08/17/17
dog bites who gets bitten by which dogs

Which people get bitten by which dogs?

dog bites who gets bitten by which dogs

Dog bites are one of my niche areas of interest, so I when I came across this 2008 bite study, I was keen to read. The overall objective of this study was to work out the similarities between biting dogs and people injured by them, to be able to understand dog bites in such a way that public health could be influenced.

And dog bites are a bit public health problem. In 1986, dog bites were among the top 12 causes of nonfatal injury in the US. in 2005, an estimated 800 000 dog bites needed medical attention in the US. On average, 18 people die per year in the US as a result of dog bites. The number of reported dog bites is going up each year, suggesting this is a growing problem. (Though, personally, I think the number is probably going up to growing intolerance of dog bites in the community.)

So this study was a retrospective cohort study, looking at data for incidents that occurred in the 2002/2003 financial year in Multonomah County, Oregon. In this study period, 636 dog bites were reported to Animal Control Services, while there were 47, 526 dogs licensed in the county.

What followed was a whole lot of number crunching that I don’t entirely understand. From where I’m sitting, it looks like a fair bit of extrapolation went into the figures seen below, but without sampling every single household for dogs and other aspects, I’m not sure if there’s a much better way to go about it.

But regardless, onto the results…

The Biters

From this study, dogs were more likely to bite if:

  • They were of particular types (terrier, working, herding, and nonsporting),
  • They were sexually intact and male, and
  • They were purebred.

Instead of using dog breed, they used dog type, to try to avoid problems in identification. (For example, the general public has a hard time determining between a border collie and coolie, but they do know it’s some kind of herding dog.) The breeds listed above were more likely to bite than dogs that were sporting breeds, hounds, non-AKC breeds, and toy breeds. This study suggested that the dogs in the ‘problematic’ groups have instincts they’re likely to revert to if left untrained (which doesn’t ring true to me for the nonsporting group), and threat they are a ‘size and strength’ to cause damage (which doesn’t seem right considering the size of most terriers).

More intact male dogs bit than any other neuter/sex ratio. This is different to other studies I’ve reviewed.

It’s really perplexing that purebred dogs were more likely to bite in this study. I guess this goes to the breeding practices, but it’s curious to think that crossbreed dogs, presumably bred by people who are ‘accidental’ breeders, end up with less-bitey temperaments. Something for breeders to think about. While these dog factors existed, there was also a range of other elements to a dog bite.

“Factors that determine whether a dog-human interaction will result in a bite are complex and involve characteristics of the dog, the injured person, the owner, and the dog’s environment.”

The Owners of the Biters

Biting dogs were more likely than nonbiting dogs to live in neighbourhoods where the residents’ median incomes were less than the county median income value. If controlling for breed category and controlling for sex, “dogs living in census block groups that had incomes less than the county median were 1.5 times as likely to be reported as a biting dog than reported as a nonbiting dog”. When dog owner data was compared to population density, percentage sex by age, percentage nonwhite race, and percentage without high school diploma, there was still not an association with biting. It was correlated just with income!

So what’s going on here? What’s different in areas were less income? Less money spent on training? On fences? Different attitudes towards child raising? This study suggests that people in these areas may be inclined to select particular breeds (i.e. especially those with reputations for aggressive behaviours). (Though this study didn’t look at whether some breeds were more likely to be owned by different groups.) They also suggest that low income areas may socialise their dogs in a different way, and therefore change the bite potential of the dog, or perhaps they’re not trained or supervised in a way that minimises dog bite risk.

“In another study examining dog bite injuries in St Louis, Mo, bite injuries occurring in low income areas were attributed to large numbers of children playing outdoors, few homes with adequate fencing, poor dog control, and a high proportion of large-breed dogs owned for protective purposes.”

As a personal comment, in my experience, crossbreed large dogs are cheaper than small dogs or purebred dogs. This means low income areas are likely to own bigger dogs, and we know bigger dogs are more likely to have their bites reported. While studies of the past have looked at breed and sex-neuter status, this study reveals a new area for further research: block group income levels.

But there’s more: It’s not just about the dog and who owns it, but also where the bite took place.

The Place of the Bites

Dog bites occurred:

  • 35.1% of bites happened in the dog’s home or yard.
  • 23.4% of bites happened in ‘neutral territory’
  • 17% of bites happened in dog/victim household (i.e. the parties lived together)
  • 10.1% of bites happened in household of victim (not dog’s place)
  • 7.1% bites unknown place
  • 3.8% at “place of employment” – e.g. vet clinic, rooming facility, MCAC
  • 3.6% “Neighbour’s Property” (which could be grouped with the 35.1%)

This reinstates the idea that parents need to be extra vigilant when they are visiting houses with dogs.

Other Statistics

Other tid bits of interest:

  • Boys and girls aged 5-9 years had highest rate of injury, boys a bit higher (but not significantly so).
  • Of the 636 biting dogs, 49% had a license number. There are some estimates that less than half of all dogs are registered. (I really wonder what this kind of statistic would look like in Australia.)
  • 36% of dog bite victims didn’t know the dog that bit them. (The largest portion.)
  • But: Among children, 46% were bitten by the family dog.
  • More dog bites in summer months.
  • No significant difference between male and females being bitten.

