Pronounced seasonality, with temperatures dropping as low as 5 degrees C during the dry season, has led to the hypothesis that Malagasy lemurs face cold stress and respond to this by inactivity and social thermoregulation, i.e. resting in tight body contact with conspecifics. Compared to anthropoids, lemur groups are comprised of an unusually high number of males, leading to an even or slightly male-biased adult sex ratio. According to one hypothesis, females may benefit from these surplus males in their groups if males huddle with females. The results of this study on redfronted lemurs (Eulemur fulvus rufus) in Kirindy Forest, Madagascar revealed that the animals indeed responded to cold ambient temperatures by increased inactivity and the formation of huddling groups. However, surplus males did not participate more frequently than expected in huddling groups with females and females do not, therefore, benefit from the high number of males in their groups by increased social thermoregulation.
Age Factors Animals