Alarm calls of vervet monkeys
Lethbridge, Alta. : University of Lethbridge, Dept. of Psychology, 2014
I used observational data from natural encounters with predators and the controlled pre- sentation of aerial and terrestrial predator alarm calls to assess the hypothesis that these acoustically discernable calls trigger context- and predator-appropriate behaviour in free- ranging vervet monkeys (Chlorocebus pygerythrus). my results, from two study groups in South Africa, show that the modal natural and experimental response was not to initiate escape behaviour, either immediately or in the 10s following an alarm call, but to look at the sound source. When monkeys did take evasive action, which occurred no more fre- quently than doing nothing at all, contextually- inappropriate behaviour (i.e., behaviour that was not appropriate for evading the specific predator type) was as likely to occur as contextually-appropriate behaviour. I also found that the distance at which calls were heard was negatively correlated with the probability of some form of evasive action. I suggest that the large size of our groups, and the consequently greater mean distance at which natural calls were heard, may explain why our animals displayed low levels of active response and less predator-appropriate evasion or vigilance than expected, given previous work on this species (Seyfarth et al. 1980. Science, 210, 801-803). As the frequency and rapidity with which respondents looked towards the loudspeaker confirmed the general salience of the calls, I conclude that the broader social and ecological framework in which calls occur, rather than a simple contextually regular linkage between call types and specific predators, shapes animals responses to calls in this species.
Predator alarm calls , Vervet monkeys