Being Anti-social Leads to a Longer Life. For Marmots.

For many mammals, a busy social life can be an important contributor to a long life. But some animals need more alone time than others, and failure to get it could be lethal, according to new research.

Consider the marmot. After spending 13 years tracking their interactions and life spans in Colorado, Daniel T. Blumstein, a biologist at the University of California, Los Angeles, and his colleagues found in a study published Wednesday in Proceedings of the Royal Society B that yellow-bellied marmots with more active social lives tended to die younger than those that avoided interactions.

“The difference in life span between the most social and the least social marmot was about two years,” Blumstein said. That’s significant considering that the average life span of a yellow-bellied marmot is about 15 years.

Marmots are a genus of large, squirrel-like rodents with sharp claws and furry ears. They are known as socially flexible animals: They prefer to live solitary lives, but will peacefully coexist with one another if the habitat demands it.

“The yellow-bellied marmot is more social than other marmots, like the groundhog, but it doesn’t really want to be social,” said Blumstein.

If a yellow-bellied marmot population grows too large, leading to a strain on habitable space, a female yellow-bellied marmot will sometimes allow her daughters to settle nearby, and about half will accept the invitation. (Male offspring always disperse, Blumstein said.)

The marmot social activities the researchers tracked included sitting next to each other, foraging together, playing together and grooming one another. The marmots under observation lived in 11 separate colonies near the Rocky Mountain Biological Laboratory in Gothic, Colorado.

Why socializing might be detrimental to a marmot’s health is hard to say. Perhaps, Blumstein speculated, the animals are passing diseases among themselves. Maybe they are more likely to wake one another during hibernation, causing them to starve in the barren winter forest. Or perhaps time they spend socializing would be better spent looking out for predators. “There are a variety of plausible explanations,” he said. “I just don’t know what they are yet.”

The findings offer a contrast with other mammals. Many studies have shown that highly social animals — humans, dolphins, sheep — live longer if they maintain strong social networks.

“For humans, not being social is about as bad as smoking a pack or so of cigarettes a day,” Blumstein said.

Likewise, female baboons that form strong social bonds live longer than those that don’t, as do macaques with larger families.

For these animals, social bonds are believed to provide assistance in times of danger and a buffer against stress. In humans, social mores also provide a nudge toward healthier habits, like washing your hands and not eating out of the garbage.

The researchers said that the findings warrant further study into the social habits of seemingly anti-social animals, like pumas and bears. While such animals have earned a reputation for being hostile toward one another, perhaps — knowing that familiarity breeds mortality — their isolation could be driven by a desire to preserve the species.