Assessing morphological preservation of gastrointestinal parasites from fecal samples of wild capuchin monkeys (Cebus imitator) stored in ethanol versus formalin.

The copromicroscopic identification of gastrointestinal parasites is a common, cost-effective method vital to understanding host-parasite interactions. However, its efficacy depends on effective preservation of the samples. In this study, we compare the preservation of ethanol and formalin preserved gastrointestinal parasites collected from a wild population of Costa Rican capuchin monkeys (Cebus imitator). Fecal samples were collected, halved, and stored in either 10% formalin or 96% ethanol at ambient temperature, then microscopically screened for the presence of parasites. Parasites were morphologically identified and rated based on their preservation using a newly developed rubric. We identified more parasitic morphotypes in formalin-preserved samples but found no difference in the number of parasites per fecal gram (PFG) between mediums. There was no difference in the PFG of two most prevalent parasite morphotypes, Filariopsis barretoi larvae and Strongyle-type eggs, and while Filariopsis larvae were better preserved in formalin, strongyle eggs showed no preservation difference between mediums. Our results support the suitability of both ethanol and formalin for morphological parasite identification in samples stored over 1 year, describe the morphological changes and challenges associated with parasite degradation, and highlight the potential for future studies to use both morphological and molecular methods in non-invasively collected samples.

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.