Old, socially housed rhesus monkeys manipulate objects (1993)

Novak, M. A., Musant, A., Munroe, H. et al.

Abstract

More than 10% of the [group-housed] females' time was spent in object [toy] manipulation. ... Socially housed rhesus monkeys ranging in age from 14 to 22 years showed steady rates of object manipulation, and their interest in familiar objects did not appear to wane over time. .... Several factors [for interpreting higher interaction rates in groups-housed than in single-housed animals] should be considered, the first of which is social facilitation ... Failure to manipulate objects in rhesus macaques appears to be more a function of individual housing than of old age. Factors such as environmental complexity, social needs, and early experience should be considered in order to understand why individually housed rhesus monkeys are unresponsive to objects. ... In this study, females manipulated objects much more frequently than males.