Vampire bats
| Vampire bats | ||||||||||||
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Common Vampire ( Desmodus rotundus ) |
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| Desmodontinae | ||||||||||||
| Bonaparte , 1845 | ||||||||||||
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The vampire bats (Desmodontinae) are a taxon of the bats . They are classified as a subfamily of the leaf noses (Phyllostomidae), a diverse group of bats that is restricted to the American continent . They are the only hematophagous mammals and feed exclusively on the blood of other mammals or birds. A distinction is made between three types , each of which has its own genus , the common vampire ( Desmodus rotundus ), the comb-tooth vampire ( Diphylla ecaudata ) and the white-winged vampire ( Diaemus youngi ).
distribution
The distribution area of the vampire bats extends from the southern USA ( Texas ) to southern South America ( central Chile , Argentina and Uruguay ). They can also be found on some islands off South America (such as Isla Margarita , Trinidad and Tobago ), but are absent on the other West Indies .
description
Vampire bats reach a head body length of 65 to 95 millimeters and a body weight of 15 to 50 grams. The wingspan of the common vampire is between 35 and 40 centimeters.
The fur of these animals is colored reddish-brown or gray-brown on the upper side, the underside is lighter, often grayish. The hind legs are noticeably strong; unlike many other bats, they can run and hop on the ground and even climb vertical walls like spiders. The tail is absent in all species, and the uropatagium (the flight membrane between the legs) is small. In terms of body structure, the species differ in addition to the number of teeth in the length of the thumb, in the shape of the ears and in the hairiness of the uropatagium.
Vampire bats do not have a real nasal blade, just a horseshoe-shaped pad over their nostrils. Incisors and canines are sickle-shaped and suitable for cutting open the skin of their victims, the molars no longer have any surface that is suitable for chewing. A short esophagus and a tubular stomach are further adaptations to the special diet.
Way of life
Vampire bats make no special demands on their habitat, they live in warmer, both moist and dry regions. They are strictly nocturnal, they primarily use caves as sleeping places, but can also be found in hollow trees, mines and shafts as well as in abandoned buildings.
Vampire bats live in groups that can consist of up to 100 animals. The common vampire in particular has developed a highly developed social behavior, which includes grooming each other and also choking up the consumed blood that they share with less successful members of their own species, preferably family members.
nutrition
Vampire bats are the only mammals whose diet is based entirely on blood. Their closest relatives, the leaf-nosed bats , feed on insects or fruits. In the case of the common vampire bat ( Desmodus rotundus ), mammals serve as "blood-donating" prey; the comb-tooth vampire ( Diphylla ecaudata ), however, only uses birds as a source of food. White-winged vampires ( Diaemus youngi ) prefer bird blood, but can also feed on that of mammals.
In order not to starve to death, they need a blood meal at least every three days, either from a prey or as a donation from a conspecific.
With the help of heat-sensitive sensors, the animals search specifically for the veins under the skin of their victims. After licking the selected part of the body (the saliva contains an anesthetic), hair or feathers are removed. Then they bite out a piece of skin with their sharp canines and incisors and lick the blood up or suck it through the grooves on the underside of the tongue. Anticoagulant substances in the saliva ensure that the escaping blood does not clot while drinking. Soon after the meal, during which the animals ingest around 20 to 30 milliliters of blood, they excrete a large part of the water and then return to their roosts to digest the meal.
Vampire bats are nocturnal. If you have bitten an animal once, you should visit the same animal several times if possible, as long as the wound is still open, because due to their low body weight they cannot ingest enough blood with one meal. Presumably based on the sound of breathing, they can recognize a certain prey within a herd.
The dangers of the bite lie less in blood loss than in infecting the victim with diseases such as rabies . Infections can also occur on the open wound.
Systematics
Vampire bats are classified in the family of the leaf noses (Phyllostomidae), phylogenetically they form the sister taxon of all other leaf nosed species. There are three genera, each with a recent species:
- Common vampire , also called the great vampire bat ( Desmodus rotundus ),
- White-winged vampire ( Diaemus youngi ),
- Comb-tooth vampire ( Diphylla ecaudata ).
