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Efficient detection and selection of reddish fruits against green foliage has long been thought to be a major selective pressure favoring the evolution of primate trichromatic color vision. This has recently been questioned by studies of free-ranging primates that fail to show predicted differences in foraging efficiency between dichromats and trichromats. In the present study, we use a unique approach to evaluate the adaptive significance of trichromacy for fruit detection by undertaking a functional substitution model. The color vision phenotypes of neotropical monkeys are simulated for human observers, who use a touch-sensitive computer interface to search for monkey food items in digital images taken under natural conditions. We find an advantage to trichromatic phenotypes - especially the variant with the most spectrally separated visual pigments - for red, yellow and greenish fruits, but not for dark (purple or black) fruits. These results indicate that trichromat advantage is task-specific, and that shape, size and achromatic contrast variation between ripe and unripe fruits cannot completely mitigate the advantage of color vision. Similarities in fruit foraging performance between primates with different phenotypes in the wild likely reflect the behavioral flexibility of dichromats in overcoming a chromatic disadvantage., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The frequency of anointing bouts and the materials used for self- and social anointing vary across capuchin species in captivity, but there is little published data on capuchin anointing in the wild. Here we present previously unpublished data on anointing behaviors from capuchin monkey populations at ten different field sites and incorporate these data into a review of the anointing literature for captive and wild capuchins. Using a comparative phylogenetic framework, we test four hypotheses derived primarily from captive literature for variation in anointing between wild untufted capuchins (Cebus) and tufted capuchins (Sapajus), including that (1) the frequency of anointing is higher in Cebus, (2) Cebus uses a higher proportion of plant species to insect species for anointing compared with Sapajus, (3) anointing material diversity is higher in Cebus, and (4) social indices of anointing are higher in Cebus. We found that wild Cebus anoints more with plant parts, including fruits, whereas wild Sapajus anoints more with ants and other arthropods. Cebus capucinus in particular uses more plant species per site for anointing compared with other capuchins and may specialize in anointing as an activity independent from foraging, whereas most other capuchin species tend to eat the substances they use for anointing. In agreement with captive studies, we found evidence that wild Cebus anoints at a significantly higher frequency than Sapajus. However, contrary to the captive literature, we found no difference in the range of sociality for anointing between Cebus and Sapajus in the wild. We review anointing in the context of other Neotropical primate rubbing behaviors and consider the evidence for anointing as self-medication; as a mechanism for enhanced sociality; and as a behavioral response to chemical stimuli., (© 2011 Wiley Periodicals, Inc.)

We report on the responses of Cebus capucinus in the Santa Rosa Sector of the Area de Conservación Guanacaste, Costa Rica, to the presence of observers over a 4-week period. Study groups were habituated to different degrees: (1) Cerco de Piedra (CP): continuous observations began in 1984; (2) Exclosure (EX): focus of an 18-month study on males from 1998 to 1999; and (3) NBH: never studied/followed but the group frequently encounters researchers. We collected three types of data: group scans (group state was coded as calm or agitated at observer presence), focal animal data (observer-directed behaviors were recorded), and fecal cortisol levels. The two less-habituated groups (NBH and EX) differed significantly from the habituated group (CP) in their behavioral and cortisol responses, and they showed an increase in habituation over the study period (agitation and cortisol levels both dropped). Individuals in NBH also decreased their responses to observers during focal follows; however, at the end of the study the responses of the two less-habituated groups (NBH and EX) remained elevated in comparison to the habituated group (CP), suggesting the need for further habituation. Unlike capuchin groups that rarely encounter humans, NBH and EX never fled from observers and they rarely emitted observer-directed alarm calls. We suggest that the permanence of habituation and the ability to habituate animals passively through a neutral human presence are both important considerations for researchers conducting studies in areas where animal safety from poachers, etc. cannot be guaranteed., (© 2007 Wiley-Liss, Inc.)