There are always exceptions, but new research from the April issue of American Naturalist suggests that big dogs die younger. The reason for this is that they age quicker than dogs of other sizes.
The study zeroed in on dogs because of the size variations in the species; there are many dogs on record, from a 343-pound English Mastiff to a quarter-pound terrier. No other mammal on earth has more variations in overall size, another reason dogs are so unique.
The study examined the death ages of 74 breeds, checking out over 56,000 dogs that’d visited veterinary teaching hospitals. The larger breeds seemed to age at faster rates than the smaller breeds, while the speed at which risk of death impacts larger breeds seems to arrive sooner. As the study points out, “their adult life unwinds in fast motion.”
What’s more, the study seemed to narrow things down to the pound. For every 4.4 pounds of body mass on a dog, about a month of his or her life is taken.
“This tradeoff has been known about for a long time, but nobody has yet investigated the underlying demographic mechanism,” says Cornelia Kraus, an evolutionary biologist at the University of Göttingen.
So Where Is This Going?
Researchers are hoping to look at the growth and health histories of the dogs in order to get down to the leading causes of death. Perhaps there are more correlations in this area. There may be some related information in how or why a particular type of dog was bred, too.
Consider that larger dogs are more likely to acquire cancer in part because they grow quicker than smaller dogs. Because cancer comes about due to abnormal cell growth, these dogs may be predisposed to cancer to a greater degree than dogs that weren’t bred for quick growth.
The next step is to find out why this happens, of course. Other giant species, like elephants or blue whales for instance, live longer lives because they don’t age as quickly.
There may be clues, like the fact that small dogs appear to have lower concentrations of IGF-1, a growth hormone, in their blood. Higher levels of IGF-1, like those in larger dogs, have been associated with increased risk of death from age-related conditions like cancer or heart disease. Researchers will be looking into exactly what role IGF-1 plays in the aging process for dogs, opening up some interesting and potentially life-altering doors along the way.
So it does appear that we’re getting closer to answering why big dogs die younger. Owners of large dogs may not quite be taking solace in this information, but there are reasons for hope on the horizon.