Agree with rammer. In my business I started by shooting them in the head, but they always sprayed, lung shots worked better. I have found though that if you trap them in a covered trap, then cover the door so they cant see you and transport the cage gently to a large trash can full of water, you can drown them without any problems. Just be sure to drop the cage in the water suddenly so they don't have a chance to take a breath.