Adaptation and Phylogenetic Constraints in the Antipredator Behavior of Ringtailed and Ruffed Lemurs

The antipredator responses of forest-living ringtailed (Lemur cafta) and ruffed (Varecia variegata) lemurs were documented over a three-year period at the Duke University Primate Center (DUPC, Durham, NC, USA). Vocal and nonvocal responses to naturally-occurring and simulated predators are described, and their functions are considered with respect to species-specific differences in body size, ecology, and reproductive biology. Nonvocal responses of the two lemur species differed most conspicuously in propensity of predator-directed aggression: whereas ringtailed lemurs generally evaded predators, ruffed lemurs were likely to confront or attack them. Interspecific variation in vocal responses to predators included differences in call diversity, stimulus specificity, and function. Ringtailed lemur antipredator behavior (including large group size) is viewed as an adaptation to nontrivial levels of predator pressure that stem from being a relatively small-bodied, semi-terrestrial primate living in an open habitat. In contrast, the highly aggressive antipredator behavior of the ruffed lemur is seen in part as an effect of a somewhat larger body size, but also as a constraint of producing sessile offspring that do not cling to the mother. Thus, in contrast to ringtailed lemurs, ruffed lemurs with infants cannot flee predators without risking their reproductive success.