Anderson, J. R. , Chamove, A. S. 1984. Allowing captive primates to forage. In: Standards in Laboratory Animal Management. Proceedings of a Symposium. 253-256. The Universities Federation For Animal Welfare, Potters Bar, UK.

A woodchip litter substrate reduces abnormal behaviours, primarily self-aggression, and encourages foraging, even in the absence of grain. Comparison between the bare floor and litter with grain showed that in the latter monkeys foraged more, manipulated the environment less, were less aggressive (towards others and themselves) and played less (p. 254).