Welcome to brain Stuff, a production of iHeart Radio. Hey, brain Stuff, learn vogal bomb here. Have you ever wondered why you seem to know a lot more elderly Chihuahuas than aged Rottweilers. It's just a fact of life that small dogs, if they escape disease or misadventure, live longer lives than larger ones. This trend has puzzled veterinary researchers for as long as we've been fussing over our faithful four legged friends, and it's a mystery that hasn't been
definitively solved. Conventional wisdom in the animal world dictates that between different species, larger animals live longer than smaller ones. For example, an elephant can live into its seventies, while a mouse might only have a year or two to do its earthly business. However, the opposite seems to be true within single species subsets, and although dogs come in lots of shapes and sizes, they're all the same species.
The average lifespan for an enormous dog is around seven or eight years, while a tiny dog can reliably live to the ripe old age of fourteen or fifteen. The popular adage that one human year is equal to seven dog years isn't supported by modern science. Although it's easy math and therefore sticks around. The truth is more complex. In the first year of a dog's life, it generally reaches the physical maturity of a fifteen year old human.
The second year adds another nine years, and after that the rate of aging varies widely based on breed and size. A small dog is considered senior at around age eight, while a large dog hits old age around five or six. Researchers know this, but they're not entirely sure why, and to be fair, it probably involves a combination of a lot of different factors. It turns out that a dog's size isn't the only, or even the primary factor that
determines lifespan. Genetics and breeding also play a role, with certain breeds being more vulnerable to certain life threatening or life shortening diseases and conditions than others. Basically, although the aging process for dogs is very different than it is for humans, it's also very different. Among dogs. The features that a dog has been bred for seemed to matter
more than size. There was a study published in April two in the journal Nature based on a massive database of veterinary records from the United Kingdom, and to keep it simple, they looked at the lifespans of pure bred dogs. Small jack Russell Terriers, and midsized Border collies differ substantially in size, but according to the study, they live pretty
similar lifespans twelve point seven and twelve point one year's respectively. However, flat faced breeds like pugs and French bulldogs were found to have much lower life expectancies due to breathing problems, a disease, and difficulty giving birth. The French bull dogs life expectancy is only four point five years, and none of the other flat faced breeds, no matter how small, were found to have an average lifespan of more than seven point eight years. Okay, but why might size matter.
It might have to do with how long it takes a dog to become full grown and the difference in size between its puppy body and its adult body. It seems that growing very large, very quickly takes time off of a dog's overall life span. Take, for example, a Great Dane. In the first two years of their life, they reach their full size, which can be over thirty or eighty centimeters tall, and some a hundred and seventy five pounds around eighty kilos. That's a lot, and it
apparently takes a toll. Large breeds die of cancer more often than small breeds, a trend that researchers believe has to do with how quickly they grow in their first year of life. With all that rapid expansion, it possible that abnormal cell growth is more likely, or because their lives play up more quickly, that they succumb to the
diseases of old age earlier than say a chihuahua. It takes a chihuahua about ten to twelve months to grow to full size, but that size usually maxes out at only about eight inches or fifteen centimeters tall and six pounds, which is just under three kilos. It's just not as taxing on the body to become a full grown chihuahua as it is to become a complete great dane. Finally, lifestyle and access to veterinary care can affect longevity, and these factors can depend on the role of the dog
within the family. For example, toy dogs may be pampered more than larger breeds given their lap friendly size. And all of this isn't just important in terms of figuring out how we might all spend more time with our beloved companions a dog. Research is also important because dogs die of the same illnesses that humans do, including answer heart disease and diabetes, and so as usual, learning more
about them may help us learn more about ourselves. Today's episode is based on the article the longest living dog breeds are tiny, but Why on how stuff works dot Com, written by Jesslyn Shields. Brainstuff this production of I Heart Radio in partnership with how stuff works dot Com, and it's produced by Tyler Clang. For more podcasts, my heart Radio is the I heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.