Common Vampire Bat (Desmodus rotundus): Facts and Diet

The three vampire bats

Only three of the world’s more than 1,400 bat species feed on blood, and all of them live in the Americas. Together they form the subfamily Desmodontinae within the New World leaf-nosed bats (family Phyllostomidae). They are the only mammals that live entirely on blood.

• Common vampire bat (Desmodus rotundus): by far the most widespread and abundant; feeds mostly on mammals.
• Hairy-legged vampire bat (Diphylla ecaudata): feeds mostly on the blood of birds.
• White-winged vampire bat (Diaemus youngi): also prefers birds, including free-ranging chickens and turkeys; it has white wing edges.

The common vampire bat is the one people usually mean by “vampire bat.” It can be told from the other two by its long, well-developed thumbs, which it uses like front feet. Several other bats, such as the spectral bat of the American tropics and the “false vampire” bats of the Old World, have vampire-like names but eat insects, frogs, birds or other bats, not blood.

Appearance and size

The common vampire bat is short-haired, with grayish-brown or dark brown fur on the back and paler, silvery-gray fur on the belly. It has a short, flat nose without the tall nose leaf of its relatives, pointed ears, fairly large eyes and a deeply grooved lower lip. There is no external tail.

It is much smaller than its reputation suggests. The head and body measure about 7–9 cm (2.8–3.5 in) and adults usually weigh 25–40 g (0.9–1.4 oz), with an overall range of about 15–50 g (0.5–1.8 oz). The wingspan is roughly 35–40 cm (14–16 in). Females are usually a little bigger than males.

The teeth are highly specialized. The upper incisors and canines are large and blade-like, and the incisors lack enamel, so they stay razor-sharp as they wear. The cheek teeth, by contrast, are tiny, because the bat never chews.

A bat that walks and runs

Most bats are clumsy on the ground, but the common vampire bat walks, hops, jumps and even runs on all fours. It uses its folded wings as front legs, pushing off with the powerful flight muscles and gripping with long thumbs that have pads on the underside. In laboratory tests on a treadmill, vampire bats ran at a little over 1 meter per second, about 4 km/h (2.5 mph), with a bounding gait that evolved independently from that of other mammals.

This skill matters for feeding. A vampire bat often lands near a sleeping animal and approaches it on foot, then climbs up a leg or flank. It can leap sideways or backward out of the way of a kicking hoof, and after a heavy meal it launches itself almost vertically into the air with its wings, because it is too heavy to simply drop off and fly.

Diet and feeding

The common vampire bat is an obligate blood-feeder, called a sanguivore: it eats nothing else. In the wild its original hosts were tapirs, deer, peccaries and other large mammals, and it still feeds on sea lions and even penguins on parts of the Peruvian coast. Today, though, most of its meals come from cattle, horses, pigs, goats and donkeys, which are easy to find and often sleep in the open. Given a choice, it seems to prefer horses over cattle.

The bat hunts only in full darkness, usually within about 5–8 km (3–5 mi) of its roost. It finds hosts using smell, hearing and vision, and laboratory work suggests it can recognize individual animals by the sound of their breathing. Once on the host, it uses heat-sensitive spots on its nose to find a place where blood vessels run close to the skin, often on the neck, flank, rump, ears or feet.

It shaves away hair with its teeth if needed, then cuts a small, shallow wound and laps, rather than sucks, the blood with its grooved tongue. Its saliva contains anticoagulants, including a protein named draculin, that keep the blood flowing for the 20–30 minutes a meal can last. A bat drinks about 20 ml (4 teaspoons) of blood, roughly half its body weight, and starts to pass urine within about two minutes so that it can still fly. The full story is in Do vampire bats really drink blood?

A heat-sensing nose

The common vampire bat is one of very few vertebrates known to sense infrared heat, a skill otherwise associated with pit vipers, pythons and boas. Specialized nerve endings on the nose leaf and upper lip respond to radiant warmth. A study published in Nature in 2011 showed that vampire bats achieve this by modifying a heat-sensitive channel called TRPV1 so that it switches on at about 30 °C (86 °F) instead of the usual painful-heat threshold. This lets the bat “feel” warm, blood-rich patches of skin from a short distance before it bites.

