Dry bedding provides cost-effective enrichment for group-housed rhesus macaques (Macaca mulatta)

Dry bedding has been shown to be an effective enrichment strategy for small groups of captive nonhuman primates housed in cages or in small enclosures with concrete flooring. However, dry bedding is used infrequently for large groups because of the perception that its use is time- and resource-intensive. We investigated the cost-effectiveness of this enrichment strategy in large groups (30 to 50 subjects) of rhesus macaques. Macaques were housed under 3 comparison conditions for 4 wk: pine shavings (n = 4), aspen and pine shaving mixture (n = 4), and nonbedded control (n = 4). As measures of resource consumption, husbandry tasks were documented by using time-in-motion methodology, and water usage was determined. In addition, groups underwent behavioral observations to assess the effect of dry bedding. The time required to care for units did not differ between bedded and nonbedded units. However, significantly less water was used for sanitization of bedded compared with nonbedded units. Monkeys housed in bedded units showed more foraging (13.8% ± 1.6% of time in bedded compared with 4.0% ± 0.3% of time in nonbedded units) and less aggression and self-grooming. Dry bedding benefited the macaques, reduced water usage and costs, and did not affect human resources.