog population management when methods are not used in isolation. Even where studies investigated one method alone, it is unclear whether other methods of dog population management were in place, such as sheltering or taxation. Culling might also be under-represented, as the method is often not reported due to lack of public acceptance (e.g., ad-hoc poisoning and drowning).
• To effectively review the results of dog population management intervention, it is important to not only consider what method was applied, but also how the method was implemented. This means in practice that information about the intensity of management and associated costs (logistics, training, and facilities) are required in order to fully appreciate and contextualise the results. Any management method has the potential to be effective if the intensity is large enough. For example, moving 100% of the dog population into shelters every week would be much more effective than to only 15% of the population once a year. It is therefore important to consider: (i) management coverage; (ii) length of management; and (iii) cost of management when assessing the effectiveness of different methods. Many papers in the final corpus did not provided information about the coverage of management and some did not report the length of management ( Table 2 ). Information about the cost of management was rarely provided, apart from where included as a parameter in modelling studies.

4.2. Investigated Methods and Reported Effects of Dog Population Management

The results of this systematic review highlight the scale and increasing interest in dog population management, which has been studied globally with an increase in the rate of publications in the last decade ( Figure S1 ). In particular, fertility control was often investigated, this aligns with increasing interest over recent years in the use of fertility control to manage animal populations in general [ 110 ]. Although interpretation of results from the final corpus is limited, we can still draw some tentative conclusions about the impact of the different management methods.

Overall, papers reported that fertility control had positive effects on dog health and welfare, including improved body condition score and reduced presence of injuries and some pathogens. However, this method increased skin conditions and prevalence of ectoparasites. The positive effects on body condition and presence of injuries could be explained by the lack of sex hormones caused by fertility control. This results in a reduced desire to seek out mates, as well as reduced sexual competition, which can cause weight gain [ 111 , 112 ] and decrease aggression between individuals, respectively [ 113 ]. Additionally, as fertility control methods (such as CNR) are often combined with vaccination and antiparasitic treatment, an improved health condition may be reflected in an improvement in body condition [ 50 ]. The negative effects of fertility control on the prevalence of skin conditions could relate to the specific protocols carried out by the different population management programs, such as the conditions the dogs are kept in pre- and post-surgery and the medical treatment provided (such as antiparasitics). It is therefore important that future groups carrying out dog population management through fertility control ensure they take measures to reduce pathogen transmission in clinical facilities.

The impact of different management methods on dog population demographics was measured solely through dog population size, allowing some level of comparison between papers. The comparison is still limited, however, as these effects were measured across different time scales, applied at different rates (e.g., neutering coverages), and to different populations of dogs (e.g., free-roaming owned and unowned or free-roaming unowned). For example, in the observational studies, the impact of fertility control varied from decreases in population size of 12% in 1.5 years to decreases in size of 40% over 12 years. Although all methods decreased population size, fertility control had the greatest effect in both observational studies [ 68 , 69 , 83 , 84 ] and modelling studies [ 69 , 85 , 86 , 87 , 88 , 89 , 90 ]. Fertility control decreases dog population size by preventing births, therefore allowing a reduction of numbers as natural deaths occur. This is in contrast with culling and sheltering, which reduce the population size through the removal of individuals, either through death or the moving of dogs into a shelter population. When fertility control was combined with other methods, such as movement restriction and sheltering, synergistic effects were reported [ 89 ]. By increasing the rate of fertility control and restriction status of dogs, this would both reduce the opportunities for reproduction and therefore potentially reduce the birth rate even greater than if fertility control had been used alone. Culling, by increasing the death rate of a population, may cause a rapid reduction in population numbers [ 85 , 88 ]. The culling method has been criticised as ineffective at reducing populations over longer periods of time [ 88 ]. This was supported by modelling studies that directly compared fertility control and culling. These papers found that, although culling resulted in an initial decrease in dog population size (e.g., a five-year period [ 88 ]), fertility control was more effective at reducing the population size over longer periods of time (e.g., a 20-year period) [ 85 , 88 ]. This may be because individuals removed through culling are replaced by new individuals through compensatory breeding or migration from other locations [ 114 ], therefore rendering the method less effective in the longer term. It is also important to note that there were no empirical studies investigating the impact of culling on population size, all were modelling studies, and therefore have limitations in the inferences that can be made to real dog populations.

