Behaviour 2019
Age differences in the responses of vervet monkeys (Chlorocebus pygerythrus) to terrestrial alarm calls
Colin Dubreuil1, Louise Barrett2, Peter Henzi2, Mary S Pavelka1, Hugh Notman1,3. 1University of Calgary, Calgary, Alberta, Canada; 2University of Lethbridge, Lethbridge, Alberta, Canada; 3Athabasca University, Athabasca, Alberta, Canada

Alarm vocalizations are purported to elicit reliable, predator-specific behavioural responses in several prey species. Still, less is known about the effects of ontogeny on receiver response, specifically whether the age of callers or receivers influences response intensity. Here, we investigate how developmental changes affect the response of vervet monkeys (Chlorocebus pygerythrus) to their own terrestrial alarm calls. Using a playback design, we filmed the responses of subjects along an ordinal maturity scale to alarm calls produced by monkeys of different age/sex classes. We applied a mixed-effects ordered logistic regression model within a Bayesian framework to explore interactions between the age and sex of both callers and receivers on the intensity of receiver responses. Our analysis reveals that juvenile monkeys (< 2yrs) exhibit the strongest responses to both alarm calls, and control calls, regardless of the age or sex of the caller. The intensity of responses subsequently decreases with age. We suggest that alarm responses are mediated via affect mechanisms during ontogeny, through learned associations between specific call types and the urgency of a given event.