Abstract

Group-housed mice often exhibit aggression, which, beyond a certain threshold, impact welfare and research outcomes. Severe aggression leads to injuries, stress, and potential study disruptions. The SAM (Senescence-Accelerated Mouse) model, derived from the AKR/J strain, is highly aggressive, showing frequent squeaking, struggling during handling, and early senescence-related symptoms. In group housing, despotic hierarchies emerge, with dominant males often injuring or even killing subordinates. This aggression forces separation, undermining experimental design and conflicting with the 3Rs principles of reduction and refinement.This study evaluated whether two handling methods could reduce aggression in SAM mice.