I'm petless at the moment--but in my time I've had four dogs, a cat, a turtle, tropical fish, and a litter of mice.
My daughter bought a white mouse from a pet shop (it was designed to be snake food). She did some (humane) tests with it for her school science fair. On Christmas Day we found out she was a female, because she had a litter of ten babies!
But as we were researching how to care for them, she ate them all one by one!
She didn't live much longer after that.