For decades, it has been popularly believed that 1 dog year is equivalent to 7 human years. Despite being around for a long time, this calculation is not entirely accurate, but many still use it. One reason for its popularity is that it may have been based on the fact that people typically lived to around 70, while dogs lived to approximately 10. Some speculate that it was a marketing tactic to encourage pet owners to take their dogs for regular check-ups.
How to Calculate Dog Years to Human Years
Calculating a dog’s age in human years is not an exact science, but the American Veterinary Medical Association provides a general guideline. The first year of a medium-sized dog’s life is equivalent to 15 human years, with year two of a dog’s life equaling around nine years for a human. After that, each human year is approximately five years for a dog. However, these estimates vary based on a dog’s breed and size.
While small dogs are generally considered “senior” at seven years old, larger dogs tend to have shorter lifespans and are often considered senior when they are five to six years old. Dogs do not age at a rate of 7 human years for each year in dog years, as commonly believed. For instance, a Great Dane that is four years old would already be 35 years old in human years, as the breed typically has a lifespan of 7 to 10 years.
Why do Smaller Dogs Live Longer than Larger Dogs?
Interestingly, larger mammals such as elephants and whales usually live longer than smaller ones like mice. So, why do smaller dogs have a more extended lifespan than their larger counterparts?
Experts suggest that larger dogs tend to age more rapidly, leading to a shorter life span. According to evolutionary biologist Cornelia Kraus from the University of Göttingen in Germany, for every 4.4 pounds of body mass, a dog’s life expectancy is reduced by a month. The exact reason behind this phenomenon is still unknown, although Kraus proposes several possibilities. One theory is that larger dogs may be more prone to age-related diseases, leading to a shorter lifespan. Another possibility is that the accelerated growth rate of larger dogs may increase the likelihood of abnormal cell growth and cancer, contributing to their shorter lifespan. Further research is needed to gain a better understanding of the link between growth and mortality in dogs.