Jarvis, K. A., Gould, J. E. 2007. Effects of a complex enrichment device on stereotypic behaviors, tool use, tool manufacturing, and activity budgets in captive western lowland gorillas (Gorilla gorilla gorilla). American Journal of Primatology 69(S1), 51. (30th Meeting of the American Society of Primatologists Scientific Program, Abstract #44)

As a way to reduce abnormal behaviors, specifically finger-sucking, hair-pulling, and reingestion/regurgitation, observed in two male gorillas at The ZOO Northwest Florida, a complex enrichment device that was contingent on the gorilla's ability to use tools was incorporated into their habitat. The device was made out of clear PVC pipe and was constructed into an S-shape. Each of the 3 levels was filled with food. Holes were drilled into each level for tool-use. Each gorilla was tested for 10 weeks, with observations taking place twice a week for 30 min each. A habituation period, in which the device was not present, lasted for 3 weeks in order for the gorillas to become habituated to the observer. Baseline data, in which the device was not present, were taken for 4 weeks. The experimental condition, in which the device was present, lasted for 3 weeks. Feeder activity, tool-using behavior, locomotive behavior, and abnormal behaviors were continuously recorded for each gorilla and were instantaneously sampled at 30-sec intervals. Wilcoxon Signed Rank Tests [α=0.05] showed incorporation of the device significantly increased locomotor activity and manipulation of objects for both gorillas. The device also significantly decreased abnormal behavior for Gorilla 1. Successful tool-use and spontaneous tool-manufacturing was observed in Gorilla 1. These results indicate that incorporating an enrichment device contingent on tool-use can significantly increase activity and can significantly decrease abnormal behaviors.