I've got a garage door gap too. I know we've had mice in our garage but I figure they would give the chickens something to play football with if they can catch it. I'm not aware of rats out here at all, and we have yet to see a snake close to the house. I'm going to stuff the spots I can with bricks and we'll see how it goes. I figure if my cats are afraid of the chicks they're probably big enough to handle any garage wildlife we get.