Dogs grow up much faster than humans, meaning these furry companions often do not live as long as their owners. But how long do dogs usually live?
A dog's life span may depend strongly on its breed, according to an April 2022 study in the journal Scientific Reports. By analyzing the ages of more than 30,000 dogs that died between 2016 and 2020, scientists calculated the average life expectancies of 18 breeds and crossbreeds in the United Kingdom.
The dogs had an overall average life expectancy of 11.2 years. However, the life span of these canine companions varied by breed.
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The creation of breeds about 150 years ago allowed dog breeders "to give flight to our whims and desires for how wild and extreme we could reshape the canine body," said study senior author Dr. Dan O'Neill, a veterinarian and epidemiologist at the Royal Veterinary College in Hertfordshire, England, told Live Science in an email. Given that many of these dogs no longer had a working function, such as herding or retrieving or guarding, "the requirement for good health was no longer a constraint" in creating new breeds, he noted.
The researchers found that small dogs had longer life expectancies than bigger canines.
"The life expectancy advantage for small dogs actually flies in the face of the basic rules of life expectancy across species in the natural world, where smaller species generally live shorter lives than larger species," O'Neill said. "A mouse might expect to live one to two years, whereas an elephant may expect to live 60 to 70 years." (Some other research suggests this general size-linked trend in longevity seen across species may not always hold within a species; for instance, while a 2019 study suggested larger women may live longer than smaller women, this may not hold true for men.)
One possible explanation is not that small dogs live longer, but that the larger breeds live shorter. Breeding may have resulted in large breeds that grow very rapidly compared with their predecessors, triggering early-onset diseases, such as osteoarthritis and cancer, O'Neill said.
In addition, the deaths of 90% of dogs in the United Kingdom involve euthanasia, so their life span "is heavily influenced by human decision-making," O'Neill said. It may be more difficult to care for larger breeds of dogs with mobility issues than smaller ones, or the financial costs of medical treatments may be greater for larger dogs than smaller ones as they age, he noted.
The scientists also found that the life expectancy of crossbred dogs was 11.8 years, about 6 months more than the average of the group as a whole. This matches previous research suggesting that hybrids are often healthier than purebreds, O'Neill said. Female dogs also generally lived longer than male canines, although whether this was true varied across breeds, he noted. Neutering was also generally linked with a longer life expectancy, potentially because it is often associated with stronger owner responsibility and better care, and perhaps because it may reduce or eliminate a number of health problems linked with reproductive organs and hormones, such as tumors.
All in all, the scientists found that Jack Russell terriers had the highest life expectancy, at 12.7 years, while French bulldogs had the lowest life expectancy, at 4.5 years.
"Sadly, while many breeds did retain a basic healthy body shape — for example, the Labrador retriever — several other breeds followed a pathway to extreme body shapes — for example, the English bulldog," O'Neill said. Soon after breeding created these major physical differences, "the serious health issues linked to these extreme body shapes started to become apparent," he said.
Jack Russell terriers may live longer than other breeds as part of the trend that smaller dogs live longer, O'Neill said. In addition, they were not bred to have an unusual body shape that might limit their overall health.
"These little dogs were bred to be hardy and benefited by not being constrained to fitting a pre-defined breed standard," O'Neill said. "Essentially, these are the archetypal healthy little family companion dog."
Other dogs with long life expectancies also have body shapes similar to closely related wild species such as wolves, coyotes and foxes, which evolutionary forces likely optimized for survival and health, O'Neill said. For instance, the average life expectancy was 12.5 years for Yorkshire terriers, 12.1 years for border collies and 11.9 years for springer spaniels.
In contrast, in addition to French bulldogs, similar breeds often have brief lives. The average life expectancy was 7.4 years for English bulldogs, 7.7 years for pugs and 7.8 years for American bulldogs.
Previous research found that these breeds are prone to a number of serious health disorders that are often linked with their physical characteristics, such as their short snouts or large heads. These conditions include skin fold dermatitis, breathing problems, eye ulceration, cherry eye, difficulty giving birth, slipping kneecaps, elbow joint disease and heatstroke.
"Many of these disorders are life-limiting in that they either directly lead to early death in these dogs or that owners opt for euthanasia on welfare grounds," O'Neill said.
Although a common method for guessing the life span of dogs is to use "dog years" — that is, to multiply their age by seven to get an idea of how old they might be in human terms — the recent work from O'Neill and his colleagues suggests "that such a concept really is no longer that useful," he said. "Given the wide variation in life expectancy across breeds, an alternative approach would be to generate a concept of dog years within each breed. This is much more likely to be accurate."
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