Puzzle Feeders and Gum Feeders as Environmental Enrichment for Common Marmosets.

Common marmosets (Callithrix jacchus jacchus) are highly social New World monkeys that consume a principally gummivorous and insectivorous diet. We examined the efficacy of two types of foraging devices, Puzzle-Feeders(tm) and gum feeders, as environmental enrichment for marmosets housed singly (n = 16) or in sibling (n = 4) and heterosexual (n = 8) pairs. In experiment 1, marmosets were exposed to each of the two types of foraging devices for three hours, once per week for two weeks. Thirty-minute observations were conducted at the beginning and end of each exposure period. Marmosets in all housing conditions experienced significant reductions in the frequency of stereotyped pacing and significantly less time sitting still while exposed to the foraging devices. Marmosets experienced significantly lower levels of feeder use and significantly more time sitting still at the end of the three-hour exposure than at the beginning. Marmosets that were singly or sibling housed used the devices the most and had the largest reductions in time spent sitting still during enrichment. In experiment 2, singly housed marmosets were given two types of gum feeders, a wooden and a Gumabone(tm) gum feeder, each for a week-long period. Thirty-minute observations were conducted three times per week immediately after loading the feeders with fresh gum. The wooden gum feeders were heavily gouged during the week-long exposure, although significantly less use of both types of gum feeders was observed on the third and fifth days. These results indicated that marmosets in variable social housing conditions can benefit from environmental enrichment additional to social housing, and that foraging enrichment promotes increased non-stereotyped movement and decreased pacing in this species.