Predator Vigilance Costs of Allogrooming in Wild Blue Monkeys

Abstract

AbstractAlthough allogrooming in Catarrhine primates is often interpreted as if it were a costly behavior for the groomer, such costs have not been convincingly documented. This paper presents data on rates of vigilance for aerial predators, measured as looking up toward the sky, in wild blue monkeys engaged in allogrooming, and compares these vigilance rates to those occurring when the same individuals engaged in other activities, namely feeding and resting. Grooming individuals have much lower vigilance rates than resting or feeding individuals, suggesting that grooming individuals are more likely to be at risk of being preyed upon. These results are not caused by a systematic relationship in the sample between activity and either foliage density or time of day, two factors potentially related to levels of safety from predation. Nor was there evidence that blue monkeys avoid the vigilance costs of grooming by engaging in this behavior primarily at safe times or in safe locations. Although the data suggest that vigilance costs occur, they may accrue to the recipient ofgrooming as well as the groomer, and may be compensated for both partners by long- or short-term benefits.