Recently captured wild mice

Question

Mousie   Hi Tamarah,

    We have recently just caught 3 wild mice and still at least another running around.  First thing i would like to know is what kind are they might be a little hard to see but it is the best pictures i have also fast. Needed question is i am unable at this time to tell their sex but one of the mice seems to always try to mount the others, well one on particular. Does that mean things one doing the mounting  is is the male? He will also like try either licking out biting they're back of the others neck as he does the mounting is it a foreplay thing or its he actually trying to get her? One last question is since i have caught them they seem to be " wet " all the time what is wrong with them? Is it normal or is it because their space is too small for them right now? They are in a temporary home till tomorrow.

Answer
Hi Stacey,

They look to me like regular house mice, mus musculus, but a vet or even a wildlife rehabilitator who works with small mammals would be able to tell you better than I could from a photograph.  Mounting may imply that he is male, but even females will mount when they are trying to assert dominance.  One easy way to tell is to put something in their enclosure that he can perch on, such as the side of a food bowl, and look for a scrotal sac.  In this hunched position, the testicles will descend into the sac and should be obvious.  This may not be the case if he is very young, but if he is doing a lot of mounting, he should be sexually mature.  Licking and biting while mounting is common across many species, and is part of courtship, as well as also a means to control the female and prevent her from running away.  Unless you see blood or scabbing, this is not dangerous.  Unless you want babies, however, you may want to go ahead and separate them anyways!

I am not sure what the wetness could be.  If you have a water bowl in the cage, rather than a water bottle, they may be tipping it or getting the bedding or floor wet.  It could result from overgrooming, poor coat condition from bad nutrition or environment, or any number of other things.  The mouse pictured does not look wet to me - could you provide me with more details about their living situation and I could take a better guess?

Best of luck, and let me know if I can help with anything else!
-Tam