Vampire Bat

The common vampire bat is a small leaf-nosed bat native to the Americas, ranging from Mexico through Central and South America. It feeds mainly on the blood of mammals, particularly livestock such as cattle and horses, hunting at night within 5 to 8 km of its roost. Heat sensors in the nose help it find blood vessels near the skin surface, and it bites away a small flap of skin and laps up the blood with a grooved tongue, while an anticoagulant in its saliva stops clotting. It is one of the most social bats, and unlike most bats it can run on the ground using a bounding gait driven by its forelimbs.

About the vampire bat

The common vampire bat is a small leaf-nosed bat from Mexico, Central America and South America that feeds on the blood of other animals. It is one of three living vampire bat species, alongside the hairy-legged and white-winged vampire bats. Its scientific name is Desmodus rotundus, and it is the only living member of its genus.

The fur is short, grayish-brown on the back and lighter, silvery gray underneath. The muzzle is compact and looks slightly swollen, with a flat, leaf-shaped nose and pointed ears. The lower lip has a deep groove. There's no tail, and the membrane between the hind legs is reduced. Females are usually larger than males.

Its whole skull is shaped for its diet. The braincase is large, but the snout is shortened to make room for big incisors and canines. The upper incisors lack enamel, which keeps them razor-sharp, and with only 18 teeth it has fewer than any other bat. The tongue has two grooves along its sides that expand and contract as the bat feeds.

The thumbs are long, clawed and well developed, with three pads underneath that work like the sole of a foot. Common vampire bats can be told from the other two vampire species by this longer thumb. Strong hind legs and those thumbs let them do something almost no other bat can: move confidently on the ground.

Behavior and diet

Vampire bats are nocturnal. They hunt in the dark, using echolocation, smell, hearing and good eyesight to find sleeping animals, usually 5–8 km (3.1–5 mi) from the roost. Heat sensors in the nose help pinpoint blood vessels near the skin.

A bat usually lands near its target and walks or hops up to it, then climbs on, usually backward or slightly sideways, staying highly alert. It makes a small cut, about 3 mm (0.1 in), on the rump, flank or neck and laps up the blood. The bite is relatively painless and rarely wakes the host. An anticoagulant in the saliva, named draculin after Count Dracula, keeps the blood flowing.

Common vampire bats feed only on blood. Cattle and horses are the main hosts, and given the choice they prefer horses. They also feed on wild mammals such as tapirs and occasionally on people. A bat can weigh much more after one meal, so it may not be able to take off directly from the ground and instead jumps into the air. It is the only species that can launch almost vertically into flight from a flat surface.

On the ground, a vampire bat runs with an unusual bounding gait, pushing off with its powerful wings rather than its legs. It can leap forward, backward and sideways, which helps it dodge hooves and predators such as owls and snakes.

Few bats are more social. Colonies contain both sexes, and females form bonds that last for years. Roostmates groom each other, and a bat that has fed will regurgitate part of its blood meal for a hungry companion. In a long field study in Costa Rica, 70 percent of food sharing was mothers feeding pups, and almost all of it was between close relatives. Among familiar bats, the best predictor of how much one bat gives another is how much it has received from that bat.

Vampire bats breed year-round, with more births in the rainy season. After about seven months of gestation, a female has one pup, which she raises largely on her own. Young bats start hunting with their mothers at six months and are fully weaned at nine. Daughters usually stay in their birth group, while sons leave at one to two years old.

Range and habitat

The common vampire bat lives in parts of Mexico, Central America and South America, and on the islands of Trinidad and Margarita. Its northern limit is about 280 km (170 mi) south of the U.S.-Mexico border, though fossils of the species have been found in Florida and in states bordering Mexico. To the south it reaches Uruguay, northern Argentina and central Chile. It is the most common bat in southeastern Brazil.

It favors warm, humid climates and forages in tropical and subtropical woodland and open grassland. Roosts include hollow trees, caves, abandoned buildings, old wells and mines. Vampire bats share roosts with about 45 other bat species and tend to dominate them, taking the darkest, highest spots.

Vampire bat vs other vampire bats

The common vampire bat is one of three "true" vampire bats in the subfamily Desmodontinae, all of which specialize in the blood of warm-blooded animals. The so-called "false vampires" are separate bats in other groups, such as the family Megadermatidae and the spectral bat.

Conservation status

The common vampire bat is listed as Least Concern on the IUCN Red List because of its wide range, presumed large population and tolerance of some habitat change. Populations have actually increased since livestock were introduced to South America, giving the bats an abundant new food source.

Because it feeds on livestock and carries rabies, it is widely considered a pest. Rabies is most common in the large vampire bat populations of South America, and the main danger is to livestock rather than people; losses to the Latin American cattle industry run to many millions of dollars a year. The bats also have medical value. A drug called desmoteplase, based on the anticoagulant in their saliva, has been shown to increase blood flow in stroke patients. For a look at bats with a very different diet, see the Seba's short-tailed bat and straw-colored fruit bat.