Laboratory Mice: The Most Numerous Research Animal

Laboratory mice are used in over 80% of animal research procedures globally — understanding their welfare needs and how to improve housing has major implications for both welfare and research quality.

Key Facts

An estimated 100 million mice are used in research globally each year
Standard laboratory caging gives mice roughly 25% of their minimum recommended space by RSPB standards
Mice are highly social animals that suffer in isolation — pair housing dramatically improves welfare outcomes
Environmental enrichment (nesting material, hiding places, gnawing objects) is now recommended in most guidelines
The Norecopa 3Rs database catalogues thousands of published papers on mouse welfare improvement

Welfare Considerations

Laboratory mice experience a range of welfare impacts depending on the procedure involved, but even mice used in low-severity observational studies often live in suboptimal conditions due to space limitations and inadequate social and environmental enrichment. Research demonstrates that better-housed mice show lower baseline stress hormones, which improves the translational value of research results — making welfare improvement simultaneously an ethical and scientific priority. The transition from single-housed to pair-housed or group-housed mice, with nest-building material, represents the single highest-leverage welfare improvement available at scale.

What You Can Do

Support NC3Rs and the Animal Free Research UK in funding mouse welfare improvement research
If you work in research, advocate for enriched housing standards and social housing in your institution
Engage with your institution's AWERB to ensure 3Rs principles are actively applied to mouse housing
Support regulatory changes requiring enriched housing and social housing as minimum standards for laboratory mice
Donate to humane research organisations developing validated cell and organ-on-chip alternatives to mouse models