Every animal on this planet adapted to survive based on where they live. A well-known example is the group of so-called Darwin’s finches on the Galápagos Islands. There are 14 difference species that all evolved from a common ancestor and have different beak shapes based on what they eat. And while you may have learned that some eat seeds while others eat insects, the wildest is the vampire ground finch. It uses its sharp beak to draw blood from other birds, as seen in the video below. They perch on much-larger seabirds called boobies and pull out their feathers, pecking at their skin until they bleed.

Another of the finch’s feeding strategies is to roll other bird’s eggs into rocks until they break open and feast on those. They also eat the usual seeds and insects, and even drink nectar. But they have had to resort to these more drastic measures since there is no reliable source of fresh water on the remote Wolf and Darwin Islands where they live. It may have even started as a mutually beneficial relationship, with the finches removing lice from the booby’s skin. But at some point they developed a taste for blood.

Scientists originally categorized the vampire finch as a subspecies of the sharp-beaked ground finch present on other islands. But it has recently been declared its own species and officially named the vampire ground finch. Scientists who study them report the birds have bellies full of blood and beaks stained red, so it may be a large part of their diet.  

A vampire finch sits on the tail of a booby and drinks its blood
National Geographic

Vampire finches are not the only animal to act like they’re in horror movies. While they doesn’t feast on blood, cassowaries are quite scary. Even though human ancestors kept them as pets, the flightless Australian birds are basically still dinosaurs. There are of course also vampire bats that snack on blood. And even if it weirds us out, at least these vampires have an ecological niche to fill.

Melissa is Nerdist’s science & technology staff writer. She also moderates “science of” panels at conventions and co-hosts Star Warsologies, a podcast about science and Star Wars. Follow her on Twitter @melissatruth.