Project Objectives
- Assess how same‑sex and mixed‑sex housing influence reproductive biology and hormone regulation in mice.
- Evaluate welfare indicators such as aggression, social stress, and abnormal behaviour under different housing conditions.
- Determine how housing choices impact variability in behavioural, anatomical, and molecular outcomes.
- Produce evidence‑based recommendations for best practice when including both sexes in research.
3Rs Impact
- Variable results require larger groups to detect an effect. Identifying a source of that variability means studies can be designed without inflating numbers to compensate.
- Identifies which housing arrangements reduce stress, aggression and welfare risk.
- More reproducible results strengthen the justification for using animals at all, since an unreliable experiment uses animals for nothing.
- Produces practical guidance that facilities anywhere can apply, without new equipment or cost.
Background
Including sex as a biological variable is increasingly required by funders to improve the reliability and applicability of animal research. Most historical studies have relied heavily on male animals, overlooking important sex‑dependent effects. However, when both sexes are included, researchers must decide whether animals should be housed together or separately. This matters because odour cues and social signals from the opposite sex can influence stress levels, reproductive biology, behaviour, and the variability of experimental results.
Despite these implications, clear evidence‑based guidance on housing strategies is currently lacking. This project systematically examines how mixed‑sex versus same‑sex housing conditions affect male and female mice, in both open‑top and individually ventilated cage systems. By measuring physiological, behavioural, and molecular outcomes, the research aims to generate robust data to inform best practice. The resulting guidance will support researchers and facilities in designing studies that are scientifically rigorous, reproducible, and ethically responsible, while limiting unnecessary animal use.
