Some really interesting, maybe slightly disturbing, footage which may explain why some people are viscerally repelled by bats (fear of bats is called "chiroptophobia", FYI).

This appears to be Bat Week for me, with at least one other bat-related video (which I find to be rare and interesting) which will be posted tomorrow.

FROM WIKIPEDIA:
The common vampire bat feeds primarily on mammalian blood, particularly that of livestock such as cattle and horses. Vampire bats feed on wild prey like the tapir, but seem to prefer domesticated animals, and favor horses over cattle when given the choice. Female animals, particularly those in estrus, are more often targeted than males. This could be because of the hormones.

Vampire bats hunt at night, using echolocation and olfaction to track down prey. They feed in a distance of 5 to 8 kilometers (3.1 to 5.0 mi) from their roost, and leave in an orderly fashion: bachelor males are the first to depart, followed by the females, and finally the harem males.

When a bat selects a target, it lands on it, or jumps up onto it from the ground, usually targeting the rump, flank, or neck of its prey; heat sensors in the nose help it to detect blood vessels near the surface of the skin. It pierces the animal's skin with its teeth, peels away a small flap, and laps up the blood with its tongue, which has lateral grooves adapted to this purpose. The blood is kept from clotting by an anticoagulant in the saliva.

When feeding, the blood is stored in the cardiac notch. Bats feed for 30 minutes and become so swollen with blood, they can barely fly. They must then hide themselves and wait for the blood to digest and some of the water to be excreted before taking off.

Vampire bats commonly return to the same host on consecutive nights, after marking the animal with urine. They are protective of their host and will fend off other bats while feeding. It is uncommon for two or more bats to feed on the same host, with the exception of mothers and their offspring.