Social Organization of the Fat-Tailed Dwarf Lemur (Cheirogaleus Medius) in Northwestern Madagascar

Abstract

The strictly nocturnal dwarf lemurs (Cheirogaleus) are extraordinary among pri- mates in showing extensive torpor phases during the austral winter, which is thought to be an adaptation to seasonal variation in food availability. The Fat-tailed Dwarf Lemur (c. medius) is found throughout the west and south of Madagascar and enters torpor for six to eight months. Such a long period of dormancy may influence their social organization. A 20-month field study carried out at the Station Forestiure d' Ampijoroa revealed a monogamous social pattern for C. medius. Data from this study are presented on group composition, sleeping associations, and home range organization over two seasons in order to elucidate the basis of C. medius' unusual social organization. All studied groups contained one adult pair and their offspring from one or more birth seasons. Members of a group regularly sleep together, which might be an important means of social contact. In groups containing more than one offspring, brothers and sisters had the closest relationship. The adult pair remain together within the same home range for more than one season and pre- sumably for life. Subsequently, some hypotheses about when monogamy should evolve are discussed.