How should mice be housed in terms of social interaction and what factors influence this decision?

• A. Most mice are social and do better in groups, but strain-specific aggression, breeding status, and experimental requirements may necessitate single housing or barrier separation.
• B. Mice should always be singly housed to prevent fighting.
• C. Mice must be housed in large groups regardless of strain.
• D. Housing in pairs only.

Answer: (A)

Mice are generally social animals and benefit from group housing, but the best arrangement depends on several practical factors. The tendency of a given strain to be aggressive, whether animals are breeders or have just litters, and the specific needs of the experiment all influence whether mice can stay in groups, need to be housed singly, or require barrier separation to prevent fighting while preserving some social cues. In strains known to fight, especially unfamiliar males, single housing or a barrier-equipped setup helps avoid injury and stress. Breeding situations also matter because pregnant or lactating females and their offspring may require separation to protect the pups and manage mating outcomes. Experimental requirements, such as preventing cross-contamination or meeting study-specific environmental controls, can further dictate housing needs. So the best approach acknowledges the social nature of mice but uses single housing or barrier separation when aggression, breeding status, or experimental needs make it necessary.