Housing and welfare in laboratory rats: Welfare implications of isolation and social contact among caged males (1997)

Hurst, J. L., Barnard, C. J., Nevison, C. M. et al.

Abstract

Singly housed males showed reduced activity and a greater incidence of self-directed behaviors, especially tail manipulation and self-grooming than males housed in small groups of three. They also performed behaviors apparently related to escape or seeking social information. ... Exposure to neighbours [visual contact only] reduced the aggressiveness of singly-housed males when they were eventually introduced into an unfamiliar group, suggesting that a degree of exposure to neighbours may have some welfare benefits for laboratory-housed rats.