Careful mouse introduction.

Question
I figure it's best to get as many knowledgeable opinions as I can.
I've had three sisters for nine months, and they are ten months old. They came from a breeder, and on Dec. 23, I brought home three more, all from the same litter, and from the same breeder. The new mice were born Nov. 26, and assuming a 3 week quarantine, they will be 7 weeks old when I plan to introduce them to the older mice.

I know about the neutral territory, the need for toys and distractions in the introduction area, and the vanilla extract trick. The old mice have never been aggressive with each other, and even the alpha does not assert her dominance often.

Are there any other tips and tricks you would suggest to make the transition of new cagemates as seamless as possible? The cages I have them in are Habitrail OVO sets, which I will alter to make it a 'new' cage, so no one will be familiar with the layout after they're put together.

I appreciate your thoughts!

-Emily the Mouse Mom

Answer
Dear Emily,

Sounds like you pretty much have it covered. Most mouse intros go pretty well.

It is nice for the little mice to have somewhere to go that the big mice can't fit-- like pieces of a wrapping paper tube tunnel. That gives them a break from getting chased. There should always be TP tubes in any mouse cage of course.  Set it up so there is only one, very obvious place to nest. You want them to sleep together.

These are the rules I use for intros:

Chasing and squeaking are fine. No one is getting hurt or even necessarily scared. The squeaking is communication. Don't be surprised to see the baby mouse stand up or even almost fall over backwards facing the adult. This exposes the delicate neck and belly, and basically means "I'm only a baby! You could kill me! I throw myself upon your mercy!" Adults generally respect this. This chasing and squeaking can even continue for a couple of weeks off and on as long as:

1. There is no blood
2. No one is blocked from wheel, food, water, or nest
3. No one gets depressed, lethargic, uninterested in life
4. The chasing and squeaking isn't constant.

I actually recommend not quarantining, since the mice are from the same place. The quarantine is usually in case the new mice come in with something that the others have not been exposed to. But I am pretty lax about it. Your breeder may disagree with me. The reason I bring it up is, the smaller the babies, the better the intros go. Not that 7 weeks is exactly old.

If there is an actual problem-- one of my above 4 is violated-- you will do something counter-intuitive. You will take a smallish container (like a ten gallon tank), take out every toy, and put them all in. The smaller the space and the fewer the toys, the less there is to argue over, and the more time there will be to snuggle and get to know each other. But there should always be toilet paper rolls so they feel safe. However, I do not think it will come to this.

If there is a problem with just one big mouse, you would take her out and keep her nearby so she didn't get lonely; but the cage should smell like everyone but her. Wait 5ish days and put her back in, without vanilla.

It's great to get them in threes.  That's what I do. That way, in each generation, when one goes there are still at least two left to comfort each other, and there is plenty of time to get more. I always stay between 3-6 mice, replacing at least by the time I get down to two.

Sounds like you are a great mouse mom. Have fun with your little gals.

Squeaks n giggles,

Natasha