Food puzzle for singly caged primates

To enhance environmental complexity for singly caged pigtailed macaques (Macaca nemestrina), we designed a food puzzle to promote foraging. The puzzles, made of clear plastic tubing and loaded with peanuts in the shell, were suspended from linked chains and attached to the fronts of the cages. Animals manipulated the puzzles by reaching through a cage opening. Upon presentation of loaded puzzles, most animals attempted to remove the peanuts. More peanuts were removed within an hour after the puzzle was loaded than at any other time during the day. Young adult animals showed no sex differences in number of peanuts removed and were more proficient than middle‐aged animals in removing peanuts during the first hour of testing. Middle‐aged females were more proficient than middle‐aged males. The food puzzle enhanced the animals' cage environment by providing a goal‐oriented activity that they could control. © 1992 Wiley‐Liss, Inc.