Common Vampire Bat

Only three bat species drink blood, and the common vampire bat is the most widespread. It lands beside a sleeping animal, often livestock, makes a painless razor-thin cut with its sharp front teeth, and laps the trickling blood — anticoagulants in its saliva keep the wound open for the half hour or so it feeds.

A failed hunter can starve within days, so roostmates share swallowed blood by mouth-to-mouth regurgitation, one of the few food-sharing systems known in any wild animal.