Impact of Predation Risk on the Behaviour of Propithecus Diadema Edwardsi in the Rain Forest of Madagascar

The main predators on large-bodied primates in rain forest are birds of prey and mammalian carnivores, which may require distinct strategies by prey for successful detection and defense. In the three dimensional rain forest environment with diminishing light at lower levels, downward visibility is difficult, and keen eyesight may not be as effective for detecting in-forest predators as soaring ones. It is therefore predicted that cryptic behaviours, where the problems of detection are shifted to the predator, may be used in these conditions. In Madagascar there is debate on whether extant eagles are a threat to the largest primate species, while there is mounting evidence that a mammalian carnivore, the fossa, impacts heavily on lemur populations. In a new approach to understanding the differential impact of raptor and carnivore hunting styles on lemur anti-predator behaviours, I analyzed ten years of behavioural data on Milne-Edwards' sifakas in the rain forest of Madagascar. I show that Propithecus diadema edwardsi responds to aerial predators by giving loud alarms calls with responsive avoidance behaviour, and by choosing daytime rest sites lower than feeding sites. In response to the mammal predator, Propithecus gave a distinct ground predator call, used higher nighttime sleep sites than daytime rest sites, and males were in most dangerous spatial positions during travel and feeding. The combination of protective travel order, high sleeping sites and small sleeping parties suggested behaviours against fossa predation. However, the dramatic 'alarm call and drop low in the canopy' response to birds of prey is an indication that avian predators are feared.