The Art of Sanguinivory

Desmodus rotundus will not be seen swooping down and attacking the neck of an innocent bystander.  Rather, the nocturnal bat finds its prey in the dark and lands near it before running over to the sleeping animal using its long front legs.  The vampire will then position itself near a blood-rich area and use heat-sensitive cells in its nose to detect the location of capillaries.  Once it finds a capillary, it slashes tiny cuts in the skin and licks the area with anticoagulant-filled saliva.  As the blood seeps out of the small wound, the bat simply licks it up with its tongue.  


Vampire bat feeding off the wound of a pig.

It can take roughly half an hour for the bat to drink its fill before leaving the animal, although the bats are often known for drinking so much that they cannot leave the ground immediately after a meal.  The amazing efficiency of the bats kidneys allow it to expel excess plasma from the blood meal even while they are still eating, thus lightening their load.  As they finish eating, the kidneys then switch over to allow the plasma to remain in the bat to help dilute the nitrogenous wastes resulting from the metabolism of the proteins in the blood (Altringham, 1996).  

Aside from the subtleties of vampire bat feeding, it is of note that Desmodus rotundus can run on the ground rather well.  It is one of only two species of bats capable of this type of terrestrial motility.  Most bats are capable only of hopping awkardly along, but the common vampire bat has evolved the ability to run with a gait like that of a mouse, except that the role of the fore and hind legs are reversed (Riskin et al., 2006).

In Light of Taste Aversion (or Lack Thereof...)

It is also known that vampire bats have the ability to regurgitate facultatively when feeding its young, a behavior not observed in any fruitivirous bat species. This has interesting implications when considering the reasons why vampire bats may lack taste aversion.  A bat may not be capable of or restrained in both regurgitating its food as a taste aversive reaction and regurgitating its food as a response to feeding its young.  In short, the ability to vomit in the absence of toxicosis would have preadapted early vampire bats for mother-offspring regurgitation (Wilkinson 1984).