Primates that Hibernate: Two New Lemurs Discovered in Madagascar (Video)

Primates aren't known for hibernation. In fact, the only known primate species thought to hibernate is a creature called the western fat-tailed dwarf lemur from the African island of Madagascar. Now, it seems like this lemur isn't alone. Researchers have discovered that two other lemurs also hibernate underground.

The two lemurs are called the Crossley's dwarf lemur and the Sibree's dwarf lemur. About the size of large squirrels, these creatures burrow into the soft, spongy rainforest floor in the eastern part of Madagascar. They then spend the next three to seven months sleeping away before waking up.

Yet these creatures don't hibernate because of the cold. Madagascar is a warm environment, which means that the lemurs don't have to face the harsh conditions that are associated with winter temperatures that plummet well below freezing. What they do have to face, though, is hot weather. The related western dwarf lemurs hibernate to survive during western Madagascar's long dry season, a time when temperatures top at 85 degrees, trees drop their leaves and food and water are in short supply.

While it's possible these two lemurs hibernate to avoid the harsh conditions associated with hot weather like their cousin, researchers weren't sure. The two actually thrive in the eastern part of Madagascar in high-altitude forests. There, winter temperatures occasionally dip below freezing.

In order to find out more about their hibernation patterns, the researchers trapped and fitted the animals with temperature-sensitive radio collars before the start of the hibernation season. This allowed the scientists to find the lemurs' underground burrows and monitor their body temperatures once they began to hibernate.

"To the casual observer, it looks for all the world as if the animals are dead," said co-author Anne Yoder, in a news release. "Their bodies are cold, they are utterly still and they take a breath only once every several minutes or so."

Despite their appearance, though, the lemurs are very much alive. The researchers found that, surprisingly, the lemurs' body temperature didn't drop that much--a stark contrast to the western dwarf lemur. Instead, they kept a relatively constant body temperature in cozy, underground burrows.

The findings reveal that lemur hibernation--and therefore primate hibernation--may not be all that unusual after all. They may actually reflect the behavior of temperate hibernators, despite being primates.

The findings are published in the journal Scientific Reports.

Want to see the lemurs? Check out the video below, courtesy of Duke University.