Abstract
Avoiding biological contaminants is a well-known manifestation of the adaptive system of disgust. In theory, animals evolved with such a system to prevent pathogen and parasite infection. Bodily products are human-universal disgust elicitors, but whether they also elicit avoidance behaviour in non-human primates has yet to be tested. Here, we report experimental evidence that potential exposure to biological contaminants (faeces, blood, semen), as perceived via multiple sensory modalities (visual, olfactory, tactile), might influence feeding decisions in chimpanzees (Pan troglodytes troglodytes)—our closest phylogenetic relatives. Although somewhat mixed, our results do show increased latencies to feed, tendencies to maintain greater distances from contaminants and/or outright refusals to consume food in test versus control conditions. Overall, these findings are consistent with the parasite avoidance theory of disgust, although the presence of biological contaminants did not preclude feeding entirely. The avoidance behaviours observed hint at the origins of disgust in humans, and further comparative research is now needed.
Highlights
Many major infectious diseases are transmitted via contact or ingestion of particles of bodily products such as faeces, blood, semen and saliva
In the first set of experiments, 20 chimpanzees at the Centre International de Recherches Médicales de Franceville (CIRMF) in southern Gabon were given access to bananas placed atop different substrates
Subjects did select the banana atop the control foam (GLMM, p = 0.029; figure 2, table 1) and the pink faeces replica (GLMM, p = 0.049; figure 2, table 1) first significantly more often than the banana atop the brown faeces replica, which they tended to consume last
Summary
Many major infectious diseases (e.g. infectious intestinal diseases, herpes, hepatitis) are transmitted via contact or ingestion of particles of bodily products such as faeces, blood, semen and saliva. Reported observations of potential infection risk avoidance behaviours include chimpanzees using leaves to wipe body parts soiled with faeces, sticky food, blood, urine, mud and semen [26,27], and Japanese macaques washing food with sea and fresh water [28,29]. Such examples provide the first insights into contaminant-avoidance behaviours in non-human primates, but studies experimentally testing contaminant avoidance are needed to deepen our understanding of the behavioural immune system in our closest phylogenetic relatives. We predicted that individuals would be more cautious regarding food associated with contaminant-like stimuli compared to control stimuli, manifest as lower probabilities to feed and higher avoidance of contaminated areas
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
