Evidence-Based Enrichment for Laboratory Rodents
Environmental enrichment is a legal and ethical requirement for laboratory animal housing. The scientific evidence supports specific enrichment strategies:
Nesting material: Cotton nestlets or shredded paper reduce corticosterone levels and improve thermoregulation. Breeding females with nesting material show better pup survival rates. Hess et al. (2008) demonstrated that nesting material is the single most impactful enrichment for mice.
Gnawing objects: Rodent incisors grow continuously. Without gnawing substrates, dental malocclusion can occur, causing pain and inability to eat. Aspen wood blocks are preferred; avoid cedar and pine (aromatic hydrocarbons are hepatotoxic).
Foraging enrichment: Scattering small amounts of sunflower seeds or other treats promotes species-typical foraging behavior without significantly altering body weight or experimental outcomes (Hutchinson et al. 2005).
Structural enrichment: Shelters (igloos, tunnels) reduce aggression in group-housed males by providing escape routes. Red-tinted polycarbonate provides darkness while allowing staff observation (Sherwin 2007).