What is a vampire bat
|D. rotundus preferably horses & mules (assembly)|
If you look around in brochures and exhibitions and on Internet sites on the subject of bats, you will always discover references to "blood-sucking vampires": The sensation-seeking mention is immediately followed by the reassuring conclusion that we do not even find them and therefore cannot be dangerous to us . This kind of education is not even necessary: Anyone who speaks to randomly selected people about "vampires" hears a lot about Count Dracula, but very little about bats: many believe that vampire bats actually exist in South and Central America Superstitions like the nocturnal undead that leave their sucking holes on necks in horror novels and horror films. Actually, one should free one's fellow human beings from the superstition that there are no vampires ...
1. Three types of vampires
Of the total of 16 bat families, only one has specialized in drawing blood in their diet: the family Desmodontidae, the z. B. in German-language literature also as Desmodidae referred to as. It comprises the three existing vampire genera, each with only one species and a total of four subspecies:
- Diphylla ecaudata, Spix 1823 - Comb-tooth vampire, small bloodsucker (26 teeth)
- Diphylla ecaudata ecaudata: South America and Eastern Panama
- Diphylla ecaudata centralis: western Panama to Texas
- Diaemus youngi, (Jentik) 1906 - white-winged vampire (22 teeth)
- Desmodus rotundus, Thomas 1901 - Common vampire bat (20 teeth)
- Desmodus rotundus rotundus: South America including Trinidad
- Desmodus rotundus murinus: Central America to Mexico
The numerical ratio of the three species and genera to the remaining more than 150 bat genera and up to 700 species shows how unusual this diet is among bats. Nevertheless, it is by no means unknown in the animal kingdom: everyone knows blood-sucking insects and arachnids (ticks), and leeches are still used in medicine today. After all, some vertebrates use blood as an additional source of food: There is a tradition of one type of Galapagos finch and the New Zealand keas (a type of parrot) of chopping up quills and skin in seabirds or the fur of sheep in order to then suck up the blood that escapes. The East African tribe of the Masai (also: Maasai or Maasai) traditionally use their cattle from the carotid artery: This is shot from a short distance with an arrow, the emerging stream of blood is caught in a calabash and immediately drunk or processed first. And our butchers produce black pudding from pork, bacon and the blood of the slaughtered animal ...
2. Body features
A characteristic of the vampires that is unique in the animal kingdom is their stomach: it measures Desmodus rotundus from the entrance (Cardia) the esophagus (Esophagus) to the so-called gatekeeper (gastric exit or Pylorus) only one millimeter; the CardiaRegion, however, has expanded into an incredibly long gastric appendix that fills almost the entire abdominal cavity. This blind sack is approx. 6 cm long when empty, but 11–16 cm when full.
Because vampire bats do not have tail-skin (Patagium) need to catch insects, this is reduced to a semicircular hem between the legs and with Diphylla ecaudata hardly recognizable. After all, the spur is (Calcar) in this species it is small, but still present, while in the other two species it is severely stunted.
The diet is also the reason for the less powerful ultrasonic echo tracking compared to other bat species: Since vampires are not air hunters, they only have to be sufficient for nightly orientation in the air and on the ground. In turn, vampire bats can see better than many other bats at dusk. The location of the "blood donors" as well as their most favorable places to bite occurs acoustically (for example by the snorting of a horse) and above all via the fine sense of smell (olfactory) and the warmth of the nose: film recordings with an infrared camera show that the animals are targeting taper to the areas of the host body that appear brightest on the film, as this is where the blood flows close under the skin and consequently gives off most of the heat.
3. Food intake
Vampire bats do not pounce on an animal in order to beat the canine teeth into the bloodstream of the panicked victim in a wild bloodlust, rather the blood acquisition takes place in several phases:
- First, vampire bats circle over their hosts in small groups and then land either next to or on top of them.
- On the ground they approach carefully so as not to alarm or wake the host, and then look for a convenient place to bite. If they have not landed carefully enough on the back or neck of large host animals, they are first shaken off and have to fly again.
- Once a suitable place to bite has been found, the vampire carefully prepares the bite: First, he sticks out his tongue and touches the skin with the tip of his tongue. Then he licks a circular area of initially 10-15 cm in diameter and after about a minute presses his mouth onto the surface of the skin. While the pressure is getting stronger and the licking gets faster and faster, the saliva-covered area of skin shrinks to half a centimeter in diameter and protrudes into the mouth, where it is finally pinched by the incisors.
