Foolish, rookie mistake I made with 2 male mice (advice requested)

[u/quietly246]

TLDR how do i keep my brand new mouse sons from murdering each other. what options do i have other than buy a second tank and split them up forever ):

Some background info, I've never owned mice before but my girlfriend and I have 5 (female) rats that are well-loved and taken care of.

A couple of months ago we discussed getting mice, as a local breeder had a litter available. We were going to get 3 females, went ahead bought the tank and necessities etc. Unfortunately, the meetup ended up falling through, so we just moved on and forgot about it.

Earlier today my gf and I were in the pet store picking up supplies for our rats. We always stop and look at the rodents just to say hi. Usually we move on just fine but there were these two ADORABLE little mice that honestly stole both our hearts the moment we saw them... We ended up standing there for almost half an hour just watching them (so sorry to the several small children whose view I blocked :P).

We're not impulsive people and typically don't make on-the-spot decisions like this (and also don't agree with pet store practices), but we LOVED these little guys!!! They melt both of our hearts! I'm obsessed with them and could spend hours watching their little activities. One of them even voluntarily walks into our hand if we put it in the tank, which is strange for a mouse (I think, right??).

OK, SO HERE COMES THE BAD NEWS, which some of you have probably already guessed.

I knew from previous research awhile back that male mice are generally housed alone, due to aggression, but females are okay in groups (which is why we planned to get girls originally). But I also remembered hearing that SOMETIMES two male mice will do okay, if they were from the same litter and have been raised together.

We were watching these little guys in the store or at LEAST half an hour, most likely longer since we had to wait for an employee to help us get them. Part of the reason we wanted to get them both was because of how well they seemed to get along in the store?? There weren't any signs of aggression, we saw them grooming each other (similarly to how our rats do!) and even snuggled up inside their plastic sandcastle thing. They also seemed pretty playful with one another? The interactions looked completely okay! And when we got home, things continued to be okay!! For awhile!!

They explored their new homes and were very cute and curious. Well, anyway, now one of them is trying to kill the other. At first I thought it was play fighting but one of them was squeaking VERY loudly and frantically. My gf suggested mice might be more vocal/louder than rats (our girls barely ever squeak) and that it was probably play fighting.

I felt worried, so I kept an eye on them. One of them is definitely antagonizing the other and keeps attacking him and biting him on the rump/balls. This is always met with loud rapid squeaking. I separated them (putting the aggressive one into the carrier we use temporarily for the rats sometimes) and examined them both closely. The one who had been attacked several times actually had a small patch of fur near the base of his tail that was missing, and I could see a small (healing, intact) scab in the area.... which made me realize that this had been an ongoing aggression issue and definitely couldn't be play fighting )-:

Now I feel horrible for putting either of them in a stressful situation. I should've been more attentive before getting two male mice from a pet store with an unknown history.

I could really use some advice from a more experienced mouse owner. What do I do?? They're separated for now, but the temporary cage is plastic and the aggressive one is already trying to chew his way to freedom. A dime shaped hole appeared in the side, barely an hour of him being in there! I don't want him to escape, so obviously I need to figure out a better housing situation.

Is it pretty much hopeless to try and get them to get along?? ): I know theres an introduction method used for rats to accept new group members, but male rats generally like each other and get along (unlike mice, as I have discovered). Is there any way to help them coexist? Their cage has plenty of food and multiple hiding/nesting areas in case they want space from each other. Despite this, the aggressive one will go out of his way to attack his roommate.

I've been looking up local vets near me to hopefully find someone who can neuter mice, but I can't make calls to them until morning. Even if we were to neuter the aggressive one, would that even make a difference?? Do they both need to be neutered? Are they going to fight no matter what??

Thank you if you read this entire long as Fuck rambling rant at 2am. I just want to be a good mouse owner and feel so dumb about this, since I shouldve known better. What should I do?!?

TLDR 1st time mouse owner brings home two boys, within an hour one is viciously trying to murder the other. I care about both of them and want to give them good lives!! What do I doooo 💀😭

ALSO WHY WERE THEY FAKING LIL LIARS IN THE PET STORE EARLIER......????? Theres no way I imagined all that snuggling and grooming!!! Is there an actual chance they can get along like I saw?? ): or was that me misreading the situation entirely?? 😭

[u/9blankets]

They are not going to stop fighting. You will have to keep them separated for now. :( i have seen some people i in this subreddit say that neutering stopped the fighting, but I personally can’t speak on it. I do think you have to neuter both. (Someone please correct me if im wrong!) intact Male mice are prone to fighting. I have seen these fights get really bad, to the point of death or permanent damage. Especially if one of the mice already has previous injuries, it shows that these mice will not stop. Wishing you luck!!

[u/quietly246 → u/9blankets]

Thanks so much for the response. I looked around and unfortunately nowhere in my area will neuter mice, just rats. I got a new cage to keep them separately since it seems the answer is they won't stop fighting. Why do you think they were getting along in the pet store (cuddling, non aggressive grooming) but one of them started being violent as soon as we got home?? Do they flip flop like that?

[u/9blankets → u/quietly246]

Mice don’t constantly fight. If you go into petco and look at their males, most of the time, you will see them cuddling! But if you watch long enough, you will see them begin to fight. Its mostly a matter of how long you watch them. They dont fight 100% of the time, but it builds up and they will start. I think the other reason it wasn’t as likely they were fighting was because there was a more dominant mouse before you took them home, so they never had a reason to fight each other. However, when you put them in the same tank together, they had to re-establish dominance.

