Madagascar's western forests have a long dry season with little food. Grey mouse lemurs meet it physiologically. In the weeks beforehand they build fat reserves concentrated at the tail base, and through the dry months they enter torpor, allowing body temperature to fall towards ambient and metabolic rate to drop sharply, then rewarming to forage.
Females tend to spend more time torpid than males, and in some populations individuals remain inactive for extended periods rather than only through daylight hours. Related dwarf lemurs of the genus Cheirogaleus go further, undergoing prolonged hibernation in tree holes, which makes them the only obligate hibernating primates known.
The grey mouse lemur is heavily used in ageing research because it is small, short-lived and shows brain changes with age that resemble human patterns. Whether torpor extends life in this species, as it appears to in some hibernating mammals, has not been demonstrated.