Multiple different measures were reported to assess effects on public health risk, again making it difficult to compare methods directly. Culling had decreasing effects on the various indicators of public health risk in both observational [ 105 , 106 ] and modelling studies [ 91 , 100 , 101 , 102 , 107 , 108 ]. This contradicts previous literature suggesting that culling is ineffective at controlling disease in free-roaming dogs [ 115 , 116 ]. For the measurement “prevalence of visceral leishmaniasis”, culling only decreased prevalence over shorter study periods of up to two years (e.g., up to 69% over 14 months [ 105 ]), and had no effect over longer periods [ 106 ]. This is potentially due to other mammalian disease reservoirs that would allow continued transmission of Leishmania infantum to the remaining dog population [ 106 ] or by the number of free-roaming dogs recovering after culling, through immigration or compensatory breeding mechanisms [ 114 ]. In addition, culling decreased both dog rabies prevalence [ 100 , 101 ] and the basic reproductive number of rabies [ 91 , 107 , 108 ] in modelling studies. However, when disease control through vaccination was included in the analysis, all papers in the final corpus reported that culling was not as effective as vaccination alone [ 91 , 102 , 107 , 108 ] or combined vaccination and fertility control [ 100 ]. The prevalence of Echinococcus granulosus in humans, livestock, and dogs decreased where culling was combined with fertility control [ 103 , 104 ]. The two studies reported either large decline [ 104 ] in dog prevalence or complete eradication [ 103 ]. However, neither study uses experimental design or statistical analysis that would allow inference to the association between the management methods and the effect. All papers in the final corpus agreed that fertility control decreased the public health risk indicators [ 99 , 100 , 117 ]. The reduction in human bite cases can be linked to a reduction in sex hormones, which can in turn reduce the occurrence of aggression and dog bites [ 118 ]. The impact of sterilisation on owned dog aggression has long been debated within the literature, some studies finding a reduction in aggressive behaviour and others finding no effect, or increased aggression (see McKenzie (2010) [ 119 ] for review). In terms of free-roaming dogs, Garde et al.’s (2016) [ 120 ] behavioural observations in free-roaming dogs found no decrease in aggressive behaviour towards conspecifics or humans. The reduction in human bite cases reported in our findings may instead be due to an overall reduction in the free-roaming dog population size or a reduction in the number of puppies, therefore reducing protective behaviour of adult dogs [ 99 ].

4.3. Study Quality and Recommendations for Future Work

Good quality reporting of research methods and results is vitally important in understanding the validity and reliability of research findings. Additionally, research conclusions should be supported by appropriate study design and statistical modelling approaches. To improve reporting quality and study design, we suggest the following simple refinements for studies investigating the effectiveness of these dog population management approaches:

4.3.1. Increase Reporting Quality

Reporting guidelines are available for a number of biological areas (see [ 78 , 79 , 121 , 122 , 123 ]). In general, recommendations include reporting specific details about the experimental design, study subjects, statistical analyses, and modelling approaches. In particular, to increase reporting quality in studies investigating the impact of dog population management, we recommend reporting the following:

Power and Sample Size Calculations

We found the reporting of power calculations (11%) and sample size calculations (11%) to be low across the published papers. By not reporting this information, the value of the findings and recommendations resulting from the research are limited [ 79 ]. Therefore, power and sample size calculations should be clearly reported to increase reporting quality, replicability, and confidence in results.

Defined Target Dog Population under Investigation Using Clear Common Terminology

We suggest grouping dogs into: (i) unowned, free-roaming; (ii) owned, free-roaming; (iii) unowned, restricted; and (iv) owned restricted. Reporting which target dog population is under investigation would allow the effects of dog population management to be compared between different studies and between studies in different countries. This is particularly important where the definition of dog ownership might differ, for example in areas where there are community dogs that are loosely owned.

Management Intensity and Cost

Papers in the final corpus often did not explicitly state the length, coverage, and cost of the applied management method. As described above, to assess management effectiveness, it is important to report the length and coverage of management (e.g., the number of dogs neutered as a percentage of the total population). Reporting management coverage requires knowledge of the dog population size and this can be achieved through methods such as mark-recapture (see [ 124 ] for review of dog population estimation methods). Conducting population estimation requires time, manpower, and expertise in study design and analysis. Dog population management is often carried out by charities and government agencies ( Table S2 ) and these organisations may lack the financial and logistical power, as well as the expertise to conduct such ecological methods. This might partly explain the lack of reporting of management coverage. It is also important to consider and report the population management history in the study area, as previous management may impact the effectiveness of successive management. This information may also be difficult to access, but should be reported if available.

