Development of snake-directed antipredator behavior by wild white-faced capuchin monkeys: I. Snake-species discrimination.

Young animals are known to direct alarm calls at a wider range of species than adults. Our field study examined age-related differences in the snake-directed antipredator behavior of infant, juvenile, and adult white-faced capuchin monkeys (Cebus capucinus) in terms of alarm calling, looking behavior, and aggressive behavior. In the first experiment, we exposed infant and juvenile white-faced capuchins to realistic-looking inflatable models of their two snake predators, the boa constrictior (Boa constrictor) and neotropical rattlesnake (Crotalus durissus) and a white airplane as a novel control. In the second experiment, infants, juveniles, and adults were presented photographic models of a coiled boa constrictor, rattlesnake, indigo snake (Drymarchon corais), a noncapuchin predator, and a white snake-like model. We found that antipredator behavior changed during the immature stage. Infants as young as 4 months old were able to recognize snakes and display antipredator behavior, but engaged in less snake-model discrimination than juveniles. All age classes exhibited a lower response to the white snake-like model, indicating that the absence of color and snake-scale patterns affected snake recognition. Infants also showed a higher level of vigilance after snake-model detection as exhibited by a higher proportion of time spent looking and head cocking at the models. Aggressive antipredator behavior was found in all age classes, but was more prevalent in juveniles and adults than infants. This study adds to the knowledge of development of antipredator behavior in primates by showing that, although alarm calling behavior and predator recognition appear at a very young age in capuchins, snake-species discrimination does not become apparent until the juvenile stage.

Development of snake-directed antipredator behavior by wild white-faced capuchin monkeys: II. Influence of the social environment.

Young animals are known to direct alarm calls at a wider range of animals than adults. If social cues are safer and/or more reliable to use than asocial cues for learning about predators, then it is expected that the development of this behavior will be affected by the social environment. Our study examined the influence of the social environment on antipredator behavior in infant, juvenile, and adult wild white-faced capuchin monkeys (Cebus capucinus) at Lomas Barbudal Biological Reserve in Costa Rica during presentations of different species of model snakes and novel models. We examined (a) the alarm calling behavior of the focal animal when alone versus in the vicinity of conspecific alarm callers and (b) the latency of conspecifics to alarm call once the focal animal alarm called. Focal animals alarm called more when alone than after hearing a conspecific alarm call. No reliable differences were found in the latencies of conspecifics to alarm call based on age or model type. Conspecifics were more likely to alarm call when focal individuals alarm called at snake models than when they alarm called at novel models. Results indicate (a) that alarm calling may serve to attract others to the predator's location and (b) that learning about specific predators may begin with a generalized response to a wide variety of species, including some nonthreatening ones, that is winnowed down via Pavlovian conditioned inhibition into a response directed toward specific dangerous species. This study reveals that conspecifics play a role in the development of antipredator behavior in white-faced capuchins.