Posts by cynologyuk

Researching for a PhD in canine skull shape and dental health

Why the flat face?

In response to growing concerns over the welfare of animals with extreme morphology (shape), the British Veterinary Association have outlined their position on the matter in a recent policy statement

Extreme conformation, the body shape or structure of an animal (usually referring to a pedigree dog) having a direct impact on its health and welfare, is a hot topic at the moment. This policy likely came about following the increasing population of flat-faced (currently called Brachycephalic) dogs such as the French Bulldog and Pug (pictured above). The policy sets out guidelines for those involved in the care of affected animals, with a specific emphasis on caution when breeding them. In the majority of cases, people are breeding to encourage these extreme traits. This has led to research into the under-lying desire for these excessive morphological features.

Why do people want a dog that has no nose? Why is a slanted back more attractive in a German Shepherd than straight? Publications such as that of a Danish group of scientists, have tried to find the answer. It seems there are different types of dog owner. Those who see the dog as a pet or working animal, consider health and appropriate conformation to be essential, compared to those who see their dog as a surrogate (or in some cases, actual) child and rate personality as a much more desirable trait. This would go some way to explaining the move towards flatter-faced, wider eyed dogs that look more like a human baby. Or tiny, handbag sized dogs that are easily carried as an accessory. More research into the profile of the breeders and owners of these extremely shaped dogs is needed. Particularly as results from a group at the Royal Veterinary College suggest that owners view health defects such as difficulty breathing, as ‘normal’.  Perhaps if we can empathise more with the people who choose these dogs, we can start to encourage healthier desires? Maybe we need a new pug version of Cujo? Whatever we do, we need to do it soon.

What is a Brachycephalic, anyway?

I was recently asked by a vet friend of mine  for a list of all the pedigree breeds that are ‘brachycephalic’. This should have been a simple task,

white and brown bulldog on brown wood planks

Photo by Pixabay on

I was recently asked by a vet friend of mine for a list of all the pedigree breeds that are ‘brachycephalic’. This should have been a simple task, which I expect she thought someone researching dog skull morphology would be able to send across in a few minutes. But, despite the term being widely used in the veterinary world and ever growing in popularity, a single list has yet to be established. Largely, this is due to the discrepancy among veterinary scientists and researchers as to what exactly brachycephalic should mean for a dog, how we should go about measuring it and hence classifying dogs by this term. The word brachycephalic has recently become a more familiar term outside of the field of skull morphology. This is likely due to the combination of increasing popularity of dog breeds with very short noses (pugs and French bulldogs) as well as the serious health conditions associated with these breeds.

Originally, a term used to define the skull shape of humans, brachycephalic (meaning broad headed in Greek, βραχυκεφαλικό where βραχύς=Broad and κεφαλή=head) is categorised when the breadth is at least 80 per cent of the length. Brachycephalic e.g. bulldogs, mastiffs, comes as the first of three skull shape categories, the others being mesocephalic or sometimes mesaticephalic (Greek for middle headed, Μεσοκεφαλικο where μέσος=middle and κεφαλή=head) e.g. Labradors, Dalmatians and dolichocephalic (Greek for long headed, Δολιχοκεφαλικο where δόλιχος=long and κεφαλή=head) e.g. rough collies, greyhounds, each defined by the proportion of skull breadth to length. There is much disparity as to the precise separation between each of these categories (Hussein, Sullivan and Pendris, 2012).  Most use the rule that width to length ratio of the head should be the guide. If this is to be considered the defining criterion, using data collected by Carrasco et al. (2014) of the cephalic indices of pedigree dogs, the following list would be created:


  • Bullmastiff
  • Shih Tzu
  • Tibetan Spaniel
  • British Bulldog
  • Boston Terrier
  • Griffon Bruxellios
  • Pug
  • French Bulldog


The data collected by these authors however, only lists 80 dog breeds (around 65% of the total UK Kennel Club list) so could have omitted influential breeds. The study was also carried out using the Australian Kennel Club breed standards, which could differ from those in the UK. Also, as already stated, this method of categorising dogs as brachycephalic has been criticised as insufficient.


Originating in human medicine, this technique is not designed for categorising dog skulls. The initial method of calculating the ratio of breadth to width includes only measurements of the cranium itself. The cephalic index, as it is known, neglects to include any aspect of the rostrum, a fundamental region for distinguishing dog skulls since they can vary so greatly. It is not completely clear from the methods of the study used for the CI data whether rostrum length was included. This could obviously have a substantial impact on the results. It is therefore becoming increasingly evident that three categories are overly simplistic for the diversity of dog skull shapes and a more detailed morphometric classification is required (Georgevsky et al., 2014).


At present, there is a great deal of research interest in the potential relationship between a dog’s skull shape and its health. Studies have investigated various disorders such as Syringomyelia, as well as bite force, breathing and behaviour (Ellis et al., 2009; Koch et al., 2003; Knowler et al., 2014; McGreevy et al., 2013) and the relationship of these to skull shape. There is currently a lack of evidence exploring the possible relationship between this and periodontal diseases or dental disorders and skull shape. Even though each of the studies looking into skull morphometrics intends to do so reliably, there appears to be a lot of disparity within the field as to which anatomical regions should be included in the measurements. None of the measures currently in use are scientifically validated and results may therefore be inconsistent.  Without a clear system to cover all exhibited phenotypes, any further investigation of dog skulls becomes severely hindered. With the creation of a scientific measure of canine skull morphometry and distinct set of categories, correlation between skull shape and health-related factors would be simpler


Love taking photos of your dog?

Then why not put them to good use?

I am collecting photographs of dog’s heads for my PhD looking into the impact of dog skull shape on eating and dental health. I need people to send me photographs of their dog’s heads that I can measure using image manipulation software. The measurements will then be used to establish groups of head shape that are more appropriate for the canine population than the current categories. This should be carried out in an environment that is familiar to your dog. If your dog shows any signs of stress or discomfort, please do not continue with the procedure and your dog will no longer partake in the study.

Please complete the form and here: New Poster All Dogs then email that and your images to