Frequency of feeding enrichment and response of laboratory nonhuman primates to unfamiliar people.

Although environmental enhancement plans for nonhuman primates vary between facilities, feeding enrichment represents a component of most programs. As part of a facility's feeding enrichment program, offering hand-fed food items by trained staff provides an opportunity for positive human interaction. We hypothesized that increased implementation of such enrichment would be associated with increased likelihood of a monkey accepting a hand-fed treat from a stranger. Several species of monkeys were tested at the Tulane National Primate Research Center. In 2002 and 2005, we recorded the number of caged monkeys that accepted a treat tablet from an unfamiliar person within 10 s. We compared the frequency of caretaker-implemented feeding enrichment documented for each animal room during the month proceeding data collection with the proportion of animals within the room that accepted the treat from the stranger. In 2002, 29.8% of the 500 subjects accepted the treat from the unfamiliar person. The proportion of animals that accepted the treat was significantly correlated with the number of days during which feeding enrichment had been implemented. In 2005, feeding enrichment frequency had increased by 76%, and 53.4% of the 676 subjects accepted the treat. These findings suggest that this simple form of enrichment may improve monkeys' responses to unfamiliar people, and that it holds promise as a method for mediating the stress imposed by human activity in animal rooms. In addition, a stranger's treat-feeding attempts may be a useful indicator of an institution's implementation of their environmental enrichment program.