FYI.

This story is over 5 years old.

Tech

Social Structure May Be the Reason Naked Mole-Rats Live So Long

The merits of a eusocial lifestyle.
​A bunch of naked mole-rat babies. Image: Robin L/Flickr

​The naked mole-rat is a wonderfully unique anomaly in the natural world. Its enormous front teeth and pale, saggy skin distinguish it as one of the most ugly-cute animals known to science, but its looks aren't even the weirdest thing about it.

These rodents are also famous for their extreme longevity and resistance to cancer, traits that scientists hope could inform treatment plans in humans. Though they are about the same size as mice, naked mole-rats can reach the age of 30, about ten times as long as other rodents that size. The question is: what is the secret to the naked mole-rat's impressive durability?

Advertisement

Scientists have already established that specialized protein production and maintenance are partly responsible. But according to a study published today in The Proceedings of the Royal Society B, the naked mole-rat's unusual social structure may also play a role in its long lifespan.

Unhappy female naked mole-rat. Image: Jedimentat44.

For you see, in addition to its odd appearance and freakish super-health, the naked mole-rat is also eusocial. Like ants and bees, these rodents produce only one reproductive female, the "queen," and the rest of the colony is made up of subordinates relegated to support roles. They are the only mammals to have evolved this highly coordinated social structure.

"The advantages, in terms of longevity, of eusociality is that the number of breeders is reduced and they are protected, and fed, by other group members," study author and anthropologist Scott Williams told me.

Williams, along with co-author and fellow anthropologist Milena Shattuck, came to this conclusion after statistically analyzing datasets on hundreds of mammals.

They found a strong positive correlation between body size and lifespan; the bigger the animal, the longer it lived. As mentioned above, the naked mole-rat, which typically weighs about an ounce, flagrantly contradicted this rule.

Williams and Shattuck also confirmed that fossorial (burrowing) animals have longer lifespans than their surface peers, because they are better able to escape predation. Naked mole-rats live their entire life underground and, in this way, avoid the bulk of the land hunters.

Advertisement

Lifespan increased with social cooperation

But the most interesting correlation was that lifespan increased with social cooperation, and this is where the naked mole-rats truly shine (or they would, if they were ever exposed to light).

Even when they are confronted with subterranean predators, these rodents are incredibly committed to protecting the breeding female and her elite cadre of male lovers. Indeed, sometimes they make the ultimate sacrifice for the colony.

"A researcher [observed] a queen literally tossing worker mole-rats at an intruding snake so that the predator would take its prey and leave," Williams said. Wow. That's cold, but you have to appreciate the queen's no-nonsense attitude.

The naked mole-rat's talent for avoiding predation, augmented by its eusociality, have thus become drivers of its longevity, suggests the team. "The evolutionary theory of aging predicts that when species are faced with reduced extrinsic mortality, including predation and other environmental hazards, they delay reproduction," Williams said. When reproduction is delayed, so is senescence, and that may be contributing to the naked mole-rat's extended old age.

There may be other forces at play in the mole-rat's subterranean fountain of youth as well. "The longevity disparity could be related to diet, and that's something we're currently looking into," Williams said. "We're also carrying out studies on the relationship between brain size and longevity, not just in fossorial mammals, but across mammals more broadly."

"We're both anthropologists, and in the end, we're really interested in primate and human evolution," he continued. "That's one reason we put a nod to the grandmothering hypothesis and the unique sort of sociality that characterizes humans. We think it very well may have played a major evolutionary role in our own longevity."