IMPACT OF PREDATION RISK ON THE BEHAVIOR OF PROPITHECUS-DIADEMA-EWARDSI IN THE RAIN-FOREST OF MADAGASCAR

The main predators on large-bodied primates in rain forest are birds o f prey and mammalian carnivores, which may require distinct strategies by prey for successful detection and defense. In the three dimensiona l rain forest environment with diminishing light at lower levels, down ward visibility is difficult, and keen eyesight may not be as effectiv e for detecting in-forest predators as soaring ones. It is therefore p redicted that cryptic behaviours, where the problems of detection are shifted to the predator, may be used in these conditions. In Madagasca r there is debate on whether extant eagles are a threat to the largest primate species, while there is mounting evidence that a mammalian ca rnivore, the fossa, impacts heavily on lemur populations. In a new app roach to understanding the differential impact of raptor and carnivore hunting styles on lemur anti-predator behaviours, I analyzed ten year s of behavioural data on Milne-Edwards' sifakas in the rain forest of Madagascar. I show that Propithecus diadema edwardsi responds to aeria l predators by giving loud alarms calls with responsive avoidance beha viour, and by choosing daytime rest sites lower than feeding sites. In response to the mammal predator, Propithecus gave a distinct ground p redator call, used higher nighttime sleep sites than daytime rest site s, and males were in most dangerous spatial positions during travel an d feeding. The combination of protective travel order, high sleeping s ites and small sleeping parties suggested behaviours against fossa pre dation. However, the dramatic 'alarm call and drop low in the canopy' response to birds of prey is an indication that avian predators are fe ared.