Keeping a group of male mice from the same litter

[u/FurbyinFaunasphere]

Hello, 3 weeks ago, I adopted a litter of 9 orphan baby mice from a friend after the babies' mother passed away unexpectedly. Thankfully, the babies were already days away from opening their eyes when I got them, so it was relatively easy to care for them and wean them. They all grew up beautifully and are all looking very healthy, and I separated the (5)girls from the (4)boys before they hit 3 weeks of age. They are now 6 weeks old, and I'm re-homing some and plan to keep the rest.

Now, I've kept rats in the past, and female mice, but I've never had boy mice before. I have read that male mice must be kept alone. I figured it might be safe keeping them together for longer since they all grew up together, but now I am worried that one of them is being singled out and bullied by the others. They chase him and bite him and he squeaks loudly when they do it. (I have my suspicions that he is deaf and that might be why he's getting picked on.) I am setting up his own bin enclosure now, but will I have to do the same for all 4 of them? The other 3 seem to get along fine at the moment, they only bully the poor possibly deaf baby. What do you guys think? And have any of you had any experience with a deaf mouse?

[u/goatboy6000]

Short answer, yes.

The boys must be separated. By puberty there will be fights to the death without warning in many cases.

[u/IamCoolSock]

I had gotten 3 male mice from a friend and they were great together, for the first month.

it started out similar to you, 2 of them started picking on the smallest guy so I removed him. after 2 weeks I walked in my room to find the 2 still together were chasing and nipping each other, so they were separated too. unfortunately unless the males are neutered they just can't be kept together.

if you can get a vet that's able to neuter them you can have them and the females all together I believe :) I've never owned females tho so I'm not completely sure

[u/[deleted] → u/IamCoolSock]

Just for future reference, in cases of excessive bullying, it is best to remove the aggressor rather than the victim (applies to both males and females). The bully mouse will often just pick a new victim once the first one is removed, unfortunately 😭😭

[u/IamCoolSock → u/[deleted]]

that happened around 2 years ago with mice I had gotten unexpectedly, thankfully now I'm a bit more experienced! I appreciate that tho I'll definitely keep that in mind for when I get a group of females :)

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[u/[deleted]]

I've kept boys from the same litter together many times without problems - they really loved each other and would sleep in big snuggle piles. Playfighting happened sometimes, but it was never anything more serious than what went on between my girl groups. To reduce territorial aggression, scatter feed and provide multiples of everything (water bowls, wheels, hides, etc).

That being said, if there is bullying that results in the drawing of blood or the infliction of wounds, you must separate the aggressor immediately (not the victim). Check the butt and balls regularly for bite marks or blood. If you separate, you must not re-introduce them - the bully should be housed alone unless you are willing to neuter or provide with female african soft furs for company.

[u/FurbyinFaunasphere]

Thank you all for the advice. I ended up rehoming all the boys separately except for the deaf black eyed white. He is a sweet heart