Cost and Effectiveness of Commercially Available Nesting Substrates for Deer Mice (Peromyscus maniculatus).

Provision of nesting material promotes species-typical behaviors in rodents including deer mice (Peromyscus maniculatus). The purpose of this study was to determine which commercially available nesting material best promotes complex nest building in the subspecies P. m. bairdii yet remains cost-effective for use as enrichment in a laboratory research setting. An existing breeding colony consisting of cages containing all male mice, all female mice, and breeding pairs was evaluated. Five commercially available substrates-compressed cotton squares, cylindrical compressed cotton, cellulose bedding containing small pieces of evenly dispersed compressed paper, brown crinkled paper, and white crinkled paper-were provided according to the manufacturer's recommendation. Nests were evaluated at 24 h after cage change and scored for complexity. Nest complexity was compared between breeding pairs and single-sex cages and between male and female mice. Cages housing breeding pairs with pups had the highest average complexity score. The dispersed paper substrate was the least expensive substrate tested but had the lowest average nest complexity score. Nesting scores for brown crinkled paper, compressed cotton squares, and compressed cotton cylinders did not differ significantly despite the range in cost. Brown crinkled paper was the second least-expensive substrate tested, and mice used it to build consistently complex nests, making it the most practical substrate for use as enrichment for deer mice in a laboratory setting.