Aggressive Breeds via Owner Accounts

Establishing ‘aggressive breeds’ without using dog bite data: Using owner reports to establish the most aggressive dog breeds


ResearchBlogging.orgIn 2008, data was published on the ‘most aggressive dogs breeds’, with dachshunds, chihuahuas, and jack russells, coming out on top. Recently, various media reports having been reappearing on my newsfeed on this study, with titles like “The 3 Most Aggressive Breeds Revealed“.

Before we begin, please do acknowledge that I adamantly against BSL. I am heavily influenced by research and evidence and, currently, all the evidence points to breed specific legislation never being effective in reducing the incidence of dog bites, in any place globally.

That being said, because I am interested in science, I am interested in studies like this.

So what can this study teach us about aggression in particular dog breeds?

Cindy the Jack Russell Terrier: In the top three aggressive breeds according to this study.

A Jack Russell Terrier: in the top three aggressive breeds according to this study.


The Flaws in Breed Aggression Research

Aggression is a difficult characteristic to assess in dogs.  There are a variety of methods that researchers have used, and all have their ‘downsides’.

Using dog bite statistics is not the best course, as most dog bites go unreported, the dog breeds involved cannot be verified and, even if they are verified, it is impossible to understand how many dogs of that paricular breed exist in the community.

If you’re only looking at caseloads from behavioural clinics, then this data is likely to be biased.  Generally, people with larger and more dangerous (because of their size) dogs are more likely to seek help, as are people who have dogs aggressive to members of their family. (This article doesn’t mention it, but finances also play a role here – only those owners with the finances to attend behavioural clinics would be represented in such a study.)

There has been some popularity in behavioural tests (cough – D&CMB proposal – cough) where they do threatening or scary things to a dog and score their responses.  The problem with this is how this actually relates to the ‘real world’ and the aggression the dog displays in everyday life.

When you ask owners about their dog’s behaviour, their experiences and responses are subjective. And ‘experts’ aren’t much better, with many of them representing ‘shared stereotypes’ whether conclusions from their own experiences.


Study Design

In this particular study, C-BARQ was used. C-BARQ has a good record as being pretty reliable when it comes to asking owners what their dogs are like, temperamentally.

Members of 11 AKC club (‘club sample’) and vet clinic clients (‘online sample’) were invited to partake.

1,553 C-BARQs were completed by the club sample, with 29 excluded as they did not meet criteria.

8,260 C-BARQs were completed by the online sample, with 1,257 excluded for being mixed breeds or with no breed indicated, and 2,051 excluded as there was less than 45 of that breed represented – so in the end the sample was 4,952 responses for 33 different breeds.

They were rated on aggression towards strangers, owners, and other dogs.


Summarised Findings

The online sample and breed club sample differed in some ways.  Breed clubs submitted more intact dogs, more female dogs, and older dogs than those in the online sample. Despite this, the results were quite consistent across the two samples.

Dog aggression was the most common and most severe type of aggression in the study, but dog aggression was not correlated with aggression to people. This supports the widely held view that ‘dog aggression’ does not indicate a risk to people. Similarly, aggression towards household-dogs was not associated with aggression towards other dogs or people. From the data in this study, more than 20% of Akitas, Jack Russell Terriers, and Pit Bulls had serious aggression towards unfamiliar dogs.

When it came to aggression towards people, the highest rates were found in smaller breeds, ‘presumably’ because aggression from smaller (and so more manageable and less dangerous) dogs is more tolerable.

When it came to aggression towards owners, more than half of the aggressive displays towards owners were associated with the owner taking food or something else away from the dog.

While fear in animals is associated with aggression, fear was not strongly correlated with aggression in this study. Some dogs were aggressive but not fearful, some were fearful but not aggressive, and some were fearful and aggressive.

A quote from the study on their findings,

“Although some breeds appeared to be aggressive in most contexts (e.g., Dachshunds, Chihuahuas and Jack Russell Terriers), others were more specific. Aggression in Akitas, Siberian Huskies, and Pit Bull Terriers, for instance, were primarily directed toward unfamiliar dogs. These findings suggest that aggression in dogs may be relatively target specific, and that independent mechanisms may mediate the expression of different forms of aggression.”

