GROUP ENCOUNTERS AND TERRITORIALITY IN WILD ALAOTRAN GENTLE LEMURS (HAPALEMUR GRISEUS ALAOTRENSIS)

During a 3 month field study, 18 group encounters between four groups of Alaotran gentle lemurs (Hapalemur griseus alaotrensis) were observe d in the Lake Alaotra marshland in Madagascar. Behaviors observed duri ng group encounters are described, and quantitative data on intergroup interactions and ranging patterns are discussed in the context of ter ritoriality. Intergroup interactions varied in their intensity, rangin g from visual monitoring, scent marking, and display locomotion to pen etrating the neighboring range. A quarter (27%) of the encounters were aggressive, involving chases and confrontation displays, and no affil iative interactions were observed. Both adult males and females were i nvolved in intergroup encounters, with males playing more active roles . All encounters took place in the small overlapping areas of neighbor ing home ranges. The outcome of an aggressive encounter was determined by its location, with the resident group always driving out the intru ding one. The Alaotran gentle lemur actively advertised and consistent ly defended a large area of its home range against intrusion of neighb oring groups and can therefore be considered territorial. Am. J. Prima tol. 46:251-258, 1998. (C) 1998 Wiley-Liss, Inc.