Female-committed infanticide followed by juvenile-enacted cannibalism in wild white-faced capuchins.

On 5 February 2021, we observed the first instance of female-committed infanticide followed by cannibalism in a long-studied (> 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.

Infant cannibalism in wild white-faced capuchin monkeys.

Cannibalism has been observed in a variety of animal taxa; however, it is relatively uncommon in primates. Thus, we rely heavily on case reports of this behavior to advance our understanding of the contexts under which it occurs. Here, we report the first observation of cannibalism in a group of wild white-faced capuchin monkeys (Cebus imitator). The subject was a dead infant, estimated to be 10 days old, and the probable victim of infanticide. Consumption of the corpse was initiated by a 2-year-old male (second cousin of the infant), though it was eventually taken over and monopolized by the group's alpha female (grandaunt of the infant). Although most group members expressed interest in the corpse (sniffing, touching, and threatening it), no others made an attempt to consume it. Given that this is the only observation of cannibalism recorded in over 37 years of study on this population, we consider it to be a rare behavior in this species. This detailed record contributes new data, which, when combined with other reports within and across species and contexts, enables the evaluation of adaptive explanations of cannibalism.

Differential impact of severe drought on infant mortality in two sympatric neotropical primates.

Extreme climate events can have important consequences for the dynamics of natural populations, and severe droughts are predicted to become more common and intense due to climate change. We analysed infant mortality in relation to drought in two primate species (white-faced capuchins, Cebus capucinus imitator, and Geoffroy's spider monkeys, Ateles geoffroyi) in a tropical dry forest in northwestern Costa Rica. Our survival analyses combine several rare and valuable long-term datasets, including long-term primate life-history, landscape-scale fruit abundance, food-tree mortality, and climate conditions. Infant capuchins showed a threshold mortality response to drought, with exceptionally high mortality during a period of intense drought, but not during periods of moderate water shortage. By contrast, spider monkey females stopped reproducing during severe drought, and the mortality of infant spider monkeys peaked later during a period of low fruit abundance and high food-tree mortality linked to the drought. These divergent patterns implicate differing physiology, behaviour or associated factors in shaping species-specific drought responses. Our findings link predictions about the Earth's changing climate to environmental influences on primate mortality risk and thereby improve our understanding of how the increasing severity and frequency of droughts will affect the dynamics and conservation of wild primates.