female rat who bites

Question
Hello, I have a pair of female rats that are sisters. they both came from a private breeder and were handled from birth. they are now about 5 months old. I have had many female rats in the past, and am generally familiar with rat behavior, but one of my girls is really stumping me.She is overall a pretty fearful rat, although she has experienced nothing traumatic that I know of. She has always been a nipper--playfully at first, when she was little. Now she has bitten be out of fear at least once, and broken the skin--I learned from that not to reach for her too quickly. She has bitten me many times by mistake, thinking my hand is food, and she had nipped me a few time as a warning, when I touched her in a way she didn't like (I have been trying to get her used to being touched and petted, but she frequently nips me when I do this, no matter how I approach her). Pretty much any time I put my hand near her, she puts her teeth on me. Sometimes she grooms me, too, and whenever I actually pick her up, she shows no fear, but most of the time she puts her teeth on me again and again (usually gently), until I take my hand away. Her sisters does none of these things, and is totally trusting. I am stumped as to how I can get my fearful rat to change this behavior and trust me more. What should I do to get her to stop biting so much?

Answer
Hi Rachel,
It could be she was not as well socialized as her sisters, or she just has a more suspicious dominant personality, which needed more socialization than she got. Or, she could have too much testosterone that makes her extra dominant and aggressive.

The article called Trust Training on my website at www.ratfanclub.org might help some. It also might help to have her spayed. Spaying will not only reduce aggression but also help prevent mammary and pituitary tumors!
Deb