The assessment by vervet monkeys of their own and another species' alarm calls

Abstract

In Amboseli National Park, Kenya, both superb starlings, Spreo superbus, and vervet monkeys, Cercopithecus aethiops, give acoustically different alarm calls to different classes of predators. The ‘raptor alarms’ of starlings and vervet monkeys are so called because they are given exclusively to avian species that attack from the air. In contrast, while vervets give ‘leopard alarms’ to a narrow array of terrestrial predators, starlings give terrestrial predator alarms to a wide variety of species, including some birds. Habituation experiments demonstrate that monkeys compare vocalizations according to their referents, not just their acoustic properties: vervets who learned to ignore playback of a starling's raptor alarm subsequently also ignored playback of a vervet's eagle alarm. Experiments also demonstrate that vervets are sensitive to the breadth of referential specificity exhibited by different calls. Subjects who learned to ignore playback of a starling terrestrial predator alarm subsequently also ignored playback of both vervet leopard and vervet raptor alarms.