Are you a canine champion of the small and fluffy Shih Tzu? The big and responsible Great Dane? Or a wonderful dog?
Although superficial aesthetic traits have guided the development of modern dog breeds over the past 200 years, they may not be the most important factor in choosing a canine companion.
Researchers turned their attention to a few important questions for anyone with a furry companion: Which breeds have the longest lifespans? Or does race predict behavior?
According to a new study published in Scientific reportsJack 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 better for those obsessed with pugs and pugnacious bulldogs, a genetic study of more than 2,000 dogs suggests that breed alone is a poor predictor of dog behavior. The findings challenge current stereotypes of popular dog breeds – often used to explain why certain breeds are more aggressive – and are published in Science.
Live long and prosper
An interdisciplinary team of researchers analyzed 30,563 dog death records from veterinary practices across the UK between 2016 and 2020, using the VetCompass database.
They were able to calculate the life expectancy of 18 breeds of dogs and a group of mixed-breed dogs by constructing mortality tables that show, for each age, the probability that a breed will die before its next birthday.
Unexpectedly, mortality tables varied greatly from breed to breed.
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 old).
But the results are particularly disappointing for flat-faced breeds such as English Bulldogs and Pugs, which have one of the lowest life expectancies – 7.39 years and 7.65 years, respectively.
The smallest of them all is the French Bulldog, which had the lowest life expectancy at birth of just 4.53 years.
The authors propose that these short life expectancies may be a result of the known high health risks of these breeds.
Mixed-breed dogs, or pooches, had a life expectancy of 11.82 years at birth.
Race is not a good predictor of behavior
Despite widely held assumptions about certain breeds of dogs and their temperaments, there is a lack of genetic research linking breed and behavior.
Now, bioinformatics researchers have used genome-wide association studies to search for common genetic variations that could predict specific behavioral traits in 2,155 purebred and mixed breed dogs.
They combined this data with 18,385 surveys of pet owners from Darwin’s Ark – an open source database of owner-reported canine traits and behaviors – and identified 11 genetic loci (a fixed position on a chromosome where is a particular gene) that are strongly associated with behavior.
But none were breed specific.
According to the results, breed explains only 9% of behavioral variation in individual dogs, and for some behavioral traits and survey items, dog age or sex were instead the best predictors.
“The majority of behaviors that we consider to be characteristics of specific modern dog breeds are most likely the result of thousands of years of evolution from wolves, to wild dogs, to domestic dogs, and finally to modern breeds,” the author explains. Elinor Karlsson, director of the Vertebrate Genomics Group at the Broad Institute of Massachusetts Institute of Technology (MIT) and Harvard University in the United States.
“These inherited traits predate our concept of modern dog breeds by thousands of years.”