Sex-specific differences in activity patterns and fattening in the gray mouse lemur (Microcebus murinus) in Madagascar

Abstract

The gray mouse lemur (Microcebus murinus) is a small, nocturnal primate endemic to Madagascar and has evolved specific activity patterns to survive the dry season, a period of low food availability and low ambient temperatures. These patterns are sex-specific. I determined seasonal fluctuations of body mass and tail circumference in M. murinus under natural conditions in a dry deciduous forest of western Madagascar in 1994-1995. I compared those variables among individuals during different activity patterns. Based on mark-recapture and monitoring of sleeping sites, 73.1% of adult females but only 18.9% of adult males remained inactive for the several weeks to 4-5 months throughout the cool dry season. Inactive females stored fat before the onset of the inactive phase and lost 31.7% of their mass during the dry winter, but inactive males hardly stored fat, and their body mass did not change between onset and end of the period of inactivity. Duration of inactivity was significantly longer for females than males, due to earlier emergence of males. At the end of inactivity and activity periods, respectively, body masses and tail circumferences did not differ between inactive and active males and females. Thus, M. murinus has evolved two different strategies to survive the cool dry season: being generally active but combined with daily torpor of <24 h, and remaining inactive for days to several weeks, which might be associated with prolonged bouts of torpor.