Group-housed male C57BL/6J mice in standard shoebox caging developed dysfunctional social hierarchies, with frequent aggressive encounters, bite-wound injuries, and elevated anxiety-like behavior, because there was nowhere for a subordinate mouse to break line of sight from a dominant cage-mate.

The hack / solution

Switch standard cages to partially divided caging: opaque plastic dividers split part of the cage into burrow-like compartments while keeping a shared common area and shared food/water access. 2) Hold the dividers in place with the feed hopper and cage lid instead of adding extra hardware, so it fits existing cage sizes. 3) Add dividers to already-established C57BL/6J groups, not only at cage setup — this reduced aggression even in mice that already had ongoing dominance conflicts. 4) Expect roughly a four-fold reduction in bite-wound counts compared to standard undivided cages, plus more open-arm exploration on elevated plus maze testing, which indicates reduced anxiety.

📎Source: PMC — Partially divided caging reduces overall aggression and anxiety in group housed male C57BL/6J mice🔗View source🗓️Added: 2026-07-16✅Reviewed by: MouseStuff Admin

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