Introducing male mice to same cage?!

by WBCarson Sun 12 May 2019, 11:36 am

I just read on mouse facts that male mice will kill each other.
My "wild" mice brother and sister had babies so i separated her into her own cage with the babies.
They are getting older now and i think 2 out of the 3 are males. My plan was to have a large aquarium with the males
and the smaller one for the females.

Has anyone else introduced males together? I would hate for him to kill one of the little ones. Ive been working with them and can hold them and such.
Time is getting short and i need to sort this out

by WBCarson Sun 12 May 2019, 4:40 pm

After much and long reading my question is answered.

No... you cant.

by WBCarsen Mon 22 Mar 2021, 5:29 am

Research has found that you CAN have male mice in the same cage but it is only recommended if they are siblings and have grown up together. They have also found that mice that were adults and used to living in social environments were alot less agressive when a new male was introduced at adulthood. Although I would steer clear of that. I believe if they are siblings that it will be fine. Some good tips tho.. make sure there is plenty of space, nesting material and food. This way there is no urge to fight over these things. Also male mice are very territorial. Sometimes they will fight. If blood is drawn that is where you need to remove the problem mouse or if you notice a mouse being excluded from the sleeping area picked on etc might be time for a solo cage etc. A great suggestion is to make sure to clean the cage often . If you notispats do a deep clean. Researches believe this does like a reset to the male mice territorial aggression . Male mice do not usually kill eachother. They have a hierarchy or pecking order. Once this is established they will usually get along fine. Again if they are wounding eachother then I would step in but spats are normal way if establishing pecking order. I am almost certain that as long as they have grown up together it will be fine but def do the things like making sure they are in a big enough cage with plenty of stuff to go around to avoid fights. It's hard to tell when they are young what sex they are but 1 is a female genitals are much closer to it's anus. Like 1/4 inch . They have a vaginal plug that looks like a lil bulge or bump and can be mistaken for a boy but again a females lil bump will be much closer to her bottom ( might not have vaginal plug if young but again that area is pretty close to the tail Wink

I hope this helps! Good luck

by River Mon 22 Mar 2021, 10:26 pm

This thread is over a year old and unfortunately these mice are likely no longer with us. However I will say, the studies show that when housing intact males together, more space encourages fighting over territory. Smile

by P.m.Bardii Tue 25 Apr 2023, 11:36 am

I realize this is quite an old post but it seems like this user was badly misinformed several times here and elsewhere about the care of these mice, including the incorrect sexing of them leading to this accidental litter.

The pictures they posted are very clearly a male deer mouse Peromyscus sp. which can't be sexed by reference to "true" old world mice genus Mus.

Almost none of the research being discussed applies to Peromyscus sp. more than any other rodent except by coincidence. Mus is more closely related to true rats, and Peromyscus to gerbils and voles than to each other.

Depending on (US or Native American) jurisdiction re-releasing wild Mus is generally illegal and Peromyscus might be legally required, or it might be a serious crime (requiring you to euthanize them or turn them in to be euthanized.)

Any specific advice likely depends on knowing at least the genus and the country+region in question.

Leaving aside the other common "wild mice" such as wood mice.

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Introducing male mice to same cage?!

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