So I want to breed rats because I need something bigger than an adult mouse and smaller than a small rat.. So I need to breed rats so I can get the right size. ALso, I don't want to pay upwards of $50 after shipping and handling for frozen rats from some website. Here's my question. I've had 2 female rats for a while now and I just bought a male rat today. How do I go about introducing them? I tried earlier and one of the girls nipped at the male? Any ideas? Thanks. If you have any other insight that has to do with the entire process of breeding rats, it would be appreciated.