Case study: Diet and social grouping have an effect on regurgitation and reingestion in two captive great apes

Citation

Kappen KL, O’Hara JL, Deever RM, Iske CJ, and Morris CL. 2019. Case study: Diet and social grouping have an effect on regurgitation and reingestion in two captive great apes. In Brooks M, Freel T, Koutsos E Eds. Proceedings of the Thirteenth Conference on Zoo and Wildlife Nutrition, Zoo and Wildlife Nutrition Foundation and AZA Nutrition Advisory Group, Saint Louis, MO.

Abstract

Regurgitation and reingestion (R&R) is commonly seen in zoos but is considered undesirable, since is not necessary to digestion and has not been observed in wild great apes. The causes of this behavior are multifactorial and not well understood, and not all proposed solutions work for all individuals. This makes it necessary to approach every case independently to find solutions that can reduce or eliminate R&R for each affected individual. In this case, one male western lowland gorilla (Gorilla gorilla gorilla) and one female northwest Bornean orangutan (Pongo pygmaeus pygmaeus) at Omaha’s Henry Doorly Zoo and Aquarium (OHDZA) have exhibited recurring R&R. Multiple strategies, including dietary starch reduction, addition of browse, and scattered forages, have been employed to reduce this behavior with mixed results. This study observed behavior in response to varying levels of browse, both in addition to a standard diet and as a substitute for dietary greens. Housing arrangements for the orangutan also made it possible to observe whether R&R happened more frequently during hours spent alone or when housed with conspecifics. In this study, browse increased time spent feeding in both orangutan and gorilla, regardless of total diet volume. Browse reduced R&R in only the orangutan, and housing with conspecifics was associated with lower rates of R&R in the orangutan.

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