Energetic advantage of nest-sharing in a solitary primate, the lesser mouse lemur (Microcebus murinus)

Energetic benefits provided by sharing a nest were investigated by measurin g resting metabolic rate in the lesser mouse lemur (Microcebus murinus), a nocturnal solitary primate that usually groups in a nest during its diurnal rest. Resting metabolic rate was measured on 32 individuals maintained eit her alone or grouped with one, two, or three conspecifics originating from the same social group. In this seasonal breeder, individual resting metabol ic rate varied significantly from 1.08 +/- 0.03 to 1.47 +/- 0.05 (SE) ml O- 2 h(-1) g(-1) for nonbreeding and breeding seasons, respectively. During th e breeding season, both sexes reduced their energetic expenditure by 20% wh en grouped in pairs, and maximal energetic benefit (40%) was achieved when three animals nested together. During the nonbreeding season, maximal energ etic gain was observed when as few as two animals nested together because r esting metabolic rate was already decreased. Finally, when three or four an imals shared the same nest, resting metabolic rate was minimal, independent of sex and season, at 0.88 mi O-2 h(-1) g(-1), suggesting that nest-sharin g in this solitary primate is an important strategy to minimize energetic c osts to cope with seasonal shortage of food.