Common Vampire Bat
Encyclopedia
The Common Vampire Bat (Desmodus rotundus) is a small leaf-nosed bat
Leaf-nosed bat
The New World leaf-nosed bats are found throughout Central and South America, from Mexico to northern Argentina. They are ecologically the most varied and diverse family within the order Chiroptera...

 native to the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

. It is one of three extant species of vampire bat
Vampire bat
Vampire bats are bats whose food source is blood, a dietary trait called hematophagy. There are three bat species that feed solely on blood: the Common Vampire Bat , the Hairy-legged Vampire Bat , and the White-winged Vampire Bat .All three species are native to the Americas, ranging from Mexico to...

, the other two being the Hairy-legged Vampire Bat
Hairy-legged Vampire Bat
The Hairy-legged Vampire Bat is one of three species of vampire bat. Despite connotations of vampires, it mainly feeds on the blood of birds. This vampire bat lives mainly in tropical and subtropical forestlands of South America...

 and the White-winged Vampire Bat
White-winged Vampire Bat
The White-winged Vampire Bat is a species of vampire bat. It is the only member of the genus Diaemus. It is found from Mexico to southern Argentina and is present on the islands of Trinidad and Isla Margarita...

. Along with them, it is the only parasitic mammal. It mainly feeds on the blood of livestock
Livestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...

 and is considered a pest. It is also a carrier of rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...

. The conservation status of the bat is categorized as Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...

 by the IUCN because of "its wide distribution, presumed large population tolerance of a degree of habitat modification, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category."

Taxonomy

The Common Vampire Bat was first classified by Étienne Geoffroy Saint-Hilaire
Étienne Geoffroy Saint-Hilaire
Étienne Geoffroy Saint-Hilaire was a French naturalist who established the principle of "unity of composition". He was a colleague of Jean-Baptiste Lamarck and expanded and defended Lamarck's evolutionary theories...

 in 1810 as Phyllostoma rotundum. The species would go through several binomial nomenclature
Binomial nomenclature
Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...

s before being given it's current name, Desmodus rotundus, by Oldfield Thomas
Oldfield Thomas
Oldfield Thomas FRS was a British zoologist.Thomas worked at the Natural History Museum on mammals, describing about 2,000 new species and sub-species for the first time. He was appointed to the Museum Secretary's office in 1876, transferring to the Zoological Department in 1878...

 in 1901. The Common Vampire Bat is classified under the subfamily Desmodontinae, which are considered the "true" vampire bats as opposed to the "false" vampire bats like the Spectral Bat
Spectral Bat
The Spectral Bat is a large, carnivorous leaf-nosed bat. Some alternate names for this species are the False Vampire Bat, Linnaeus's False Vampire Bat and the Spectral Vampire Bat...

 and the Megadermatidae
Megadermatidae
Megadermatidae, or False Vampire Bats, are a family of bats found from central Africa, eastwards through southern Asia, and into Australia. They are relatively large bats, ranging from 6.5 cm to 14 cm in head-body length. They have large eyes, very large ears and a prominent nose-leaf. They have a...

 bats. There are two other members of Desmodontinae, the Hairy-legged Vampire Bat
Hairy-legged Vampire Bat
The Hairy-legged Vampire Bat is one of three species of vampire bat. Despite connotations of vampires, it mainly feeds on the blood of birds. This vampire bat lives mainly in tropical and subtropical forestlands of South America...

 (Diphylla ecaudata) and the White-winged Vampire Bat
White-winged Vampire Bat
The White-winged Vampire Bat is a species of vampire bat. It is the only member of the genus Diaemus. It is found from Mexico to southern Argentina and is present on the islands of Trinidad and Isla Margarita...

 (Diaemus youngi). All three species are specialized for feeding on the blood of warm-blooded animals. However, the Common Vampire Bat feeds on mammalian blood more than the other two species, which primarily feed on avian
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

. The three species reasonable each other. However, the Common Vampire Bat can be distinguished by its longer thumb.

