Abstract # 240:

Scheduled for Monday, September 19, 2011 03:15 PM-03:30 PM: Session 34 (Salon F (Sixth Floor)) Oral Presentation


AGE OF ACHIEVEMENT OF MAXIMUM FORAGING RETURN RATES IN WILD CAPUCHIN MONKEYS (CEBUS CAPUCINUS): A TEST OF THE ECOLOGICAL COMPLEXITY MODEL FOR LONG JUVENILE PERIODS

E. C. Eadie
University of New Mexico, Department of Anthropology, Albuquerque, New Mexico 87131, USA
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The determining factors leading to the evolution of long juvenile periods remain unclear. One hypothesis is that of ecological complexity, it posits that— organisms relying on difficult-to-acquire diets need added time to attain skills in juvenescence. To test this hypothesis I studied foraging return rates in a primate known for long juvenile periods—capuchin monkeys. If capuchins evolved a prolonged juvenile period to learn foraging skills, return rates for difficult-to-acquire foods should not be maximized until near the end of this period. Returns maximized earlier would indicate that a long juvenile period evolved for an alternative reason. Foods were assigned strength and skill difficulty levels based on force and number of manipulations necessary for foraging. Food samples were analyzed for nutrient content. Five minute focal follows (n=917) were conducted on three groups (27 adults; 20 juveniles) of capuchins at the Pacuare Reserve in Costa Rica. The time took to find, harvest, and process food items, and the quantity obtained, were recorded. Return rates (nutrients ingested/foraging time) for difficult foods were significantly higher for older juveniles, for foods that required strength, but not for foods that required skill alone [ANOVA: alpha=0.05]. The implication is that capuchins do not need the entire juvenile period to learn foraging skills (the ecological complexity hypothesis was not supported), but do need it to develop physical strength to harvest foods effectively.