Monitoring Welfare in Captive Chimpanzees (Pan Troglodytes) Using Individual Positional Behavior and Substrate Use Profiles

Abstract

The welfare of captive chimpanzees partly depends on the structural features present in their enclosure. An individual’s manner of expressing positional behaviors depends on these environmental characteristics and may be reflective of their physical and mental health. This thesis seeks to further the scientific understanding of the relationships between positional behavior, substrate use and captive chimpanzee welfare. In pursuit of this goal, I designed and installed a novel vertical climbing aid onto a climbable platform structure within an enclosure at the chimpanzee sanctuary, Chimp Haven, in an effort to encourage mobility and vertical space use in the enclosure’s residents. Additionally, I assessed the chimpanzees’ tendencies for engaging in positional behaviors and using present substrates and enclosure areas. Finally, I examined the associations between particular substrates and the expressions of positional behaviors. The vertical climbing aid's effectiveness was assessed by reviewing video recordings of the two platform structures within the enclosure before and after the installation. Positional behavior and substrate use data were recorded for each subject via focal animal scan sampling. The novel climbing aid was not effective during the study’s duration. Occupation rates and elevation level change frequencies decreased on the experimental structure. Alternative approaches should be taken to future structural modification designs, implementations, and assessments. Individuals demonstrated unique profiles of positional behaviors and substrate use tendencies. The detailed positional behavior profiles and diversity could be useful in assessing and promoting physical health and welfare once validated with established welfare measures and medical records. Substrate use profiles and diversity metrics could similarly be used to determine the degree to which individuals avoid or are receptive to various stimuli. Hence, changes to substrate use profiles can be monitored to assess progress in efforts to encourage individuals to embrace diverse experiences as is the goal of provisioning enrichment. Finally, the associations between substrate use and positional behavior expression may be used to direct changes to enclosures based on the needs of its residents. Deficiencies in positional behaviors for a given chimpanzee may be addressed through the addition of substrates that are most associated with a desired positional behavior. This preliminary study outlines a new approach to measuring welfare as a function of positional behavior expression and environmental interactions. Future refinements to these methods are expected to contribute to the ability of captive management programs to infer a more complete understanding of the overall conditions of captive chimpanzees. Issues that impede a chimpanzee’s wellbeing may then be addressed with suitable captive management strategies and the informed installation of appropriate substrates to improve welfare.