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Hibernation May Be a 250-Million-Year-Old Survival Trick

Paleontologists studying this strange creature’s tusks say they’ve found evidence the animal slowed its metabolism during hard times

An artist's rendering of the 250-million-year-old animal Lystrosaurus in a hibernation-like state. (Crystal Shin)
smithsonianmag.com

New research suggests a strange-looking, 250-year-old animal may have hibernated, reports Will Dunham for Reuters. The stumpy, tusked creature, called Lystrosaurus, may be oldest example of an animal known to enter a hibernation-like state.

Researchers discovered evidence that the pig-sized Lystrosaurus slowed its metabolism to enter a state of torpor—characterized by decreased physiological activity and lower body temperature—by studying its fossilized tusks, the team reported last week in the journal Communications Biology. Despite hailing from the early Triassic and predating the dinosaurs, Lystrosaurus is actually more closely related to mammals.

“It’s an odd animal,” Megan R. Whitney, a paleontologist at Harvard University and co-author of the paper, tells Kenneth Chang of the New York Times. “It’s kind of a sausage shape. And it had no teeth except for the two tusks that came out from the face.”

In lieu of teeth, this less-than-dapper herbivore had a turtle-like beak and probably used its tusks to forage for roots and tubers across its range, which once spanned modern-day India, South America and Africa, reports Lauren M. Johnson for CNN. To learn more about the differences between these populations, the researchers compared cross sections of Lystrosaurus tusks found on different continents. Because the ancient animal’s tusks grew continuously, they created growth rings similar to a tree that can be used to infer things such as the individual’s age and growth rate.

"To see the specific signs of stress and strain brought on by hibernation, you need to look at something that can fossilize and was growing continuously during the animal's life," says Christian Sidor, a paleontologist at the University of Washington and co-author of the research, in a statement. "Many animals don't have that, but luckily Lystrosaurus did."

The team found that the Lystrosaurus specimens found in Antarctica featured densely packed, thick rings—signs that environmental stresses slowed or halted the tusk’s growth, per the Times. The specimens from South Africa, by contrast, told no similar tales of hardship.

The researchers interpret these periods of low or no growth among the Antarctic Lystrosaurus as evidence that the creatures entered a state of torpor to survive the polar continent’s long, dark winters. The Antarctic winters of a quarter of a billion years ago were much warmer than today but the lack of sunlight would have likely still snuffed out many of the mammalian ancestor’s food sources.

"What we observed in the Antarctic Lystrosaurus tusks fits a pattern of small metabolic 'reactivation events' during a period of stress, which is most similar to what we see in warm-blooded hibernators today," says Whitney in the statement. "These preliminary findings indicate that entering into a hibernation-like state is not a relatively new type of adaptation. It is an ancient one."

The ability to slow down its metabolism when times got tough may have helped Lystrosaurus survive the Great Dying—a mass extinction event that killed off 90 percent of all life in the oceans and more than two thirds of all species on land approximately 252 million years ago.

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