Hibernation in primates may not be exclusively restricted to species on the island of Madagascar, according to research published in Scientific Reports this week. The study found that the pygmy slow loris, a small primate found in the forests of Vietnam, Cambodia, Laos and China, can also hibernate.

Hibernation is defined by the occurrence of bouts of torpor - a reduction in body temperature and metabolic activity - that last for periods in excess of 24 hours. In primates, hibernation has been reported in Madagascan lemurs and appears to be geographically limited to this island.

Thomas Ruf and colleagues monitored the core body temperatures of five pygmy slow lorises during autumn, winter and spring, in outdoor enclosures in northern Vietnam. The authors found that lorises of both sexes entered a state of multiday torpor (hibernation) during midwinter (mid-December to mid-February), with bouts lasting up to 63 hours. The authors suggest that this could be an adaptation to seasonal changes in food availability, such as the low abundance of insects during winter. As body temperature decreases during hibernation, this leads to a reduction in energy expenditure to approximately five percent of the animal’s basal metabolic rate.