What is the smallest space a fisher cat has been able to fit through in your experience? The one that killed my hen wasn't able to get it back out of the enclosure because the hen was too big. I estimate that the gap that the fisher cat got through in the first place was about four inches. The gate had twisted because of the ice so it wasn't square in the frame any longer. The top was completely covered and there was no way that it could have dug under the fence because everything is frozen solid with a layer of ice on top of it.