The lasting impact of social isolation: behavioral insights from former pet and entertainer chimpanzees in a sanctuary in Spain

Human fascination with chimpanzees has driven extensive research on the species, but also led to exploitation by private owners and entertainment industries. These animals often suffer species-specific inadequate conditions, which can result in the development and display of abnormal behaviors even after rescue. These behaviors highlight the importance for zoos and sanctuaries to actively prevent worsening the effects of previous inadequate treatment by providing apes with social and stimulating environments that support their recovery. We conducted a 2-month behavioral survey on two groups of former pet and entertainment chimpanzees (n = 10) at the Fundación MONA sanctuary in Spain. From 116 h of instantaneous scan observations, we documented individual abnormal behaviors (e.g., self-poking, overgrooming, self-scratching). We assessed the association between the occurrence of these behaviors and individuals' origin, early history, age at rescue, and pre-rescue social conditions. We found no significant difference in the frequency of abnormal behavior between pet and entertainer chimpanzees, and between individuals born in captivity versus in the wild. Moreover, we observed that the frequency of abnormal behaviors increased with age at rescue for previously isolated individuals, but the correlation disappeared for those socially housed pre-rescue. These findings suggest that early social isolation and a late age at rescue may impose long-term changes on chimpanzees' behavior, and they emphasize the importance of accounting for age at rescue and previous housing conditions in care management and rehabilitation procedures.