A couple of comments:
1)Even if a squirrel fell in there, what’s to stop them from just climbing out? An animal that can climb up the side of a tree and walk on a electric power line like a tightrope walker could surely climb up the side of a hole. You need a cage kind of trap to catch an animal like a squirrel.2) How did Monty fall in the hole in the first place? In the third panel it shows he was leaning forward to pick up the whatevers, if he did that consistently, he shouldn’t have been in any danger at all. He would have had to walk directly on to the leaves to fall in and if he had he would have fallen in feet rather than head-first as depicted.