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Key Words
Cercopithecines Feeding behavior. Competition
Introduction
Cercopithecine monkeys are readily distinguished from all other primates by the presence of cheek pouches. Cheek pouches are bilateral sacculations found in the lower portion of the cheek wall; food moves between these pouches and the oral cavity through a slit-like opening [1, pers. observation]. It has been suggested [1-3] that a major selective pressure in the evolution of this anatomical feature comes from maximizing energy extraction in a context of both inter- and intraspecific feeding competition over limited resources. For example, both red-tail monkeys (Cercopithecus ascanius) and grey-cheeked mangabeys (Lophocebus albigena) in Kibale National Park, Uganda, are significantly more likely to use their cheek pouches in the presence of conspecifics and when feeding on clumped and high-quality resources such as fruit [3].
Wild cercopithecines have the capacity (at least potentially) to reduce feeding competition by increasing interindividual feeding distances or by switching to less contested food resources. This flexibility is not available to captive animals, however, whose foraging spheres are defined by their enclosure size and whose feeding options are limited to zoo diets. We predicted that these features of captivity might lead to increased reliance on cheek pouches for minimizing within-group contest competition and for thereby maintaining a high food harvest rate.
In this project, we evaluate patterns of cheek pouch use in captive adult baboons (Papio cynocephalus) and specifically address the following questions: (1) Under what circumstances are cheek pouches used by captive baboons? (2) Is there a subset of the social group that is more likely to use cheek pouches than others (e.g. males vs. females)? (3) How do these results compare with data from wild cercopithecines?
Methods
Observations of 48 captive P. cynocephalus were conducted at the Brookfield Zoo, Brookfield, Ill., USA, between June and September 1998. The baboons inhabit a multi-level, gunite grotto comprised of a complex of artificial rocks and measuring 57.3 x 42.7 m. Animals in the outdoor enclosure have access to an indoor holding area where they are fed each day at about 11.00 h. Animals in this colony are on birth control; there is...