Department of Anthropology, Yale University

Saturday All day, Clinch Concourse

Prehensile tails have evolved independently in several arboreal mammalian lineages, yet our understanding of the behavioral impact of morphological differences in these analogous tail types remains unclear. To help address this uncertainty, I recorded segment-specific patterns of tail flexion and weight support in white-faced capuchins (Cebus capucinus) and mantled howler monkeys (Alouatta palliata), representative species of primate lineages with anatomically distinct prehensile tails. The caudal vertebrae of capuchins and howler monkeys differ in number, robusticity, muscular process shape and size, and articular surface curvature, while tail musculature differs in cross-sectional area sizing patterns. Sixteen and a half hours of behavioral data were collected on habituated capuchins and howler monkeys at the La Suerte Biological Research Station in northeastern Costa Rica using instantaneous focal animal sampling at one-minute intervals. I tested whether segments of the tail are used with differing degrees of flexion and weight support within species and whether the two species use the same segments in different ways. Behavioral observations indicate that howler monkeys have more flexibility in all tail segments, with particularly significant differences found in proximal segments. Though capuchins demonstrate less tail flexibility, they more frequently use proximal segments for weight support. Howler monkeys use distal segments to support weight more frequently and in greater amounts. These results corroborate documented morphological differences and address how capuchins and howler monkeys solve similar ecological problems in different ways. Linking such specific behaviors with morphology can provide valuable information for ecological interpretations of the fossil record.