How to Introduce Two Pet Mice to the Same Cage

Updated on July 26, 2019
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I hold a master's degree in English. I like writing about various topics.

Can two (or more) mice live together happily?
Can two (or more) mice live together happily? | Source

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.

So How Do I Keep Multiple Mice in One Cage?

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 our mice, Sasuke and Gaara—tend to cohabitate as adults better than mice who don't know each other. We introduced two children to one adult, which initially gave our adult mouse, Hannibal, the edge in becoming the alpha mouse; this 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. However, you may find that you're unable to get mature mice. Pet stores usually sell child 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.

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Introduce mice in a box and they won't fight for territory.Mice are social and enjoy doing things together.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?
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?

How to Introduce Your Mice

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.

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.

Know Your Alpha Mouse

Since writing this article, 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.

Expect Changes When the Alpha Mouse Passes Away

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.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

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      • profile image

        Owner of 12 mice :))) 

        2 months ago

        I bought two mice (knowing they were male and female) and they had 10 babies. 10. I didn’t want them to breed again and I love the male (Optimus Prime (OP)) so i decided i wanted to keep him but needed another male so they wouldn’t breed. I took one of his male offspring and put him in a new and separate cage with OP and they get along great. He didn’t have a problem with any of the babies, so i’m very glad it worked out that way because i know they eat them a lot of the time. It was risky but I kept a close eye and I did see him pick on the baby a few times but that was the end of it. They live in peace now :)

      • profile image

        Jade 

        6 months ago

        I bought two females a few months ago and one had babies (three boys and a girl), I later donated the boys to a pet store and bought what I was told were two female mice later but on two different occasions (I should have checked for myself that both were female). The new female Polly Anne is very timid but also very friendly to people and the other is Dutch, who I double checked two days later to find is a male. I was hoping to slowly integrate Polly to the other females, but Tofu and Marble are the largest and most territorial (after trying to introduce Polly, Marble pounced on her and I took her out immediately and Marble's daughter Jasmine tried to box with her mother as a challenge for alpha). Tofu was separated out already from trying to eat Marble's litter and hasn't been reintroduced yet from both being very territorial. So I'm worried about having no spot to place Dutch away from the others and the fact that he already was in Polly's cage for two-three nights before I picked them up to socialize them to see that he was male (I'm worried she's too small, and I didn't want any of the mice to get pregnant again since that was the whole point of donating the boys from Marble's litter, temporarily named Billy, Jo, and Billy Jo). If I return Dutch now I'm worried Polly is already pregnant and would be lonely on top of that. Any good advice? Aside from always being sure to check the mice before getting them. That was on me.

      • profile image

        Jackie Kamins 

        6 months ago

        I adopted 4 male mice, all from the same litter. I brought them home at about 2 months old and it seems that now that they’re growing into maturity they’re fighting more. It’s hard to identify which one or two are picking on the others, but I have a good idea of who it/they could be based on their personalities (they all look the same except for 1 has a white tipped tail). They have 2 connected cages but still wake me up squeaking and fighting at night. I’m wondering if I should just put them in another room and let them battle it out for dominance or if I should separate them. To my knowledge no one has been hurt yet but the way some of the fights sound I’m worried they may escalate as they get stronger and older. Most of the time they get along great, sometimes all four will sleep together in one of their little cotton bedding areas. It’s just the occasional fights that worry me.

      • profile image

        Jean 

        12 months ago

        I saved a tiny field mouse last Thanksgiving from a glue trap. I named him King Arthur. I kept him all winter and released him the following June in our yard. I had my carpenter build him a double walled plywood insulated house to live outside He was outside from June to October until it got cold. I had hoped he would have moved on but instead he moved closer to my house and held up in a crack in our cement near the garage. It got very cold and one night I set a have a heart and re-trapped him. He is inside in a terrarium.He is very lonely and waits for my company. Tonight I set a trap in my basement because I thought there was a mouse in our house and I was right. I trapped a mouse. After reading your story about introducing mice I would be very fearful to introduce these two strangers to each other. For now I'll wait for a warm day if we get one and release this mouse. If no warm days I'll keep him all winter and release him in the spring. I feel bad for King Arthur being so alone is there anything else I can do to make him feel less lonely. Thanks

      • profile image

        David Eustache 

        15 months ago

        It didn't work for us. My favorite male Mouse was killed and he was the alpha. The other male mouse was half his age and we raised him from birth. I am very saddened.

      • profile image

        juseleienez 

        16 months ago

        I love how they’re named after Naruto characters

      • profile image

        Mysterious stranger 

        18 months ago

        Probably something like nutmeg or cinnamon

        Responding to Olivia

      • profile image

        Olivia 

        21 months ago

        Could you use anything other than vanilla?

      • profile image

        Mouse owner 

        23 months 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.

      • profile image

        cassie 

        2 years 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 ?

      • profile image

        Peachy_Mouse 

        2 years 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.

      • profile image

        Experienced mouse owner 

        2 years 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.

      • profile image

        Vanessa 

        2 years 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

      • profile image

        Miss lol 

        2 years 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

      • profile image

        Ckkprincess 

        2 years ago

        What kind of vanilla do you put on the mice?

      • profile image

        MouserMom 

        5 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 :(

      • profile image

        dbbbbbbbbbbbbbbbffv 

        7 years ago

        cool

      • holdenh13 profile image

        holdenh13 

        8 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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