About 2 yrs ago one of my breeder boys was in the process of dying, I did not know this and was trying to feed him some wet bread, he latched onto my finger, then died. It was only after he passed that I was able to pry his mouth off my finger.. it hurt a ton, it almost got infected.

Yeah, momma rats can be VERY protective of their young, but you can usually lure them away with food if you need to steal her babies.