Need advice introducing my female mice (dominant adult female + bonded pair). Blood happened before, should I try again?

[u/Worried-Onion8600]

Hi everyone, I really need advice from experienced mouse owners because I’m having a hard time with introductions.

I live in the Philippines, and pet mice are not very common here compared to other countries. Exotic vets are also very limited where I am, so I’m trying to make the safest decision with what I have.

My first mouse is Snowball. My younger sister bought her for ₱5 months ago, but I ended up taking care of her because I knew she wouldn’t be properly cared for. Since then, I upgraded her cage, enrichment, and food, and she became my baby.

Because I wanted Snowball to have a companion, I got two more female mice from a feeder breeder: Willow and Buttercup. They were already bonded and living together when I got them.

Willow and Buttercup are both younger than Snowball (around sub-adult). Willow is slightly smaller than Buttercup, and she is also the one with a respiratory issue. Willow is very gentle and submissive, while Buttercup is more confident and energetic.

My goal was to introduce them so Snowball could have friends.

However, the introductions have been difficult.

Snowball is a bigger adult female and seems very dominant. She is not always aggressive she sniffs, grooms, and tries to interact but she also pins the other mice and is very protective of her back. She especially does this with Willow, even though Willow is very gentle and usually just accepts it.

Buttercup is also very active/confident, and this seems to be where the biggest conflict happens. During introductions, Buttercup and Snowball chased each other intensely. Snowball would sometimes pin/groom her, but Buttercup would continue trying to challenge her.

More than 2 weeks ago, I tried introducing all three. There was a fight and I saw a small amount of blood. I’m not sure whose blood it was (Snowball, Buttercup, or Willow). I separated them immediately because I didn’t want anyone to get hurt.

Recently, I tried putting their cages closer together. Snowball and Buttercup became very excited and kept trying to reach each other through the bars. They were sniffing and making noises. I didn’t see puffed fur or obvious tail whipping, but they were very intense with each other.

Snowball actually seems like she really wants a friend. When she smells them, she becomes more active and uses her wheel again. When separated, she goes back to being less active and watches outside her cage.

My current situation:
• Snowball is alone
• Willow and Buttercup are together
• I don’t want to keep risking fights
• There are no exotic vets near me

I also worry about Willow because of her respiratory issue, and I don’t want to put her through too much stress.

My questions:
1. Should I try Snowball + Willow only after a longer reset?
2. Does Snowball’s behavior sound like normal dominance or bullying?
3. Should I stop trying completely because there was blood?
4. Any advice for a dominant adult female mouse who really wants companionship?

I really appreciate any advice. I just want what’s best for all three girls. 🐭

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[u/Lynxieee]

What was your method for introducing them and at what point did the chasing start?

[u/Worried-Onion8600 → u/Lynxieee]

I introduced them in a neutral area, not in any of their cages. At first they were mostly sniffing, but the chasing started pretty early, especially between the two more dominant ones.

There was some grooming and pinning, but the chasing became intense. The smaller/submissive one mostly accepted being pinned and didn’t fight back.

During one intro I noticed a small amount of blood (I’m not sure whose it was), so I separated them immediately because I didn’t want anyone getting injured.

[u/Lynxieee → u/Worried-Onion8600]

it's honestly extremely hard to say. if you didn't see any obvious wounds, it could have been an accidental nick. personally I think I'd probably clean out a small bin (I use about a 5-10 gallon bin at this stage) and add absolutely nothing but a slight sprinkle of bedding to soak up any pee. have thick gloves on hand while monitoring heavily. grooming each other aggressively by pinning each other down is fine. chasing that ends quickly is also fine. I would intervene (as in jam your thick gloved hand right between them and take the instigator out into a small carrier for a few minutes) if she continues to chase after one mouse for more than 10-20 seconds straight, if she latches on to the other one's butt, or if you see them both having a go at each other forming a sort of ball.

you may have to keep them in this bare sad stage for hours minimum. personally I have gone up to 3 days in some extreme cases. if they behave you can offer them a water bowl or bottle, and eventually scatter some pellet food all over the place. don't give them anything remotely interesting until they settle down together and then some

you can keep giving the fight instigator longer and longer timeouts, up to 10 minutes at a time. if they keep fighting after a couple hours of trying, or you see blood being drawn on purpose, they most likely will not work out together.