Factors affecting the daily rhythm of body temperature of captive mouse lemurs (Microcebus murinus)

Microcebus murinus, a small nocturnal Malagasy primate, exhibits adaptive energy-saving strategies such as daily hypothermia and gregarious patterns during diurnal rest. To determine whether ambient temperature (T(a)), food restriction and nest sharing can modify the daily body temperature (T(b)) rhythm, T(b) was recorded by telemetry during winter in six males exposed to different ambient temperatures (T(a) = 25, 20, 15 degrees C) and/or to a total food restriction for 3 days depending on social condition (isolated versus pair-grouped). At 25 degrees C, the daily rhythm of T(b) was characterized by high T(b) values during the night and lower values during the day. Exposure to cold significantly decreased minimal T(b) values and lengthened the daily hypothermia. Under food restriction, minimal T(b) values were also markedly lowered. The combination of food restriction and cold induced further increases in duration and depth of torpor bouts, minimal T(b) reaching a level just above T(a). Although it influenced daily hypothermia less than environmental factors, nest sharing modified effects of cold and food restriction previously observed by lengthening duration of torpor but without increasing its depth. In response to external conditions, mouse lemurs may thus adjust their energy expenditures through daily modifications of both the duration and the depth of torpor.