Anatomy of a dog bite: The when, where, and why of dogs that bite

Sharing your life with a dog has lots of positives — companionship, the health benefits of regular dog walks, and being greeted with a wagging tail when you get home. But along with the positives come some potential negatives, including the possibility of a dog bite.

 A new University of Calgary study found that when a dog bites someone badly enough to seriously injure them, it’s more often in the home, and the victim is most often a child or an older adult.

“All dogs are capable of biting,” says Dr. Sylvia Checkley, DVM, PhD, associate professor in the Faculty of Veterinary Medicine (UCVM). “To prevent dogs from biting, first we need to understand the circumstances in which they are likely to bite, and then apply that information and an understanding of dog behaviour to improve public awareness and tailor prevention strategies.” 

Mining six years of detailed dog bite data  

Checkley and her co-researchers studied extensive data on more than 2,000 biting incidents collected by the City of Calgary from 2012 to 2017. Bylaw officers gather a treasure trove of information when investigating bite complaints. They record where the bite took place — at home, at an off-leash park, or another public space — along with the victim’s age, the dog’s age and sex, and other factors.

They rate the severity of bites using an assessment tool called the Dunbar aggression scale, created by Dr. Ian Dunbar, a veterinarian and dog behaviour expert. The scale has six levels, from dogs that snap without biting to those that bite repeatedly, causing deep puncture wounds or the death of a person or animal.

“Calgary has great data on dog-bite incidents compared to many cities, which gave us insight into different associations with different types of bites,” says Dr. Niamh Caffrey, PhD, a postdoctoral scholar at UCVM with a strong background in animal behaviour and welfare, who led the analysis. Doug Anderson and Melissa Parkinson, with the City of Calgary, provided insight on the data.

Any dog can be a biter

Because of the subjectivity and huge variation in the breeds reported, the researchers sorted biting dogs into the Canadian Kennel Club’s breed groups — terrier, hound, working, sporting, non-sporting, herding, and toy.

“Dogs in all breed groups are capable of biting, and the probability of a high-severity bite was not significantly higher in any group. And no one breed group stood out as being responsible for more bites,” says Caffrey. “Our findings support the growing body of research indicating breed-specific legislation is not a successful way to deal with dog aggression issues.”

A One Health approach to preventing dog bites

The researchers used a One Health or transdisciplinary approach to address the problem, which looks at the interaction between humans, animals, and their shared environment. “You have to consider the whole picture — human behaviour and injury; animal health, behaviour, and welfare; the circumstances in which the dog was raised; and the environmental aspects including the urban environment, parks, and the home. Dogs react differently in different places,” says Checkley.

The collaboration of professionals from different disciplines was critical to better understand the entire scope of the bite problem. As well, provincial public health and city government officials are key partners in public education campaigns and policy development. 

“Educational information for parents, grandparents, and other caregivers should emphasize that constant supervision of dogs, including family dogs, around children is vital. And more attention should be paid to the larger risk dogs pose to older adults,” says Dr. Melanie Rock, PhD, associate professor, Cumming School of Medicine (CSM) and adjunct associate professor at UCVM.

“Failure to protect people from dog bites has implications for the dogs’ welfare, as well. Dogs are most likely to bite when they feel insecure in the first place, and in cases of severe dog-bite injuries, dogs are often rehomed or euthanized.” 

Training of both dogs and people critical to reduce bites

“We like the Calgary approach because of the positive way they've worked towards using education and licensing to support dogs and dog owners,” says Rock, a co-author on the study.

“Veterinarians are also important,” adds Checkley. “At every wellness or new puppy exam, veterinarians talk about dog behaviour, training, and other things that can prevent bites. That’s what we teach our veterinary students, too, how to better read the dog. Through their behaviour, dogs usually warn before they bite, but you have to be able to understand what they’re saying.”

Olivia Schmidtz, a fourth-year veterinary student who helped with the project, gained a deeper understanding of the issue, which she hopes to put into use during her fourth-year clinical rotations and in veterinary practice when she graduates.

“Socialization of dogs and basic obedience training are critical,” Checkley says. “Through education and training of both people and dogs, it’s possible to limit severe bites and dogs being euthanized as a result of biting.”

Sylvia Checkley is an associate professor in the Department of Ecosystem and Public Health at UCVM and a member of the O’Brien Institute for Public Health. As part of UCVM’s Strategic Plan, she leads a One Health Research Group to support opportunities for interdisciplinary One Health research and discussion.

Melanie Rock is an adjunct associate professor at UCVM and an associate professor in the Department of Community Health Sciences at the CSM. She is also a member of the O’Brien Institute for Public Health and the Hotchkiss Brain Institute.

Learn more about how Rock's research can inform policies that could lead to better lives for people, pets and wildlife in cities.