Wild female vervet monkeys change grooming patterns and partners when freed from feeding constraints

Abstract

Social animals face daily challenges to fulfil feeding, resting and social needs. In vervet monkeys, Chlorocebus pygerythrus , females are the core of the social group, in which relationships are mainly established and maintained through grooming. However, social relationships are not necessarily mutual or driven by the same interests. In a complex and diverse social environment, individuals may benefit from the ability to adapt their manoeuvring to different pressures. We experimentally manipulated the activity budget of two adult females (fed subjects) per group in four wild groups to investigate activity budgets, grooming behaviour variation and the implications for possible changes in social interactions. Specifically, we provisioned food to one fed subject at a time for 2 weeks (treatment), evaluated changes in their grooming behaviour before, during and after being fed, and compared their behaviour with that of the remaining adult females in the group (nonfed subjects) over the same period. In the provisioning phase, the fed subjects decreased feeding time, but increased resting and social time. We found that fed subjects increased their grooming strength and ratio of grooming given to received and showed preferences to groom existing partners, kin and adult females. Moreover, we found no carryover effect of provisioning on grooming strength after the treatment terminated. Our results demonstrate rapid social behaviour plasticity following manipulation of ecological conditions for specific female individuals, allowing for flexible shifts in grooming patterns that hint at Machiavellian-like adjustments that may help achieve social benefits through, at least partially, restructuring their social network when experimentally released from daily feeding obligations. • Grooming is a key behaviour for primates to keep social relationships. • With an experimental approach, we compare female vervet monkeys' grooming dynamics. • The fed subjects increased their grooming given compared to grooming received. • The fed subjects preferentially groomed bonded, kin and adult female individuals. • Vervet monkeys flexibly changed their grooming during and after the treatment.