4.3.2. Improve Experimental and Statistical Modelling Approaches

Experimental approaches.

Where possible, researchers should consider their experimental approach and use an intervention (e.g., randomised control trials) or observational (e.g., cohort studies) study design that allows cause and effect to be determined, therefore allowing assessment of the true impact of dog population management. Where appropriate for the study design (i.e., intervention and analytical observational studies), appropriate numbers of groups and replication should be included, such as multiple treatment and control groups. This ensures that any effects reported are caused by the dog population management method and not by other causes (e.g., differences in population numbers between years due to differing mortality rates because of weather or other events).

Statistical Modelling Approaches

Due to practical, logistical, and financial constraints, studies that are observational (including cohort, cross-sectional, and case-control studies) are often the only feasible options for assessing dog population management. These studies may result in datasets that include large variability due to biological processes, sampling methods, and context (e.g., the specific country the study was conducted). Statistical modelling approaches can be used to deal with the limitations in inferring causal relationships using observational data. These include controlling for variables in statistical models, or matching of additional variables. We recommend using approaches such as directed acyclic graphs [ 125 , 126 ] to help to identify when controlling for variables in the statistical analysis is appropriate, and what variables to control for (see [ 127 ] for primer on creating acyclic graphs, dealing with measurement error, and statistically controlling for variables). For example, in a study investigating the impact of population management on dog health, it would be appropriate to control for age of dogs, as young dogs have a different probability of developing certain health conditions than older dogs. Therefore, if age were not controlled for in these analyses, the causal relationship between population management and dog health might not be observed. Additionally, process based modelling approaches have been developed to incorporate the underlying processes in the statistical analysis [ 128 ]. These modelling approaches incorporate both the sampling and biological processes that create the patterns observed in the data (e.g., hidden process models [ 129 ]), leading to better interpretation of complex causal relationships, where context creates differing outcomes. An example of datasets where hidden process models could be used includes data collected about dog population size through mark–recapture methods or citizen science [ 129 , 130 , 131 ]. This would therefore incorporate the processes involved in observing dogs (sampling process—e.g., detection probability) and the biological processes involved in the dogs being in the sampling area (biological process—e.g., the probability of migration, birth, or death). It is worth noting that these approaches require statistical and modelling knowledge that may be challenging for the organisations involved in dog population management to acquire/access.

5. Conclusions

Our systematic review found that dog population management is conducted in many countries globally [ 15 , 16 ], carried out by different groups (e.g., researchers and animal welfare or government agencies), applying different methods to different populations types (restricted and unrestricted) and using different indicators to monitor the impact of the intervention. It is therefore difficult to synthesise the evidence base and assess the true impact of dog population management techniques [ 3 , 16 ], despite the quantity of work being conducted. Very few of the reviewed studies allowed robust conclusions to be drawn. We recommend that future studies: (i) increase reporting quality; (ii) clearly define target populations; and (iii) increase the use of study design and modelling approaches that allow causality to be determined, in order that cross-study data synthesis and learning can be conducted for a stronger evidence base to support interventions.

Acknowledgments

The authors would like to thank Steven Sait, Helen Gray, and Mary Friel for their useful comments on an earlier draft of this manuscript. We would also like to thank the three anonymous reviewers for providing valuable feedback on the manuscript.

Supplementary Materials

The following are available online at https://www.mdpi.com/2076-2615/9/12/1020/s1 , Figure S1: Cumulative number of publications in the final corpus per year between 1977 and 2018, Table S1: Key words and combinations, Table S2: Papers in the final corpus by subject, dog population management method, country, economic status of that country, and funding organisation. Table S3: Number (and ratio) of published articles from the final corpus that measure the impact of the management method(s) studied. Table S4: Number of papers investigating combinations of dog populations. Table S5: Summary of the reporting of study quality indicators in final corpus (excluding modelling studies).

Author Contributions

Conceptualisation, L.M.S., L.M.C., and R.J.Q.; methodology, L.M.S., L.M.C., and R.J.Q.; formal analysis, L.M.S.; investigation, L.M.S.; data curation, L.M.S.; writing—original draft preparation, L.M.S.; writing—review and editing, L.M.S., L.M.C., S.H., A.M.M., P.D.V., and R.J.Q.; visualisation, L.M.S.; supervision, L.M.C. and R.J.Q.; and funding acquisition, L.M.C.

This research was funded by VIER PFOTEN International.

Conflicts of Interest

The authors declare no conflict of interest. The funders were involved in the reviewing of the manuscript.