Researchers believe that they have found the oldest evidence of an animal hibernating during the cold winter months. Around 250 million years ago during the Triassic period, a hairy creature with four legs, a turtle-like beak and two tusks survived the cold winters in Antarctica by possibly sleeping for several months.
When animals hibernate, they enter into an inactive state like a deep sleep. In order to survive the harsh winters, their body temperature lowers while their breathing and heart rates get slower. When they hibernate, it protects the animals from the cold temperatures and reduces the need for them to eat.
The creature from the Triassic period was part of the extinct genus called Lystrosaurus that were ancient relatives of mammals. Surprisingly, they survived the mass extinction that occurred 252 million years ago that killed off approximately 70% of land vertebrates. They could grow as long as 8 feet and several fossils have already been unearthed in Africa, Russia, China, and Antarctica.
Even though they were alive hundreds of millions of years ago, they hibernated in a similar manner to today’s animals. Megan Whitney, who is a postdoctoral researcher in the Department of Organismic and Evolutionary Biology at Harvard University as well as the lead author of the study, said in a statement, “Animals that live at or near the poles have always had to cope with the more extreme environments present there,” adding that “these preliminary findings indicate that entering into a hibernation-like state is not a relatively new type of adaptation. It is an ancient one.”
Researchers from the University of Washington and Harvard University analyzed six tusks from the Antarctic and four from South Africa by slicing them open. The tusks from both locations were very similar in regards to the growth patterns that were made of concentric circles of dentine (hard, thick bony tissue). However, one major difference was that the tusks from Antarctica had several thick rings that were spaced closely together that the South African tusks didn’t have.
The thick rings had a less amount of dentine deposition which indicates that the creature had stress for long periods of time. “The closest analog we can find to the ‘stress marks’ that we observed in Antarctic Lystrosaurus tusks are stress marks in teeth associated with hibernation in certain modern animals,” Whitney explained.
The stress marks could have also been caused by a less amount of activity for a period of time, so the researchers aren’t conclusively certain that the animal did in fact fully hibernate. Since it may have been a warm-blooded animal, it could have reactivated its metabolism at different times during the winter season which is what the evidence from the tusks suggests. (Pictures can be seen here.)