Do chemical cues in the venom of slow lorises repel avian predators?

Abstract

Raptors are confirmed predators of Asian slow lorises (Nycticebus spp.), the only primates with a toxic bite. A possible function of this venom is to protect against predators. Slow lorises release volatile chemicals when threatened, thus potentially communicating their venomous status towards predators. Crested Serpent-eagles (Spilornis cheela) and Changeable Hawk-eagles (Nisaetus cirrhatus) are known to prey on venomous snakes and small mammals and are potential predators of slow lorises. We tested the anti-predator potential of slow loris venom by presenting pieces of chicken combined with swabs of Greater Slow Loris (Nycticebus coucang) venom to 10 Changeable Hawk-eagles and 5 Crested Serpent-eagles. The eagles showed few behavioural responses in reaction to slow loris venom, examining swabs with venom or control scents equally. Both eagle species did show higher rates of face-rubbing behaviour following consumption of foods paired with venom compared with control scents. Our data suggest that slow loris venom does not function to repel avian predators, but may have an anti-predator defence function. While the eagles are not repelled by the smell of slow lorises, contact with their venom causes discomfort, potentially limiting the palatability of slow lorises to eagles.