DEAR PET TALK: Why do smaller dogs live longer than bigger dogs? —Students in Mr. Wironen’s 4th grade, Reingold Elementary School, Fitchburg
DEAR STUDENTS: This is a heartbreaking anomaly that pet owners know well: the enormous ranges of longevity between dog breeds. Scientists studying animals have found that expectations of life-span for smaller dogs ranges from 10 to 14 years; larger breeds may live much more briefly: five to eight years.
Some 400 dog breeds are officially recognized — this translates to an unlimited number of “mutts” or “mixed breeds.” My initial thought when researching this answer was that relative heart size might be a factor, but in fact, the science behind a predictably short life is the rate of growth.
Consider this: puppies of large breed dogs grow very large, very quickly, such as the Great Dane. A Dane’s weight at birth might be one to two pounds. By one month, they weigh five to eight pounds, but they gain weight at the rate of 10 to 20 pounds a month for a year or more.
That is an enormous rate of growth for weight. Also, a Dane will likely double its height between two and 12 months. Now, consider a Chihuahua. Their weight is measured in ounces for weeks after birth, and they gain weight and height at a slower rate.
Of course, there are exceptions, and I’ve seen big dogs who are more than 10 years old, and smaller dogs who die relatively young. Factors that go into health for all dogs are food, exercise, care, and of course veterinary attention.
Whatever the size of your dog — make sure you are feeding it healthy and appropriate dog food.
Sources: “The Size–Life Span Trade-Off Decomposed: Why Large Dogs Die Young” by Cornelia Kraus, Samuel Pavard and Daniel E. L. Promislow, The American Naturalist (April 2013).
Sally Cragin is the director of Be PAWSitive: Therapy Pets and Community Education. Visit us on Facebook and call/text questions to 978-320-1335