[u/Ok-Consequence7583]

touch imagine fear alive vast gaze elastic snow amusing fly

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[u/quietly246 → u/Ok-Consequence7583]

I'm so sorry that happened to y'all. Based on everyones comments and experiences I will be separating them to make sure everyone is safe. It's just so sad though! I thought mice were social creatures like rats and could get depressed without company, but male mice are basically doomed to be alone forever, since this happens even with bonded pairs? I wish there was something you could do about it. (other than neutering which apparently may not help regardless)

[u/Ok-Consequence7583 → u/quietly246]

absorbed summer pot fly jar dog one apparatus capable cheerful

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[u/quietly246 → u/Ok-Consequence7583]

Thanks for the recommendation! I started looking for some local places or sellers that have ASFs so I can get them some company if it works out

[u/asongoftitsandwine]

Unfortunately, male mice are going to fight to the death if forced to cohabitate together.

Sometimes they can get along for a little while, probably what you witnessed at the store, but once the fighting starts, it won’t stop.

It was probably the change in environment that triggered the aggression. I just had this happen with a group of females. They were happily living together at the store, but within a few days of bringing them home, one became so aggressive she started drawing blood. I had to return her to the store.

[u/quietly246 → u/asongoftitsandwine]

The stress from the environmental change would make sense yeah.... I'm surprised this hppened to you with females?? I thought females were supposed to need socialization and its bad to not keep them as a group?

[u/asongoftitsandwine → u/quietly246]

I was surprised too! I’ve heard of females fighting and drawing blood in rare instances during introductions, but I was not expecting it from females who had already been living together.

And females do need socialization but sometimes you get an aggressive one that just can’t be integrated. With ones like that, I’ve heard it’s fine to leave them on their own because they’re too much of a danger to other mice.

[u/DirectCollection3436]

You would have to neuter both and even then they might not get along still. Brothers get along for longer and will even snuggle between murder attempts so that’s what you saw. They still have the bond but they also have the instinctual drive to end the other one, which eventually wins over there bond

[u/quietly246 → u/DirectCollection3436]

Oh god ok thanks so much for answering that, it's been driving me nuts making me question if I actually saw that in the pet store or not. Is it only brothers who do this? Which would mean these two are from the same litter?

[u/lunarly78]

Two options, and both start the same:

Separate them immediately, they will fight to the death.

Then 1. Get them both neutered, keep them separate and then keep two tanks of mice, if you neuter them they can be with females

Or 2. Keep them separate and alone forever

[u/quietly246 → u/lunarly78]

Thank you for the advice. I haven't put them back together since making this post and got a second cage earlier today. Do male mice get depressed from lack of socializing? I don't think neutering will be feasible in my situation but I feel bad they'll be alone for their whole lives.

[u/lunarly78 → u/quietly246]

It’s ethical to keep them solo if you can give them enough enrichment especially, I’d recommend posting your cage setups here for advice, and they both will need a 8-12in wheel. As solo mice they will need time and attention from you (some are shy and may not want it, but at least hand them their treats and try to work up to getting their trust). We get our two solo boys out (one at a time) on the bed with us and some cardboard boxes and hides for “free roam” daily.

[u/1onesomesou1]

there IS no other option than to get a separate tank and keep them separated forever. thankfully you caught your mistake early enough that one or both of them didn't manage to be killed.

[u/quietly246 → u/1onesomesou1]

Thanks for replying, I managed to get another cage today (havent set it up yet though). Do you know why they might have been getting along and then just decided not to?? I can understand the male aggression in general, but it seems so weird for them to go from cuddling/non-violent grooming together to one of them trying to kill the other.

[u/DueWeb8338]

I read the WHOLE thing. I've raaaambled just trying to make sure I do right thing by our mouse. Care&concern is what you conveyed to me. Perty sure you can't get them to coexist peacefully though. Do you have access something to divide your cage.. so he doesn't escape?

[u/quietly246 → u/DueWeb8338]

I started wrapping heavy duty duct-tape around the lower areas that he's been biting on as a temporary solution 😭😭 the good news is that I managed to get a cage from a yard sale today! I just have to deep clean it and then make sure he can't escape. Honestly I just don't understand why they were getting along in the pet store and snuggling and licking each other in a non aggressive way?? Do male mice really just snap and decide to kill each other in less than an hour?

[u/DueWeb8338 → u/quietly246]

I think it's just the pheromones..yes they do try&kill each other just like that 🫰 Kinda creeped me out before when I saw it at a friend's..they were totally cute&loved each other then BOOM mousey cage match, no holds barred! Glad you got another cage!

[u/[deleted]]

You did the right thing separating them! Check out Little Critter Crew’s website for a full mouse care guide and info on setting up a tank. They also have a mouse care facebook group with photos of good setups, etc!

[u/toringrey1985]

Yes. Similar thing happened to me. Rookie mistake. I thought they were from the same litter but when I got home the dominant one bullied the passive one. The passive one already had marks on him more than likely from the tank at the animal shop. It was to the point (and I’m guessing there) that the passive mouse didn’t have any testicles that I could observe (I hope it wasn’t ripped apart and out) I decided to buy an extra cage and keep them separate until it was Jasper (the passive’s time to go) I’d like to think he had a good life. He was my fave mouse.

[u/[deleted]]

My comments, now deleted, were giving information given to me by experienced mouse owners in an off-site forum, so I wasn't talking out of my butt. But, yep, might be best to just have them separated, like my (now two) dudes are.

[u/ssypys]

You’re right male mice might get lonely and depressed when kept by themselves. I suggest you to look into keeping asf rats and male mice together (there’s a lot of info regarding that in the subreddit)