Mice are by far the most used laboratory animals. Improving their welfare through the 3Rs framework — Replace, Reduce, Refine — can reduce suffering for the tens of millions used in research annually.
The scale of mouse use in research makes their welfare one of the most numerically significant animal ethics issues. Standard housing without nesting material causes measurable chronic stress — yet nesting material is inexpensive and simple to provide. Tail suspension, forced swim, and other common behavioral tests cause acute suffering that refinement could reduce. Genetic modifications can cause painful conditions that require proactive welfare monitoring. The refinement pillar of the 3Rs has strong scientific support: stressed animals produce more variable data, meaning better welfare and better science are aligned goals. Institutional animal care committees play a critical role in driving refinement.