How to Introduce Two Pet Mice to the Same Cage

Updated on July 25, 2015

Pet stores like to confuse mouse owners. Nearly every store I've visited has a little card or plaque that says, "Mice are social animals and get depressed without other mice." However, every time I've tried to buy two mice--especially male mice--the pet store worker will tell me, "If you get two, they'll fight." Advice like this makes it hard to make the right decision for your would-be pets.

While it seems contradictory, however, both of these statements are true. Mice will fight, but they like the company of other mice. They have instinctual issues to resolve--mostly male mice, and for the rest of the article I will discuss male mice unless otherwise noted--and that can lead to fighting and sometimes bloodshed. For more information about this, you can read my hub at, but I'm sure some of you need to integrate separate mice into the same cage. I can't provide an all-encompassing guide to do that, but I can relate what I did to integrate my mouse, Hannibal, with two new friends, Sasuke and Gaara.

The easiest way to keep multiple mice in one cage is to buy them young, preferably from the same litter, and buy them all together. Mice who live together as children--such as Sasuke and Gaara--tend to cohabitate as adults better than mice who don't know each other. Furthermore, we introduced two children to one adult, which initially gave Hannibal the edge in becoming the alpha mouse, which turned out to be a mistake. Mice fight for dominance and generally accept the chain of command once they establish it. When Sasuke grew up, though, he had a stronger alpha-mouse behavior, and challenging Hannibal for the position turned bloody.

Therefore, I recommend introducing mice before they've all matured, or after they've all grown completely. Introducing animals at mixed stages of development might not help in the long run.

Introduce mice in a box and they won't fight for territory
Introduce mice in a box and they won't fight for territory
Mice are social and enjoy doing things together
Mice are social and enjoy doing things together
Sometimes, even mice who live together peacefully will have conflicts
Sometimes, even mice who live together peacefully will have conflicts
What do you see: Two mice having fun by offsetting the weight of their wheel, or two mice fighting for control?
What do you see: Two mice having fun by offsetting the weight of their wheel, or two mice fighting for control?

But you may find that you can't do that. Pet stores usually sell children and adolescent mice exclusively. We could have waited until Gaara and Sasuke had matured, but we didn't quite have the experience to know better.

Either way, here are some techniques we tried, and I'll note how effective we suspect it was. To start, this is a list of things you need.

  • At least one cage for every mouse, even if you only have small travel cages
  • A box with very tall sides, preferably plastic but thick cardboard works too.
  • Fresh bedding
  • A few tubes and small boxes to give them personal space if they want it.

Introduce them on neutral ground

Mice claim territory. Throwing new mice into a pre-marked cage will start a fight. Instead, place them all together in a box. Mice jump and climb, especially young ones. Make sure the sides are about two feet tall and smooth. If the water bottle gets them high enough to jump out, stick it in a corner and put a sheet of cardboard over the top of that part of the box.

No one has marked the box. Without territory disputes, the mice probably will be more interested in each other.

Wipe their haunches with vanilla

Vanilla overpowers the individual scents of each mouse. If all the mice smell identical, we've been told, they will accept each other as friends.

We did this. It may have helped. It certainly didn't hurt. What we saw, though, was three mice spending twenty minutes wiping vanilla off their fur, then sniffing around each other. Each attempt we made to introduce them with vanilla failed. This is only one case, however, so I wouldn't rule out the option completely.

Wait until just before their bedtime

If you've had at least one mouse for any amount of time, you should know its sleep patterns. Most mice sleep during the day, so if you drop them in the box in the morning, they may be too tired to care about strange mice. But unlike the vanilla, this forces them to do something together. If they don't know each other (and even if they hate each other), mice will sleep together for warmth. Our mice seemed to bond over it.

Tolerate little squabbles

When you put them together, they will prioritize the establishment of a hierarchy. You will hear squeaking, and you'll probably see a good deal of male-on-male mounting. Just let it slide. The subordinate mice don't like it, but it doesn't hurt them and they need to resolve who's the king. (The alpha mouse seems to be responsible for grooming the others and for building the nest. Dominance doesn't indicate a tyrannical mouse.)

Pay close attention, though, to see that they're working out the pecking order and not fighting legitimately. Read this to help distinguish the two:

Be Patient and Persistent

We tried introducing these mice on three separate weekends. The first two failed miserably and we gave up. Hannibal went back to living alone and Gaara and Sasuke moved into the new cage together. After a few days, however, I noticed Gaara--a generally laid-back mouse--started picking on Sasuke. It annoyed me, but rather than split them up I wondered what introducing the more aggressive alpha male would do. For some reason, when I stuck them back in the box with Hannibal, they began to play nice with each other.

Give it Time

One source told us that if they didn't fight within the first hour, they probably wouldn't fight at all.

Not true.

Leave them in the box for at least 24 hours. Watch them closely--I had to keep the box by my bed. If they still seem cool with each other after a day or two, you can put them in a cage together.

Use boxes, cardboard tubes, and slats to create a changeable environment. Mice will more likely accept new friends if the cage feels different.
Use boxes, cardboard tubes, and slats to create a changeable environment. Mice will more likely accept new friends if the cage feels different.

Housing them Together

At this point, you should still have one cage for each mouse. If you own three or more, get at least two that connect. An average cage should house a maximum of two mice. So if you have a lot of mice, make sure a lot of cages can be strung together. Mice need space.

