Which factors influence the decision to single-housing a mouse instead of group housing?

• A. Breeding status, experimental requirements, and fur color.
• B. Strain-specific aggression, breeding status, and experimental requirements.
• C. Cage cleaning frequency and noise sensitivity.
• D. Diet preference and litter size.

Answer: (B)

When deciding whether to single-house a mouse, the important consideration is the risk to welfare and the integrity of the study from social housing. The factors that drive this decision are strain-specific aggression, breeding status, and the requirements of the experiment. Some strains are more prone to fighting, especially among males or unfamiliar cage mates, so isolating individuals helps prevent injuries and stress. Breeding status is another key driver: pregnant or lactating females and their litters are protected by separating them to prevent maternal aggression and protect pups, and researchers may need to manage mating or pup care with separation. Experimental requirements can also necessitate single housing when data integrity or contamination control requires isolating animals from each other, or when the study design calls for specific environmental or behavioral conditions that group housing would confound. Other factors like fur color, cage cleaning frequency, noise sensitivity, diet preference, or litter size are not primary reasons to single-house in standard practice, though they can influence welfare and husbandry decisions in different contexts.