Vervet monkeys (Chlorocebus pygerythrus) produce alarm calls and anti-predator behaviors that are specific
to a threatening predator’s mode of attack. Upon hearing a leopard alarm, the monkeys will run up
trees where they are relatively safe. In contrast, eagle alarms prompt the monkeys to run under bushes
and snake alarms stimulate bipedal standing. Early researchers proposed that the meaning of each alarm
call is conveyed by observational learning. If this true then absence of the predator that elicits the alarm
call may lead to alteration or decay of the alarm’s meaning since there is no longer opportunity for observational
learning to occur. The present study tested this hypothesis by presenting alarm calls to a closely
related species of monkeys (Chlorocebus sabaeus) that have been isolated from their ancestral predators
for more than 350 years. The monkeys ran up trees in response to a leopard alarm, but not when the
same alarm was played backwards and not in response to a snake alarm. Snake alarms failed to reliably
elicit bipedal standing. These results suggest that the leopard alarm call conveys the same information to
Barbados green monkeys as West African green monkeys despite generations of isolation from leopards.