The common vampire bat is found from Mexico to Argentina and Chile. (Turner, 1975)
Common vampire bats are limited to warm climates. They can be found in both arid and humid parts of the tropics and subtropics. They occur up to 2400 meters in elevation (Dr. A. Ramirez, National Coordinator Rabies Program, México, pers. comm.). The distribution is thought to approximate the extent of the 10 degree minimal isotherm for January.
The bats usually live in colonies ranging from 20 to 100 individuals although much larger colonies (up to 5,000) have been reported. Desmodus rotundus roosts in moderately lighted caves with deep fissures, and in tree hollows. Vampire bats can also be found in old wells, mine shafts, and abandoned buildings. Roosts often smell strongly of ammonia because of the digested blood that has collected in the crevices and on the floors of the roosts. (Brass, 1994)
Desmodus rotundus has grayish-brown fur which is lighter on the ventral side. The muzzle is compact and looks swollen, and the ears are pointy. The wing span averages 350-400mm and the head and body length is usually 70-90mm. The common vampire bat has no tail and the membrane between the hind legs, called the uropatagium, is reduced. Females are usually larger than males.
The common vampire bat is highly adapted for its specialized feeding behavior. The braincase is large and the rostrum is reduced to accomodate large razor-sharp incisors and canines. There are two lateral grooves in the tongue that expand and contract as the bat feeds. Desmodus rotundus has an acute sense of smell and large eyes.
The limbs are also specialized. The thumb of the wing is long and well developed, and the hind legs are strong. (Altenbach, 1979; Brass, 1994; Macdonald, 1984; Walker, 1975)
Males compete for space in roosting places containing females. When more than one male occupies a roost, each defends a small part of the roost from other males. Wilkinson observed resident males in tree roosts actively defending their territory from other wandering males. Defense often includes chasing, pushing, and fighting. Fighting consists of gesturing, striking with the wings, and biting.
Mating behavior begins with a male climbing onto a female's back, grasping her folded wings with his wings, and holding the back of her neck in his mouth. Copulation lasts three to four minutes. (Wilkinson, 1985; Wilkinson, 1986)
Desmodus rotundus is believed to be sexually active throughout the year. Although young may be born at any time during the year, peak times for births occurred during April and May and in October and November. A higher number of pregnant females were seen during the rainy season in Mexico and Costa Rica. Most females have one pregnancy per year, but it is possible to have more than one pregnancy in a year. The gestation period is about seven months. Usually only a single young is born, but occasionally there are twins. The newborns are well developed and weigh between five and seven grams at birth. For the first month, the young feed strictly on the mother's milk. Their weight doubles during this time. The young are introduced to blood meals by receiving regurgitated blood from the mother during the second month of life and they accompany their mothers on hunts when they are four months old. The rapid growth is complete in five months. (Lord, 1992; Turner, 1975)
The life span of vampire bats may be as long as 12 years.
Much of the behavior exhibited by common vampire bats revolves around their methods of obtaining food. Terrestrial movement is a critical part of stalking and attacking prey. Unlike other bat species, Desmodus rotundus can walk, run, and hop quadrupedally along the ground. The weight of the bat is supported by the strong hind limbs and modified thumbs. When faster accelerations are necessary, hopping and jumping are preferred (see Altenbach, 1979 for detailed descriptions and pictures of locomotion).
This species is agile and stealthy. Usually when a bat approaches its prey, it does not land directly on the animal, but rather, lands nearby and walks or hops up to the unsuspecting victim. It then climbs up the animal and finds a suitable meal site. Desmodus rotundus usually climbs backwards, or slightly sideways and is always highly alert while climbing. It is light on its feet and moves delicately to avoid detection. Once the site has been chosen the bat makes a 3mm incision in the skin and laps up the blood from the wound. The bite is relatively painless and rarely wakes a sleeping victim.
Quick reflexes and agile movement are important qualities when avoiding the unpredictible responses of large prey such as livestock. Jumping is one of the vampire bat's main avoidance techniques. It has the ability to jump forward, backward, and laterally. These movements provide quick escape routes from kicking hooves, swishing tails, and even other predators such as owls and snakes.
Jumping is also used to initiate flight. Particularly after a large meal, a bat may not be able to take flight directly from the ground. Jumping allows Desmodus rotundus to get a heavy stomach off the ground at the end of a meal. It is the only species that can launch itself almost vertically into flight from a horizontal surface.
Desmodus rotundus is a social animal that hunts and lives in groups. The bats live in colonies consisting of both males and females. In captivity, dominance hierarchies based on access to food were observed, but there is little conclusive evidence of complex hierarchies in the wild.
Curiously, most close associations are formed between several females or females and their offspring; adult males do not form close social ties in the roost. Females frequent more roost site than males, making associations in many different places. The associations between females are maintained over many years.
