Search

Brown capuchin monkeys (Cebus apella apella) in Suriname forage on larvae enclosed within healthy bamboo stalks. We applied the searching versus handling dichotomy of optimal foraging models to highlight developmental processes contributing to foraging on embedded prey. Larvae acquisition begins with search; selecting an appropriate stalk and locating the embedded larvae; followed by handling, ripping the stalk open, and extracting the larvae. Although extraction behaviors were present at low rates in infant capuchins' repertoire, we found that the acquisition of adequate detection techniques was fully completed in subadults, aged around 6. Selecting appropriate foraging substrates, requiring accurate assessment of the physical properties of bamboo stalks, gradually increased with age and experience. We showed that both components of searching required extended practice beyond that required to master the handling components. We conclude that the developmental sequence of skill acquisition goes counter to the preceding logical sequence of foraging process and suggest that searching components present greater challenges than handling components in extractive foraging. Specifying the searching components of foraging more precisely will enhance understanding of species variation in the developmental schedule of foraging skills. Keywords: extractive foraging, searching and handling components, detection techniques, ontogeny, Cebus apella apella DOI: 10.1037/a0017723

In addition to being frugivorous, Cebus and Saimiri stand out among the New World primates of similar body size in being heavily dependent on animal matter for protein (faunivory). A detailed description of the morphology and behavior of the two genera is presented with the object of evaluating the interaction and respective contributions of morphological and behavioral adaptations to foraging patterns. Our conclusions include the following: First, body size is extremely important in explaining the observed variation in diet. Second, the emphasis on faunivory is facilitated more by behavioral than by morphological specialization. Third, whatever morphological specializations are present, particularly in Cebus, are probably favored by diet at the most food-depauperate time of year. Fourth, although morphology may well reveal what a primate may potentially eat, to map this potential onto actual diet requires a detailed knowledge of its natural ecosystem. Finally, we consider whether the behavioral data support the tenuous morphological evidence for grouping Cebus and Saimiri within the clade Cebinae.

Continuous focal recordings were collected of the vocalizations of 21 marked adult female squirrel monkeys, Saimiri oerstedi, in their natural Costa Rican habitat. Concurrent data were also obtained for each focal female on her foragng activity, distance from the nearest neighbouring adult female, spatial position within the troop, and ongoing troop activities and movements. A cumulative 18.6 h of continuous samples and 3080 sonagrams were analysed. Consistent with earlier studies, four major call types were identified: smooth chuck, bent mast chuck, peep and twitter. As the distance from the nearest adult female increased, the rate of vocalizations increased dramatically, the peep call disproportionately so. A rapid rate of vocalization, with an increased proportion of twitters and a decreased proportion of bent mast chucks, was strongly associated with the initiation of troop movement and with females in the vanguard of a moving troop. No direct relationship was found between foraging and vocal behaviour. Even the most narrowly defined call types were likely to be uttered in sequences. There was no evidence that sequential patterns of calls (syntax) differed across contexts.