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Further results on a more breed-by-breed basis (breeds listed alphabetically):

  • Akitas rated higher for aggression towards other dogs than other breeds.
  • American Cocker Spaniels rated higher for aggression towards their owners than other breeds.
  • Australian Cattle Dogs rated higher for aggression towards other dogs than other breeds, and also rater higher for aggression towards strangers.
  • Basset Hounds rated higher for aggression towards their owners than other breeds, but were below average when it came to stranger directed aggression.
  • Beagles rated higher for aggression towards their owners than other breeds.
  • Bernese Mountain Dogs were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Boxers rated higher for aggression towards other dogs than other breeds.
  • Brittanys were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Chihuahuas rated higher for aggression towards people (both owners and strangers) and higher for aggression towards other dogs than other breeds.
  • Dachshunds rated higher for aggression towards people (both owners and strangers) and higher for aggression towards other dogs than other breeds.
  • English Springer Spaniels rated higher for aggression towards other dogs than other breeds, and also rated higher for aggression towards owners. Showed bred English Springer Spaniels were more aggressive than field bred lines.
  • German Shepherd Dogs rated higher for aggression towards other dogs than other breeds.
  • Golden Retrievers were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Greyhounds were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.
  • Jack Russell Terriers rated higher for aggression towards people (both owners and strangers) than other breeds and higher for aggression towards other dogs than other breeds.
  • Labrador Retrievers were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression. Field bred labradors were more aggressive than show bred labradors.
  • Pit Bulls rated higher for aggression towards other dogs than other breeds.
  • Siberian Huskies ranked below average on stranger directed aggression.
  • West Highland White Terriers rated higher for aggression towards other dogs than other breeds.
  • Whippets were among the breeds least aggressive towards people and dogs, and ranked below average on stranger directed aggression.


Warning against reaching conclusions on the genetic basis of aggression…

The authors caution, “Demographic and environmental risk factors for the development of canine aggression need to be investigated across a variety of breeds so that both generalized and breed-specific influences can be identified.”


So what do you think? Are these studies results consistent with your experiences?



Deborah L. Duffy, Yuying Hsu, & James A. Serpell (2008). Breed differences in canine aggression Applied Animal Behaviour Science, 114 (3), 441-460 DOI: 10.1016/j.applanim.2008.04.006

View PDF.


Further Reading

More on C-BARQ: Can breeders breed better?


McGreevy’s Thoughts on Dog Breeding

This post is part of the McGreevy seminar series. Click here for the index.


Throughout Paul McGreevy’s two day seminar, he expressed a number of opinions regarding dog breeding. Being a dog breeder myself, I anticipate I paid particular heed to his comments.  I find that, in the current climate of dog rescue and puppy farms, dog breeders are constantly under scrutiny and, in general, I find myself a little defensive to conversations surrounding dog breeding.

However, McGreevy had some very interesting and thought-provoking ideas surrounding dog breeding, and he presented them in a very amenable way.  That is: McGreevy didn’t breeder bash!  He approached matters surround breeding dogs in a matter-of-fact way.  Indeed, he spent more time blaming the system of dog breeding (i.e. breeding purebred dogs to a standard) for the problems in dogs today than critiquing breeders themselves.  Fundamentally, McGreevy believes that the system for breeding dogs need to change in order to emphasise the health and temperament of dogs, and not their physical appearances.


Bitch with puppy

Couldn’t resist including a photo of my current singleton litter.  See here border terrier mum with her 2 day old puppy.

Domestication and dog breeds

Domestication and selective breeding have changed dogs from their wolf ancestors.  For example, dog skulls have changed a great deal from the skull of a wolf, and there is also much variation between dog breeds.  Not surprisingly, the brains of dogs have changed too, with a wolf brain weighing three times as much as a dog brain.  Considering that the dog’s brain is part of its central nverous system, it is reasonable to assume that there may be implications for the dog’s entire nervous system.  McGreevy said, “We are only just beginning to learn what we’ve done.”

One thing is for sure: We don’t have a wolf in our lounge room.

In times gone by, breeding dogs were selected on the ability to perform tasks, such as herding, retrieving, carting, or any other purpose.  These days, selection is mostly based on conformation, and emphasis is being place on ‘beauty’ traits such as coat and colouration instead of structure.  McGreevy believes that this current system ineffective, as 150 years of breeding dogs ‘to standard’ has resulted in a host of inherited disorders.  Considering this, McGreevy believes that the dog breeding system needs to change.


Current dog breeding practices are cruel

McGreevy asserted that inherited disorders are a form of cruelty.  He also put forward that, considering that the main reason dogs are euthanised in shelters is due to their temperament, breeding for good temperaments is imperative.  Neither of these traits are overly considered in the current breeding system.

McGreevy believes that breed standards often are in contradiction to animal welfare.  He used the British Bulldog as an example.  He criticised the standard for asking for a head that is “the larger the better”, while at the same time calling for a narrow pelvis – an obvious problem for the whelping abilities of the breed.  Furthermore some of the points in the standard are actually unhealthy (for example, loose skin in Shar Pei has been found to correlate with joint problems, and the skull shape of a dog influences its vision).  In McGreevy’s opinion, dog breed standards have been written in a manner that is sometimes contradictory to dog well being.


