Urbanization does not increase ‘object curiosity’ in vervet monkeys, but semi-urban individuals selectively explore food related anthropogenic items

Abstract

Urban environments expose animals to abundant anthropogenic materials and foods that facilitate foraging innovations in species with opportunistic diets and high behavioural flexibility. Neophilia and exploration tendency are believed to be important behavioural traits for animals thriving in urban environments. Vervet monkeys (Chlorocebus pygerythrus) are one of few primate species that have successfully adapted to urban environments, thus making them an ideal species to study these traits. Using a within-species cross-habitat approach, we compared neophilia and exploration of novel objects (jointly referred to as ‘object curiosity’) between semi-urban, wild, and captive monkeys to shed light on the cognitive traits facilitating urban living. To measure ‘object curiosity’, we exposed monkeys to various types of novel stimuli and compared their approaches and explorative behaviour. Our results revealed differences in the number of approaches and explorative behaviour towards novel stimuli between the habitat types considered. Captive vervet monkeys were significantly more explorative than both semi- urban and wild troops, suggesting that positive experiences with humans and lack of predation, rather than exposure to human materials per se, influence object curiosity. Across habitats, juvenile males were the most explorative age-sex class. This is likely due to males being the dispersing sex and juveniles being more motivated to learn about their environment. Additionally, we found that items potentially associated with human food, elicited stronger explorative responses in semi-urban monkeys than non-food related objects, suggesting that their motivation to explore might be driven by “anthrophilia” i.e., their experience of rewarding foraging on similar anthropogenic food sources. We conclude that varying levels of exposure to humans, predation and pre-exposure to human food packaging explain variation in ‘object curiosity’ in our sample of vervet monkeys.