The behavioral ecology of Hapalemur griseus griseus : the influences of microhabitat and population density on this small-bodied prosimian folivore
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In this study I analyzed the effects of microhabitat (botanical structure and composition within the home range) on the behavioral ecology of a small-bodied folivorous lemur, Hapalemur griseus. I found that despite being a bamboo specialist, this species is flexible in its diet, activity, and ranging patterns. I followed three groups of H. griseus for one year (Jul. 1998-Aug. 1999) at two sites within Ranomafana National Park, in southeastern Madagascar. The two sites differed in altitude, degree of habitat disturbance, and lemur species composition. The two sites also differed in population density, with Talatakely (Tala), the more disturbed and lower altitude site, having a population density nearly three times that of Vatoharanana (Vato). I found not only site differences in botanical structure and composition, but differences between the home ranges within site as well. These differences impacted the diets of each group, which differed on an annual and seasonal basis. Diet was most influenced by the resources available within the home range, as each group focused feeding on more abundant species. All groups ate large amounts of bamboo, but leaves of Ficus spp., fig and guava fruit, mushrooms, and dirt also played a large role in the diet of this species. All groups of H. griseus supplemented their mostly bamboo diet with new and mature leaves and fruit during the rainy season, birth, lactation, and weaning. Increased dietary diversity during reproduction may help female H. griseus combat their high metabolic needs, provide infant H. griseus with better weaning foods, and help male and female adult H. griseus to prepare for the upcoming mating season. The diet of the group followed at Tala also differed from other H. griseus groups at the same site. Despite differences in the diet of the three groups, annual and seasonal activity budgets did not differ. The correlation between feeding, resting, and traveling differed for each group. Although home range size did not differ significantly between the three groups, the home ranges of one Vato and one Tala group differed by 43%. Daily path length, as measured by GPS readings, differed significantly between the three groups, with the largest group having the longest mean daily path length. The three study groups were different in size, social structure, and social organization: one group was monogamous, the other two were polygynous. Regardless of group size, females were dominant to males. Both male and female H. griseus migrate from their natal groups, but it appears that females may leave at an earlier age than males. The group composition of the two Vato groups was fairly stable throughout the study, whereas the Tala group, the largest of the three, had two immigrations and three confirmed emigration events. Infant mortality varied between the three groups from 0-100%. This study shows that this bamboo specialist is flexible in diet, activity, ranging patterns, and social structure and organization. Each aspect of this species’ behavioral ecology is adapted to suit the home range used and the resources available therein.