[1] The three species of vampire bats are the only mammals that have evolved to feed exclusively on blood (hematophagy) as micropredators, a strategy within parasitism.

[4][5] Hematophagy is uncommon due to the number of challenges to overcome for success: a large volume of liquid potentially overwhelming the kidneys and bladder,[6] the risk of iron poisoning,[7] and coping with excess protein.

[15] Recent analyses suggest that vampire bats arose from insectivores, which discount the frugivore, carnivore, and nectarivore hypotheses of origin.

[15] Within 4 million years of diverging from other Phyllostomidae, vampire bats had evolved all necessary adaptations for blood-feeding, making it one of the fastest examples of natural selection among mammals.

The common vampire bat, Desmodus rotundus, also has specialized thermoreceptors on its nose,[16] which aid the animal in locating areas where the blood flows close to the skin of its prey.

[21] Vampire bats also have a high level of resistance to a group of bloodborne viruses known as endogenous retroviruses, which insert copies of their genetic material into their host's genome.

A recent study has shown that common vampire bats tune a TRP-channel that is already heat-sensitive, TRPV1, by lowering its thermal activation threshold to about 30 °C (86 °F).

Vampire bats tend to live in colonies in almost completely dark places, such as caves, old wells, hollow trees, and buildings.

[30] Another ability that some vampire bats possess is identifying and monitoring the positions of conspecifics (individuals of the same species) simply by antiphonal calling.

Once the common vampire bat locates a host, such as a sleeping mammal, it lands and approaches it on the ground while on all fours.

Vampire bats, like snakes, have developed highly sensitive thermosensation, with specialized systems for detecting infrared radiation.

However, vampire bats tune a channel that is already heat-sensitive, TRPV1, by lowering its thermal activation threshold to about 30 °C (86 °F), which allows them to sense the target.

[35] If there is fur on the skin of the host, the common vampire bat uses its canine and cheek teeth like a barber's blades to shave away the hairs.

The stomach and intestine rapidly absorb the water in the blood meal, which is quickly transported to the kidneys, and on to the bladder for excretion.

[41] Typically, within two hours of setting out in search of food, the common vampire bat returns to its roost and settles down to spend the rest of the night digesting its meal.

[43] In a 2024 study published in Biology Letters, researchers explored how vampire bats generate energy from their blood meals, hypothesizing that they metabolize amino acids due to their low-carbohydrate and low-fat diet.

The team captured two dozen vampire bats in Belize and fed them cow blood enriched with glycine and leucine.

After consumption, the bats were placed on a treadmill for up to 90 minutes, during which breath samples were collected to measure oxygen intake and carbon dioxide output.

Michael Hiller, a researcher at the LOEWE Center for Translational Biodiversity Genomics in Frankfurt, noted that this rapid metabolization of amino acids is "unparalleled in mammals" and described it as a compelling example of convergent evolution, where both vampire bats and blood-feeding insects developed similar strategies to adapt to their extreme diets.

[44] This metabolic specialization presents drawbacks, as vampire bats have diminished their ability to store alternative energy sources, rendering them susceptible to starvation if they experience prolonged periods without feeding.

To counteract this vulnerability, vampire bats engage in reciprocal altruism, regurgitating blood to assist conspecifics in need.