Size Matters: Exploring Why Larger Dogs Have Shorter Lifespans
Australian scientists from the University of Adelaide have come up with an explenation as to why larger dogs have shorter lifespans than smaller dogs . It all comes down to breeding, with selective breeding for size making large breeds more susceptible to cancer according the research.
The study examined the causes of differences in lifespan and death in 164 dog breeds, ranging in size from chihuahuas to Great Danes.
“When we analysed these data sets, we discovered that larger dogs were more likely to die from cancer at a younger age when compared with smaller dogs,” said Dr Jack da Silva from the University of Adelaide’s School of Biological Sciences.
“Larger dogs didn’t necessarily age faster than the smaller breeds, but the research did show that as the breed’s average body weight increased, so did the rates of cancer.
“We believe the relationship between a dog’s body size and their lifespan may be caused by an evolutionary lag in the body’s cancer defences, which are unable to keep up with the rapid and recent selective breeding of bigger dogs.”
The study , which was published in the The American Naturalist , found the shorter lifespans were consistent with a theory of ageing known as life history optimisation or the ‘disposable soma’.
“This theory is based on the idea that if you invest most of your resources and energy into growth and reproduction, you can’t also invest them in cell repair and cancer defences,” Dr da Silva said.
“In all organisms, the focus is on reproducing early, even if it comes at the expense of maintaining and repairing the body and living longer.
“Dogs represent a good model for studying ageing in humans,” Dr da Silva added.
“Dogs, like humans in the industrialised world, live in an environment that tends to protect them from accidental and infectious causes of death and are thus more likely to die from age-related diseases, such as cancer.”
Although the results of this survey may be concerning for owners of large dogs, the researchers predict bigger breeds will evolve to develop better cancer fighting genes.
This research was the result of a year-long comparative analysis study using published data about dog breeds from across the globe.
It is well understood that the average lifespan of dogs varies depending on factors such as breed, size, and overall health and , smaller dog breeds tend to live longer than larger breeds.
For small breeds like Daschunds and Maltese Terriers, the average lifespan ranges from 12 to 16 years.
For large breeds like Labradors, Retreivers and German Shepherds, the average lifespan ranges from 8 to 12 years. Very large dogs have even shorter average life spans. The life span for a Great Dane is just 7 to 10 years.