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Belyaev’s Fox Experiment – Index

After frequently finding myself encountering references to Belyaev’s fox experiment in a number of dog-related texts, I felt the need to investigate his experiment more thoroughly.  This has resulted in a lot of reading, but a lot of new found knowledge.  From this reading, I hope to have a better understanding of the connection dog-authors are trying to make between dogs and the fox experiment. I hope it also proves useful for my readers.

Part I – Introduction
A summary of the work of Belaev in his ongoing experiment with foxes.

Part II – Changes
Description of the changes observed in Belyaev’s fox experiment.

Part III – Answers
Possible reasons for the changes seen in the foxes in Belyaev’s experiment.

Part IV – Dogs?
Why does the Belyaev fox experiment matter to dogs?

I hope this series has been of interest, as I thoroughly enjoyed researching.  I did cut out some bits and pieces, so please feel free to comment if you feel I haven’t answered a burning question for you! Additionally, if you would like in text referencing, I can provide such.

References: Continue reading


Belyaev’s Fox Experiment – Dogs? – Part IV

This post is part of the series on Belyaev’s fox experiments.
(index | part I | part II | part III | part IV )

You may have read my previous three posts, which have explained details of Belyaev’s fox experiment.  And you may have wondered the relevance of studying foxes on a blog about dogs.

Obviously, foxes are not dogs. They’re not even wolves. However, they aren’t far off it.  Regions of fox chromosomes correspond with those of the dog (to be specific, fox chromosome 1 seems to indicate a fusion between chromosomes 1, 33 and 12 as we see today in the dog).  That means that we should not disregard this research because it is a different species.

Chiefly, this study can be used to examine the process of dog domestication. Because domestication and associated variability seemingly occurred relatively quickly, there have been doubts that Darwinian theories are applicable. However, this study shows that significant changes can be seen in a brief period of time and generations. Coppinger (in his book Dogs) uses this study to show how quickly a significant change can take place – in the foxes here, significant morphological and physiological changes were seen in just 8-10 generations. This all occurred with just one selection pressure – selecting for ‘tameness’.

Dogs are very different to wolves.

This is surprising on a surface level, but when considering the causes of these changes it is not so remarkable.  Indeed, these changes have been seem occur in a similar way in terms of wolf’s domestication to dogs.  For example, dogs play as adults while wolves do not, and dogs carry many other juvenile-wolf characteristics.  Furthermore, dog puppies respond to human cues like fox domesticated pups and indeed are ‘dog like’ in many behavioural ways.  It is likely that the causes of the foxes changes are also the reason the wolf is the dog we know today.

On a larger scale, this research shows that we can select for nature.  Consider that these dogs were never trained, but were selected on their genetic amicability to humans.  This is a loud message on how we should be selecting dogs to breed from.

I hope this series has been of interest, as I thoroughly enjoyed researching.  I did cut out some bits and pieces, so please feel free to comment if you feel I haven’t answered a burning question for you! Additionally, if you would like in text referencing, I can provide such.

References: Continue reading


Belyaev’s Fox Experiment – Answers – Part III

This post is part of the series on Belyaev’s fox experiments.
(index | part I | part II | part III | part IV )

There are several theories that have been put forward regarding the origins of the physical characteristics seen in Belyaev’s foxes.  I will rebut some theories, and consider the plausibility of others. There are no definite answers, just some realistic theories.

Experimenter bias

One of the most popular anecdotal suggestions is that perhaps the experimenters unconsciously selected for more dog-like physical characteristics.  Personally, I think this illustrates a lack-of-faith in the scientific method.  The nature of the tests has been clearly outlined, and we must have confidence that this method was adhered to.  If there were serious doubts, the method allows for replication.  As replication has not occurred (mostly due to expense inhibiting the experiment) we can conclude that the experiment’s results are plausible in its current form. (The empirical world loves nothing more than proving others ‘wrong’ through replication.)

Mutations and Inbreeding

Another loud argument is the notion that the initial stock was carrying mutations or unusual traits, or that these changes were as a result of mutations.  Because of the inbreeding of the experiment, these mutations were amplified. This can be rebutted in a number of ways.

Firstly, the foxes were not inbred.  This fox population was frequently outcrossed to other commercial fox farm stock, and this has meant that the domesticated fox population has an inbreeding coefficient of 0.02 to 0.07.

Secondly, many of the novel traits outlined in part II are in fact not recessive. This means that the foundation population’s mutations would have been apparent on commencement of the experiment. This was not the case – these traits became apparent over the course of the experiment, and not in the beginning stages.

