The pygmy slow loris, which lives in Cambodia, China, Vietnam, and Laos, has been documented using hibernation to conserve energy.
Previously, the only known primates to hibernate were lemurs living on the island nation of Madagascar.
The findings come from a paper just published in the journal Scientific Reports by a team of researchers from Vetmeduni Vienna in Austria.
The pygmy slow loris (Nycticebus pygmaeus) is small, at about 7 to 9 inches long and typically weighing about 1 pound. The nocturnal creature lives in trees and, unlike other primates, it can't leap. Its diet includes tree gum, insects, and fruit.
The scientists studied the animal's body temperature in the fall, winter and spring in Vietnam. They found that the creature engaged in episodes of hibernation between December and February that lasted up to 63 hours each.
The researchers suspect both an internal clock mechanism that kicks in during seasons of food scarcity and ambient temperature drops each help induce the hibernation periods.
"In Vietnam, where we studied the animals, there are pronounced seasons," said the study's lead author Thomas Ruf in a statement. "Ambient temperature can drop to 5 centigrade. This is exactly when the probability of animals entering a hibernation episode was highest."
Hibernation can last anywhere from days to months and helps many species conserve energy during periods when food is tough to come by. It's characterized by decreased metabolism, a sharp drop in body temperature, lowered heart rate, and slowed breathing. Colloquially, it's often considered a kind of deep sleep.
Three species of lemur on Madagascar conserve water by hibernating during the dry season. But outside of that location, hibernation in primates has not until now been documented.
"Our new finding of a hibernating primate species outside Madagascar sheds new light on the evolution of hibernation," said Ruf. "Possibly, hibernation as an overwintering strategy was lost in other primates in Africa, Asia, and the Americas. However, perhaps hibernation is also used by further primate species which have not been studied yet."
Hat tip PhysOrg