About twenty years ago, I knew a guy who owned a snake that was fed with live white mice. Once, around feeding time, he and another guy we knew ended up making a bet about what would happen if the mouse was exposed to vacuum prior to becoming lunch. Long story short, it was put in a glass chamber from which the air was evacuated over the course of about a minute. Basically, it sniffed around for a few seconds then abruptly fell over dead, with the only external sign of damage being a small dot of blood on its nose.