Concerned about female mice getting along

Question
Hi Natasha,
I recently rescued 2 female mice from someone who bought them as feeder mice for a snake who normally eats rats. The snake didn't end up eatting them thankfully and he was just gonna throw them outside to fend for themselves which I just couldn't allow. This was a traumatic event for the poor mice, they were actually left in the cage with the snake for many days before I found out what was happening and they were obviously terrified. So heartbreaking when I realized what was going on. Anyways I immediately took the mice and gave them a nice safe home inside an aquarium. They have a wheel, tunnels, a little playhouse with different openings and a little slide, as well as an igloo that they nest in. One (nibbler) is bigger than the other (miss squeaks) and recently I've noticed fighting between the two. It's always the bigger one chasing the smaller one around, also she's always hogging the wheel. Well today I happened to get a good look at one of these fights and nibbler was actually seen biting miss squeaks in the lower back leg region while she was trying to exercise on the wheel. No blood was drawn and she immediately stopped once I walked up to the cage but I'm concerned for the little one and am seeking any kind of advice you may have as to how I can get the bully to leave squeaks alone. I'm confused because they sleep/nest together in their igloo so nibbler isn't being a complete bully but I feel so bad for squeaks and don't know what to do. I want them both to be happy and be able to live together. Is this normal behavior? What are some things I might could try to end these squabbles?
Thanks a bunch for your help---

Answer
Dear Alison,

Oh the poor, poor little girls. People can be so mean and so stupid. Just yesterday someone told me she took in a rat that was bought for a school play and then "not needed." Of course it hadn't been treated well and it was sick. It breaks my heart.

It is of concern that Nibbler won't let Miss Squeaks in the wheel. Chasing and squeaking is fine, but blood is not.

My recommendation is to get another mouse. Usually one tries to get mice as babies, but in this case you want to get one who will stand up to Nibbler. Often a new mouse can upset the balance of things. And in fact, if Nibbler were too mean to Miss Squeaks, you would have to get at least one more mouse anyway, because female mice should not live alone. Or get two more young ones- Nibbler would probably not be able to keep the upper paw with three mice. Of course, maybe Nibbler is just an aggressive mouse. If she can't live with any other mice, the other three will happily live together. It is best to have mice in threes because when one dies, the other one isn't both devastated *and* lonely, both conditions which easily lead to sickness, depression, and mites. And if it turned out Nibbler got along with one other mouse, the cages could be divided two and two.

If you do ever have a mouse living alone, her cage must be near the other cage so they can communicate, which they do in frequencies that we can't hear. Don't worry; there is no threat of meanness when there is no shared territory.

Of course if you got a dozen more mice... Just kidding!  I do understand that you may not even have intended to have these two.

If you really don't want to get more mice you can try getting another wheel and waiting to see what happens. My criteria for separating mice are that chasing and squeaking are fine, but exclusion from wheel, food, water, or nest are not; nor is blood; nor if one mouse is depressed.

Best of luck, and let me know what happens. Poor, poor little mice.

Squeaks,

Natasha

By the way, if this is someone you know, please try to convince them to feed frozen. Every snake can learn to eat frozen. In the UK it is illegal to feed live, and their pets do fine. It is horrible to put any rodent through that terror, not to mention that mice and rats may bite a snake, causing infection and death.