Physical description

Common Vampire Bats have burnt-amber colored fur on their backside while soft and velvety light brown fur covers their belly. They have large pointy ears and a flat leaf-shaped nose. They a well-developed clawed thumb on each wing, which are used to climb on prey. Vampire bats are about 9 cm (3.5 in) long and have a wingspan of 18 cm (7 in). They commonly weigh about 57 grams (2 oz), but that can double after just one feeding. Vampire bats have sexual dimorphism in favor of females, a trait unusual among bats. The vampire bat has a relatively large braincase and its rostrum is reduced to accommodate large razor-sharp incisors and canines. The upper incisors lack enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

, which keeps them permanently razor sharp. Vampire bats also have the fewest teeth among the bats. The tongue has two lateral grooves that expand and contract as the bat feeds.

While most other bats have almost lost the ability to maneuver on land, vampire bats can run by using a unique bounding gait. The forelimbs instead of the hind limbs are used for force production since the wings are much more powerful than the legs. This likely evolved independently within the bat lineage. It is also capable of doing leaps in various directions, magnitudes and temporal sequences. When making a jump, the bat uses its pectoral limbs to generate an upward thrust. The hindlimbs act as stablizers and orient the body over the pectoral limbs and the thumbs or pollices stabilize the pectoral limb and contribute to extending the time over which vertical force is exerted.

Common Vampire Bats have fairly good eyesight compared to other bats. They have a visual acuity angle of 0.7, and are able to detect single cattle at 130 m. They also emit echolocation signals, orally and thus fly with their mouths open for navigation. Experiments have should that their capabilities have a threshold of identitying 1 cm mm wires at 50 cm, which is moderate compared to another bats.

Range and habitat

The Common Vampire Bat is found in parts of Mexico, Central America and South America. It can be found as far north as 175 mi from the US border. Fossils have been found of this bat in border states and in Florida. These places provide suitable habitat for the bat and it has been suggested that it may "have yet to reoccupy" these places. In addition it is the most common species in southeastern Brazil. The southern extent of its range is Uruguay, northern Argentina, and central Chile. In the West Indies, the bat is only found on Trinidad. The vampire bat is an ecologically flexible species and lives in rainforests, arid coastal plains, mountains, brush and mesquite plains and deserts. It prefers warm and humid climates.

Bats roost in trees, caves, abandoned buildings, old wells, and mines. Vampire bats will roost with nine other bat species and tend to be the most dominate at roosting sites. The bats occupy the darkest and highest places in the roosts and when they leave, other bat species move in to take over these vacated spots. Vampire bats can thermoregulate down to 0°C.

Feeding

The Common Vampire Bat feeds primarily on mammal blood, particularly that of livestock such as cattle and horses. Vampire bats will feed on wild prey like tapir
Tapir
A Tapir is a large browsing mammal, similar in shape to a pig, with a short, prehensile snout. Tapirs inhabit jungle and forest regions of South America, Central America, and Southeast Asia. There are four species of Tapirs: the Brazilian Tapir, the Malayan Tapir, Baird's Tapir and the Mountain...

s but seem to prefer domesticated ones. Bats prefer to feed on horses over cattle when given the choice. Female prey, particularly those in estrous, are more often targeted than males. This could be because they tend to be on the perimeter of the herd or perhaps because of the hormones. Young animals are also preferred over adults, possibly because of their thinner skin or because that are less active at night.

Vampire bats hunt at night. They leave their roosts in an orderly fashion. Bachelor males are the first to leave, followed by the females and lastly, the harem males.

The bats use hearing and smell to track down prey. They tend to feed in an area 5–8 km from their roost. When a bat targets a victim, it will land on it or walk and jump on it. The bat the sometimes lands near the prey and feeds on it from the ground. The victim doesn’t feel the land on it as the bat has padded feet and wrists.

"In addition to excellent vision, sense of smell, and acute hearing, vampire bats (Desmodus rotundus) have heat detectors on their noseleaf."


The heat sensors in the nose help the bat detect a blood vessel near the surface. Vampire bats commonly return to the same host on consecutive nights. They mark their host with urine. Vampire bats are also protective of their host and will fend off any other bat that lands while it is feeding. Thus it is uncommon for two or more bats to feed on the same host and cases of such are usually mothers and their offspring.

