The Alpha Mouse: How to tell if your mice are fighting or playing

Mice sometimes need to be separated
Mice sometimes need to be separated

Should you separate your mice?

Mice fight for the same reasons humans do. Power. Girls. Territory. Sometimes they're bored and need entertainment. Females will fight for their children's safety. And sometimes, they just need to take a swing at the jerk who stepped on their tail. Whatever their reasons, if you keep more than one mouse in a cage, understand that they may fight. If they're males, expect it. But also like humans, mice will display different levels of aggression which can range from playful wrestling to fighting to the death. Since mice often live healthier lives in social settings, separating them can lead to loneliness and depression, but if you can't identify when fighting becomes serious, keeping them together might threaten their lives.

Female mice tend to be less aggressive. I've only seen them fight to prevent another female from getting close to her babies. This situation resolves itself after time. Both mice played well together in settings other than the mother's cage. Chances are if this happens, once the babies are old enough to fend for themselves, mom won't feel the need to fight for them.

If you house two or more males together, the situation isn't as simple. Boy mice have an instinct to establish a pecking order. Not being as democratic as humans, they will probably fight each other until one mouse--the alpha--subjugates all the others. This is normal, and you have to let it go. Sometimes my mice would squeal in terror in the middle of the night. I separated them, but it didn't do any good. I tried to train the wanna-be alpha that any time he made the others squeak I would put him alone in the travel cage for five to ten minutes. It didn't work. For mice, as well as humans, order needs to be established, and you should just sit on the sidelines and observe until it's over.

Is my mouse gay?

Please note that these animals practice male-on-male mounting as a way of dominating each other. If you see this, your mouse isn't gay. While the subordinate mouse may not like it, it doesn't harm him and breaking up the event probably will make the dominance process last longer.

Once the mice have sorted out which one is king, they probably will continue to fight now and then. Sometimes they're only playing, other times it serves as a challenge or reminder as to who's in charge. But again, this won't hurt them.

So when are they fighting for real?

When an aggressive mouse fights beyond what is necessary, we call it a "bully mouse." Watch the subordinate mice in the cage. They may call uncle by crouching submissively, holding their front paws together in front of them, or even lying on their backs, spreading their legs to the aggressor. If this doesn't stop the fighting, you may have a bully.

If you catch it early, you can break up a serious fight before it starts. Mice will face-off by rearing up on their hind legs. They'll slap their tails against the floor to threaten each other. If you see this, grab them before they bring their teeth into the situation. You won't find an easier time to stop the fight.

Never take the submissive mouse out of the cage. When you see bullying, you don't want the bully to think he won, so you have to pull him out for a while--ten or fifteen minutes will usually cool him off. I recommend having at least one cage--even a small one--for each mouse that you own. This way you never have to scramble for a makeshift holding pen if your mice start squabbling in the middle of the night.

You should be concerned if one of your mice starts bleeding. If someone bites them hard enough that it opens a wound, immediately take the bully out of the cage--use gloves. If they can wound other mice, they can wound you. Keep a pair of leather work gloves by the cage if you have two or more male mice.

Sometimes it can be hard to determine the aggressor. Don't assume. I took my alpha out one night because he constantly picked on one of the smaller mice in his cage. When I held him for a few minutes I noticed his back and bits of his tail were oozing blood. The younger, submissive mouse just got tired of being picked on and he fought back. (That's them in the picture below.) When this happens, don't ever put them in the same cage again. It may be possible that the fight was a single event, but three days later, the submissive tried to finish the job and gave the alpha a severe beating. If that can happen, don't risk the health of your pets. Always keep a cage on hand, and be prepared to separate them permanently at any moment. You may have read about techniques for introducing strange male mice to each other--don't try it. These mice aren't strangers to each other. Look at the picture--I wanted to put the mice close together to stave off loneliness in the former submissive. It just made him mad. Any time the former alpha came close, he would swipe at him and bite through the bars, hoping to resolve their fight.

It was an unfortunate situation, but they've lived quite happily in separate cages, so sometimes you should just let an antisocial mouse be antisocial.

