It could be a possum. Check the to see if there is a hole where they can get in. I had to place a 4x4 board around the bottom of the fence. Check your fence to make sure there is not any hole they can get in. Can you tell if they were tring to pull the hen though the face, if so that means your fence may have to large of a hole. As for snakes I put out moth balls. It work !!! I hope this helps. PS I use chain link fence. So sorry this is happening )))))hugs(((((