Dog Bite Strength: It's Not What You Think

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Dog Bite Strength: It's Not What You Think

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Scientists tracked down the evidence for a common statement about bite strength in dogs – and found it lacking.

Have you ever read comments about the strength of a dog’s jaw when it bites? These statements are often made in relation to certain types of dog, like pit bulls. Maybe some people take it as fact. But what if it’s not true?

A recent paper by Dr. Gary Patronek (Cummings School of Veterinary Medicine, Tufts University) et al traced citations in the literature and went back to the original sources to investigate the truth of the published statements. They say they chose the literature on the strength with which a dog can bite for several reasons, including that this is a salient figure that jumps out at people and is remembered, and that the literature was large enough and easy to assess for accuracy.

They picked a topic on which people have been sceptical for some time. Writing on his blog in 2010, Stanley Coren PhD said,

“Let’s put these numbers into a meaningful context. Imagine a bite force of 2000 pounds. To achieve this, suppose that we had a dog’s jaw and wanted to press the upper portion down with this force, it would require our putting a pressure equivalent to the weight of a subcompact automobile (like a smaller Toyota or Hyundai) on the top jaw. That simply did not make sense.” 

In fact a Smart Fortwo weighs 1808 lbs, and a Mitsubishi Mirage is 1,973lbs. So those are the cars we can think of if we’re going to use Dr. Coren’s analogy.

Patronek et al wanted to know what the evidence is for this. They looked at papers from 1969 – 2009, and two court cases, that referred to canine bite strength. They went through the literature to trace the statements back to the origin. So what did they find?

“We tracked each citation to 1 of 7 original sources,” they write, “and did not find verifiable evidence (or data obtained from a controlled experiment) about bite force in any of the articles. In 2 of the original sources, statements about bite force were found, but there were neither data nor a citation to support those statements. In 4 other original sources, none contained any statement or data about bite force, despite being cited by other scientific articles as though they had. The final original source was not a scientific article at all, but a newspaper article that again provided no source for the data presented.”  [references omitted for ease of reading – see link below]

In other words, there is no evidence for the statement that a pit bull, or any other kind of dog, has a bite strength of 1800 or even 2000 PSI.

For scientists, this is a reminder to be careful to verify sources. Patronek et al are not suggesting anyone has deliberately misled – rather, that mistakes have been made, and over successive papers by different authors, they have been amplified. These days, with more articles available electronically, it is easier than ever to verify original sources (although no university library will have everything).

A particular problem is what they call ‘daisy-chaining’ – basically the use of secondary sources (rather than the original) and not being clear when information is from the introduction section rather than actual results.

At other times, however, they say it’s hard to know why these mistakes occurred.

“Four articles specifically claim that the bite force of a “pit bull” type dog can be as much as 1,800 pounds per square inch. There is not a single original source reporting a Result that substantiates this claim. And what are we to make of cases where a source that literally did not contain any information about bite force was cited.” [references omitted]

I find it interesting that the four articles referring to a pit bull bite strength of 1,800 PSI (and indeed almost all of the papers making comments about bite strength) are from the medical literature, not from journals on animal behaviour or biology.

Patronek et al point out there are consequences to this, not just for the scientific literature but also real life (as in the court cases they studied).

More generally, we can consider what if people are afraid of certain dogs because they’ve been erroneously told about this supposed enormous bite strength? What if people cite this information in support of breed specific legislation, even though it's wrong?

Preventing dog bites is complicated. Breed specific legislation isn't the answer because any dog can bite. Fortunately fatal dog attacks are incredibly rare and involve many factors that could potentially be prevented. Programmes to educate children about dog bites work to reduce risky behaviour around dogs. Better education for adults on dogs and canine behaviour can help too. But approaches to dog bite prevention also need to take into account that many people think ‘it won’t happen to me’ and so may not pay attention to information about dogs in general, or to their dog’s behaviour in the moment.

Patronek et al’s paper shows a commonly-held belief about certain types of dog is wrong. Flawed research write-ups have given pit bulls and other dogs a bad name, and it’s important to set the record straight.

The paper is open access and you can read it at the link below. There is a handy diagram if you want to follow the faulty references back.


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Reference
Patronek, G., Bradley, J., & Cleary, D. (2016). Who is minding the bibliography? Daisy chaining, dropped leads, and other bad behavior using examples from the dog bite literature Journal of Veterinary Behavior: Clinical Applications and Research, 14, 17-19 DOI: 10.1016/j.jveb.2016.06.004
Photos: Matthew Lyon (top) and Zuzule (both Shutterstock.com)

Educating Children Reduces Risky Behaviour Around Dogs

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Educating Children Reduces Risky Behaviour Around Dogs

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Dog safety education for children works, according to a systematic review of existing research.

