Abstract
Captive chimpanzees (Pan troglodytes) are highly inactive compared to their wild counterparts, who spend most of their day engaged in activities, such as feeding and traveling. Enrichment programs aimed at promoting natural behaviors and decreasing inactivity for captive great apes are common at zoological institutions in the United States. Previous studies on feeding-based enrichment have either not documented the benefits of feeding enrichment on the overall activity budget of chimpanzees or have shown that feeding programs have not been successful in increasing feeding times to levels observed in the wild. The introduction of temporary objects (e.g. plastic balls) for use by great apes has been shown to increase activity over short periods of time, but a study by Brent and Stone (1996) indicated that the long-term introduction of temporary objects is not effective for increasing captive chimpanzee activity levels. An analysis of the Sacramento Zoo enrichment program was conducted to determine if the program is effective at increasing the amount of time captive chimpanzees spend feeding, compared to previous research on captive and wild chimpanzees. The efficacy of introducing temporary objects was also evaluated to determine if this an effective method for increasing activity. Five subjects were observed using focal sampling for a total of 112.5 hours (22.5 hours per individual) from November 2017 through July 1, 2018. The results show that the Sacramento Zoo chimpanzees fed an average of 34% of their daily activity budget, which is comparable to what has been observed for chimpanzees in the wild. These results are contrary to the findings of other research conducted on captive chimpanzees. The introduction of browse material with or without primary food items was successful in significantly increasing feeding times compared to only feeding with primary food items. The introduction of temporary objects had little to no effect on chimpanzee activity levels, confirming the observations of Brent and Stone (1996). Overall, the multifaceted feeding enrichment program at the Sacramento Zoo is successful in increasing foraging time, due to the frequency of feedings and the diversity of fresh browse that is provided for the chimpanzees.