Old post but good topic. It is probably either a fox, coyote or feral cat. I like the live trap because most of the events will be at night and I like to sleep at night. I have never seen a fox or feral cat sit still long enough for me to get a good shot. You should be able to keep coyotes out of a chicken coop as they are larger and less agile than foxes and cats. Is an electric fence feasible? I use one to keep coons away from biddies in the smaller elevated pen and it also works on the larger coop. I have not yet seen an animal, myself included, that likes touching an electric fence. I have killed all of the above mentioned predators with a .22 but I prefer a shotgun since they generally are on the move.