Toys as environmental enrichment for captive juvenile chimpanzees (Pan troglodytes) (1993)

Shefferly, N., Fritz, J., Howell, S.

Abstract

Whereas contact with the indestructible toy ball decreased over time, destructible objects maintained a consistent level of interest throughout the toys lifespan. ... Provision of both types of toys did not result in significant differences in the time individuals spent in abnormal, or aggressive behavior. ... There were no health problems or injuries associated with the destructible objects. No pieces of plastic were found in feces, indicating that none had been ingested.