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Shrew-like Ancestor Slept Through Dino Extinction

Oct 23, 2014 12:54 PM EDT

There was no escaping extinction for dinosaurs some 65 million years ago, but one clever, or simply drowsy, shrew-like ancestor slept through the catastrophic death and destruction, new research suggests.

A tiny mammal called a common tenrec (Tenrec ecaudatus), weighing a mere two pounds and found in the forests of Madagascar, is considered a living fossil from the Late Cretaceous. Their sleeping habits are shedding light on their early ancestors, which appear to have peacefully hibernated below ground without a stir 65 million years ago, even while aboveground the end-Cretaceous extinction event killed off all the dinosaurs, most likely from a cosmic impact.

To find out how the ancestors of today's mammals managed to survive this catastrophe, researchers outfitted 15 tenrecs from Madagascar with a radio transmitter device that included a body temperature logger. Then they released the hedgehog-resembling animals back into the wild.

After tracking the animals for a two-year period, they found some shocking results.

"One adult male hibernated for nine months until we were forced to dig it up, because the radio transmitter batteries were dying," study lead author Barry Lovegrove, an evolutionary physiologist at the University of KwaZulu-Natal in South Africa, told Live Science.

Normally we associate hibernation with animals living in temperate regions going into torpor during cold, winter conditions. But the tenrec is the first known tropical mammal found to hibernate for long stretches without waking, for as long as nine months straight - normal mammals periodically arouse for 12 to 24 hours before going back into hibernation. It's a good indication that tenrec ancestors were also heavy sleepers, capable of hibernating through something as catastrophic as the event that wiped out the dinosaurs.

"The use of torpor or hibernation would have reduced the need (during the 65.5-million-years-ago extinction event) for food at a time when resources were limited," researcher Frank van Breukelen told Discovery News.

While the body temperature data researchers used is an indirect indicator of sleep/wake cycles, measuring metabolism would provide a clearer picture of the tenrecs' sleep.

"It will be important to actually measure metabolic rates during this prolonged hibernation period in tenrecs in future experiments," developmental biologist Dr. Sandy Martin, who was not involved in the study, told Australian Geographic.

Not only does this data shed light on how early mammals survived when the dinosaurs did not, but it also has important medical implications for extended period manned space flights in the future. A trip to Mars would take about nine months, equivalent to the time that the male tenrec hibernated.

The findings were published in the journal Proceedings of the Royal Society B.

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