The CDC estimates that 4.5 million Americans are bitten by a dog every year. Children are at high risk, and bites to children are often more severe than those to adults. Bites to the head and neck are more common than for adults because children are smaller.

The CDC says “Among children, the rate of dog-bite–related injuries is highest for those 5 to 9 years old. Children are more likely than adults to receive medical attention for dog bites.”   When young children are bitten by a dog, it is typically indoors and by a dog they know or live with, often when the child approaches a dog that is lying down or stationary.

The best ways to teach children about dogs are investigated in a systematic review of the literature by Jiabin Shen (University of Alabama at Birmingham) et al.

The review focussed on cognitive and behavioural interventions aimed at children (such as how to behave around dogs), rather than management interventions aimed at parents (such as close supervision of dogs and children).

Some of the interventions involved showing videos to children or using computer programs, while others involved a real dog for children to interact with. They took place in a variety of settings including the children's classroom, hospitals, and university laboratories.

“The results showed that interventions have a moderate effect on improving children’s safety knowledge around dogs,” write the authors, “and a relatively large effect on promoting safe interactions between children and dogs. Video-based interventions were most effective in the improvement of safety knowledge, while instruction with live dogs was most effective in increasing children’s safe behaviours with dogs.”

The behavioural measures differed from study to study, but included visits to emergency because of a dog bite, whether or not the child went to pat an unfamiliar dog, role plays, and acting out behaviour in a dolls house. Knowledge was also assessed differently in each study, but typically included yes/no questions about dog safety, often with pictures.

It’s interesting that effects on children’s behaviour were larger than those for children’s knowledge. This is a surprising finding; in the field of health promotion, it’s more common that people know they need to change but don’t actually change their behaviour. For example, people might know smoking is bad for them but not give up smoking.

Only some of the studies looked at behaviour changes, and the authors say these studies tended to be better designed, and potentially also had better interventions. But it could also be that it’s easier to teach young children appropriate behaviour around dogs rather than knowledge.

The authors reviewed studies of dog bite prevention and selected those that met certain quality criteria, including having a control group and being specifically focussed on dog bite prevention amongst 0 – 18 year olds. 12 papers were included in the final review, and 9 in the statistical meta-analysis.

The studies included in the review took place in the US, UK, Canada, Australia, and one in China. The authors say programs developed in the West are still relevant to other countries to some extent, in that all children go through the same developmental stages. Therefore programs designed to teach age-appropriate knowledge will still be useful.

However, while the main risk in the West is pet dogs, in developing countries street dogs are the more common cause of bites. This is especially serious because of the risk of rabies. So adaptations to the programs to reflect the source of risk would be necessary.

Although the paper did not look at management interventions (such as fencing), the authors recognize these are also an important factor in preventing dog bites. In the case of (incredibly rare) fatal dog attacks there are often multiple preventable contributing factors, including the isolation, mismanagement and abuse of dogs.

The authors also highlight a problem with the “poor quality of evidence in this field.” They say this is a general problem in pediatric injury prevention. Other meta-analyses in the field of human-animal interaction have also highlighted problems with the quality of evidence,  including on dog walking behaviour and the use of animal-assisted therapy to help adolescents with psychiatric problems. As the field grows, hopefully we can look forward to more high quality research.

The good news is the interventions did improve children’s interactions with dogs. Earlier work has found parents would welcome more education on dog safety for children  This study shows that wider availability of education for children on how to behave around dogs would be a very good thing.

There’s some useful advice on preventing dog bites at stopthe77.com.




Reference
Shen, J., Rouse, J., Godbole, M., Wells, H., Boppana, S., & Schwebel, D. (2016). Systematic Review: Interventions to Educate Children About Dog Safety and Prevent Pediatric Dog-Bite Injuries: A Meta-Analytic Review Journal of Pediatric Psychology DOI: 10.1093/jpepsy/jsv164
Photo: Vasil Syniuk (top) and Grezova Olga (Shutterstock.com).
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A New Approach to Dog Bite Prevention

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A New Approach to Dog Bite Prevention

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Strategies to prevent dog bites need to get past the belief that ‘it won’t happen to me.’

4.5 million people a year are bitten by a dog in the US, of whom 885,000 need medical attention (Gilchrist et al 2008). In England in the last year, there were 7,227 admissions to hospital for injuries due to dogs, over 3000 more than a decade earlier. Developing a better understanding of how to prevent dog bites is essential. 

