Laboratory mice are the most commonly used research animals and their social housing welfare needs are increasingly recognized, with evidence that isolation compromises both welfare and research validity.
Laboratory mouse welfare has been transformed by the recognition that isolated, barren housing compromises both animal welfare and research quality simultaneously - a rare alignment of ethical and scientific incentives. An isolated mouse is chronically stressed, showing elevated corticosterone that affects metabolic, immune, and neurological function relevant to many research applications. Research conducted on stressed, isolated animals produces results that may not translate to unstressed social animals or humans. Social housing of male mice requires management strategies to prevent aggression, but is achievable with appropriate group sizes, stable housing without excessive cage changes, and environmental complexity that allows establishment of stable hierarchies.