- At that moment the vampire closes his jaws, bites off the small fold of skin, jumps back, spits it out and immediately returns to the open wound to take in the blood that is leaking out. The landlord usually does not feel any of this.
- The blood uptake cannot be appropriately described as either sucking the mouth or licking the tongue; rather, the tongue moves two to three millimeters into the wound up to five times per second and, by means of two channels on its underside, creates a negative pressure that creates a small flow of blood between the wound and the underside of the tongue the forked lower lip, a groove on the top of the tongue and the throat. The blood is drawn in partly actively and partly by capillary action. The hard tip of the tongue also deepens the wound with its prick and thus keeps the blood flowing. The most likely would be the term Tongue sucking apply to this type of blood intake.
- Since blood consists predominantly of water, a vampire bat can ingest more of it than it weighs even when sobered; on average it eats more than half of its actual body weight. If the wound is bleeding profusely, it takes at least 8-10 minutes to full, but a meal can take over an hour.
- After eating, the vampire bat flies off, rests for a while to thicken and digest the blood, excretes part of the liquid (approx. 25%) and returns to its roost. Sometimes the animals urinate while they are taking blood. Due to anticoagulant substances in the saliva, the wound continues to bleed for some time, which gives other people the opportunity to indulge in the same area. Vampires can starve for a maximum of 2-3 days.
The diets of these animals are often misrepresented, especially on websites and in brochures. In principle, vampires can bite their hosts anywhere if the bite site is only sufficiently accessible, has support structures and is well supplied with blood:
- Horses, donkeys and mules z. B. next to the tail or mane, where the little blood drinkers can hold on;
- Cattle on the neck and ears, on the flanks and legs, on the tail, on the vulva and on the udder;
- Pigs on the muzzle, behind the ears, on the neck and in the teats;
- Chickens on the comb and between the toes;
- People are usually bitten on the fingers and toes, nose and ears; Such a bite is of course uncomfortable, but not as dramatic as one initially imagines with disgust: The research results presented here were, among other things. determined by self-experiments by researchers who consciously allowed themselves to be bitten.
The specialization in blood probably developed as a result of an originally carnivorous diet: Even today, vampires jump on mice at lightning speed and bite them just as other species do - for example Vampyrum spectrumwho have favourited The Great Spit-Leaf Nose or False Vampire Bat, which despite its scientific generic name is not a vampire. The approximately 13 cm long animal with a wingspan of about 70 cm prey on fruits and insects as well as small vertebrates, e.g. B. Birds and Mice ...
The specialization of real vampires in blood has advanced so far that the three types can no longer take in any other food and are even dependent on certain animal groups, whose blood responds differently to the various anticoagulant substances in the saliva of the three types of vampire:
- Diphylla: only birds;
- Diaemus: preferably birds; also mammals: goats, donkeys, guinea pigs, but no cattle;
- Desmode: Mammals: mainly cattle, also horses, goats, pigs, coyotes, humans; Birds: chickens, eagles; Reptiles: real rattlesnakes, coral snake, iguana; Amphibians: toads.
The diet of the vampire bats indicates this as Parasites or. Parasitic out. This term, which is generally used negatively (because it is used in an evaluative social context), does not assign the vampires a special position, since parasitism is widespread in the animal kingdom: Ento- and Ectoparasites (Worms, ticks, mosquitoes, etc. that parasitize in or on the body) have always haunted us humans, and brood parasitism can be observed everywhere: not only in the bird world (cuckoos), but above all in insects: 24% of all Bee species z. B. parasitize other nest-building bees! Unlike them, vampires usually don't kill their victims ...
4. Social and reproductive behavior
If the vampires' diet does not arouse sympathy, their social behavior is suitable to make up for the aversion of emotionally stressed people towards them. Investigations on the still relatively (!) Common "common" vampire bat (Desmodus rotundus) have shown that these animals live in more or less fixed groups and fly together for food. In their quarters they spend a lot of time grooming each other. Aggressive behavior also occurs: vampires threaten each other by drumming on the ground with folded wings, and they beat each other in the same way; but they never bite each other in such comment fights! The lifting of a folded wing is a reassurance gesture that a dominant conspecific who approaches from the side of this wing can perceive with its echolocation even in the dark.
It is also instructive to observe that young animals whose mothers do not return to breastfeeding or do not return in time are also suckled by other lactating females. The reason for this social behavior in two senses is that young animals have to be suckled for up to nine months in order to survive, which increases the risk of losing their mother. If necessary, they are even adopted: non-lactating females initially feed the orphans with blood, which is possible as early as the second month; after a few days, their mammary glands are already active and give milk. It's hard to believe: males also feed young animals.
