Boldness towards novel objects predicts predator inspection in wild vervet monkeys

Abstract

Although the number of studies documenting animal personalities has increased over the last decade, ecological validations of animal personality traits remain relatively rare in the behavioural ecology literature. I examined whether wild vervet monkeys, Chlorocebus pygerythrus, were consistent in their responses to diverse novel objects, and tested whether experimentally assayed boldness predicted the number of times individuals were observed inspecting naturally occurring snakes at close range. Boldness was repeatable across three novel object tests, and boldness scores were correlated with the number of snake inspections. An additional novel object, a toy lizard, elicited antipredator behaviour and was reclassed as a potential predator stimulus; both novel object boldness and the number of snake inspections predicted approach of this item. Age–sex class differences in boldness and in predator approach and inspection were found to be highly consistent across these different contexts. Subadult males were bolder than adult females and had higher snake inspection counts. These age–sex differences fit well with expected variation in risk–reward ratios of exploratory risk-taking behaviour considered within a life history framework for this species. The results of this study provide a crucial ecological validation of using novel object tests to assay boldness in a wild primate.