Short of cats? When older vehicles are left unattended, mice find a way to get inside. It’s their natural instinct! The damage they do with their families over a few years is a disaster to metal. They don’t seem to leave the nest when their bladder says “it’s time”.
This nest was recently found inside a 1941 Chevrolet ½ ton door when the inside panel was removed. There it was as you see it, the past home for many generations of mice. It appears they removed much padding from the adjacent seat!
See below this 1940 Chevy upper air dam under the hood. What a perfect place for a mouse house. Out of the reach of cats, hawks, snakes, wind and rain! The little guys just keep bringing in more nesting materials. They make more and more babies and of course we know what else they do that rusts out the sheet metal.