Limitations

Like all studies, there are a number of problems. In this study, the results are limited by.

  • Not all dog bites will be reported. Dog bites are a reportable incident in Oregon, but the records are incomplete. There’s a problem with recording of dog bites. A previous study, referenced in this one, suggested that only 17% of bites are reported to any authority. (And while this may be the case, how else should we be analysing dog bites except through dog bite records? This model is probably the best we have.)
  • We know members of the public are not very good at reporting dog bites by breeds.
  • Dog license data can only be used as an estimate of breed-populations – especially because we know perhaps only half of all dogs are registered. Further, if owners of some breeds are less likely to license their dogs, the breed specific bite rates are further skewed.
  • When a large-breed bites, that bite is more likely to be reported and more likely to need medical care, meaning that there is a reporting bias that can increase the number of these dogs seemingly involved in incidents.

 

Conclusion

This study made recommendations for reducing dog bites:

  • Combined approaches from human medical communities, veterinary communities, and animal control to help foster healthy relationships between people and pets.
  • Focus on low income neighbourhoods.
  • Paediatricians to counsel parents (dog owning and not) on dog safety during routine medical visits.
  • Low cost spay neuter.
  • Education programs (perhaps through animal control).

“Innate tendencies dictated by breed, sex-neuter status, and size play a role in the potential of a dog to bite, but owners are ultimately responsible for their dogs’ action[,]… and need to make every effort to minimisze their dogs’ bite potential through obedience training; neutering; and supervision, especially around children.”

Source:

Shuler, CM, DeBess, EE, Lapidus, JA, and Hedberg, K 2008, “Canine and human factors related to dog bite injuries”, JAVMA, vol 232, no 4.

07/16/17
Litter Size - Can we predict it?

Litter Size – What the research says

Litter Size - Can we predict it?

There is an ongoing paucity in the literature surrounding most dog matters, and that means dog knowledge is often based on anecdotes and experience instead of facts and figures. Dog breeding is no exception. Breeders will tell you that they get bigger litters if x, smaller litters if y, that they’ll never mate a bitch if z. While personal experiences can provide case studies, I am interested in much bigger data.

Enter a Norwegian study looking at 10,810 litters.

This study used data held by the Norwegian Kennel Club to look at every litter registered in 2006 and 2007, across 224 breeds. Statistical analysis was then done to determine all the wonderful figures summarised below.

The aim of this study was to determine what actually makes a difference in litter size. (Litter size being the number of puppies born, alive or dead.)

Firstly, an overall average had to be determined. For this data set, the average litter size, considering all breeds, was 5.4 puppies.

For those interested in average litter size by breed: The largest average litter size was in the Rhodesian Ridgeback with an average of 8.9 pups per litter. The Toy Poodle and Pomeranian had the smallest average litter size – 2.4 pups per litter. And the Border Terrier (because I’m biased) had an average litter size of 5.1 pups per litter.

This study found that litter size was influenced by the size of the breed, the method of mating, and the age of the bitch. Litter size was not affected by season of birth, or the number of litters a bitch had had.

Size of the breed

This study examined dogs based on average breed size. They were classed as miniature breeds (<5kgs), small breeds (5-10kgs), medium breeds (10-25kgs), large breeds (25-45kgs), and giant breeds (>45kgs). Bitches were recorded against the average size of a dog for their breed and not specifically on the size of that given bitch.

“When looking at all the … litters…, mean litter size increased with the size of the breed. The mean litter size was 3.5 in miniature breeds, 4.2 in small breeds, 5.7 in medium breeds, 6.9 in large breeds, and 7.1 in giant breeds.”

The feature of larger dog breeds having larger litters is not a new thing – this phenomena is consistent across other studies. But this study is different as it found that it wasn’t just size of the breed that mattered…

Age of the bitch

The first analysis of this data showed no significance with the age of the bitch, however, once breed size was taken into account, there were two trends apparent:

  • In small and miniature dogs, young and old bitches had smaller litters than the ages in between.
  • In larger breeds, increasing age corresponded with decreasing litter size. (Young bitches of larger breeds produced the largest litters – unlike small and miniature breeds.)

Predicted litter size by the age of the bitch for the five different breed size groups from Borge et al. study.These results are a little different to other studies, which have shown smaller litter sizes as bitches get older. (As in, the results this study got for larger breeds was seen in all breeds in previous studies.) It could be that smaller sample sizes in other studies may have missed this, or that other studies used larger breeds as their data set instead of small or miniature breeds. One suggestion is that small breeds may not mature as quickly as previously believed, and so they’re not able to reproduce until they reach that mark. (To me, this kind of makes sense – considering small breeds often live longer, then it’s likely that they mature more slowly, too.)

Method of mating

Like the age of the bitch, the first analysis on the data didn’t show a significance change in litter size based on mating method. However, when the data set was adjusted for breed, breed size, and age, naturally mated bitches had significantly larger litters than those who had been AIed (either fresh or frozen).

