LOCOMOTOR ECOLOGY OF LEPILEMUR-EDWARDSI AND AVAHI-OCCIDENTALIS

A well-known principle holds that where food supply is limited, two sy mpatric species with the same diet, morphology, and behavior will comp ete, leading to exclusion of one species or differentiation of their e cological niches. Avahi occidentalis and Lepilemur edwardsi are two sa ltatory, nocturnal folivorous lemurs of similar body size which live s ympatrically over much of their range and may often be seen feeding in the same trees. We report a study of their locomotor behavior, carrie d out in order to determine to what extent locomotion might contribute to niche separation. Avahi lives at a higher level in the forest and is the more committed leaper, with a much larger home range and nightl y travel distance, while Lepilemur climbs more and has a very small ni ghtly travel distance. Avahi uses small, low-angled supports more ofte n, while Lepilemur makes more use of large, high-angled supports (howe ver, neither species uses vertical supports at a frequency greater tha n the availability of such supports in the forest stratum in which the y Live). Both species tend to land on larger-diameter supports on long er leaps, but Avahi also takes off from larger-diameter supports in lo nger leaps, reducing loss of energy to the substrate during takeoff. W e suggest that the differences in locomotion and ranging behavior betw een them are consistent with niche differentiation on the basis of foo d quality, Avahi investing more energy in harvesting better quality bu t more patchy food, Lepilemur minimizing expenditure in harvesting a l ess selective, quantitatively poorer diet. (C) 1997 Wiley-Liss, Inc.