The ontogeny of foraging skills in wild brown capuchins (Cebus apella)
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Extractive foraging refers to the complex food-searching patterns needed to forage on foods that are difficult to locate and obtain, such as invertebrates encased in protective matrices. The study of extractive foraging emphasizes the selective impact of dealing with embedded foods for the evolution of slower development since prolonged immaturity may provide additional learning time to develop adult-level foraging skills. This research aims to understand the complementary contribution of physical maturation and experiential factors to the ontogeny of an extractive foraging behavior in wild brown capuchins (Cebus apella) in Raleighvallen, Central Suriname Nature Preserve: foraging for larvae hidden inside bamboo stalks. I partitioned the processes of foraging for embedded invertebrates into 1) handling components leading to the extraction and consumption of larvae after ripping bamboo stalks apart (Chapter 2), and 2) searching components via specific detection techniques to locate hidden larvae (Chapter 3). I found that the former is mainly explained by age-related morphological changes in size, weight, and dentition, whereas the latter is more dependent upon individual behavioral practice and socially-biased learning allowing immature individuals to gain experience at locating and extracting hard-to-process foods. In Chapter 2, I found that developing proficiency at obtaining encased larvae extends through several years of juvenescence. Supportive conditions include morphological changes and indirect social influence through foraging artefacts left in the habitat by conspecifics. Chapter 3 shows that young capuchins become efficient foragers through the progressive disappearance of ineffective food-searching behaviors, and the gradual emergence of effective detection techniques applied to appropriate foraging substrates (bamboo stalks likely to contain larvae), which is not fully mastered before the age of six years. This is consistent with the “perception-action” perspective on the development of foraging competence. The behavioral complexities involved in the detection techniques used for locating hidden foods develop over several years of juvenescence and fit the “needing-to-learn” hypothesis. I addressed these issues from a comparative perspective among primates, as a way to provide an evolutionary view on interspecific similarities and differences in the acquisition of complex foraging competence in various primate species.