Another idea is that random mutations are the cause of these traits.  However, Belyaev determined that the rate of change in the domesticated strain was “2 or 3 orders higher than the expected frequency of spontaneous mutations”. This means that it probably not mutations that have caused the changes documented.

If we consider the mutation route as plausible, the suggestion with the most worth is Vavilov’s theory of homologous variability.  Vavilov’s theory suggested that similar gene sets can give rise to similar mutations, and so we can apply the term ‘similar gene set’ to all foxes, and mutations to their unique traits. This explains how foxes, despite being unrelated, developed similar traits just by the nature of being a fox with a fox gene set.

However, mutations probably did not have a role in the changes seem in the foxes.  What is more likely is that behaviour and anatomy may be linked in some way.

Depigmentation is a characteristic in dogs that was also seen in domesticated foxes. Photos © Ruthless Photos

Depigmentation is a characteristic in dogs that was also seen in domesticated foxes.Photos © Ruthless Photos

Selecting for many genes

The behaviour of ‘tameness’ is a varied trait, and so is controlled by a number of genes.  Because there are a number of genes involved, this means that selecting for tameness, and so also a number of genes, could have a profound affect.

Selecting for important genes

However, what is a more convincing suggestion is that perhaps this rapid change may have been as a result of selection may have been acting on relatively few genes, and genes that have an important regulatory role.  This would mean that if a ‘master’ gene was being selected for, this could have far reaching implications.  Here we reach the most convincing theory: That selecting for tameness was selecting for a major, complex, hormonal regulatory gene (or genes) which has far ranging implications on the rest of the animal.

The traits in foxes are found in many different domesticated species. Because of these similarities, Belyaev thought that early changes for amenability to domestication must be related to domesticated physiologies.  Because behaviour is regulated by neurotransmitters and hormones, modifying these elements through selecting behaviour would also have affects physiological parts of the animal.  Even though mammals are varied, their physiological processes are quite similar (their hormones, neurotransmitters, etc) – so this would be the basis for many domesticated mammal species showing similar traits.

Domestication/tamability is behaviour that is rooted in physiological changes and systems (e.g. hormones and neurochemicals).  Changing these complex systems would have far-reaching effects on the development of the animals themselves. And as all mammals are controlled by similar bigger-regulatory systems, this is seen as a reasonable explanation for the changes.

Hormone selection

‘Tameness’, ‘nervousness’ and ‘aggression’ is probably controlled by the endocrine system.  As described in the last post, serotonin, corticosteroid, cortisol, and adrenocorticotropic hormone were all found to be reduced in domesticated foxes. These hormones are responsible for behaviour that was selected for.  However, these hormones have a much bigger role in the endocrine system, so selecting for hormones would have had an extensive role and account for many of the changes observed in the domesticated animals.

Indeed, even the colour changes seen can be accounted for by hormones.  Hormones are linked to pigmentogenesis, agouti, and melanin.  The endocratic system can also explain the moulting changes in the domesticated foxes.

The endocrine system can explain many of the changes in the domesticated foxes behaviour, but this system also has a big role in development.  In selecting for genes that control behaviour, selection was also made for genes that control development.

The presence of juvenille traits (e.g play) in adult dogs was also seen in foxes. Photos © Ruthless Photos

Development mechanisms

The characteristics that the foxes adopted are those that are similar to juveniellism.  In this way, the development of the domesticated foxes can be described as ‘retarded’, as even adults have juvenile behaviours.  In this way it is thought that genes responsible for development have in some way been selected for.

These developmental changes start from embryos, with the hormones already described affecting the whole development process.  Even colouration/pigmentation has been linked to melanocyte and melanoblast activity in embryonic stage.  Neucrocrest cell migration would be delayed, which means messages to mature would not get to some body parts.  This would also have implications to the socialisation period, and be responsible for the floppy ears. Changes in the maturation timing have been seen.

Behaviour selected for seems to have been controlled by a few genes, but these genes were also responsible for a high level of regulation (i.e. hormonal level, and influencing development) and hence the foxes had a range of phenotype changes that accompanied the selected behaviours.

This is what domestication looks like

The literature review strongly stated that domesticated foxes, and their characteristics, are not terribly surprising.  Belyaev says that the “data demonstrate for foxes the kind of variability in similar characters and functions that is often observed in the domestication of other species of animals.” Because all domesticated animals have ‘done the same thing’ (in terms of phenotype traits), then this must be an implication of domestication and not an innate genetic quality of the fox population.

It is from these conclusions that the next post will start to make conclusions that relate to the domestication of dogs.  As our dogs display the domestication characteristics of the fox, this experiment is valid to our understanding of the history of dogs.

References: Continue reading