Laboratory Rats and Mice: Improving Welfare for the Most Used Research Animals

Mice and rats account for over 95% of animals used in biomedical research globally. Improving their welfare through the 3Rs framework has both ethical and scientific benefits.

Key Facts

Approximately 100 million mice and rats are used in biomedical research globally each year, making them by far the most numerous research animals
Common welfare problems include barren housing, social isolation, chronic stress from repeated handling and procedures, and inadequate anaesthesia
Mice are highly social — solitary housing causes measurable psychological harm and alters experimental results through stress-induced physiological changes
Enrichment items including nesting material, shelters, and chewing material are now recognised as essential for meeting baseline welfare needs
The 3Rs framework (Replace, Reduce, Refine) provides a systematic approach to improving research animal welfare adopted by regulators worldwide
Refinement interventions including anaesthetic pre-medication, analgesic provision, and training animals to cooperate with procedures reduce suffering
Positive reinforcement training of mice and rats — teaching them to voluntarily enter handling tubes — reduces stress markers compared to tail-scruff handling

Welfare Considerations

The sheer number of mice and rats used in research means that even modest welfare improvements translate to enormous reductions in aggregate suffering. Housing improvements — provision of nesting material, group housing, shelters, and environmental complexity — are low-cost interventions shown to improve welfare indicators and, critically, to improve the reproducibility and translational validity of research results. Stressed animals in barren environments produce different biological responses to experimental treatments, reducing the scientific value of the research. The welfare and scientific cases for better laboratory rodent housing are aligned. Where replacement with non-animal methods is not yet possible, refinement — through pain management, humane endpoints, and gentler handling techniques — should be a mandatory minimum.

What You Can Do

Advocate for mandatory provision of nesting material, shelters, and group housing in regulatory standards for laboratory mouse and rat housing
Support funding for development and validation of non-animal research methods as replacements for animal models
Push universities and research institutions to publish annual 3Rs implementation reports demonstrating welfare improvement progress
Choose to support or donate to research charities with explicit 3Rs commitments in their funding criteria
Raise awareness that laboratory animal welfare is a legitimate consumer concern — public pressure influences institutional culture
Advocate for refinement training in animal handling as a mandatory component of researcher certification programmes
Engage with the National Centre for the 3Rs and equivalent bodies in your country to support their practical welfare improvement work