Vampire Bats - Vertebrate Sanguivores
Of the 1100 species of bats, only three are vampire bats. They are the common vampire bat (Desmodus rotundus), the white winged vampire bat (Diaemus youngi), and the hairy legged vampire bat (Diphylla ecaudata).
These mammalian sanguivores are only found in Mexico, Central America, South America, and two Caribbean islands (Trinidad and Marguarita). So contrary to what many people may think, vampire bats do not occur in North America (or Europe, Asia, Africa, and Australia for that matter). Unfortunately, this has not stopped people from destroying millions of beneficial bats.
Where vampire bats do occur, Desmodus rotundus is responsible for most of the bat related problems - which include the spread of diseases like rabies and the loss of revenue due to livestock deaths.
Desmodus sneaks up on its warm-blooded prey and makes a painless bite using razor-sharp incisor and canines. The small, divot shaped wound is often made on the animal's back (see photo), ears, nose, or behind a hoof. Unlike normal wounds, vampire bat bites can bleed for many hours because of the potent anticoagulants contained in their saliva (which is applied by a piston-like motion of the bat's tongue).
Diaemus and Diphylla, on the other hand, are more rare throughout their ranges, and feed primarily on birds - especially human introduced poultry.
In prehistoric times (and until relatively recently according to the late vampire bat expert Arthur Greenhall), a giant vampire bat, Desmodus draculae, lived in South America, ranging as far north as the US. This super-sized sanguivore was thought to have preyed on the large mammals (e.g., giant ground sloths) that once inhabited these regions. Greenhall's belief that Desmodus draculae may still be alive somewhere in the Brazilian wilderness served as the inspiration for "draculae", Bill Schutt's upcoming novel about these blood-feeding creatures.
But as spectacular as Desmodus draculae must have been, the three extant vampire bats species remain fascinating subjects for research. For example, with a diet completely devoid of fat, vampire bats cannot store energy or nutrients like non-blood feeders creatures. As a result, these winged sanguivores must obtain blood meals each night or risk starvation.
To cope with this problem, and other constraints related to their unique liquid diets, vampire bats have evolved some rather incredible adaptations. These include blood sharing with relatives or roost mates who have been unsuccessful at finding a meal that night. This altruistic behavior (rare in the animal kingdom) has a unique anatomical component as well. The blood regurgitated during this process is stored undigested in a small pouch-like section of the donor bat's stomach (which actually looks more like an intestine). Razor sharp teeth, stealthy behavior, and a face equipped with temperature sensing organs called thermoreceptors, enable these bats to exploit an abundant food source - blood.
So vampire bats aren't monsters. They're merely taking advantage of our annoying habit of destroying natural habitats and bringing in livestock like cows and chickens (see photo below). It's the presence of these walking blood bags that can lead to increases in vampire bat population size.