A decrease in mean litter size of 0.4 puppies would be expected for litters conceived with AI with fresh semen and 1.3 for AI with frozen semen, both compared to natural mating.

Things that didn’t matter

The number of litters a bitch had previously didn’t influence the size of her litter. (However, older bitches normally had had more litters – and their age did influence litter size.)

The season the litter was born in did not influence litter size.

Conclusion

Size of the breed, age of the bitch, and the method of mating are three factors work together in determining litter size. It’s not one thing – it’s all three.

“… the size of the breed, the age of the bitch and the method of mating were found to influence litter size in purebred dogs when controlling for breed, with the size of the breed as the strongest determinant.”

This study is better than past studies in this area for its huge sample size, its variety of breeds, and the fact that it considers all puppies in a litter (not just those registered, as some past studies have done). In this way this study is unique. It is probably a pretty reliable data pool for purebred dogs, too, as 90% of purebred dogs in Norway are registered with their kennel club.

Things to consider regarding the vigour of the results:

  • It’s a retrospective study.
  • It does not include data from litters where all pups were born dead.
  • Calculating mean litter size is hard, because of % made up of small or large breeds. Small breeds are currently popular, so could perhaps pull down the mean litter size seen in this study. Studies done in different countries, with different breeds being popular, is likely to result in different results.
  • There is a relatively small sample of bitches who were mated not-naturally in this study, so the results should be interpreted cautiously, however the results are consistent with previous findings.
  • This study only groups dogs by weight – not by body shape. This might yield differences. (A neapolitan mastiff is really different to a greyhound.) And they group them by weight average of breed, not the weight of the individual bitch
  • This study looked at only two years and the researchers wonder if there might have been more variation in season of birth if there was more time taken into consideration.

In conclusion: Based on this study, breed size is the strongest determinant for litter size in a dog. The age of the bitch and the method of mating were also significant predictors of litter size. These three things interact, making litter size predictions difficult!

Acknowledgements:

Borge, KS, Tonnessen, R, Nodtvedt, A, & Indrebo, A 2011, “Litter size at birth in purebred dogs – A retrospective study of 224 Breeds”, Theriogenology, 75, 911-919.

Thank-you to Waldwiese Kennels for the cover image – a litter of longhair weimaraner puppies.

11/16/12

Research Finds: Hungry Dogs are Hungry

Some Thoughts About Dogs welcomes guest blogger Michael D Anderson from NerdWallet.

Photo © Ruthless Photos.

Biologists at the University of Vienna published a study last month about dogs’ temperament in relation to their owners. The study hypothesized that without their owners, dogs would be more likely to view ambiguous events as negative ones. This is a common feature of human cognition – you’ll often hear that depressed people “see the glass as half-empty.”

The abstract of the study is available here.

The Vienna researchers found that, unlike in humans, when presented with ambiguous stimuli, dogs don’t have a negative judgment bias when they’re in distress. This is a jargon-loaded, awkward way of generalizing on the following: These scientists found that, when hungry, dogs don’t become emotional if their owners are absent—they go right to the bowl of food because, following one of the experiment’s stipulations, these dogs hadn’t eaten in at least three hours.

Experimenters measured how long it took each of 24 dogs to approach a bowl—the study had initially included 32 animals, but the scientists decided to exclude dogs that had unusually extreme separation anxiety.

In training—before the two testing days—the biologists conditioned the dogs to identify one side of the testing room as positive—where a bowl had food—and the other side as negative—where a bowl was empty.

On testing days, they refreshed dog’s memories about the room, but then they changed up locations a bit. They established near-negative (i.e. closer to the original negative location), middle and near-positive locations. At the beginning of each test, they approached one of these new locations with a bowl.

The experimenters then tested for “latency,” or long it took the dogs to approach the bowl, when the owner was present and when he or she was absent. The owner, they said, had an effect. The dogs took longer to approach the near-negative location and shorter to approach the near-positive; in tests without the owner, they approached at the same rate to each respective location.

What I don’t understand is how the biologists so tightly connect dogs’ approach to food—which they measure as “latency”—to their mood. The idea, I think, was that dogs should take longer to approach a bowl—even if the location is near-positive—when the owner isn’t there. The idea is that the dog is distressed without the owner around—they’ll start barking, toileting, or whatever else instead of going right to the bowl.

But these dogs were hungry: as I mentioned at the beginning of this piece, owners were asked not to feed their dogs in the 3 hours before the study.

The whole premise of this experiment is odd. What they pose is that dogs are less temperamental than humans: emotional distress or not, they’ll logically discern where the food is. What I think they meant to ask is whether or not dogs behave any different after domestication: Are they still primal? The answer, I think, didn’t even require extensive experiments: yes, they’re hungry, owner be damned.

 

Further reading:

“Animal Behaviour: Cognitive Bias and Affective State”

“Bias in Interpretation of Ambiguous Sentences Related to Threat in Anxiety”

“Dogs Showing Separation-Related Behavior Exhibit a ‘Pessimistic’ Cognitive Bias”

 

This article comes from NerdWallet, a consumer-focused, analysis-driven website dedicated to dissecting the data behind the story.