https://phys.org/news/2018-10-vampire-traits-natural-world.html

The primary characteristic of a vampire is feeding on blood. Although many ectoparasites such as mosquitoes and leeches also drink blood, the vampire bat is the only species of mammal that is truly haematophagic (feeds exclusively on blood).

Vampire bats prey on warm-blooded animals such as livestock, locating blood hotspots with their inbuilt infra-red heat sensors, and even utilise a protein called "draculin" to keep their prey's blood flowing.