Cercopithecus diana

Abstract: West African Diana monkeys (Cercopithecus diana) and Campbell's monkeys (Cercopithecus campbelli) frequently form mixed-species associations. Males of both species produce acoustically distinct alarm calls to crowned eagles (Stephanoaetus coronalus) and leopards (Panthera pardus), two of their main predators. Field playback experiments were conducted to investigate whether Diana monkeys respond to Campbell's alarm calls and whether they understand the calls' semantic content. Diana monkeys responded to playback of Campbell's leopard or eagle alarm calls as though the original predator were present. In a second experiment, Diana monkeys were primed with either Campbell's eagle or leopard alarm calls and then subsequently probed with the vocalizations of a crowned eagle or a leopard. Results showed that monkeys used the semantic information conveyed by the Campbell's alarm calls to predict the presence of a predator. The data are consistent with the hypothesis that non-human primates are able to use acoustic signals of diverse origin as labels for underlying mental representations.

Abstract: One of the most prominent behavioural features of many forest primates are the loud calls given by the adult males. Early observational studies repeatedly postulated that these calls function in intragroup spacing or intergroup avoidance. More recent field experiments with Diana monkeys (Cercopithecus diana) of Tai Forest, Ivory Coast, have clearly shown that loud male calls function as predator alarm calls because calls reliably (1) label different predator classes and (2) convey semantic information about the predator type present. Here, I test the alarm call hypothesis another primate, the Campbell's monkey (C. campbelli). Like Diana monkeys, male Campbell's monkeys produce conspicuous loud calls to crowned hawk eagles (Stephanoaetus coronatus) and leopards (Panthera pardus), two of their main predators. Playback experiments showed that monkeys responded to the predator category represented by the different playback stimuli, regardless of whether they consisted of (1) vocalisations of the actual predators (crowned hawk eagle shrieks or leopard growls), (2) alarm calls to crowned hawk eagles or leopards given by other male Campbell's monkeys or (3) alarm calls to crowned hawk eagles or leopards given by sympatric male Diana monkeys. These experiments provide further evidence that non-human primates have evolved the cognitive capacity to produce and respond to referential labels for external events.

Abstract: Some mammals distinguish between and respond appropriately to the alarm calls of other mammal and bird species. However, the ability of birds to distinguish between mammal alarm calls has not been investigated. Diana monkeys (Cercopithecus diana) produce different alarm calls to two predators: crowned eagles (Stephanoaetus coronatus) and leopards (Panthera pardus). Yellow-casqued hornbills (Ceratogymna elata) are vulnerable to predation by crowned eagles but are not preyed on by leopards and might therefore be expected to respond to the Diana monkey eagle alarm call but not to the leopard alarm call. We compared responses of hornbills to playback of eagle shrieks, leopard growls, Diana monkey eagle alarm calls and Diana monkey leopard alarm calls and found that they distinguished appropriately between the two predator vocalizations as well as between the two Diana monkey alarm calls. We discuss possible mechanisms leading to these responses.