Pulling through the holes is a typical raccoon behavior. They have those little hands and can do it. Other animals just have paws.
That's why hardware cloth is the best for prey animal containment. Once they've had a nice dinner, they will be back for more...
I do have hardware cloth around the side of the tractor. Whatever it was pulled the chicken's leg underneath the side of the tractor where the bottom of the tractor meets the ground. It now has chicken wire around the ground outside of the tractor like a skirt to keep anything from digging under.
The rabbits on the other hand do have larger holes on their cages. The next cages will definitely have hardware cloth.
I did read you'd made the skirts for the tractors and knew that was a good idea!
Re: rabbits whatever it was, will be back in time for the next dinner...