When it comes to life expectancy, bigger dogs get the short end of the stick. Canine life span seems to be based on size, with smaller dogs living longer, and bigger dogs dying young. Small dogs -- like miniature poodles and Chihuahuas, for example -- can easily live for 12 to 14 years, while massive breeds like mastiffs and Newfoundlands might only live half that long.
Giant breeds that weight more than 90 pounds, like great Dane, Irish wolfhound and St. Bernard, have the shortest life expectancy. On average, they live only six to eight years. According to the International Institute for Applied Systems Analysis, heart problems, arthritis and joint disease are common in many large breeds, giving them a shorter lifespan. Researchers theorize that extra stress placed on the heart and organs during periods of rapid growth might be the reason larger dogs die at a younger age than small dogs.
Large breeds of dogs -- like German shepherds, Labrador retrievers, Irish setters and Doberman pinschers, which usually weight between 70 and 90 pounds -- live longer than their giant counterparts, but not as long as dogs that weigh less. The life expectancy of most large breed dogs is 10 to 13 years, according to MSNBC. Large breeds fall victim to many of the same type of health problems as giant breeds, including heart failure and joint disease, but tend to do so a little bit later in life, giving them a longer life expectancy.
There are several breeds that might be considered medium-sized dogs but have the life expectancy of larger breeds. English bulldogs, for example, don't have the height of a large dog like a retriever, but fall into the category of large dogs because of their weight, according to the International Institute for Applied Systems Analysis. Total size and weight seems to influence a dog's lifespan, not just height, with heavier dogs dying at a younger age. Dogs that are short in stature but have a lot of mass have a life expectancy of 10 to 13 years. Some, like the bulldog and bull terrier, may only live six to eight years like some of the giant breeds.
Genetics and Healthcare
Regardless of the size and weight of a dog, genetics and healthcare play a major role in a dog's lifespan. A large breed dog whose parents lived to be 14 years old might be expected to live 14 years or longer, defying the 10- to 13-year average simply because of genetics. A large or giant breed puppy who receives the right nutrition at a young age might also live longer because the rapid growth is not as stressful on his body. Dogs who are thin or at a healthy weight and get regular exercise live longer than dogs who are allowed to become overweight, regardless of the size of the breed.