Doctoral Dissertation Research: Positional Behavior and Limb Use in Cebus, Alouatta, and Ateles

University Of Arizona, Tucson AZ

Investigators

Abstract

Studies of positional behavior (locomotion and posture) are central to key issues in biological anthropology including primate origins and arboreal adaptations, hominoid climbing, and hominid bipedalism. The study of locomotion and posture provides critical information concerning ecological, anatomical and evolutionary relationships in living species, a comparative framework for interpretation of the fossil record, and as an educational tool for conservation and ecological planning. This research examines the ontogeny (the life history of an individual) of positional behavior and details of limb and prehensile-tail use in three New World primate species (Ateles geoffroyi, Alouatta palliata, and Cebus capucinus) inhabiting a tropical rainforest in Costa Rica. During the course of growth and development, individuals face different challenges in exploiting their environment. Ontogenetic data allow assessment of behavioral and morphological changes as they occur and developmental constraints on positional behavior among closely-related species. While ontogeny is critical to our understanding of positional behavior, there are no field studies that assess its effects on New World primates. White-faced capuchins (Cebus), black handed spider monkeys (Ateles), and mantled howling monkeys (Alouatta) will be examined at La Suerte Biological Research Station in Costa Rica. Behavioral observations in conjunction with digital video recording will be used to document positional strategies during infancy, juvenescence, and adulthood to address the following objectives. First, this research will provide a comprehensive, systematic, and quantified description of expressed behavior, functional morphology, and ecological context of three prehensile-tailed species. Second, data on juvenile and adult positional strategies will provide information on how growth and development may influence feeding and foraging strategy, social behavior, and ultimately survival during the juvenile period. Third, because the prehensile tail has evolved independently in the subfamily Atelinae (Alouatta, Ateles, Brachyteles, and Lagothrix) and Cebus, this study will allow comparison of the prehensile tail as a shared-derived feature in two more closely-related species (Ateles and Alouatta), and as an analogous feature in the more distantly- related Cebus. Closely-related howler and spider monkeys are biobehavioral variations on the ateline theme, that is, large-bodied, long-tailed New World primates with extensive gripping capabilities. Capuchin monkeys, also with prehensile abilities of the tail, differ in body size and tail anatomy (and evolutionary history). This project will contribute a comprehensive, systematic, and quantified description of expressed behavior and ecological context in three New World primates inhabiting the same rainforest. By focusing on questions of ontogenetic differences in positional behavior, this study examines the degree to which adult-like patterns of locomotion and posture develop in primate ontogeny and how patterns may differ within and between age and sex categories. Finally, the results of this research will be used in the conservation planning and maintenance of the rainforest surrounding La Suerte Biological Research Station. As part of these efforts, results will contribute to educational programs in the surrounding community and in the United States.