Exploration of potential triggers for self-directed behaviours and regurgitation and reingestion in zoo-housed chimpanzees

•Self-scratching and yawning are considered indicators of anxiety in primates.•Yawning was more likely in zoo-housed chimpanzees during longer inter-feed intervals.•Regurgitation and Reingestion (R/R) is an abnormal behaviour in captive chimpanzees.•We found no immediate dietary, visitor or social triggers for R/R.•R/R did not spread to naïve individuals despite chances to regularly observe R/R.