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Comments 28 comments

Rebecca 2 years ago

What do I do if my females and males are fighting

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jplaj 2 years ago from Duluth, MN Author

The simple answer is to separate them. Make sure you have a second cage. Figure out which mouse is initiating the fights and put that one into the new cage. When they get older, they'll mellow out and you can reintroduce them to each other, but you can't really teach a mouse to stop being aggressive.

Generally, you should also avoid housing male and female mice together unless you intend to breed them--you might be witnessing something other than a fight.

Dilon 2 years ago

Yea but mine will just start buying eachother and then they will scrap for like 5seconds and stop they are female and a male

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Draya D Person 2 years ago

Hi, I have 3 does in one cage and one of them seems to be a bully. She chases the other two around every single night and there are multiple times that I hear squeaking. I hate it and I don't know what to do. They fight but there hasn't been blood. Will it stop eventually if I just leave them alone? Or do I have to separate them? Thanks.

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jplaj 2 years ago from Duluth, MN Author

Female behavior is harder to diagnose than for males. There's a good chance they're just playing--even females will wrestle with each other to keep themselves amused, but even girl mice can be bullies. What do the squeaks sound like? Short little chirps generally mean playing. Longer, repeated squeals usually indicate that one mouse wants the other to stop--that's what you want to look out for. If that's the case, you might want to pull the bully out of the cage. Otherwise, watch their behavior for a few nights (does the suspected bully try to steal food, keep others from eating or socializing, or try to push them out of a certain territory in the cage?), and be on the look out for injuries.

Also, does she pick on one mouse specifically or both of the others equally? With our males, we had a situation where the older alpha mouse constantly picked on one of the others, I believe referred to as a "gamma" personality--think the mouse equivalent of nerds on a playground. When the little mouse got bigger, though, he turned out to also have an alpha personality, and almost killed the one who kept picking on him.

Mystic Baby Jade 2 years ago

I have 6 female mice in a large 25 gallon aquarium. Three of them had already lived in there for a few weeks. When I got the 3 newbies, I cleaned the cage thoroughly, washed all the exercise wheels & water bottles, and didn't put anything else in there that the originals had ever touched. I put a big, new popsicle-stick mansion in there. (It had 13 rooms). I introduced all of them by putting them into a cage none of them had ever been in before. (Newbies first). They were together for at least 45 minutes & everything was fine. Eventually, I put the newbies into the newly cleaned & redecorated cage, let them run around for about 30 minutes, then put the original 3 in there. After about 30 minutes, the chaos started. Luckily, the newbies had a corner to hide in. They would come out occasionally, only to be chased back into the corner. (No blood, but a lot of pushing & some nipping). My newbies were in that corner for 2 weeks. One of them was more bold & would come out anyway & the elders chased her a little less. I waited to clean the cage, in hopes that they would get used to each other's smells, but ended up cleaning it out yesterday. I noticed the elders didn't chase the newbies while they were in the smaller, temporary cage. It made me wonder if it was because there wasn't really any territory (house) to fight over. So when I put them back in the big, cleaned cage, I only gave them their 3 wheels, some cardboard tubes, and one small burrow. To my surprise, there was no fighting! One of the elders even started to groom the newbies, in the burrow. When I woke up today, ALL the mice were in the burrow together. However, as the day & night progressed, the chaos started again. Sometimes the elders are nice & sometimes they're not. I hate for my newbies to be terrorized like that... Should I keep waiting it out or go ahead & separate them? No blood or missing fur, but lots of nipping, chasing, and squealing.

Also, I took the elders out to play earlier, and they started chasing the newbies when I put them back. Sorry this is so long, but I wanted to give details for a full view of the situation.

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jplaj 2 years ago from Duluth, MN Author

Mystic Baby Jade -

Thanks for the details. They help, even if it is a long post. Initially, I thought the problem was you let the newbies run around in the cage before introducing the elders. Even that small amount of time helps establish a territory. When you put them in the smaller cage, they all went in at the same time, right?

My first reaction is to say they'll be fine. Female mice can still be territorial, but much less so than males. They'll sometimes nip and chase for fun, and as long as they haven't drawn blood or gouged out fur that's probably what they're doing. Keep an eye on them, though. See if they're chasing the newbies out of a specific part of the cage, or if they're preventing them from eating. These are signs of dominance and are not friendly.

