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Dietary niches have widespread effects on individuals life histories, behaviors, and morphologies. Capuchin monkeys inhabit a complex dietary niche that often entails hunting of relatively large vertebrate prey, tool-use, and extraction of embedded resources that other closely related and sympatric species do not exploit. In this dissertation I examine, a) how juvenile capuchins overcome the challenges of reliance on a difficult-to-acquire diet, b) at what age juveniles achieve maximum foraging return rates for difficult-to-acquire foods, and c) what nutritional benefits capuchins obtain from exploitation of these foods. In the process of addressing these questions I test two prominent hypotheses regarding reliance on a difficult-to-acquire diet. First, I test two predictions form the food scarcity/difficulty hypothesis which posits that species who rely more heavily on foods that are either rare or difficult to acquire should exhibit higher rates of food transfers, because juveniles in these species face greater foraging challenges. Second, I test two predictions from the ecological complexity hypothesis which proposes that species that rely on more difficult-to-acquire foods require longer juvenile periods, in order to learn the skills necessary to exploit these foods. Foraging return rates and rates of food transfers were calculated for individuals in three groups of wild capuchin monkeys inhabiting the Pacuare Nature Reserve in Costa Rica. Foraging return rates were measured in terms of bites ingested per forage time. In addition, food items were analyzed for nutritional content which enabled calculations of nutrient return rates. The major results include: 1) food transfer rates were highest in infants, and food items that were more difficult to acquire and had more nonstructural carbohydrates were transferred more frequently; 2) juvenile foraging strategies for difficult-to-acquire foods can be distinguished from adult strategies; 3) maximum foraging efficiency was not achieved until well into adulthood for difficult-to-acquire fruits. These findings support the food difficulty hypothesis regarding food transfers and the ecological complexity hypothesis regarding long juvenile periods. A final goal for this study was to evaluate the benefits of foraging for difficult-to-acquire foods. Results imply the most likely benefit accrued from difficult-to-acquire foods is as a source of fallback nutrients.'


primate, Cebus, capuchin, foraging, ecology, life history, feeding

Document Type




Degree Name


Level of Degree


Department Name

UNM Department of Anthropology

First Advisor

Lancaster, Jane

First Committee Member (Chair)

Kaplan, Hillard

Second Committee Member

Kodric-Brown, Astrid

Third Committee Member

Perry, Susan

Fourth Committee Member

Emery Thompson, Melissa

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Anthropology Commons