Wilkinson (1985, 1986) reported that although self-grooming occurs more often, social grooming is an important part of the vampire bat's behavior. Social grooming usually occurs between females and their offspring, but it is also significant between adult females. The adult females participating in grooming are usually closely related or roostmates. Wilkinson (1986) found that social grooming has more to do with food sharing than with the removal of ectoparasites. In many instances, social grooming begins with one female approaching another and grooming her for as long as two minutes. The female being groomed then regurgitates part of her blood meal for the grooming female. It is also common to see females regurgitate food for their offspring.
Young vampire bats do not exhibit aggressive behavior, although they play and wrestle with other juveniles. In order to avoid aggressive encounters with older bats in the roost, juveniles perform a gesture of appeasement where one folded wing is lifted and the body is bent to one side. (Altenbach, 1979; Brass, 1994; Macdonald, 1984; Turner, 1975; Walker, 1975; Wilkinson, 1985; Wilkinson, 1986)
Vocalizations are most common between mother and offspring. Small contact cries have been heard from the offspring at 6-12kHz. These usually occur during food sharing. Contact calls are also given when the offspring is trying to find its mother. Chemical cues and touch are also likely to play an important role in communication.
Vampire bats use echolocation and vision to navigate and find prey. They may also use olfaction and auditory cues to identify prey.
Desmodus rotundus feeds exclusively on the blood of other vertebrates. The species is an obligate parasite. In the wild, the bats feed preferentially on livestock because of their abundance, but also prey on wild animals and humans. In captivity, these bats have also been known to feed on snakes, lizards, toads, crocodiles, and turtles. (Brass, 1994)
Research on the anticoagulant agents in vampire bat saliva may improve medical treatment of some human injuries and diseases. Guano can be harvested and used as a fertilizer.
A bite from Desmodus rotundus can cause infections and transmit diseases carried by the bat. Infections can spread rapidly and cause death. The vampire bat transmits rabies to both humans and domestic livestock. Losses to the cattle industry in Latin America amount to many millions of dollars every year. (Brass, 1994; Lord, 1992)
Vampire bat populations have increased because of the introducion of livestock in South America, providing an abundant new source of food. (Turner, 1975)
Researchers have isolated an anticoagulant called draculin in the saliva of vampire bats. The anticoagulant is a glycoprotein that stops wounds from clotting so that the bat can gain a full meal from its prey.
Vampire bats have been the source of many myths and superstitions throughout the world. The Europeans have traditionally associated bats with the devil. In European pictures, the devil often has bat wings. The Persians and the Chinese, on the other hand, have chosen to depict the bat in a different light. The bat is a symbol of longevity and happiness in traditional stories and legends. (Fernandez, et al., Oct. 23, 1998; Walker, 1975)
Michael Mulheisen (author), University of Michigan-Ann Arbor, Rebecca Anderson (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
either directly causes, or indirectly transmits, a disease to a domestic animal
uses smells or other chemicals to communicate
a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease
The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
having more than one female as a mate at one time
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
an animal that mainly eats blood
scrub forests develop in areas that experience dry seasons.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
Greenhall, A.M., G. Joermann, U. Schmidt, and M. R. Seidel. 1983. "Mammalian Species, No. 202 pp.1-6, 3 figs, Desmodus rotundus". April 8. American Society of Mammalogists
Altenbach, J. 1979. Locomotor Morphology of the Vampire Bat, Desmodus rotundus. Pennsylvania: Special Publications 6, The American Society of Mammalogists.
Brass, D. 1994. Rabies in Bats, Natural History and Public Health Implications. Ridgefield, Connecticut: Livia Press.
Fernandez, A., A. Tablante, F. Bartoli, S. Beguin, R. Aptiz-Castro. Oct. 23, 1998. Expression of biological activity of draculin, the anticoagulant factor from vampire bat saliva is strictly dependent on the appropriate glycosylation of the native molecule. Biochemica et Biophysica Acta, 1425 (2): 291-299.
Lord, R. 1992. Seasonal reproduction of vampire bats and its relation to seasonality of bovine rabies. Journal of Wildlife Diseases, 28 (2): 292-294.
Macdonald, D. 1984. Encyclopedia of Mammals. New York: Facts on File.
Turner, D. 1975. The Vampire Bat, A Field Study in Behavior and Ecology. Baltimore and London: The Johns Hopkins University Press.
Walker, E. 1975. Mammals of the World, 3rd Edition. Baltimore and London: The Johns Hopkins University Press.
Wilkinson, G. 1986. Social grooming in the common vampire bat, Desmodus rotundus. Animal Behaviour, 34 (6): 1880-1889.
Wilkinson, G. 1985. The social organization of the common vampire bat. Behavioral Ecology and Sociobiology, 17 (2): 111-122.