A new paper by Carri Westgarthand Francine Watkins (University of Liverpool) suggests new directions for dog bite prevention. They interviewed 8 women about their experience of being bitten by a dog. Four of the participants had received medical attention for their bite, and six had also been bitten by a dog before. The results show that dog bites are a complex phenomenon. 

Dr. Westgarth told me, “the most important finding is the belief that it wouldn't happen to them, or that dog bites are just one of those things that happens and it's no big deal. People won't see the need to engage with (or apply) dog bite prevention initiatives without tackling these barriers, no matter how much 'dog behaviour' education we try to give.”

People blamed the owner, not the dog. For example, one participant said, “Yes, I’m to blame. I still hold that my reactions to his [dog] aggression are what caused the bite.”

In two cases, the person was not aware a dog was present until they were bitten (e.g. they were out jogging and a dog ran up and bit them).

Participants did not expect a bite. One spoke of how she felt as the situation with the dog ramped up: “A little bit nervous, because it was like two dogs jumping around there. But I still at that point didn’t think I was going to get bitten... Not for a moment did I think I was going to get bitten.”

Another person knew she was taking a risk, but still didn’t expect a bite: “Basically as he was asleep, I was reaching to grab the remote from near him and, I should have known better, and I knew he’d go for me but you kind of expect that when you’ve got that trust bond with your dogs that they maybe wouldn’t, even if you do something to upset them.”

If people don’t believe they are at risk of dog bites, then they are not likely to change their behaviour, say Westgarth and Watkins. 

Dog bites were also seen as one of those things that ‘just tend to happen’. For two participants the risk of bites was high, but they did not feel they could do much about it. One said of her dog, “She didn’t want me to do what I was doing. And she’d already told me not to. But I carried on.” This low self-efficacy is another barrier for dog bite prevention programs to overcome.

Reflections after the bite suggest people had learned from the incident. One said, “It just makes me more aware of what people have said to me, you know when I was younger, you know you don’t just go straight up to a dog and pat it on its head.” But despite this, the people who had been bitten by their own dog did not see a behaviourist or change the way they interacted with the dog.

Westgarth and Watkins say, “Rather than assigning fault to victims or owners and targeting ‘high-risk’ individuals, the focus should be on intervention at the population level: on creating a primary environment where dog bites are less likely to occur in the first place and minimising damage caused when dogs do bite.”

Strategies they suggest include focussing on realistic situations in education campaigns and using social contacts or social media to spread information. A wider focus for dog bite prevention includes borrowing ideas from other injury prevention campaigns, looking at where people get dogs and puppies, breeding, the importance of socialization and acquired bite inhibition, and dog training. 

For example, if puppies are taught bite inhibition (how not to apply too much pressure with their jaws), this reduces the amount of damage they will cause if they ever put teeth on skin.

Like the participants in this study, a tendency to “assume safety” around an unknown dog has also been found in parents (Morrongiello 2013) which is especially worrying because children are most at risk. These results are also consistent with a US report by Patronek et al (2013) into the very rare cases of fatal dog bites. Such cases were multi-factorial, typically with five (potentially preventable) contributing factors, including husbandry.

The paper is open access and can be read via the link below. I’m delighted to report that Dr. Carri Westgarth agreed to answer some questions about her research. 

References

Gilchrist, J., Sacks, J., White, D., & Kresnow, M. (2008). Dog bites: still a problem? Injury Prevention, 14 (5), 296-301 DOI: 10.1136/ip.2007.016220
Morrongiello BA, Schwebel DC, Stewart J, Bell M, Davis AL, & Corbett MR (2013). Examining parents' behaviors and supervision of their children in the presence of an unfamiliar dog: does The Blue Dog intervention improve parent practices? Accident; analysis and prevention, 54, 108-13 PMID: 23499982 
Patronek, G., Sacks, J., Delise, K., Cleary, D., & Marder, A. (2013). Co-occurrence of potentially preventable factors in 256 dog bite–related fatalities in the United States (2000–2009) Journal of the American Veterinary Medical Association, 243 (12), 1726-1736 DOI: 10.2460/javma.243.12.1726 
Westgarth, C., & Watkins, F. (2015). A qualitative investigation of the perceptions of female dog-bite victims and implications for the prevention of dog bites Journal of Veterinary Behavior: Clinical Applications and Research DOI: 10.1016/j.jveb.2015.07.035
Photos: ARENA Creative (top) and Tomasz Nieweglowski (both Shutterstock.com)

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