My Rat Bit Me And Drew Blood, Why?

Have you washed your hands after you ate your food? i have 3 rats and anytime my hands smell like my food they like and nibble my fingers and bite a few times. Was he in his cage? if so he probably thought you were giving him a treat or food and had mistaken your hand for food and bit you. I wouldn't get mad about it. It was probably an accident. But if this continues, do some research on rats and i am sure you will find and answer. :)