Apart from two fossil Desmodus species from the Pleistocene , no fossil ancestors of the vampire bats are known. How this specialized diet came about is still unclear. Two explanations have been proposed for this:
- According to one hypothesis, vampire bats developed from fruit-eating ancestors, the specially shaped incisors and canines were initially an adaptation to biting hard-shelled fruits.
- One after the other, vampire bats evolved from insectivorous ancestors who specialized in ectoparasitic animals. Possibly the wounds the insects inflicted on their hosts attracted these ancestors.
In addition to the actual vampire bats, other bats are also known as vampires:
- The fruit vampires (Stenodermatinae), which are also counted among the leaf noses, are a group of mainly fruit- eating bats that have external similarities.
- The false vampires ( Megaderma ) from Asia also show external similarities, but belong to the large-leaf noses (Megadermatidae), a group of bats that is not closely related.
evolution
The three species of vampire bats are closely related. It is believed that the blood-eating (sanguivore) diet developed only once in the course of the evolution of bats.
Molecular genetic studies have now shed light on the relationships within the three vampire species. Researchers have investigated genes that are responsible for the production ( expression ) of a specific anticoagulant substance in the saliva of these bats. This is the so-called plasminogen activator (PA), an enzyme (of the serine protease type ) that prevents blood from clotting. It has long been known that Desmodus rotundus has four different forms of PA in saliva (and has four corresponding genes in the genome); the four forms not only differ in their molecular structure, but also have different enzymatic properties within the coagulation processes. In contrast, as recent research has shown, Diphylla and Diaemus only have a single PA type (and one gene). In Diphylla the PA corresponds to that of leaf-nosed bats and is similar to that of other mammals; in Diaemus certain parts ( domains ) of the molecule are missing .
The results of the molecular genetic work suggest that the evolutionary line of development within the vampire bats is based on nutrition solely from bird blood (Diphylla) and, via an "intermediate stage" (Diaemus), leads to nutrition exclusively with mammalian blood. In the course of this evolution, the PA genes that are active in the respective species have been increased ( gene duplication ) and significantly modified: While the PA in Diphylla is adapted to the coagulation properties of bird blood, the four PA molecules in Desmodus are optimally suited to the composition of mammalian blood adapted. The Diaemus molecule is a transitional form.
This evolution towards a mammalian blood diet occurred long before large mammals such as cattle and horses were introduced into Latin America . The fact that Desmodus rotundus was best adapted to this diet is clearly the reason why the common vampire is by far the most common of the three species today.
Vampire bats and humans
The legendary figure vampire
Myths and legends of vampires , beings that feed on human blood, can be found in many cultures around the globe, in some cases since prehistoric times. Also because of the geographical distance, these ideas cannot be influenced by the bats that are only recorded from America. The word "vampire" itself comes from Serbian and has been used in German since the 18th century , just as many of the modern ideas about vampires have their origins in the Balkans . The myths are varied, the ability to transform into bats is by no means found in all, other legends tell of vampires in wolf or owl form . When the diet of these bats later became known, the parallels to the mythological figure were established. The animals therefore get their name from the legendary figure and not the other way around.
Regardless of this, in Mayan mythology there was a bat-shaped monster called Camazotz that attacked humans and animals and drank their blood. To what extent these ideas of the common vampire or Desmodus draculae , an extinct, even larger species of vampire bats, are influenced, is unclear.
Damage from vampire bites
Every year, numerous farm animals and pets fall victim to vampire bites. Detailed studies are available on the common vampire , which is the only vampire bat that primarily bites mammals, including domestic cattle and occasionally humans, and is considered a risk primarily through the transmission of diseases such as rabies . Estimates put up to 100,000 cattle dead per year due to bites of the common vampire, which also represents enormous economic damage. Humans, too, repeatedly fall victim to the common vampires. In 2004 in Brazil, for example, there was one case in which they infected up to 22 people with rabies. All persons infected in this way had no vaccination protection and therefore died as a result of the disease without a subsequent immediate vaccination. In August 2010, a young man died in the USA of rabies, which he had been infected with a few weeks earlier in Mexico by a bat bite.
