Why Don’t Big Dogs Live as Long as Small Dogs?

iStock / yellowsarah
iStock / yellowsarah

Large animals tend to live longer (sometimes much more so) than smaller ones*. A cat is going to live longer than a rat, you’re going to live longer than a cat and a Galapagos tortoise is going to live longer than you. The world’s smallest mammal, the bumblebee bat, is thought to live 5 to 10 years, while the largest, the blue whale, lives for 80 to 90. Scientists think that this happens because of the way differently-sized animals use energy. Big animals’ cells are slower and more efficient, so their parts wear out slower and last longer.

Forget about all the other animals and focus on just one species, though, and you see this trend reverse. Within a species, larger size seems to carry a longevity cost. Scientists have seen this is in mice, horses, and even humans**. The phenomenon is well known to dog lovers: Dogs from bigger breeds don’t live as long as smaller ones. The small breeds have an average life expectancy of 12 to 14 years; for larger breeds, it's 8 to 10; and for the so-called “giant breeds,” lifespan is 5 to 8 years. 

This strange flip in the relationship between size and lifespan isn’t completely understood, and many, if not all, of the factors at play are probably species-specific. This is certainly the case for dogs, and scientists think that the reasons big breeds die young have to do with the way humans have bred them and the way they grow. 

Larger dogs grow very big very fast. Take a one-year-old Great Dane, for example. It’s huge. From birth to their first birthday, they increase 100-fold in weight. In that same time frame, wolves increase 60-fold, poodles 20-fold and humans only threefold. Research in the last decade has suggested that larger individual animals die younger because this sort of accelerated growth comes with increased free-radical activity. 

A new study published last month focused only on dogs and likewise concludes that big dogs die young because they age quickly. The European researchers looked at veterinary data for 74 breeds and more than 50,000 individual dogs, including when and how they died, and found that “large dogs age at an accelerated pace, suggesting that their adult life unwinds in fast motion.”

Faster aging isn’t the only explanation, though. Larger dogs are more prone to health issues like developmental disorders, musculoskeletal and gastrointestinal diseases, and tumors—all of which are also linked to their accelerated growth and appear to be the nasty side effects of selective breeding for large size over a short (relative to the millennia other animals have had to evolve by natural selection) period of time.

There are some notable exceptions, of course, like the relatively small African grey parrot, which can live 50 to 60 years. 

Tom Samaras has been studying links between human height and other characteristics for decades. After looking at height and age of death for people in a number of historical samples, he found that shorter stature is strongly linked to longer life. Among 3200 deceased pro baseball players, for example, he worked out that every cm of height a player had over the average shortened his life by .35 years.

A Same-Sex Penguin Couple Has Adopted an Egg at a Berlin Zoo

LisaStratchan/iStock via Getty Images
LisaStratchan/iStock via Getty Images

At first glance, king penguins Skip and Ping don’t appear to be too remarkable a sight when viewed by spectators at their enclosure at Germany's Zoo Berlin. But look closer and you may see one of them nurturing an egg under one of their skin folds. Skip and Ping, a same-sex penguin couple, have effectively adopted an egg and hope to raise it as their own baby.

A story by writer Liam Stack in The New York Times details their pursuit of parenthood. According to Stack, the penguins arrived at Zoo Berlin in April and were observed to have a degree of baby fever, trying to coddle everything from a rock to a fish. Taking note of their coupling, zookeepers passed on an unhatched egg laid by a female at the zoo. They immediately took to it, taking protective measures and growing ornery when employees got too close. Ping has taken to sitting on the egg in the hopes it will hatch.

That’s not guaranteed. Zookeepers aren't certain whether the egg was fertilized. If it is, it’s likely to crack open in early September, giving Skip and Ping an opportunity to expand their family.

Earlier this year, a same-sex penguin pair named Sphen and Magic began rearing a chick in Australia’s Sea Life Sydney Aquarium. The doting parents sang to and fed their adoptive offspring.

[h/t The New York Times]

Airlines Are No Longer Allowed to Ban Service Dogs Based on Breed

chaivit/iStock via Getty Images
chaivit/iStock via Getty Images

As the species of service and emotional support animals have become more diverse, airlines have had to make some tough decisions. Birds, monkeys, and snakes have been barred from boarding airplanes with passengers, but even more conventional pets like dogs have been rejected based on their breed. A new rule from the U.S. Department of Transportation (DOT) aims to change that. As Travel + Leisure reports, the agency now forbids airlines from discriminating against service dogs of particular breeds, including pit bulls.

Last year, Delta banned all pit bulls from flying, regardless of whether or not they were certified therapy animals. United Airlines also banned pit bulls last year, along with 20 other dog breeds, including pugs, bulldogs, mastiffs, and shih tzus.

Under the new DOT guidelines, these policies are no longer legal. The statement reads: "The Department’s Enforcement Office views a limitation based exclusively on breed of the service animal to not be allowed under its service animal regulation. The Enforcement Office intends to use available resources to ensure that dogs as a species are accepted for transport."

The new rule applies specifically to service animals, or animals that have been trained to perform a job that's essential to their owner's wellbeing. Emotional support animals, which don't require special training and aren't covered by the Americans With Disabilities Act, don't qualify.

Even if a pet is a certified service animal, airlines still have the right to reject them in certain cases. Air travel companies can request documents related to an animal's vaccination, training, or behavior history. If they find anything in the papers that indicates they're not safe to fly, airlines can turn them away on that basis.

In the same statement, the Department of Transportation clarifies which species of service animals should be allowed on flights. Miniature horses are now included on the list of service animals airlines must allow to fly, while ferrets, rodents, snakes, reptiles, and spiders are the only species airlines can ban outright.

[h/t Travel + Leisure]

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