On 5 February 2021, we observed the first instance of female-committed infanticide followed by cannibalism in a longstudied (> 35 years) population of wild white-faced capuchins (Cebus imitator) in the Santa Rosa Sector of the Área de Conservación Guanacaste, Costa Rica. The events leading up to and including the infanticide and cannibalism were observed and documented ad libitum, with segments digitally recorded, and a post-mortem necropsy performed. Here we detail our observations and evaluate the events within the framework of leading adaptive explanations. The infanticide may have been proximately motivated by resource competition or group instability. The circumstances of the observed infanticide provided support for the resource competition, adoption avoidance, and social status hypotheses of infanticide, but not for the exploitation hypothesis, as neither the perpetrator nor her kin consumed the deceased infant. The subsequent cannibalism was performed by juveniles who observed the infanticide and may have been stimulated by social facilitation and their prior experience of meat consumption as omnivores. To our knowledge, cannibalism has been documented only once before in C. imitator, in an adjacent study group, with the two cases sharing key similarities in the context of occurrence and manner of consumption. These observations add to our growing knowledge of the evolutionary significance of infanticide and its importance as a reproductive strategy in nonhuman primates.

In human-modified tropical landscapes, the survival of arboreal vertebrates, particularly primates, depends on their plant dietary diversity. Here, we assessed diversity in the vegetative diets of Costa Rican non-human primates (i.e. Alouatta palliata palliata, Ateles geoffroyi, Cebus imitator, and Saimiri oerstedii) inhabiting a range of habitat types. Specifically, we assessed: (i) richness and dietary plant diversity, (ii) the β-diversity of dietary plant species and the relative importance of species turnover and nestedness in contributing to these patterns, and (iii) the main ecological drivers of the observed patterns in dietary plant assemblages. Data on diet were available for 33 Alouatta, 15 Cebus, 8 Ateles, and 5 Saimiri groups, from 37 published and unpublished studies. Considering all studies, dietary plant species richness was highest in Alouatta (454 spp.), followed by Ateles (329 spp.), Cebus (237 spp.), and Saimiri (183 spp.). However, rarefaction curves indicated that the diversity of plant species in diet was higher in Ateles than in the other three primate species. The diversity of plants was 868 species (range=1664-2041 species). The three top food species were Spondias mombin, Bursera simaruba, and Samanea saman. Species turnover was the mechanism responsible for most of the dissimilarity in the plant assemblages in diet (Beta-sim = 0.76). Finally, primate species, habitat type and, to a lesser degree, sampling effort were the best predictors of the dietary plant assemblages. Our findings suggest that primate diets are diverse, even in severely-disturbed habitats.

In human-modified tropical landscapes, the survival of arboreal vertebrates, particularly primates, depends on their plant dietary diversity. Here, we assess the diversity of plants included in the diet of Costa Rican non-human primates, CR-NHP (i.e., Alouatta palliata palliata, Ateles geoffroyi, Cebus imitator, and Saimiri oerstedii) inhabiting different habitat types across the country. Specifically, we analyzed 37 published and unpublished datasets to assess: (i) richness and dietary α-plant diversity, (ii) the β-diversity of dietary plant species and the relative importance of plant species turnover and nestedness contributing to these patterns, and (iii) the main ecological drivers of the observed patterns in dietary plants. Dietary data were available for 34 Alouatta, 16 Cebus, eight Ateles, and five Saimiri groups. Overall dietary plant species richness was higher in Alouatta (476 spp.), followed by Ateles (329 spp.), Cebus (236 spp.), and Saimiri (183 spp.). However, rarefaction curves showed that α-diversity of plant species was higher in Ateles than in the other three primate species. The γ-diversity of plants was 868 species (95% C.I. = 829–907 species). The three most frequently reported food species for all CR-NHP were Spondias mombin, Bursera simaruba, and Samanea saman, and the most consumed plant parts were leaves, fruits, and flowers. In general, plant species turnover, rather than nestedness, explained the dissimilarity in plant diet diversity (βsim > 0.60) of CR-NHP. Finally, primate species, habitat type (life zone and disturbance level) and, to a lesser degree, study province, were the best predictors of the dietary plant assemblages. Our findings suggest that CR-NHP diets are diverse, even in severely disturbed habitats.

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