Researches Desmodus rotundus have even shown that hungry adult vampires regularly and successfully beg their conspecifics. According to calculations by the researchers, 82 percent of adult vampires would starve to death each year without feeding one another; in fact, only a quarter die.
Female vampires can only give birth to a single cub every 9-10 months; In view of this low rate of reproduction, the described care is not surprising. European bat conservationists would be happy if this behavior were also common among the local bat species.
5. Harmfulness and control
The oldest vampire bat fossils found so far date from the Plestocene, so they are up to 1.8 million years old. They belong to the genus Desmodewhich at that time also occurred in the area of what is now the USA and Cuba. The host animals of the first vampires were wild animals, which probably showed a more pronounced defensive behavior towards them as pets, lived individually or in smaller herds and some of them are now extinct. The waves of human colonization in the New World were followed by long millennia of peaceful coexistence between vampires and humans: These do not correspond to the primary host scheme of the vampires, and the deliberate extermination of an animal species was alien to the Native Americans and hardly motivatable, as most of them are in America today kept pets were still unknown. When the Europeans introduced horses, cattle, goats, sheep and pigs into their colonies from the 16th century onwards, a huge "blood supply" arose on the pastures for centuries, with the vampires leading the way Desmodus rotundus, benefited.
It was normal for grazing animals to be bitten by vampire bats for centuries and not a cause for undue concern, since large animals like cattle or horses seldom died of vampire bites due to their defenses being weakened; only piglets were at risk if the teats of the sows were injured, and chickens that lost too much blood. Along with the pets came their diseases, but for a long time they were not properly diagnosed and certainly not associated with vampire bats.
That changed with scientific advances since the 1920s when Desmodus rotundus as a carrier of infectious diseases could be proven:
- Trypanosoma hippicum, a horse disease also known as "Murrina"
- Trypanosoma equinum, a similar cattle disease called "Mal de caders"
- Paralytic rabies, also known as "Derriengue" or "Peste der cadeiras", which between 0.5 and two million cattle and allegedly humans are killed every year. Vampires are only about 0.5–1.6% infected with rabies viruses and some are resistant to them.
Resolute attempts were now being made to eradicate the diseases; But since one could not fight the pathogens oneself, one tried to eradicate their vectors, and since hardly anyone could distinguish a vampire from another, perhaps insect or nectivorous bat species, one fought all bats. Thousands of bat caves have been blown up in Brazil alone; more than 44,000 bat roosts were poisoned in Venezuela between 1964 and 1967, killing an estimated two million bats. While the vampires suffered the least under such maddened measures, they were and are being pursued in other places (e.g. in Trinidad) in a very targeted and quite successful manner, for example by professional vampire catchers, nets in front of stables and strychnine syrup that is spread on freshly bitten wounds and kill the next vampires. A particularly perfidious method is to spread slow-acting poison on the fur of captured vampires and let them fly back to their quarters; Due to the pronounced social grooming of the species, almost all members of the colony are then exterminated and many other bats that inhabit the same cave are killed. Cattle are even injected with a substance that is only mildly toxic to them in order to exterminate the blood drinkers. As a result of this campaign, large areas are already vampire-free and bats-free.
Are such control measures justified? Even if the measures only affected vampire bats, they would of course not be justified for several reasons:
- Economic claims are not yet a reason to exterminate an animal species: In Africa, too, there are regions in which, due to the spread of the tsetse fly, only wild animals and no domestic animals sensitive to the transferred protozoa thrive, which has saved these areas from excessive human use and destruction.
- European settlers have to attribute the damage to themselves, since they only imported the domestic animals, which are now endangered, into a world in which vampire bats are part of the natural equilibrium. Even if some would like to dismiss it as "romantic" or "unrealistic": Anyone who exterminates hundreds of Indian peoples and appropriates their land cannot derive any right to destroy their nature. The danger is not the vampires, but our civilization.
- the "Derriengue" has long been combated by vaccination campaigns - similar to rabies in foxes in Europe.
The extermination campaign carried out in South and Central America should remind us in Europe not to deal with other alleged "pests" (crows, pigeons, gray geese, cormorants, beavers, etc.) in a similarly stupid and irresponsible way. And scientists should not put themselves in the service of anti-natural economic interests in order to develop methods of extermination, which are then euphemistically referred to as "control measures" - a wrong translation of the hardly less euphemistic English term plague control.
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