Document Type


Date of Degree Completion

Summer 2020

Degree Name

Master of Science (MS)


Primate Behavior

Committee Chair

Mary Lee Jensvold

Second Committee Member

Jessica Mayhew

Third Committee Member

Kathleen Barlow

Fourth Committee Member

Clay Arango


More than 1,400 chimpanzees live in captivity in the US and each has complex social needs. The humans who care for captive chimpanzees occupy a place within chimpanzee social structures and their actions have consequences on chimpanzee behavior and welfare. Two studies compared chimpanzee responses between a condition in which humans used chimpanzee behaviors (CB) and another in which they use human behaviors (HB) during informal interactions. The chimpanzees showed more affiliative behavior during the CB condition in one study and strong individual variation in responses to the two conditions in both studies. Individual variation in adult primate behavior can be influenced by early life experiences, such as rearing history and prevalence of human and conspecific interaction partners. The current study aimed to expand on previous research comparing chimpanzee responses between a CB and HB condition and to determine the influence of early life experiences on responses. Nine chimpanzees residing at Wildlife Waystation in California experienced two or three interaction trials in each experimental condition. For each interaction trial sampled, there was a corresponding carry-over sampling period on the same day and matched control sampling periods on the following day. This provided a full picture of differences in responses. The chimpanzees exhibited a significantly greater proportion of certain types of prosocial behavior and a higher frequency of event behaviors indicative of anxiety and attention-getting in the HB than they did in the CB. They spent significantly more time in prosocial behaviors and aggression and significantly less time in inactivity during interaction trials than they did during any other sampling time period. The chimpanzees showed variation in behavior among early life experience categories overall but not between experimental conditions. Two chimpanzees showed significant increases in affiliative behaviors towards humans throughout the course of the study. To optimize captive chimpanzee welfare, human caregivers should be knowledgeable of and practiced in using chimpanzee gestures, vocalizations, and postures in interactions. Caregivers should be mindful of chimpanzee sensitivity to human behavior and interact with kindness and patience. They should know each chimpanzee’s history and individuality and let this inform husbandry practices.

Available for download on Monday, August 25, 2025