The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Spatial position in feeding trees and its relationship to nutritional quality in wild howler monkeys (Aloutta palliata)


1Anthropology, Rutgers, the State University of New Jersey, 2Anthropology, Hunter College of the City University of New York

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Howler monkeys are the most folivorous primates of the New World. To process the large volume of leaves, they have developed a suite of behavioral adaptations to aid in digestion. Many studies have shown that howlers are selective in the types of leaves and species of trees from which they feed. Recent studies suggest that the nutritional quality of leaf parts vary according to the section of the tree crown they occupy, with the upper and terminal sections containing the highest quality resources. We tested the hypothesis that mantled howler monkeys (Aloutta palliata) position themselves within high quality sections of the tree crown, so as to forage on more nutritious leaves, while expending little energy. Data were collected at La Suerte Biological Field Station in northeastern Costa Rica in July, 2012, using continuous focal animal sampling and recording behavior and position of individuals in the tree crown. Howler monkeys spent 65% of their total resting time and 84% of their total feeding time in the upper-terminal sections of the tree crown. Thus, it appears individuals exhibit preferential placement in high quality sections of the tree crown. However, this correlation is greater during feeding bouts and other variables may contribute to their selection of position within the tree crown while resting. These findings, combined with planned nutritional analyses of leaves in different parts of the canopy, indicate possible complexities, not only in the foraging strategies of the genus Alouatta, but also perhaps in the foraging of all folivorous, arboreal mammals.

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