Cooperative rescue and predator fatality involving a group-living strepsirrhine, Coquerel's sifaka (Propithecus coquereli), and a Madagascar ground boa (Acrantophis madagascariensis).

The interactions between primates and their snake predators are of interest because snakes have influenced the evolution of primate visual systems and predation has driven the evolution of primate behaviour, including group living. However, there are few accounts of primate-snake interactions in the wild. We report an incident from Northwest Madagascar in which a large female Madagascar ground boa (Acrantophis madagascariensis) captured an adult female Coquerel's sifaka (Propithecus coquereli); upon capture, the prey's group members proceeded to bite and scratch the snake until it released the prey, which survived. However, a broken mandible suffered by the boa during the incident led to its death by starvation 2 months later. Our observations demonstrate that, in addition to improved predator detection and deterrence (i.e., mobbing), active defence against some predators may provide an additional benefit to group living in Coquerel's sifaka, and suggest that predation on group-living primates may be more costly for predators than attacking a solitary species of similar body size.