Human threat
Because of these risks, vampire bats, especially common vampires, are tracked and hunted using various methods. Sleeping areas are blown up or fumigated, which also affects many harmless bat species. The bats should also be rendered harmless with poison or safety nets. Overall, however, vampire bats are widespread and are not endangered species, only the comb-tooth vampire is listed as low endangered by the IUCN .
Importance for research
The anticoagulant enzyme found in the common vampire's saliva was only isolated and bio-engineered a few years ago. It is primarily intended to be used as a preventative drug against heart attacks and strokes . For more information, see the importance of the common vampire for research .
literature
- Ronald M. Nowak: Walker's Mammals of the World . 6th edition. Johns Hopkins University Press, Baltimore 1999, ISBN 0-8018-5789-9 (English).
Web links
Individual evidence
- ↑ Katrin Blawat: Vampire bats share their prey with those in need. Retrieved April 6, 2020 .
- ↑ AM Greenhall, G. Joermann, U. Schmidt: Desmodus rotundus (PDF; 753 kB). In: Mamm. Spec. 202, 1983, p. 1.
- ^ RA Hoyt, JS Altenbach: Observations on Diphylla ecaudata in captivity. In: J. Mammol. 62, 1981, p. 215.
- ↑ AM Greenhall, U. Schmidt, G. Joermann. Diphylla ecaudata (PDF; 348 kB). In: Mamm. Spec. 227, 1984, p. 1.
- ↑ AM Greenhall, WA Schutt: Diaemus youngi (PDF; 776 kB). In: Mamm. Spec. 533, 1996, p. 1.
- ↑ Katrin Blawat: Vampire bats share their prey with those in need. Retrieved April 6, 2020 .
- ↑ Infrared Sensing in Vampire Bats (Eng. WP)
- ↑ TS Adams: hematophagy and hormone release. In: Annals of the Entomological Society of America. Volume 92, No. 1, 1999, pp. 1-13, doi: 10.1093 / aesa / 92.1.1 .
- ↑ William A. Wimsatt: Transient behavior, nocturnal activity patterns, and feeding efficiency of vampire bats (Desmodus rotundus) under natural conditions. In: Journal of Mammalogy. 1969, pp. 233-244, doi: 10.2307 / 1378339 , JSTOR 1378339 .
- ^ William N. McFarland, William A. Wimsatt: Renal function and its relation to the ecology of the vampire bat, Desmodus rotundus. In: Comparative Biochemistry and Physiology , Vol. 28, No. 3, 1969, pp. 985-1006.
- ↑ AL Wetterer, MV Rockman, NB Simmons: Phylogeny of phyllostomid bats (Mammalia: Chiroptera): data from diverse morphological systems, sex chromosomes, and restriction sites. In: Bull. Am. Mus. Nat. Hist. 248, 2000, p. 1.
- ↑ A. Tellgren-Roth, K. Dittmar, SE Massey, C. Kemi, C. Tellgren-Roth, P. Savolainen, LA Lyons, DA Liberles: Keeping the blood flowing - plasminogen activator genes and feeding behavior in vampire bats. In: Natural Sciences . Volume 96, 2009, p. 39.
- ↑ J. Krätzschmar, B. Haendler, G. Langer, W. Boidol, P. Bringmann, A. Alagon, P. Donner, WD Schleuning: The plasminogen activator family from the salivary gland of the vampire bat Desmodus rotundus: cloning and expression . In: Genes . Volume 105, 1991, p. 229.
- ^ "Human Rabies from Exposure to a Vampire Bat in Mexico - Louisiana, 2010". Retrieved August 15, 2011 .