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What to Expect When Introducing Female Mice

Male mice may be the ones who have the reputation for being difficult but that doesn’t mean you shouldn’t be careful when introducing females as well. As with any social interaction, it all depends on the personality of the individual. Trends are all very well, but the ‘typical’ situation does not account for every incidence. There is always someone who has a different experience, whether it be good or bad. The idea of this short article is to prepare you for the different scenarios that may arise when you attempt to introduce female mice.

Black banded doe (Minstrel) grooms cagemate Eve as she rests

1. Selecting suitable cagemates

It might sound like a dumb thing to say but it can make all the difference, believe me. Knowing the personalities of the does you intend to house together is very important and can be crucial to your success. Just putting two or more females together and expecting them to get along is silly – you don’t get along with every person of the same gender as you, so why should mice be expected to do the same?

Make sure you take different personalities into consideration when selecting which does will belong to which colony. For example, it is not a good idea to put two extremely dominant does in together as they are likely to fight and may hurt each other. A balance of personalities is more suitable for a harmonious colony. If you have ‘laid back’ mice that will get on with most or all other mice then they may be good companions for more difficult mice who feel most comfortable at the top of the hierarchy.

Personally I do not split families up. For example, in my largest doe colony I have had at the same time (among others) a mother and two of her daughters, another mother and one of her daughters and two sisters. A family relationship will tend to mean that the mice get along better without squabbling. However, unrelated mice can be just as comfortable together if introduced correctly and matched for personality.

When I am placing a group together for the first time – let’s say adding one or two does to a large group of eight or more – I tend to put the lowest mice in the established hierarchy in with the new mice first. If you put the most aggressive or dominant mouse/mice in first then there may be more fighting straight away, whereas putting the less dominant ones in first gives the new mice a chance to begin interacting without being attacked.

2. Finding the right introduction turf

Make sure the place you decide to introduce the mice is suitable. If you are introducing a pair who are both comfortable with you and with being handled, you may choose to try introducing them on your hands. A table or somewhere the mice can come into contact is sometimes used but I know I would prefer somewhere I could have more control over the interaction – if the mice begin to fight and jump around on the table they may fall off and injure themselves.

A medium sized temporary tank can be used as a meeting ground as long as it is clean, just to allow the mice to sniff each other and have a preliminary introduction. The other main idea is to introduce the mice in the tank they are thereafter to share, which is more suitable when there are larger numbers of does it is impractical to introduce using other methods.

When introducing the does into a tank, people tend to take the view that the tank will be new and will not have been previously inhabited by either group of does. Often this is not true and this can affect the success of the introduction. The familiarity of territory does play a part, since this may mean it is more defended by the mouse that has lived there who knows the layout well, despite the clean smell. If you have to use a tank that has been used by one group before, make it the tank used by the smaller or less aggressive group. This way they will have a small advantage and avoid getting picked on.

Two does sniffing each other - this is seen a lot when introductions have just been made

3. Keeping the balance fair

The theory is that neutral territory is the best place to introduce mice. This can often be right but tends to apply most when the mice are the same age. When mice are different ages you may have to tip the balance a little in favour of the smaller or less dominant group. This will mean that the mice are introduced on equal footing.

For example, let’s say we are introducing two pairs of does to each other. One pair have dominant personalities while the other are your average mice. It is likely that the dominant pair may make trouble and fight with the ‘normal’ mice on neutral territory. To try and prevent this and give the ‘normal’ mice a helping hand to keep the balance fair, it may be an idea to introduce the four mice in a tank that smells of the ‘normal’ pair so the dominant mice are not on territory that they will immediately make their own. I have had this work with bucks and does several times, where the dominant mouse would otherwise attack another mouse.

If you are moving the mice to a bigger tank you can take some bedding from the less dominant pair to make them feel more at home and include a couple of their (unwashed) toys if you do not want/can’t have one group live in the tank before the introduction.

4. Watching the results/checking the mice

When you put a new group of mice together you must be able to watch them for an hour or more to make sure that everything is going ok and no major fighting is taking place. I tend to keep newly introduced groups in my bedroom for the night, since mice are active at night and that way I will be aware of what they are up to.

Females can be funny creatures – whereas male mice usually fight fairly early if they are going to, female mice may wait an hour or so before starting to make digs at each other. It is for this reason that they should be paid attention to quite closely for a while after the introduction. If they do scuffle a little then fights can be broken up by spraying the aggressor gently with a thoroughly rinsed empty hairspray bottle filled with clean water. I have also given a couple of mice a pat on the bum before and told them no – it distracts them and stops them continuing to attack the submissive female.

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