Small vs large dog breeds: Which live longer and why?

A Chihuahua having a much longer life span than a German Shepherd. Or, a Pug outliving a Great Dane. We all have seen such instances. It leads to a pertinent question: is the size of the dog inversely proportional to the life in it?

The issue of body size and lifespan is a fascinating topic in biology, says genomics researcher Adriana Heguy, Director of the Genome Technology Center at New York University School of Medicine, replying to a question on Quora. “It’s strange that across species, at least in mammals, large-bodied animals live longer than small-sized animals. For example, elephants live a lot longer than mice. The theory is that bigger animals have slower metabolisms than small animals, and that faster metabolisms result in more accumulation of free radicals that damage tissue and DNA.”

Then, how is it possible that smaller canines survive longer than their larger cousins? A study conducted by The American Naturalist points out several possibilities, including that larger dogs may succumb to age-related illnesses sooner than their smaller counterparts. “Also, larger breeds grow from puppies to adults at an accelerated rate, and this may lead to a higher likelihood of abnormal cell growth and death from cancer,” observes the study’s lead researcher Cornelia Kraus.

A possible explanation, in the words of Ms Heguy, is that larger dogs (or mice, or people) grow faster than their smaller counterparts because they reach a larger size in more or less the same time, and that faster growth could be correlated with higher cancer rates.

This is one hypothesis and we could still be too far from the fact. The jury is still out on what exactly shorten the lives of bigger pooches, as deeper research is still under way.