I wouldn't worry too much. My Dog Felice kills little animals too when ever she gets the chance. Last summer he killed two skunks and a count less number of rats. I just try to make sure nothing can get into the pen because I know that what ever gets in is fair game to her. I know if a cat got in(its alright if our cats come in but no one elses!)or if a small dog got in it would be all over! When she started doing this it scared me. I thought she had gone nuts but I relized that she just has a HIGH prey drive and I just have to live with it.