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.

Pet Obesity is Causing Big Health Problems, According to a New Report

iStock/dennisvdw
iStock/dennisvdw

If you’ve recently picked up your cat and felt your back give out, your furry friend may be among the 60 percent of the feline population that’s overweight. Dogs are also getting chubbier: about 56 percent of pet pooches are obese.

According to Banfield Pet Hospital, America's largest general veterinary practice with more than 1000 hospitals nationwide, those fat cats and chunky puppies are at risk for chronic health issues. In a new report, the hospital finds that osteoarthritis (OA) in pets is on the rise, with a 66 percent increase in dogs and a 150 percent increase in cats over the past 10 years.

Osteoarthritis is a kind of arthritis caused by inflammation or damage in joint tissue. Genetics, injury, or bone abnormalities can all be factors. The disease is chronic and degenerative and can make it difficult for pets to move around as they get older.

Excess weight can both precede OA and make it worse. When a pet is overweight, they can develop chronic pain that leads to stress on joints. If they already have OA, that joint discomfort can prevent them from being active, leading to weight gain. That worsens the condition, and the cycle continues.

A dog is 2.3 times more likely to be diagnosed with OA if it's obese, while cats are 1.2 times more likely. Dogs suffering from the condition tend to display symptoms like putting their weight off to one side when sitting, avoiding stairs, or appearing uninterested in playing. Cats might have loose or matted hair because they can't maneuver to groom certain parts of their body.

Although OA can be seen at any age, it’s often mistaken for old age and a pet slowing down naturally. If you notice your pet is either soft around the middle or moving more slowly, it’s best to see a veterinarian. Pets who are overweight or suffering from OA—or both—can benefit from treatments like special diets.

There Are 2373 Squirrels in New York's Central Park, Census Finds

iStock/maximkabb
iStock/maximkabb

Central Park in New York City is home to starlings, raccoons, and exotic zoo animals, but perhaps the most visible fauna in the area are the eastern gray squirrels. Thanks to a team of citizen scientists, we now know exactly how many of the rodents occupy the space—approximately 2373 of them, according to a census reported by Smithsonian.

In October 2018, a group called the Squirrel Census—with help from the Explorers Club, the NYU Department of Environmental Studies, Macaulay Honors College, the Central Park Conservancy, and the New York City Department of Parks & Recreation—organized a squirrel survey across all 840 acres of Central Park. For 11 days, more than 300 volunteers staked out their sections of the park twice a day—at dawn and dusk when the crepuscular animals are most active—and noted each squirrel they spotted. They also recorded how the squirrels looked, vocalized, behaved, and reacted to humans.

The research was analyzed and presented at an Explorers Club event in New York City on June 20. All the non-peer-reviewed findings—which includes a printed report, an audio report on a vinyl 45, 37 pages of data, collectible squirrel cards, and large maps of the park and the squirrel locations—are available to purchase for $75 from the Squirrel Census website.

This isn't the first time a massive census has been conducted of a public park's squirrel population. In 2011, the Squirrel Census launched with its first survey of Atlanta's Inman Park. They've conducted satellite squirrel counts at other parks, but Central Park is just the second park the organization has investigated in person.

[h/t Smithsonian]

SECTIONS

arrow
LIVE SMARTER