Try to notice if one mouse seems more domineering than the rest. I've never experienced this with females, but if we kept an alpha male alone in a cage, as long as he was nearby, the other males could live in a cage together with no conflict. I'd be more hesitant to separate a lone female, though, since they tend to be more social. If it comes to that, you may be better off with two cages of three mice each.

One last thing to look for, if the babies are young enough, sometimes even pet stores can't tell the gender. If one of your mice turns out to be a boy, that might explain the trouble.

I hope this helps.

Mystic Baby Jade 2 years ago

Thank You for the response! I've watched them a lot - and its just so odd to me... I still haven't picked up on any real pattern. For clarity, the elders are named Peachy, Silverbelle (SB), and Creampuff (CP).

CP was the baby of that group and Peachy is the oldest. SB used to chase CP around. When they had the mansion, all 3 elders could be sleeping and if a newbie came out, they'd get up and go chase the newbies into the corner. They didn't want them in the mansion, on the wheels, or anywhere else. I have food dishes and water bottles on both ends of the cage, and food spread around the entire cage. The newbies had easy access to food and water but the elders still didn't like it.

Anyway, SB, who is quite large, seems to chase the newbies just for fun. Just because they'll run. At first, Peachy just seemed really annoyed they were there - but that seems to have leveled-off. CP wasn't that bad at first but now, she seems to be the main "bad girl". She actually seems to be ANGRY that they're there.

Another strange thing is when I have my hand in the cage and the elders are climbing allover it, the newbies come up to see too, and CP and Peachy attack them. Are they being possessive of my hand? They're getting better about everything... they will share exercise wheels and don't chase them away from food/water... and will even groom/sleep with the newbies. Until A newbie runs OR tries to get in my hand.

One of the newbies is older than the other two, who are quite young. I'll keep my eye on those two babies, to make sure they're not males. I'm still trying to gain the trust of the newbies but its really hard when they can't even sniff me without being scared away.

The "attacks"don't seem too violent- in comparison to a female mouse I used to have, who was really vicious to other mice. It's just been going on for so long! Cats accept a new member faster than this!

Oh, one last thing, there is a male mouse in the room- about 5 feet away. Could his scent be causing some of their behavior? At the pet store they come from, they are housed in a cage that's beneath a cage full of males, so I thought they'd be used to that scent. Sorry again, for such long posts! I just want to try to figure this out!

Although, they do seem to be slowly getting better, except for the hand thing. Crazy little mousies!

Mystic Baby Jade 2 years ago

Okay... I've been watching them non stop since my last post. All 3 elders are clearly targeting the smallest mouse. They grab onto her back end and hold on hard. It's odd because if she's already in the burrow and they go in there, they don't do it. They will groom her. But if she comes out, it's "on". I just took the 3 elders out so the babies could have some time to sniff my hand and get treats. They came out immediately and are having a blast. I really don't want to separate them permanently but I hate for the babies to not even be able to roam the cage freely. It's been 2 weeks of this.

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jplaj 2 years ago from Duluth, MN Author

Mystic Baby Jade,

They're definitely exhibiting territorial behavior, and you don't want the babies to grow up like that. I suggest separating them into the two groups of three; they'll be happy enough, with each mouse having two friends. If you want them all to live together, wait a few more weeks until the babies have grown up. Then clean out some area where none of the mice has ever been and where they can hang out for a day or two. Introduce all six mice to that new area at the same time and watch them to make sure they're not fighting.

I've seen that behavior in our male mice (the two pictured at the top of this post, actually). Hannibal, the white one, tried to assert his dominance, but would only ever target baby Sasuke. When Sasuke got a little bigger, he started picking fights and almost killed Hannibal.

Mystic Baby Jade 2 years ago

Jplaj, Thank you so much for taking the time to read my detailed posts & for your advice. :) I appreciate it!

As of tonight, the eldest of the newbies has also started chasing the babies & now hangs out with the original 3.