When feeding, vampire bats target the rump, flanks or neck of the victim. Bats use their razor sharp teeth to pull a flap of skin off the victim. A bat uses its tongue to lap up the blood. The blood is kept flowing by an anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...

 which the bat has in its saliva. The kidneys of the vampire bat are effective in extracting water from the blood when it is feeding, so the bat can consume more blood without being overloaded with water. A bat will feed for thirty minutes and will become swollen with blood. At this time the bat can barely fly and it will hide and wait until its body processes the blood enough to the point where it can fly.

Mating and reproduction

Male vampire bats defend and maintain roosting sites that attract or contain females. A male and his females make up a harem. A harem male is the only male that mates with the females. Females in a harem rarely mate with an outside male, despite having opportunities to do so. Bachelor males will try to mate with females when possible but the females usually refuse them. Vampire bat harems may also contain multiple males maintaining and defending a roosting site. In the groups, the males have a dominance hierarchy, with the most dominant male fathering most of the offspring (which is about half), the next dominant male fathering the second most offspring and so on. In multiple male harems, a female may reject mating with the dominant male possibly to avoid inbreeding. Harems males defend their territories from intruders even after females have left.

During estrous, a female will release only one egg despite both ovaries being functional. Mating usually lasts 1–3 minutes. The male bat will mount the female from the posterior end. He grasps her back with his teeth and inseminates her. After mating, the male leaves a vaginal plug containing sperm in the female. Vampire bats are reproductively active all year around, although peaks in conceptions and births occur in the rainy season. The gestation period of a common vampire bat lasts about 205 days. Females give birth to one offspring per pregnancy. Raising of the young is done primarily by the females. Young are fed their mother’s milk for the first three months and are then fed mixtures of milk and regurgitated blood. A mother will leave the young in the roost when she goes to feed, and upon returning, calls her young so she can feed it regurgitated blood. Young will accompany their mothers in hunts at six months but are not fully weaned until nine months. Female offspring usually remain in their natal groups unless their mothers die or move. Several matrilines can be found in a group as unrelated females regularly join groups. Nevertheless, females are usually reluctant to join a new group as a bat survival rate depends on long lasting social bonds. A female who enters a new group may not incorporate into that group's social activities. Male offspring tend to live their natal groups until they are about two years old, sometimes being forcefully expelled by the resident adult males.

Cooperation

Common vampire bats display a high amount of cooperative behaviors. Females in a harem have strong social bonds that are reinforced through interactions in the roost. A harem male has moderately strong relationships with his females. In harems with multiple males, the males may have social bonds but they are not as strong as those of the females. While the harem males relations with outside bachelors males is mostly agonistic, bachelor males are accepted into the harems when the ambient temperature lowers, possibly a form of social thermoregulation. A notable cooperative behavior among bats is reciprocal altruism, which is when bats share food with each other. In food sharing a bat regurgitates blood to feed to another bat. Some bats are unsuccessful in feeding and will thus solicit blood from a roost mate. This behavior likely evolved to combat starvation as a bat cannot live for more than three nights without blood. In addition to the females sharing blood with one another, the harem male will also share blood with his females. Harem males may also share food with each other.

Female vampire bats also display alloparenting
Alloparenting
In biology and sociology, alloparenting is where individuals other than the actual parents act in a parental role.One common form of alloparenting is where grandparents adopt a parental role. This is sometimes named a "skipped generation household"...

. Lactating females in roosts will feed both young whose mothers have died and those whose mothers are still alive. This mechanism evolved to keep the young from starving as well help with the burden of raising offspring. Vampire bats will also participate in mutual grooming
Social grooming
In social animals, including humans, social grooming or allogrooming is an activity in which individuals in a group clean or maintain one another's body or appearance. It is a major social activity, and a means by which animals who live in proximity can bond and reinforce social structures, family...

. Two bats will groom each other simultaneously. In addition to cleaning, bats may also groom to strengthen social bonds between those that share blood. Bats who groom one another also share food. With grooming, a bat can assess if a bat that is begging for food is well feed or if it is really starving. A bat will assess the swollenness of its partner’s body to see if it really needs food. Grooming is also dependent on kinship and relatedness. Mothers groom offspring more than other bats and this may promote recognition in parent and offspring.

