Redoing introductions for a group of 6 - advice?

by sleepybirde Mon 16 Oct 2023, 4:32 pm

Hello everyone!

Initially, introductions for my girls went really well. I had one lone mouse, Otter, who is a little over a year, be introduced to 5 girls ranging from 2-4 months. I was worried about her possibly being overbearing with the babies, as she was top-dog in her old group, but she was very friendly and seemed to take to them all well, and the babies didn't challenge any dominance behaviors she displayed (grooming, light chasing). I started them on neutral territory in my bathtub, then moved everyone into a 10 gal tank for a few days, then moved them into their current cage (a little bigger than a 40 gal).

Everyone was fine for the first two or three weeks, but slowly problems began to emerge. One of the younger mice, Blue, had started to harass everyone, including Otter. Tail rattling, persistent chasing, intense rump biting, the works. Initially I didn't do anything because Otter wasn't really fighting back, so I thought if Blue was trying to establish her dominance and Otter was going to let her, I shouldn't intervene. However, she continued to ramp up her aggression to the point that I was concerned for the other girls, so I began giving her "time-outs" by putting her in the 10 gal for 24 hours alone after I would catch her being aggressive. I've had success with this method curbing unwanted behavior in the past, but this time it didn't seem to help. Otter has now begun fighting Blue back, and it gets ugly- rolling in a ball kind of ugly. Neither of them have drawn blood, but they are certainly not big fans of each other right now. Otter has also started bullying the others too (chasing, rump biting), which she had never done before. I believe this whole thing with Blue has made her very insecure.

In addition to all that, another of the young girls, Nelly, steers clear of Otter and Blue but bullies the other three just as relentlessly as they do. So I have 2 girls who are peached at each other, one opportunistic mean girl, and 3 poor ladies who just want to hang out in peace.

At this point I think I should restart introductions and/or separate, but I really want this group to work out. I went out and got a 20 gal to have a "middle-point" between the tiny 10 gal and the big cage. I'm just wondering if should keep everyone together to begin with, or should I separate the bullies and the bullied into two groups and reintroduce them later once the bullies seem more bonded to each other? Or would that just make them more likely to gang up on the others? I also am unsure how long I should keep them all in the 10 gal -- I rushed through that process last time because I was worried about 6 girls being cramped in such a small space for very long. Any advice for how to proceed would be appreciated!