You might have to deworm them periodically. Not sure what you could do about making sure the 'kill' hasn't been poisoned. That would be my main concern.
They won't eat voles. Don't' think they eat moles either but can't remember.
It's MICHELLE, scarfish! My name is MICHELLE! Jax is my DOG!
~The strength of one's opinion should not exceed their knowledge on the matter~