I got four baby rats a few months ago, (1 female, 3 males) and it had been over 5 years since I last had a female rat. Anyway, virtually from the start of me getting her (The Duchess is her name), she started to do a certain behavior that some of my previous females had done also. This is chew on the soles of my feet. Now all this is cute and all when you have a hard callous on your feet, but over the last couple of months, she has chewed through the callous and is now hitting fresh skin/flesh (And a couple of weeks ago, one of my males watched her do it and now he wants to do it too). How can I stop them? (squeaking only seems to work with the male, but Duchess totally ignores the squeaks). I am not even sure why it seems to be something females like to do.