It's like the mouse version of "The Bad Girls Club"! Haha

So, yes, I'll definitely separate those 2 babies tonight & get out the biggest aquarium I have (100 gallon aquarium) to relocate all of them all to, after the babies have gotten bigger. Hopefully that will work. If nothing else, at least I'll now be able to bond with the two babies while they're still young, without interference from the others!

sockybump 2 years ago

This post has been extremely helpful. Myself and my girlfriend have 6 mice. 2 hairless and 4 with hair. (All bucks)

We had heaps of fights between hairless and haired. So much so that one of the hairless is missing is his tail. We now house the hairless (hicks and assange) in a smaller enclosure and they love life.

Infact they dont even fight.

The other 4 mice. Bear, chief, xavier and rogue all get along. Have done for weeks until I cleaned there home out about 3 days ago. Bear instantly started trying to dominate Chief. I let them go it went for a good day on and off. I got up this morning everyone is best buds again. Cleaned the tank again just cos I had some new things to put in. That none of the 6 mice have had and all is still fine :))

Mystic Baby Jade 2 years ago

I have a new weird thing going on. The two babies are happy and doing great now... but the other, older newbie I left in the cage with the the elders started attacking the white elder, Cream Puff! At least CP knows how to react and is bigger. Situation seems to be calming down.

I used to have rats. A lot of them. Never had these sorts of problems with the rats.

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jplaj 2 years ago from Duluth, MN Author

sockybump - After writing this post, I noticed that if we kept the alpha mouse housed on his own but still near the others, none of the others will assume an alpha mentality and will cohabitate just fine. As soon as our alpha died, though, one of the other males started getting really aggressive with the other.

Mystic Baby Jade - I'm guessing that the older newbie is the most alpha out of the six. Watch her personality as she gets older. I'm guessing she'll take over the group. Also, watch their gender. This sounds more like male behavior and is a little extreme in females.

Heather 20 months ago

i got 2 mice and one is chasing the other around a lot and trying to push her out of a wheel on the outside of there cage now theres 2 wheels in there now as i want to see if they with just use both and see if that helps. and at time trying to take her food and i have seen her case the other out of there nest. and both are girls.

first time i have herd them do this so its a little scary.

i got them both from petsmart they where in the same tank so i am not sure is this one of=s being mean or not but if she hurts the other she is getting taken out right away as i wont staid the other being hurt

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jplaj 20 months ago from Duluth, MN Author


Even girl mice sometimes feel the need to display dominance. Watch them carefully. Is the bully mouse letting the other get food at all? Do they keep their distance from each other most of the time? Does the smaller mouse squeal when she gets pushed around? If so, you may have a problem. Otherwise, it might just be a behavioral issue that they need to get used to.

A) I've found that with the more intelligent mice, blowing a sharp blast of air at them will start to send a picture (kind of like using a spray water bottle on a cat) without actually hurting them.

B) Keep a close eye on the bigger one. Sometimes pet shops make mistakes in sexing their animals. If it starts to look like she's dragging a grape around behind her, put her--him--in his own cage right away.

helmet head 17 months ago

We got mice from our neighbor. Her mouse turned out to be pregnant so she gave us the 2 male offspring. They have grown up together and are not even a year old (born in July). They were totally fine until about a month ago. We noticed that one mouse was jumping on the other, and the other was squeaking, but submitting. We separated them for a short time and it seemed to get better, but then my sister noticed a scratch under the bullied mouse's eye. We took him out to make sure he was okay, and noticed that the tops of his front legs were covered in dried blood. im worried that the bully will kill the other.

Please respond soon. Thanks.

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jplaj 17 months ago from Duluth, MN Author

Helmet Head: I'm not sure what to tell you. Your mice are definitely fighting and you're probably right--the bully mouse may end up killing his brother. Sometimes you just have to separate them. I built adjoining cages for mine. The bully tried to reach through to take a few swipes at his brother, but after he realized he couldn't do anything, they both seemed to calm down. They could still see each other if they felt the need to socialize, but they couldn't get at each other to cause damage.

You may have to keep them apart. The good news is when mine were nearing about two years old, they calmed down, and we put them in the same cage for a few weeks before they died of old age.