Relationship with humans

Only 0.5% of bats carry rabies. However, of the few cases of rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...

 reported in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 every year, most are caused by bat bites.
The highest occurrence of rabies in vampire bats occurs in the large populations found in South America. However there is less risk of infection to the human population than to livestock exposed to bat bites. Dr. Joseph Lennox Pawan
Joseph Lennox Pawan
Joseph Lennox Pawan M.B.E. was the first person to show that rabies could be spread by vampire bats to other animals and humans.-Education and career:...

, a Government Bacteriologist in Trinidad
Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...

, the West Indies, found the first infected vampire bat in March 1932. He then soon proved that various species of bat including the Common Vampire Bat, with or without artificial infection or the external symptoms of rabies are capable of transmitting rabies for an extended period of time. "Perhaps, the most heretical disclosure was that vampire bats could recover from the furious stage of the disease and were capable of spreading the disease up to five and one half months." It was later shown that fruit bats of the Artibes genus demonstrate the same abilities. During this asymptomatic stage the bats continue to behave normally and breed. At first, his basic findings that bats transmitted rabies to people and animals were thought fantastic and ridiculed.

Although most bats do not have rabies, those that do may be clumsy, disoriented, and unable to fly, which makes it more likely that they will come into contact with humans. There is evidence that it is possible for the bat rabies virus to infect victims purely through airborne transmission, without direct physical contact of the victim with the bat itself. Although one should not have an unreasonable fear of bats
Fear of bats
Fear of bats, sometimes called chiroptophobia, may refer both to a specific phobia associated with bats and to common negative stereotypes and fear of bats stemming from prejudices and misinformation.-Roots and misconceptions:...

, one should avoid handling them or having them in one's living space, as with any wild animal. If a bat is found in living quarters near a child, mentally handicapped person, intoxicated person, sleeping person, or pet, the person or pet should receive immediate medical attention for rabies. Bats have very small teeth and can bite a sleeping person without being felt.

The unique properties of the vampire bats' saliva have found some positive use in medicine. A study which tested a genetically engineered drug called desmoteplase
Desmoteplase
Desmoteplase is a novel, highly fibrin-specific thrombolytic agent in phase III of clinical development. In 2009, 2 large trials were started, and the results of these studies will determine whether desmoteplase will gain marketing authorization as a safe and effective treatment for patients with...

, which uses the anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...

 properties of the saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

 of Desmodus rotundus, and was shown to increase blood flow in stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...

 patients.

Further reading

  • Greenhall, Arthur M. 1961. Bats in Agriculture. A Ministry of Agriculture Publication. Trinidad and Tobago.
  • Greenhall, Arthur M. 1965. The Feeding Habits of Trinidad Vampire Bats.
  • Greenhall, A., G. Joermann, U. Schmidt, M. Seidel. 1983. Mammalian Species: Desmodus rotundus. American Society of Mammalogists, 202: 1-6.
  • A.M. Greenhall and U. Schmidt, editors. 1988. Natural History of Vampire Bats, CRC Press, Boca Raton, Florida. ISBN 0849367506; ISBN 978-0849367502
  • Joseph Lennox Pawan
    Joseph Lennox Pawan
    Joseph Lennox Pawan M.B.E. was the first person to show that rabies could be spread by vampire bats to other animals and humans.-Education and career:...

    ,(1936). "Transmission of the Paralytic Rabies in Trinidad of the Vampire Bat: Desmodus rotundus murinus Wagner, 1840." Annual Tropical Medicine and Parasitol, 30, April 8, 1936:137-156.
  • Pawan, J.L. (1936b). "Rabies in the Vampire Bat of Trinidad with Special Reference to the Clinical Course and the Latency of Infection." Annals of Tropical Medicine and Parisitology. Vol. 30, No. 4. December, 1936
  • Walker, Steven. 1996. Desmodus. University Editions. Virginia. ISBN 1-56002-637-5
  • Kishida R, Goris RC, Terashima S, Dubbeldam JL. (1984) A suspected infrared-recipient nucleus in the brainstem of the vampire bat, Desmodus rotundus. Brain Res. 322:351-5.
  • Campbell A, Naik RR, Sowards L, Stone MO. (2002) Biological infrared imaging and sensing. Micron 33:211-225. pdf.

External links

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