Effects of a running wheel-igloo enrichment on aggression, hierarchy linearity, and stereotypy in group-housed male CD-1 (ICR) mice (2008)

Howerton, C. L., Garner, J. P., Mench, J. A.

Abstract

Environmental enrichment is an important strategy to improve the welfare of laboratory animals. Running wheels might serve as enrichment devices for laboratory mice, since mice use them extensively when they are provided. However, competition among group-housed mice for such highly preferred enrichment devices could also lead to injurious aggression. We therefore assessed the effects of providing a running wheel-igloo enrichment on the social behaviour of group-housed male mice. .. Thus, providing the running wheel-igloo enrichment had a negative effect in that it increased potentially injurious aggression. Additionally, the decrease in hierarchy linearity suggests that the social structure in enriched groups was disrupted. The cause of the decrease in cage stereotypies in WHEEL is unknown, but could be because these stereotypies were re-directed towards stereotypic wheel-running, or because wheel-running reduced frustration due to limited opportunities for exploratory locomotion or caused a shift in the behavioural time budget. Despite this decrease in stereotypy, this form of enrichment is not beneficial for group-housed male CD-1 mice due to the associated increased aggression. However, female mice or males of less aggressive mouse strains might respond differently, and singly housed mice should generally benefit from such enrichment.