Threats from the past: Barbados green monkeys (Chlorocebus sabaeus) fear leopards after centuries of isolation

Ability to recognize and differentiate between predators and non-predators is a crucial component of successful anti-predator behavior. While there is evidence that both genetic and experiential mechanisms mediate anti-predator behaviors in various animal species, it is unknown to what extent each of these two mechanisms are utilized by the green monkey (Chlorocebus sabaeus). Green monkeys on the West Indies island of Barbados offer a unique opportunity to investigate the underpinnings of anti-predator behaviors in a species that has been isolated from ancestral predators for over 350 years. In the first experiment, monkeys in two free-ranging troops were presented with photographs of an ancestral predator (leopard, Panthera pardus) and a non-predator (African Buffalo, Syncerus caffer). Relative to non-predator stimuli, images of a leopard elicited less approach, more alarm calls, and more escape responses. Subsequent experiments were conducted to determine whether the monkeys were responding to a leopard-specific feature (spotted fur) or a general predator feature (forward facing eyes). The monkeys showed similar approach to images of an unfamiliar non-predator regardless of whether the image had forward facing predator eyes or side facing non-predator eyes. However, once near the images, the monkeys were less likely to reach for peanuts near the predator eyes than the non-predator eyes. The monkeys avoided an image of spotted leopard fur but approached the same image of fur when the dark spots had been removed. Taken together, the results suggest that green monkey anti-predator behavior is at least partially mediated by genetic factors.