Girls will be Girls

A researcher friend of mine once sent me this comment in an email-

I still can't get over the difference in male and female mice. 

No joke, males will bite each other and you can't mix and match boys in cages unless they have been together their whole lives. Even then, they fight. 

Females you can mix and match til the cows come home and the worse thing that happens is you get one girl who grooms the others so much they're all naked. You can tell who she is cause she's the only one without bald patches.