Cheek pouch use, predation risk, and feeding competition in blue monkeys (Cercopithecus mitis stuhlmanni)

Abstract

The adaptive function of cheek pouches in the primate subfamily Cercopithecinae remains unresolved. By analyzing the circumstances of cheek pouch use, we tested two hypotheses for the evolution of cercopithecine cheek pouches proposed in earlier studies: (1) cheek pouches reduce vulnerability to predation, and (2) cheek pouches increase feeding efficiency by reducing competition. We studied two groups of wild blue monkeys (Cercopithecus mitis stuhlmanni) in the Kakamega Forest, Kenya, conducting focal observations of feeding individuals. Monkeys were less exposed while emptying their cheek pouches than filling them, supporting the predation-avoidance hypothesis. We investigated several measures of competitive threat, but only one supported the competition-reduction hypothesis: when the nearest neighbor's rank increased, subjects were more likely to increase than to decrease cheek pouch use. Overall, our findings supported the predation-avoidance hypothesis more strongly than the competition-reduction hypothesis. We suggest that variation in cheek pouch use may reflect differing behavioral strategies used by cercopithecines to mitigate competition and predation, as well as factors such as resource size and distribution, home range size, and travel pat- Although cercopithecine monkeys are distinguished from other primates by the presence of cheek pouches in which they temporarily store and begin to digest food (Murray, 1975), the adaptive function of cheek pouches has not been conclusively determined. As Lambert (2005) noted recently, few studies have quantified cheek pouch use and related it systematically to environmental or social variables that might shed light on its adaptive function. Even fewer studies have been conducted on primates living in natural environments. We aimed to test two nonexclusive hypotheses about cheek pouch use suggested by earlier research, using detailed observations of the foraging behavior of wild blue monkeys (Cercopithecus mitis stuhlmanni). Cheek pouch use may (1) reduce vulnerability to predation by allowing quick acquisition of food and retreat to safer positions to process food, and/or (2) increase feeding efficiency by reducing intra and/or interspecific feeding competition. These hypotheses derive from the facts that primates forage gregariously and often in polyspecific associations (which can foster competition both within and between species) and that they are frequently vulnerable to predators while foraging (Murray, 1975;Lambert, 2005).Supporting the predation-avoidance hypothesis, Lambert (2005) reported that Cercopithecus ascanius and Lophocebus albigena in the Kibale National Park, Uganda, retreated to safer places after filling their cheek pouches. Furthermore, L. albigena lived in smaller groups (suggesting reduced within-group feeding competition), yet they used their cheek pouches more frequently than C. ascanius (Lambert, 2005). In a study of three wild guenon species (C. campbelli, C. petaurista, C. diana) in the Tai National Park, Côte d'Ivoire, Buzzard...

Sleeping site selection and presleep behavior in wild pigtailed macaques

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Terrestrial Foraging by Cacajao melanocephalus ouakary (Primates) in Amazonian Brazil: Is Choice of Seed Patch Size and Position Related to Predation Risk?

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Biogeographic Variation in the Diet and Behaviour of Cercopithecus mitis

“…mitis (referred to as samango monkeys, blue monkeys or Sykes' monkeys in different parts of their range) is a medium-sized (adult females ∼ 4.4 kg, adult males ∼ 7.6 kg [Harvey et al, 1987]), arboreal, diurnal guenon, which forms single-male multi-female groups with group sizes ranging from 4 to 65 [Butynski, 1990;Beeson et al, 1996;Smith et al, 2008;Houle et al, 2010;Lawes et al, 2013]. Home ranges have been reported as large as 253 ha [Butynski, 1990], but most groups tend to have ranges of less than 80 ha [Cords, 1986;Butynski, 1990;Lawes, 1991;Beeson et al, 1996;Kaplin et al, 1998;Fairgrieve and Muhumuza, 2003;Coleman, 2013;Tesfaye et al, 2013].…”