This part is tricky. You already had one mouse living in one of the cages. Before putting your new mice in with him, clean it thoroughly. You don't want any scent lingering to suggest anyone still owns the territory. If at all possible, though, change the layout of the cage. This will make the first mouse feel like he's moved into a new place, even if he remembers his home. If one cage is new--which at least one should be, since you need one cage for each mouse--put them in that one. They'll make their way to the other soon enough, but the more unfamiliar they are with the cage, the less likely they are to fight over it.

Don't Assume You're Done

Even if they accept each other now, they may find good reason to fight each other later. After all, we've all had bad roommates. I had one who piled trash in his room, never showered, stole from me, and ate my food. After he ate most of a cake I baked, I injected laxatives into the last piece and let him have it.

Mice don't often have access to laxatives, so they probably will just fight to the death.

Hannibal, Sasuke and Gaara lived together as friends for about two months with nothing more than a few minor squabbles. Then one day, Sasuke had had his fill of being dominated, fought back, and injured Hannibal pretty badly. They both survived, but we couldn't bring them anywhere near each other ever again. They had to live in separate cages and we couldn't take them out at the same time.

While this is our story, I can't claim that this will apply to any mouse you bring home. These animals resemble humans, and therefore have a complex psychology. Just use our experience as a guideline and be prepared for failure. If you have success, though, drop a comment and let me know what you did.

Edit: Know Your Alpha Mouse

Since writing this post, we've had a number of mice come and go, and I noticed an interesting trend among housing male mice together. As mentioned above, the three mice in the picture lived in relative harmony until Sasuke grew into adulthood and became the alpha mouse of the group. We had to separate him. Sasuke went to live on his own, while Hannibal and Gaara lived the rest of their lives together with not even the smallest squabble.

When Hannibal and Gaara died, we bought two female mice to replace them, and since one of them turned out to be pregnant, we ended up with three more mice. We let Sasuke stay in a cage on his own, while the girls got one cage and the boys, Sean Bean and Jon Snow, lived together.

The two brothers lived together with a reasonable amount of discord--as you'd expect among siblings--but interacted very well most of the time. Then when Sasuke passed away, things started changing. Sean Bean became more aggressive and territorial. When the fights got worse and Sean Bean terrified Jon Snow into spending all his time in a small corner of the cage--away from the food and water--we separated them.

Test this at your own risk, and always keep a close watch over male mice living together, but I suspect male mice can live together peacefully as long as the alpha of the group is separated, but living nearby. Sasuke's death, even though they never interacted, left the room without the scent (or so I assume) of an alpha mouse, and one of the others had to take that place. Leave a comment if you try this; I want to know if it works for other people.


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      Mouse owner 5 weeks ago

      Cassie, I would try another baby mouse but make sure it is close to same age and it is same sex. I would do the box method with them and let them mingle then place them together in the cage but make sure you clean the cage before you place the new mouse in it.

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      cassie 2 months ago

      i recently bought two baby mice, and i already own two older mice, all females, i was prepared to have the older mice and younger mice in separate cages, and i was right to do so as i attempted to integrate them and one of the older mice drew blood. however one of the baby mice has gotten out of its cage, was not as well handled as the breeder led me to believe and managed to jump out of the tank while i was changing food. Now heres my issue, i am unsure the likelihood of finding the other baby mouse, sad as it is, though i will keep an eye out, the problem is my other baby mouse is now on her lonesome, she is only a little over 6 weeks old and seems very timid, so im wondering if i should purchase a new baby mouse for company for her as she is still young, and any other baby i would buy would be young as well. Would this be advisable ?

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      Peachy_Mouse 5 months ago

      Have two males I recently bought as a sibling hopper pair of mice, one came from the pet store ill with a URI and I suspect that because of this his brother views him as the weaker of the two so of no real threat to his space and for the most part they live in harmony not looking forward to any fights but if anything serious dose happen they will be separated immediately.

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      Experienced mouse owner 9 months ago

      Most female mice will like each other if introduced properly, it's very rare for female mice to try to murder each other.For males is it is the opposite of females, but sometimes males may be able to live with each other, I you see blood or blood drawn immediately remove them.

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      Vanessa 11 months ago

      Miss lol, I'm pretty sure adult males are happy on their own. Getting another male mouse can lead to them fighting to their death and finding one dead is often the first sign of an issue between them that the owner sees.

      I wouldn't buy another male mouse to accompany yours, if I were you. I would try and spend time with your mouse to get it to view you as a companion.

      I'm not an experienced mouse-owner, though

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      Miss lol 12 months ago

      I got a mouse named harry he is gray I think he is lonely so I was thinking to get another male mouse but I'm afraid they will fight what do I do if they fight I'm super scared so if anyone has any tips I'm all ears

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      Ckkprincess 12 months ago

      What kind of vanilla do you put on the mice?

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      MouserMom 3 years ago

      Growing up we had three mice in a cage at a time but they were all female and I assume litter mates as Santa had brought them all from the same shop. We joked that they had sleep overs. Each mouse had its own cage in each of the three kids' rooms and we ended up alternating which cage they stayed in each week. Your boys are super cute! My current two mice are girls and will fight over whose turn it is on the wheel every so often... At 2 am :(

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      dbbbbbbbbbbbbbbbffv 5 years ago


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      holdenh13 6 years ago from Louisiana

      lol i used to work at a pet store and i can't tell you how many dead small animals i had to throw away. the hamsters are the worst!

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