Anybody know how to tell the gender of a mouse?

[yukichigai]

Okay, this one requires a little backstory. About two months ago my cat (Ares) caught me not one but two mice which were quite literally just old enough to eat solid food. I found the momma mouse dead behind one of my bookcases so, being the bleeding heart I am, I decided to keep the little guys as pets. (It helped that they were on a cuteness scale rivaling a bucket o' kittens) Unfortunately Ares did a little more damage to the one than I first estimated and it died the next day. Since then the surviving sibling has been alone, and since mice are social creatures it's become sorta... anti-social. (I never see the damn thing)

Flash forward to about 20 minutes ago. Ares comes trotting in with another trophy mouse. (Which he promptly loses track of. Worst. Mouser. Ever.) I manage to rescue it in the hopes that maybe my first mouse will now have a playmate. So what's the problem?

Apparently if you put two adult male mice in the same cage they'll kill each other. This is undesirable. I've never been able to get hold of Quasi (the first one, named after the hunchback 'cause he/she is sorta... deformed) to figure out what sex he/she is, and inspecting the new one showed nothing real obvious. What am I looking for here?

Cliff notes:

I have one mouse
Cat just caught another
Two male mice in same cage = at least one dead mouse
How can I figure out the gender of the new mouse?

 

[Captante]

Well I know male hamsters had large & very obvious testicles if you looked ... this would or course require a close examination of the mouse in question.


Edit: Heres some more useful advice!


Some more!

 

[yukichigai]

Well that's mighty useful, thank you. I'll have to put it to use tomorrow morning.