Lab Mouse Social Housing and Welfare

Laboratory mice are highly social animals that suffer significantly when housed in isolation. The science of social housing and group stability is well-developed and provides a clear roadmap for welfare improvement in research settings.

Key Facts

House mice are obligately social animals that engage in extensive social behaviours including grooming, play, and huddling
Single housing of mice causes measurable chronic stress, elevated glucocorticoids, and altered immune function
EU Directive 2010/63 requires group housing as the default for mice unless scientific justification exists for isolation
Male mice housed together can show intense aggression, causing severe injuries particularly when groups are unstable
Stable male groups established at weaning are less aggressive than groups reformed as adults
Environmental enrichment (nesting material, huts, running wheels) significantly reduces aggression and improves welfare in group-housed males
Tube handling - using transparent tubes to transport mice instead of scruffing - reduces stress and aggression
The NC3Rs has published extensive guidance on mouse housing and refinement that represents current best practice

Welfare Considerations

Mouse social housing is a clear example where welfare science is ahead of practice. The evidence that isolation causes significant harm is overwhelming, yet single housing continues in many facilities for administrative convenience rather than genuine scientific necessity. Male mouse aggression - a real challenge in group housing - is manageable through good group formation practices, adequate environmental enrichment, and monitoring, but is often cited as a justification for isolation that is not individually justified. The welfare obligation is to pursue group housing as the default and document specific, justified reasons for any exceptions. Refinements including tube handling, adequate nesting material, and running wheel provision are low-cost, high-impact improvements that should be universal.

What You Can Do

Advocate for social housing as the default for all laboratory mice without specific scientific justification for isolation
Adopt tube handling techniques to reduce stress during routine husbandry
Provide adequate nesting material, huts, and running wheels in all mouse housing as minimum welfare standards
Engage with your institutional animal care committee to review single housing justifications regularly
Support NC3Rs and AALAS guidance on mouse housing refinement in your facility
Report unjustified single housing to institutional oversight bodies where it persists without documented scientific necessity