Male mice prefer to live on their own

Key results

1. ShownSingly housed male mice in conventional cages develop a stronger positive reward learning bias and higher sucrose preference than group-housed mice or mice in individually ventilated cages (IVCs).

   Across 96 mice (single vs group of 3, conventional vs IVC cages), cage type (F(1,87)=6.491, p=0.0126) and grouping (F(1,87)=10, p=0.0022) affected session 10 reward bias; conventional singly housed mice had higher bias than conventional group-housed (t(88)=2.391, p=0.0189) and IVC singly housed mice (t(88)=2.356, p=0.0207), plus higher 2% sucrose preference (grouping F(1,84)=13.83, p=0.0004). · Male mice housed in groups and IVC caging…; Figure legends

2. ShownChronic corticosterone administration validates the Complex Cue T-Maze (CCTM) reward bias assay by abolishing the positive reward-induced learning bias seen in vehicle-treated control mice.

   In 18 singly housed male C57BL/6 mice treated for 14 days with 25 ug/ml corticosterone-HBC or vehicle, controls showed a main effect of reward value (F=16.61, p=0.0036) across 10 sessions whereas corticosterone-treated mice did not (p>0.05) and had a significantly lower session 10 bias score (Mann-Whitney U(54, 24)=3, p=0.0216). · Development and validation of a reward bias…; Experiment 1: Validation of the complex cue T…; Corticosterone treatment and CCTM testing; Figure legends

3. ShownA replication cohort of singly housed male mice confirms that IVC housing impairs reward bias, reduces sucrose preference, and increases anxiety-like feeding latency compared to conventional caging.

   In 36 singly housed male C57BL/6 mice (18 per group, 4 excluded), conventional caging produced a significant time*reward value interaction (F(9,135)=2.857, p=0.0041) and higher session 10 reward bias than IVC caging (t=2.076, p=0.0465), while IVC mice had lower 2% sucrose preference (t=2.112, p=0.0434) and longer latency to eat in the novelty suppressed feeding test (t=2.239, p=0.0333). · Male mice housed in groups and IVC caging…; Reward Learning Phase; Subjects; Figure legends

4. SuggestedSingly housed male mice emit more ultrasonic vocalisations (USVs) over time than group-housed mice.

   In a 42-day home-cage recording study (n=3 single-housed cages vs n=3 cages of 3 mice, normalized by dividing group calls by 3), USV call rates showed a main effect of time (F(1.389,5.556)=14.52, p=0.0081), a time x housing interaction (F(35,140)=6.356, p<0.0001), and higher total calls in singly housed mice (Mann-Whitney U=0, p<=0.05). · Effects of group vs single housing on ultrasonic…; Subjects; USVs recording and analysis; Figure legends