Regurgitation and reingestion in bonobos (Pan paniscus): Relationships between abnormal and social behavior

Abstract

Regurgitation and reingestion (R/R) is an abnormal behavior observed in great apes analogous to rumination syndrome in humans. A majority of the research on R/R in non-human primates has focused on gorillas and chimpanzees with little information relating to other species that also engage in this behavior. In addition, studies on R/R in non-human primates have primarily focused on diet with little information on other potential causes for this abnormal behavior. The purpose of the current study was to examine R/R in 14 bonobos (Pan paniscus) at two zoological institutions. This included examining the relationships between R/R and other bonobo behaviors as well as the effect of a change in social groupings on R/R. On average, bonobos engaged in R/R about 3.07% of the time and there were no significant differences found in relation to sex (P=0.190), rearing history (P=0.414) or age (rs=0.254, P=0.381). There was a positive correlation between R/R and aggressive behavior (rs=0.579, P<0.05) at one facility and negative correlation between R/R and affiliative behavior (rs=−0.643, P<0.05) at the other facility. In addition, R/R significantly reduced (rs=−0.895, P<0.01) for one group over time after removing two individuals from that group while holding all other factors constant. These results suggest that that R/R in bonobos could be related to social behavior. At this time, it is unclear if this is a causal relationship or merely a byproduct of two different relationships potentially correlating with stress.