Jeannie 15 months ago

Hi, I have two male mice, one is a lot younger than my other one. I got my two male mice from Petco, Berwald is an older black mouse whom was adopted, wasn't able to tell the age, and Tino is a light cinnamon sugar color and he's obviously a baby, maybe about a month or less, I'm not sure. The first night I got them: Fabulous. Nothing, no fights, no problem, Berwald was happily grooming little Tino. Second night: I heard squeaking from Tino, and sure enough. Berwald was all over him, but as I read your posts, I couldn't see quite clearly as to whether Tino was frightened or not from Berwald attacking/"attacking" him. I separated it and went back to my book, I heard more squeaking again and sure enough, Ber was at it again. I grabbed Tino out of the cage and looked to make sure he was okay, and he was. I put him back and now he just seems to be cowering in either the bottom of a plastic bottle I put in there, or he's cowering on top of the hut while Ber watches the cage. I'm scared they're truly fighting, but I haven't seen blood yet. And this is only the second night. Is it possible that they're different species and that's causing them to fight? Or that it's not fighting at all?

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jplaj 15 months ago from Duluth, MN Author


I highly doubt the two mice belong to different species. What you're describing sounds perfectly normal for two male mice from different litters. Ber wants to tell Tino "I'm the boss," and you should watch the situation closely. While they say mice are social animals, that mostly applies to the females, while male mice don't really need friends. They might resolve their pecking order with the occasional squabble (you'll probably never get them to stop fighting completely), but if Tino looks like he's avoiding certain parts of the cage, or if Ber is keeping him away from the food dish, that could be a bigger problem, even if they're not drawing blood.

If you don't want to separate them just yet, give the bully mouse some "time out." This probably won't make him change his bullying ways, but it could give Tino a chance to get to the food and water--and for you to see how he behaves when he's alone in the cage. Always take the bully out of the cage, never the victim, and if you're trying to get them used to living to each other, I'd limit the time-out period to about a half hour. You may also want to check out my hub on How to Introduce Two Pet Mice to the Same Cage.

Jeannie 15 months ago

Thank you! An update: I forgot to mention, Berwald tries to groom Tino, but, Tino flinches as if he's being nipped and runs away from him. However, they didn't "fight" again after that. Also, is it normal for Ber to be sniffing Tino on his behind? He does it quite often.

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jplaj 15 months ago from Duluth, MN Author


That's absolutely normal. Mice don't have great vision, so they identify each other via scent instead--in fact, one of the suggestions for introducing mice to each other is to put a drop of vanilla on their fur near their tail (near the scent glands). Nothing you're describing seems out of the ordinary, though.

mirda 14 months ago

I have two male mice. Both are young, but one is a few weeks older than the other. They are almost exactly the same size. I introduced them on neutral territory, they had what I assume now was their "alpha battle", no one was hurt and for weeks they lived perfectly fine together. The only fought I think once until now. All of a sudden the first one started basically attacking the new mouse. Whether they are playing on their wheel or something or eating, or even minding their he will randomly run at the other and sit on his tail and.bite him. The other squeals every time and just last night he started to fight back a little bit. Neither of them have been injured or wounded and their is no blood. I.can't tell whether they are playing, just having a small spat, or seriously fighting. We have a large I think 40 gallon tall tank with about 1'x3' floor space plus things to climb on and hide in. They have already built their nest. We also have a small 10gallon tank we used for my snake when I had it. If they do need separated, how severely would.I need to clean that tank? What could be causing them to fight like this after they lived so well together?

Please help if you can

Kelsey 8 months ago

I got two female mice from a pet store yesterday. Both girls were in the same tank with three other girls. When I asked, the employee said she thought they were all from the same litter, but didn't know how old they were- no more than a few months, she said. One of the two mice, Phoebe, the gray one, is very sweet and friendly- likes to be held, snuggly, calm- but she is smaller than all the other mice. She's more like the size of a feeder. The other one, Penny, who is cream, beige, and white, is larger, more energetic, and kind of skittish. She's also pretty fat. I think she might be pregnant since she's fat and her nipples are more visible than Phoebe's.

