Imma Perfetto
Cosmos science journalist
Are you a canine champion of the small and fluffy Shih Tzu? The large and in charge Great Dane? Or a marvellous mutt?
Though superficial aesthetic traits have guided the development of modern dog breeds for the last 200 hundred years, they might not be the most important factor in choosing a canine companion.
Researchers have turned their attention to a couple of questions important to everyone with a furry companion: which breeds have the longest life expectancies? Or does breed predict behaviour?
According to a new study published in Scientific Reports, Jack Russell terriers and Yorkshire terriers have the highest life expectancies of dog breeds in the UK, while flat-faced breeds have some of the lowest.
But in better news for those besotted by pugnacious pugs and bulldogs, a genetic study of more than 2,000 dogs suggests that breed alone is a poor predictor of dog behaviour. The findings challenge current popular dog breed stereotypes – often used to explain why some breeds are more aggressive – and is published in Science.
Live long and prosper
An interdisciplinary team of researchers have analysed 30,563 records of dog deaths from veterinary practices across the UK between 2016 and 2020, using the VetCompass database.
They were able to calculate the life expectancy of 18 dog breeds and a group of mixed-breed dogs by constructing life tables which show, for each age, the probability that a breed will die before their next birthday.
Unexpectedly, life tables varied widely between breeds.
Jack Russell Terriers had the highest life expectancy at birth (12.72 years), followed by Yorkshire Terriers (12.54 years), Border Collies (12.10 years), and Springer Spaniels (11.92 years).
But the findings are particularly ruff for flat-faced breeds such as English Bulldogs and pugs, which have some of the lowest life expectancies – 7.39 years and 7.65 years, respectively.
Shortest of all is the French Bulldog, which had the lowest life expectancy at birth of only 4.53 years.
The authors propose that these short life expectancies could result from the high health risks known to occur in these breeds.
Mixed-breed dogs, or mutts, had a life expectancy of 11.82 years at birth.
Breed isn’t a good predictor of behaviour
Despite widely held assumptions about certain dog breeds and their temperaments, there is a lack of genetic research linking breed and behaviour.
Now, bioinformatics researchers have used genome wide association studies to search for common genetic variations that could predict specific behavioural traits in 2,155 purebred and mixed-breed dogs.
They combined this data with 18,385 pet-owner surveys from Darwin’s Ark – an open-source database of owner-reported canine traits and behaviours – and identified 11 genetic loci (a fixed position on a chromosome where a particular gene is located) that are strongly associated with behaviour.
But none were specific to breed.
According to the findings, breed only explains 9% of the behavioural variation in individual dogs, and for certain behavioural traits and survey items, age or dog sex were the best predictors instead.
“The majority of behaviours that we think of as characteristics of specific modern dog breeds have most likely come about from thousands of years of evolution from wolf to wild canine to domesticated dog, and finally to modern breeds,” says author Elinor Karlsson, director of the Vertebrate Genomics Group at the Broad Institute of Massachusetts institute of Technology (MIT) and Harvard University in the US.
“These heritable traits predate our concept of modern dog breeds by thousands of years.”
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