Reinhardt, V. 1993c. Using the mesh ceiling as a food puzzle to encourage foraging behaviour in caged rhesus macaques (Macaca mulatta). Animal Welfare 2(2), 165-172.

An attempt was made to encourage more foraging behaviour in eight pair-housed adult rhesus macaques (Macaca mulatta). No special device and no special food were used. Daily commercial dry food rations consisting of 33 bar-shaped or 16 star-shaped biscuits per animal were placed on the mesh ceiling of the cages instead of in the feed-boxes. This induced an 80-fold increase and 289-fold increase, respectively, in foraging time in the pair-housed males.