Whenever Phoebe and Penny go nose to nose, Penny squeaks her displeasure. When they both try to be in their little house, she seems hesitant and squeaks a bunch. I've also seen her push Phoebe's face away when they're both in there. It seems like Phoebe wants to be friends, but Penny hates that idea. I've also noticed a few small cuts on Phoebe's tail. They're not deep or bleeding, but they look like they could be bites. The skin is broken. There's a scratch on her ear, too. I would say it's just Penny being a bully, but Penny is the one that squeaks, not Phoebe. Could Penny be acting like this because she's pregnant and wanting to protect her babies? Phoebe has been very nice to her but isn't acting fearful at all. Also, there is no chasing, and they're both eating fine. Penny just seems to dislike sharing their little house and being too close to Phoebe. No matter where they go nose to nose, even outside the cage, Penny squeaks.

Could getting another small mouse even the score a little? Should I take Penny back and get a less aggressive mouse instead? Or should I just let them work it out?

Alyce 7 months ago

Is it possible for a mouse to become a bully because they were bullied? I had one female mouse named Holly whose friend died so I bought two more named Chloe and Crocus. At first Holly chased Chloe around and so whenever she got close Chloe would freeze and squeak and look terrified. It was like she was cringing away from Holly. I tried putting them in a different habitat so Holly wouldn't be jealous of her territory but by then Chloe was already terrified of her. Eventually though, they all seemed to be friends. Later, after Holly died, Chloe began chasing Crocus around (Crocus was a lot smaller) and I would often hear squeaking and the sound of them running around at night and I'm not sure if Chloe was letting Crocus eat. One day Crocus turned up dead but she hadn't shown any signs of being ill so I'm wondering if Chloe might have killed her somehow, although there wasn't any blood. Chloe then lived a long and happy solitary life. I don't know why she would bully Crocus though, they were in the same cage at the pet store and I'm pretty sure they grew up together.

Kastalimire 5 months ago

So I basically rescued a female mouse 9 days ago. Yesterday I got her a companion. The companion is younger and I'm seeing dominance behaviour. It is semi-confusing. They have groomed and slept together. The beginning was good before the 'attacking' started. They have bouts where they are ok and then the older one seems to attack the other causing her to squeak. She seems ok and still running and curious. The older one runs her to her loft and tries to keep her there for the most part. I've checked a few sites and I simply can't tell for sure. I'm assuming a slower integration is needed and may help as the new one ages and grows?

Shabree 3 months ago

My fancy mouse Luna (female) just lost her cage mate (also female) so I went to the pet store to adopt two new females to house with Luna since she had been acting depressed. Luna is the biggest. Toffee is in the middle size-wize and Angel is the smallest. I cleaned out the cage and bought new toys as well. I introduced them and then put them all I to the cage (I have a 3-story critter cage with lots of room).

Luna immediately went after the smallest and she managed to nip Toffee on the leg. It's not bleeding but she definitely nicked her. Now Toffee is terrified and won't go to the bottom of the cage unless I remove Luna which I did have to remove her a couple of times for being a bully.

Luna doesn't like to share the house or the wheel I put in there. While they are getting a little braver with Luna she is still chasing them a lot. I'm worried she is going to hurt the littlest one. Sometimes she just sits in a corner and the others can go to the bottom but then at times she will go after them and I'm not sure why.

I'm afraid to leave the 3 of them in there. I know females aren't usually as aggressive but she is acting territorial. None of them have babies and they are definitely not males. How long should I wait before I decide if I need them to live separately because I don't want Luna to be alone, she is actually very sweet, but I'm worried she won't bond with the new mice after losing her last cage mate.

Sarah 2 months ago

I'm having problems with my 5 does. I got a new none recently and everything was fine until a couple of nights ago. She's started attacking all of then other mice. She has andomjbate personality and I'm notnsurenif she's already taken charge, but the squeaks aren't playful. She chased my oldest around the cage at full speed while she was practically screaming and she wouldn't stop. I couldn't tell if she was trying to attack her genitals. At first inthouht she was onkynpicking on Cake but then once cake escapednshe went after one of then others. I saw aiya humping the new mouse the other day son it all very confusing, indont want to separate her because she's be lonely but I don't mnownwhat to do if it gets worse?

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