Mealworm feeders as environmental enrichment for common marmosets.

The impact of a foraging enrichment device, the "mealworm feeder," on the behavior of the common marmoset was examined. In 3-h weekly exposures to the wormfeeder device, behavioral observations were conducted to compare the rates of feeder use, use of other enrichment devices, stereotyped behavior, and inactivity, to those of control sessions in which the enrichment device was not provided. Significantly decreased rates of pacing and time spent sitting still were observed in association with placement of the mealworm feeder. Feeder use declined over a period of 3 h, even if the feeders' contents were not fully depleted, and the effects of enrichment on activity waned in a like fashion. Use of other enrichment devices, comprised primarily of cage furniture, increased in the presence of the mealworm feeder. This effect did not change significantly over the 3 h of exposure even though use of the feeder declined. There was significant variation in feeder use among sex and housing condition, with females housed singly and in peer groups using the feeders significantly more than did males, whereas subadults used the feeder significantly more often than did either the dominant female or male in family groups. The results of this study suggest that the mealworm feeder is an effective form of environmental enrichment for the common marmoset, but interest wanes after approximately 3 h.