One commonly used method of managing confiscated wild primates in Latin American countries is to release rehabilitated individuals back to their natural habitats. However, little information has been collected from confiscated animal releases, so no clear guidelines have been developed to measure the success of this type of procedure. In most countries, the collection of critical post-release data is too costly and time-consuming for it to be incorporated into the routine procedures of institutions managing confiscated fauna. Therefore, this project was carried out in conditions similar to those of other Colombian and Latin American rehabilitation centres. A group of eight confiscated and rehabilitated brown capuchin monkeys (Cebus apella) was released in Los Llanos Orientales in Colombia, and monitored for 6.5 months to determine their adaptation and survival after release. Results were analysed according to how the animals adapted to their new environment in terms of foraging, feeding, locomotion, sleeping, social interactions between the group and with other animals and species, prédation, orientation, and establishment of a territory. The results show that the short-term adaptation and survival of the group 6.5 months after release was successful. Five of the eight animals remained together, two separated, and only one was lost during the first month. Implications for animal well-being are discussed.

Rod bipolar cells in Cebus apella monkey retina were identified by an antibody against the alpha isoform of protein kinase C (PKCα), which has been shown to selectively identify rod bipolars in two other primates and various mammals. Vertical sections were used to confirm the identity of these cells by their characteristic morphology of dendrites and axons. Their topographic distribution was assessed in horizontal sections; counts taken along the dorsal, ventral, nasal, and temporal quadrants. The density of rod bipolar cells increased from 500 to 2900 cells/mm2 at 1 mm from the fovea to reach a peak of 10,000–12,000 cells/mm2 at 4 mm, approximately 5 deg of eccentricity, and then gradually decreased toward retinal periphery to values of 5000 cells/mm2 or less. Rod to rod bipolar density ratio remained between 10 and 20 across most of the retinal extension. The number of rod bipolar cells per retina was 6,360,000 ± 387,433 (mean ± s.d., n = 6). The anti-PKCα antibody has shown to be a good marker of rod bipolar cells of Cebus, and the cell distribution is similar to that described for other primates. In spite of the difference in the central retina, the density variation of rod bipolar cells in the Cebus and Macaca as well as the convergence from rod to rod bipolar cells are generally similar, suggesting that both retinae stabilize similar sensitivity (as measured by rod density) and convergence.

The diet of capuchin monkeys, Cebus apella, in a 250 ha semideciduous forest in south-east Brazil was studied for 44 consecutive months. Based on 367 feeding bouts the diet of capuchins was 53.9% fruit pulp, 16.0% seeds, 11.1% flowers, 6.3% leaves and new shoots, 1.5% roots and 13.9% corn from plantations surrounding the forest. Seventy-one plant species were consumed by capuchins. Food availability was markedly seasonal. During the dry season the fleshy fruit availability decreased, and at that time the capuchins became seed predators and flowereaters. Several fruits eaten by capuchins in the dry season were not consumed by other frugivorous vertebrates, such as howler monkeys, parrots or squirrels, allowing capuchins to avoid competition with other arboreal frugivores. In semideciduous forests where fleshy fruits are less abundant than in the wet forests capuchins are important seed predators.

Male Cebus monkeys are all dichromats, but about two thirds of the females are trichromats. M and P retinal ganglion cells were studied in the male Cebus monkey to investigate the relationship of their morphology to retinal eccentricity. Retinal ganglion cells were retrogradely labeled after optic nerve deposits of biocytin to reveal their entire dendritic tree. Cebus M and P ganglion cell morphology revealed by biocytin retrograde filling is similar to that described for macaque and human M and P ganglion cells obtained by in vitro intracellular injection of HRP and neurobiotin. We measured 264 and 441 M and P ganglion cells, respectively. M ganglion cells have larger dendritic field and cell body size than P ganglion cells at any comparable temporal or nasal eccentricity. Dendritic trees of both M and P ganglion cells are smaller in the nasal than in the temporal region at eccentricities greater than 5 mm and 2 mm for M and P ganglion cells, respectively. The depth of terminal dendrites allows identification of both inner and outer subclasses of M and P ganglion cells. The difference in dendritic tree size between inner and outer cells is small or absent. Comparison between Cebus and Macaca shows that M and P ganglion cells have similar sizes in the central retinal region. The results support the view that M and P pathways are similarly organized in diurnal dichromat and trichromat primates.