The bat also uses echolocation, calling through its mouth, but its calls are quiet and short, like those of fruit-eating bats. Compared with insect-eating bats, it relies more on smell, sight and hearing. For how other bats use sound, see How do bats use echolocation?

Habitat and range

The common vampire bat lives from northern Mexico, about 280 km (170 mi) south of the US border, through Central America and most of tropical South America to Uruguay, northern Argentina and central Chile. In the Caribbean it occurs only on Trinidad and Venezuela’s Margarita Island. It is found from sea level up to about 2,400 m (7,900 ft).

It needs warm climates: its northern limit roughly follows the line where January temperatures stay above about 10 °C (50 °F). Within that zone it uses rainforest, dry forest, scrub and open grassland, and it thrives in cattle-ranching country. More on its range and roosts is in Where do vampire bats live?

Roosts and social life

Vampire bats roost by day in very dark places: caves, hollow trees, mine shafts, wells, culverts and abandoned buildings. Colonies usually hold about 20–100 bats, although roosts with thousands have been reported. Their roosts often smell strongly of ammonia from digested blood.

Colonies are built around groups of adult females and their young, which may stay together for years. Female offspring often remain in the group where they were born, while young males leave or are driven out at about one to two years old. A dominant male defends a roosting spot used by females and fathers most of their young, while other males roost nearby.

Common vampire bats are among the most social of all bats. Roost-mates groom each other, and well-fed bats regurgitate blood to feed hungry partners that failed to find a meal. This food sharing, first studied in the wild in Costa Rica by Gerald Wilkinson in the late 1970s and early 1980s, is a famous example of cooperation in animals. Read more in Why do vampire bats share food?

Reproduction and lifespan

Vampire bats can breed at any time of year, though births tend to peak in the rainy season. After a long gestation of about seven months, a female gives birth to a single, well-developed pup weighing about 5–7 g (0.2 oz); twins are rare. For roughly the first month the pup drinks only milk, then the mother begins feeding it regurgitated blood.

Young bats start to follow their mothers on foraging trips at around four to six months old and are fully weaned at about nine months, a long childhood for such a small mammal. For a bat of its size the common vampire bat is long-lived: wild individuals have been recorded at about 12 years, and one captive bat lived to about 19.5 years.

Predators and threats

Adult vampire bats have few regular predators, but owls, hawks and snakes catch them at roost entrances or when they are on the ground, and boas sometimes take bats from cave walls. Young bats are most vulnerable.

People are the main threat. Because vampire bats spread rabies to livestock, many countries in Latin America run control programs against them, and roosts are sometimes destroyed. These campaigns can harm other, harmless bat species that share the same roosts. Research in Peru has also suggested that killing bats does not necessarily reduce rabies in colonies.

Conservation status

The IUCN Red List classifies the common vampire bat as Least Concern (assessment 2015) because it has a very wide range, a large population and tolerates disturbed habitats. It has very likely become more numerous since European settlers introduced cattle, horses and pigs to the Americas, creating a steady new food supply. Scientists are watching whether warming winters could let it spread farther north in Mexico.

Myths and facts

Myth: vampire bats suck blood. They lap it from a small cut, like a cat lapping milk.

Myth: vampire bats kill their victims. The amount taken is small. The real harm comes from infected wounds and rabies.

Myth: vampire bats inspired vampire legends. The vampires of Eastern European folklore are older than Europe’s knowledge of blood-feeding bats. The bats were named after the legends, not the other way around, and Bram Stoker’s novel Dracula (1897) later tied vampires and bats together in popular culture.

Myth: vampire bats are blind. They have good eyesight and may use vision to find their way over long distances.

Relationship with people

In Latin America, vampire bats are a serious agricultural problem because they spread rabies to cattle, causing losses estimated at many millions of dollars a year. Where dogs are widely vaccinated, vampire bats have become a leading source of human rabies in parts of the region, especially in remote Amazonian communities. Anyone bitten by a bat should seek medical help immediately.

The bats have also given something back. Their saliva contains a powerful clot-dissolving protein, and a genetically engineered version named desmoteplase was tested in clinical trials as a possible treatment for stroke, although it has not become an approved medicine. Vampire bats also remain one of the best-studied examples of cooperation and friendship in mammals.