Tibby is the same way and she's been like that since I got her. I kept hoping she would grow out of it, but so far she hasn't. It doesn't matter what it is, pens, books, paper, hair ties. She chews on it all, I have to be really careful as to what I leave lying around the house or she'll chew on it. Her favorite are straws. My roommate and I always forget and leave drinks on our coffee table, if we get up to do something when we get back the cup is turned over and the straw is gone.