Hi Hogs-R-Us
Welcome to the Forum.
Ah, the perennial problem of cats! It looks to me as if lowering the height of the entrance tunnel, or part of it might help. You could try putting a brick or a row of bricks (or offcuts of wood) along the tunnel, but maybe not too close to the actual door or the hogs might not be able to get in either! Might be worth a try, but usually a bit of trial and error is required to get it just right. The theory is that it’s hard for cats to turn at the same time as they are flattening themselves to squeeze through something low. Easier for hogs with their shorter length. Also, cats can get through a small short space quite easily, but longer is more difficult.
Good luck.
