Lemurs have presented a puzzle to scientists trying to understand their social behavior, because they do not conform to the general social patterns found in most monkeys and apes. One of the possible explanations for this difference assumes that Madagascar (the home of modern lemur species) has fewer and less dangerous predators than other areas where primates live. Anecdotal studies have questioned this assumption, but there are few systematic data concerning predation on lemurs. This study of the behavioral and ecological interactions of lemurs and raptors in Ranomafana National Park, Madagascar is designed to provide information on 1) the specific ecological interactions between lemurs and diurnal birds of prey, and 2) anti-predator behaviors of lemurs in response to distinct predator species. The first question will be addressed by measuring the actual rate of mortality on lemurs imposed by the four largest diurnal birds of prey in Madagascar (Buteo brachypterus, Accipiter henstii, Polyboroides radiatus, Eutriorchis astur). Each of these raptors will be the focus of nest observations, prey remain collections, and radio-tracking studies designed to measure the number of lemurs killed by each raptor species, the area over which this mortality occurs, and the prey population size. In addition, two experiments will address the behavioral responses of lemurs to the existing predator guild. The first experiment involves predator vocalization play backs to three species of lemurs with varying body sizes: the diademed sifaka (Propithecus diadema edwardsi), the rufous lemur (Eulemur fulvus rufus), and the gentle lemur (Hapalemur griseus). The second experiment consists of exposing three independent groups of diademed sifakas to model avian and terrestrial predators. The analysis of both raptor and lemur data will provide a clear understanding of the ecological influence of raptor predation on lemurs as well as the behavioral responses of lemurs to predation risk.
