Abstract One of the most prominent behavioural fea- tures 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 Ta 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 Camp- bell’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 mon- keys. These experiments provide further evidence that non-human primates have evolved the cognitive capacity to produce and respond to referential labels for external events. Keywords Alarm call · Predation · Semantic · Non-human primate · Communication · Animal cognition Introduction Vervet monkeys (Cercopithecus aethiops) are known to produce acoustically distinct alarm calls in response to leopards, eagles or snakes (Struhsaker 1967). Field play- back experiments demonstrated that these alarm calls were alone sufficient to elicit adaptive anti-predator re- sponses from recipients in the same way as the corre- sponding predator normally would (Seyfarth et al. 1980). When hearing recordings of conspecifics’ eagle alarm calls, for example, monkeys looked up into the sky, ap- parently searching for an eagle. Because the vervets’ alarm calls refer to external objects, similar to the way in which human words refer to external objects, they have been called semantic (Seyfarth et al. 1980; Seyfarth and Cheney 1992; but see Evans 1997). In the meantime, little research has been conducted on other simian alarm call systems. We do not know, therefore, whether the vervet alarm call behaviour, the associated mental capacities and the general theories about non-human primate communication that have been developed from the vervet behaviour are supported by data from other species. Recent work on wild Diana monkeys (C. diana) in Ta forest, Ivory Coast, however, suggests that communication about predator classes may be a common feature of primate alarm-calling behaviour. In this species, both males and females produce acousti- cally distinct alarm calls to crowned hawk eagles (Ste- phanoaetus coronatus) and leopards (Panthera pardus) two of their main predators (Zuberbühler et al. 1997). Further experiments suggested that Diana monkeys have a rather sophisticated understanding of the meaning of their own alarm calls. When primed with a playback of a K. Zuberbühler ( ✉ ) Max-Planck-Institute for Evolutionary Anthropology, Leipzig, Germany K. Zuberbühler Centre Suisse de Recherches Scientifiques, Abidjan, Ivory Coast Present address: K. Zuberbühler, School of Psychology, University of St Andrews, St Andrews, Fife, KY16 9JU, UK, e-mail: kz3@st-and.ac.uk, Tel. +44-1334-462080, Fax: +44-1334-463042 Klaus Zuberbühler Predator-specific alarm calls in Campbell’s monkeys, Cercopithecus campbelli Published in Behavioral Ecology and Sociobiology 50, No. 5, 414-422, 2001 which should be used for any reference to this work 1