Size and skull impact dog life expectancy – 02/02/2024 – Science

A study that mapped the longevity of hundreds of thousands of dogs bred in the United Kingdom, classified as members of 155 different breeds, indicates that factors such as skull size and structure have a significant impact on the animals’ life expectancy.

In general, small breeds with a longer snout (or dolichocephalic, as experts prefer to say) tend to live longer — 13.3 years, on average, according to the research, which has just been published in the specialized journal Scientific Reports. Large animals, and especially those with a flat snout (being classified as brachycephalic), can live several years less.

The analysis was coordinated by Kirsten McMillan, from the British NGO Dogs Trust, in partnership with researchers from Liverpool John Moores University, also in the United Kingdom.

To collect the data — referring to 284,734 dogs that have already died, out of a universe of almost 600,000 animals —, the group mined records from veterinary companies, universities and pet insurance companies, among other sources.

They highlight that the conclusions only refer to dogs raised on British soil, as the context in other countries can be very different. In addition to those classified as members of a single breed, the database also includes mixed-breed animals, from recent crosses of pedigree dogs to what we would call mongrels.

In this regard, in fact, the work casts doubt on a common idea: that crossbred animals tend to live longer, thanks to the so-called “hybrid vigor” (the fact that crossbreeding would tend to minimize the concentration of harmful genetic variants that occur in the mating of genetically close animals). However, on average, the “breed” animals included in the study lived 12.7 years, compared to 12 years in the case of crossbreeds.

However, one cannot rule out the possibility that owners take better care of their pedigree animals, which would end up worsening the chances of the crossbreeds reaching an advanced age. On the other hand, as happens in many species of mammals, including ours, among dogs, females are, on average, longer-lived than males (12.7 years for them versus 12.4 for men).

Another expected pattern is that, if everything else is equal, smaller individuals of a species tend to live longer than larger ones. This is what happens among human beings’ best friends.

Of the top 3 positions in the longevity ranking, 2 are occupied by small subgroups (such as the miniature pinscher and the jack-russell terrier). The only large dogs well positioned, in fourth place, are the mesocephalic (with a medium snout), a group that includes the Akita breed.

On the other hand, of the four subtypes with the worst ranking, four are brachycephalic, those with a “bulldog” pattern of snout—including animals such as bulldogs proper (both English and French) and the boxer. Flat-faced, medium-sized dog breeds live only 9.4 years, on average, being in the worst position.

It’s no surprise that brachycephalic animals are in this unenviable position, as their various health problems are well known. The facial structure of these dogs can produce respiratory stress when they exercise or are exposed to intense heat, for example, which can also affect their cardiac performance. They are also subject to so-called “reverse sneezing”, in which they appear to be choking, linked to the accumulation of fluid or dust in the airways.

These problems have led to discussions about changes in the morphological pattern of breeds and crossbreeding, to prevent animals with very extreme and less healthy facial features from continuing to reproduce.