To be honest when we first looked in I was expecting to see a dead guinea pig but to see an extra set of eyes peering back was a complete shock.
We have always had problems with cats since we moved in this house (we lost a guinea pig to a cat 2 days after moving in!!) and so we had secured both the guinea pigs runs with chicken wire. We also placed a tube between the two runs but had to make a hole in the wire to allow the tube in. Unfortunately over time a slight gap had occured between the tube and the wire with moving one of the runs, but since it was no where big enough for a cat to get in we didn't worry but it must have been big enough for the ferret
