Seasonal fluctuations in body fat and activity levels in a rain-forest species of mouse lemur, Microcebus rufus

Seasonal fattening in preparation for the dry season followed by torpor cha racterizes some members of the family Cheirogaleidae, a group of < 600g noc turnal Malagasy primates. These behaviors are associated with extreme seaso nality in dry forests, where most studies have been conducted. I aimed to d etermine if the brown mouse lemur (Microcebus rufus), a rain-forest species of cheirogaleid, exhibited similar changes. Between January 1993 and May 1 994 I conducted a mark-recapture study on Microcebus rufus in the rain fore st of Ranomafana National Park. I monitored body weight and tail circumfere nce for body fat fluctuations and inferred changes in activity levels from presence or absence in the traps. Some individuals of both sexes increased body fat and entered torpor as suggested by their absence from traps for at least I month of the dry season. Activity was resumed with body weight red uced by 5-35 g, and tail circumference by 0.4-1.2 cm. Population-level anal ysis supports these results; highest weight and tail circumference values o ccurred just before and at the onset of the dry season. Other individuals, predominantly male, exhibited no change in body fat or activity level, and some mouse lemurs increased their body fat over the course of the dry seaso n. Age, social status, and individual response may influence seasonal behav ioral strategies. Dry and rain-forest species of mouse lemur adopt similar behaviors to cope with environmental stresses. Mouse lemurs resemble nonpri mate, small-bodied mammals, in which behavioral changes related to maintain ing energy balance occur during seasonally unfavorable conditions.