AN ANALYSIS OF REGURGITATION AND REINGESTION IN CAPTIVE CHIMPANZEES

The abnormal behavioral. pattern of regurgitation and reingestion (R/R ) is poorly understood in chimpanzees (Pan troglodytes). This study as sesses R/R in 13 indoor-housed chimpanzees living in pairs and trios. Focal animal sampling data were used to calculate scores for R/R, two other classes of abnormal behavior (abnormal behaviors with oral compo nents and those without oral components), and affiliative social behav ior. R/R was observed in 85% of study subjects, an elevated proportion in comparison to a previously published survey of captive chimpanzee populations. Contexts and temporal patterns of R/R suggest that detect ion of this behavior may in many cases require observations outside of daily management routines. Social disturbances did not elicit this be havior. Statistical tests showed no relationship between individual di fferences in R/R rates and rates of other abnormal behavior classes, t ime engaged in affiliative behaviors, number of cagemates or housing h istory; nor were sex differences detected. Meal composition was not fo und to effect the time devoted to R/R. Statistical tests did show a st rong positive relationship between rates of R/R and elapsed time since feeding. These results suggest that increasing meal frequency or prov iding consistently available edible material may prove more broadly ef fective than altering meal composition. Temporal distributions of R/R differed from those of abnormal behaviors, suggesting that factors suc h as boredom, hunger or other sources of stress may differentially aff ect the expression of various classes of abnormal behavior.