Simple toys do not alter the behavior of aged rhesus monkeys

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Abstract

Simple toys and sticks have frequently been suggested as inexpensive forms of environmental enrichment for nonhuman primates. Most descriptions of these items do not provide quantitative data on their use, or the effects that their presence have on general behavior. We tested wooden sticks and four different dog toys with aged and young adult rhesus monkeys to determine whether or not they led to decreases in abnormal behaviors, or increases in activity. We monitored object-use, abnormal behaviors, and general activity in a series of three experiments. Use of all objects tested declined sharply by the second day after they were placed in the cage. High levels of use were seen each time new objects were introduced, suggesting that a regular schedule of object rotation would lead to increased interest from the monkeys. No changes in abnormal behaviors or general activity were attributed to the presence of the objects. We conclude that sticks and simple toys have limited effectiveness as environmental enrichment options for aged rhesus monkeys. Where possible, socialization and/or actively responsive enrichment devices may be more effective in enhancing the lives of captive primates. In the case of animals in zoos, responsive environments and increased social opportunities also contribute to the educational, aesthetic, and health diagnostic missions of the institutions.

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