Most Serious Dog Bites Happen at Home, and No Breed Group Can Be Blamed

A study of dog bites in Calgary finds no breed group can be singled out for serious bites, and older adults may be at more risk than previously thought.

Most serious dog bites happen at home, and BSL is not the answer
Photo: Christian Mueller/Shutterstock

By Zazie Todd, PhD

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Dog bites are a serious public health problem. According to the American Veterinary Medical Association, 4.7 million Americans are bitten every year and 800,000 require medical treatment. New research from Dr. Niamh Caffrey and colleagues (University of Calgary), published in Animals, investigates all dog bites in Calgary between 2012 and 2017. What makes this study unique is the level of detail and reliability of the data compared to most studies of dog bites.

The results show that the people most at risk of dog bites are children, youth, and older adults (aged 60 or above). While the increased risk for children and youth is as expected, the higher risk for older adults may come as a surprise. As well, the research shows no difference between breed groups in terms of serious bites.

Dr. Caffrey, first author of the study, told me in an email,
“I think the key message to take from our study is that everyone needs to be aware of the warning signs that a dog may bite. With dogs such an important part of our society, we all need to become better at understanding dog behaviour. If we can educate both dog owners and the general public in how to interact with dogs more safely then we could reduce or prevent bites.”

The city of Calgary has animal control bylaws based on responsible dog ownership. Dogs in Calgary must be licensed and have permanent identification, and spay/neuter of pets and regular veterinary visits are encouraged. Any dog bite incidents must be reported, and animal control officers will work with the dog’s owner to try to prevent future incidents. As well, funds from licensing are used to provide education programs to schools.

The city records dog bites according to a modified Dunbar bite scale (see below), and categorizes them into three levels. ‘Chases’ are bites on level 1 or 2, which can be considered low severity as they involve no punctures to the skin although there may be some bruising. It is likely there are more low severity bites than are reported to the city, given that medical attention is not needed.

Level 3 bites are medium severity and involve 1-3 punctures from a single bite, with no shaking or tearing. High severity bites comprise levels 3.5 (multiple level 3 bites) through to level 5 (multiple bites in which the dog held on and/or shook their head from side to side).

Most serious dog bites happen at home. Table shows the modified Dunbar bite scale
The modified Dunbar bite scale used in Calgary. Reproduced from Caffrey et al (2019) under Creative Commons licence.

The analysis looked at 2165 dog bite incidents, of which 51% were low severity, 35% medium severity, and 13.5% were high severity. These incidents involved 1,873 dogs, and 54 of those dogs were subsequently euthanized. The good news is that in the timescale of the study, the number of severe dog bites fell.

Because of the large number of breeds and mixed-breeds, dogs were classified according to breed group. No particular breed group was more likely to bite than any other (see graph below). For all of the breed groups, low and medium severity bites were much more common than high severity bites.

Most serious dog bites happen at home. Table shows bites by breed group; no group poses a particular risk
Bites of low, medium, and high severity by breed group. No particular breed group can be singled out as causing more bites. Image reproduced from Caffrey et al (2019) under Creative Commons licence.

The kind of bite that occurred in public places was most often of low severity. Medium and high severity bites were more likely to occur in the home or on the owner’s property, or at an off-leash dog park. The finding that high severity bites are most common in the owner’s home is in line with previous research. Children, youth, and older adults were more likely to be bitten than adults.

Medium and high severity bites were more common from male dogs (whether neutered or not). Dogs aged 3 or more were more likely to bite, although it is hard to assess the effects of age as the city uses broad age groupings rather than the actual age of the dog.

Even low severity bites can affect people profoundly, including how safe they feel when out and about in public. The researchers point out that preventing low severity bites is an important part of any dog bite prevention program. As well, responding to this kind of bite is an opportunity to prevent future bites, for example by teaching dogs to like strangers.

These results show that dog bite prevention needs to be aimed at all age groups. They also show the importance of close supervision of dogs with children, even when the dog is familiar. Other research has found that many people misinterpret dogs’ body language around children which underlines the need for more education. Learning how to recognize signs of fear in dogs,  and to give them the space to back away or not interact if they are afraid is useful for everyone to know. As well, it is important to socialize puppies during the sensitive period, something which many dog owners don’t seem to manage enough of

Calgary’s approach to dog bite prevention is internationally known as an alternative to breed specific legislation. BSL does not seem to reduce dog bites (see e.g. breed specific legislation had no effect on dog bites in Odense, Denmark). The important message is that any dog can bite.

The use of the Dunbar bite scale in this study is particularly helpful, as it provides more information about the risks and shows the most serious bites tend to happen at home. While everyone needs to know about preventing dog bites, it seems that targeting parents (e.g. at medical services, after school clubs) as well as seniors would make the biggest difference. This is valuable information because it means messages can be targeted to those groups most at risk.

The full paper is open access and can be read at the link below.

If you liked this post, check out my award-winning book Wag: The Science of Making Your Dog Happy. Modern Dog magazine calls it "the must-have guide to improving your dog's life."

Zazie Todd, PhD, is the award-winning author of Wag: The Science of Making Your Dog Happy and Purr: The Science of Making Your Cat Happy. She is the creator of the popular blog, Companion Animal Psychology, writes The Pawsitive Post premium newsletter, and also has a column at Psychology Today. Todd lives in Maple Ridge, BC, with her husband, one dog, and two cats. 

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You might also like: Preventing dog bites in children and a new approach to dog bite prevention.

Caffrey, N., Rock, M., Schmidtz, O., Anderson, D., Parkinson, M., & Checkley, S. L. (2019). Insights about the epidemiology of dog bites in a Canadian city using a dog aggression scale and administrative data. Animals, 9(6), 324.

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