Big Dogs vs Small Dogs, Life Span Science

As dog lovers we are painfully aware of the short amount of time our best friends will spend with us. Although it doesn’t seem to impact our preferences, many know from experience that big dogs don’t live as long as small dogs. As dog lovers we think their life span is much too short as it is. But when looking across species, we see bigger animals living longer than smaller, excepting predation ( Science Museum, London). Elephants can live to be 70, parrots to 80 , Swan to 100, giant whales and tortoise from more than one to nearly two centuries. The longest living of large animals all move slowly. Conversely, small animals like a house mouse can make it to 4 years, a shrew to 1.5 years, and a mayfly 1 day. These small animals move quickly.

Activity level and metabolism have much to do with this equation:

“Larger, more complex organisms can often get away with eating a few times a day, have slower metabolic rates, and are less active. It’s thought that during daily life, the process of breaking down food and turning it into energy might actually lead to aging by damaging the DNA inside cells. So the more active the organism, the faster it “burns out” and ages itself.” Science Museum

Within a species the opposite seems true. The bigger members have shorter life spans. So what does this mean for dogs?

“The apparent cost of bigger bodies is especially conspicuous with dogs, a species that people have bred over the millennia to come in an extraordinary range of sizes. The heaviest known dog may have been Zorba, an English mastiff that weighed 343 pounds (155 kilograms), while the smallest dog alive may be Meyzi, a terrier less than a quarter-pound (110 grams) in size.” LiveScience

Data from more than 56,000 dogs from veterinary teaching hospitals was taken, analyzing ages at death of 74 breeds to find why large dogs live shorter lives. Cornelia Kraus, evolutionary biologist at the University of Gottingen in Germany, explained that research established large breeds age at faster rates, and large dogs’ lives begin “unwinding in fast motion”. Proper nutrition and weight control also play a part in slowing the end of life – all things being equal: An increase of 4.4 lbs in weight deducts 1 month off life span.

Kraus, a self-described dog nerd, and her band of investigators now want to go forward with a large scale study to determine the leading cause of death for large dogs by following growth and health histories. Since large dogs appear to suffer more from cancer, the answer, or part of it, may lie in their rate of growth — cancer is all about abnormal rates of cell growth. We’ll be gathering all information on big dogs vs small dogs as it publishes.

You can read the details of this study in the April issue of the American Naturalist journal. In the meantime, are you surprised by any of this? What did you think was most important to remember for the future health and longevity of your dog?

(Photo credit: Karen Arnold)