hi we collected our beautiful two baby rats from the breeder today, having chosen them by playing with them, they were all very sweet and tame and we chose two to bring home. but one of them has bitten quite hard several times today when she has been being handled gently, and my children are very sad about this. the breeder says none of them have ever bitten before. could the rat just be stressed about her new environment, or is this going to be a problem? they have a huge cage with lots of toys and nice food so i am not sure where to go from here. thanks!