The common Vampire bat is the only species in it's genus and is highly adaptable. Contrary to the common misconception of a huge beast with blood dripping fangs, the Common Vampire bat is a small species weighing only between 15 and 50 grams!
Aside from being the most agile of bats, being able to run like a spider, jump like a frog, and even do cartwheels; they are probably the most intelligent of all bats as well. Each bat must compile and remember a detailed mental map of it's ever changing flight routes to where it has found food in the past.
The common Vampire bat is native from northern Mexico and southward to Chile, central Argentina, and Uruguay, as well as the island of Trinidad. It is found in both arid and humid regions of the South American tropics and subtropics.
Vampire bats can live up to 12 years. They usually roost in caves, in fact they are cave ceiling 'dome roosters'; but they will also roost in a variety of other less suitable sites, such as hollow trees, old wells, mine shafts, and even abandoned buildings. About twenty other species of bats have been known to share these roost sites with Vampires, although not in close proximity.
Where ever Vampire Bats roost you will notice the strong odor of ammonia from the pools of their distinctive black, tarry droppings that collect on the floor of the roost site. They will roost in numbers from as few as six to up to over two thousand, but the usual colony size is around a hundred or so. The sexes roost together, not a common occurrence among micro chiroptera; with one dominant male and his 'harem' of about six females.
Although they have actually got twenty teeth, of these only the very front incisors are used to obtain their sole source of food. The feeding habits of Vampire bats have long been the subject of much exaggeration, and have often been likened to the Old World legends of Dracula. However the truth is far more interesting than fiction. As soon as night has fallen, and usually not if the moon has risen; Vampire Bats cautiously leave their roosts, mothers leaving their young behind where it is safe; and then set out in straight low level flight about a meter from the ground in search of their usual 'donor' species. They usually feed from the fresh blood of quadrupedal mammals, such as horses, burros, cattle, pigs, and tapirs, this last one being probably their natural food source.
Feeding as they do upon animals up to ten thousand times their own size, Vampire Bats are not about to risk waking a victim, since they could easily become a victim themselves. This is the most common cause of death among young inexperienced vampires. Instead they will often choose to alight near the animal and carefully walk up to it using their strong modified thumbs and hind legs. Once within range, they will use their specially evolved nose leaf to detect where the warmth of the hosts blood flows closest to the surface of the skin. They do this in order to decide where it is safest to bite, without risking waking the animal by scrambling over its body unnecessarily through trial and error.
When a bite site is chosen, the bat carefully licks the skin in order to soften it and flatten down any hairs in the way, all the while keeping several special hairs of their own known as vibrise, which grow from the bat's chin; in contact with the animal so as to detect any slight vibration that might hint of it waking up. A tiny fold of skin is held in the bats mouth for but an instant. Then at the precise moment of the bite; the bat takes a short jump backwards. It does this so that it is in a favorable position to flee, should the need arise. The bat then spits out the tiny piece of skin before starting to feed. The front incisors are so scalpel sharp that the Vampire Bat's bite is virtually painless. The bite is tiny, measuring an average of a mere 3-5 millimeters across by a millimeter or two deep. It is a shallow bowl shaped wound, designed to bleed freely. This is further assisted by the bats special anti-coagulant saliva which flows along a tiny grove down the center of the top of the bat's tongue and into the wound. In order to further minimize disturbance, several Vampire Bats will often feed at a single bite site.
Vampire Bats are unable to utilize any source of food other than blood. In fact, they have such fast metabolisms that they will starve to death in as little as 48 hours! Their throats are too narrow to permit the passage of any kind of solid food, and their stomachs are shaped like a zig zag tube, in order to maximize its holding capacity. Blood makes an ideal food in all ways but one, it is very high in water, so in order to obtain enough nourishment from it, a Vampire Bat has the most efficient kidneys in the entire animal kingdom.
Vampire Bats actually start to urinate right there as they feed upon an animal! After feeding, they are often so bloated with concentrated blood that they can scarcely even fly. The amount of blood taken by a single Vampire bat is quite small, amounting to about a mere teaspoon. However, due to the continuing action of the bats anti-coagulant saliva, it can continue to ooze for some time, often resulting in a long streak down the side of an animal. This can certainly startle a farmer!
Vampire Bats have an unusually long gestation period for a small tropical bat that doesn't hibernate. One young is the average number born. Gestation lasts 90 to 120 days. The young Vampire Bats develop very slowly, except during their neonatal period.
At birth, the newborn weighs 0.17 to 0.25 ounces (5 to 7 grams). In 20 to 25 days the birth weight is doubled. In 50 to 60 days it has tripled, and in 120 days the birth weight has quadrupled. However, the full adult weight of one ounce (28 to 30 grams) is not obtained until 300 days of age. The young will remain dependent upon the mother for as long as 9 months in captivity. It is only at the end of this period that the young is weaned.
One would think that this long dependency by the young would have its disadvantages. However, unlike the females of many bat species, Vampire Bat females will nurse the offspring born to other females. As females with young are present almost year round in a sizable colony, if a young bat is orphaned it is very likely to be adopted by another nursing female.
Vampire Bats are one of the very few species, other than man; known to practice altruistic behavior. They will actually regurgitate part of a hard earned meal when begged by a less fortunate roost mate who hasn't fed in a given evening. For as long as ten minutes, young bats are fed with regurgitated blood from the mouths of adults, even by the males. In fact nothing is wasted in a Vampire Bat colony at the Centre, and we soon discovered that even nursing mothers will share their milk with a hungry male should the need arise.
The real tragedy surrounding the Vampire Bat is the bad reputation they have gotten as a result of a combination of the myths surrounding their feeding habits and the fear farmers have of them spreading disease. The real danger of the bite is when the bat is infected with rabies, or a common cattle disease known as murrina from biting a sick animal. However, the threat posed by such an infected bat is usually exaggerated because the infected bat soon dies of these same diseases, usually before having the chance to spread them very far.
Fear of possible epizootics all too often leads to the wide spread and highly damaging efforts of the local people who try to eradicate Vampire Bats from an area where they are feeding regularly on domestic stocks. This could be virtually eliminated if farmers would only string lights around their cattle at night. Vampire Bats won't feed unless under the cover of the darkest nights.
Instead, Vampire Bats are poisoned in great numbers, using vampiricides designed to be spread throughout an entire colony, and making use of the Vampire Bats frequent grooming behavior. The roosts they share with so many other bat species are systematically sought out and destroyed, often permanently with dynamite! Leading to the potential extinction of the many beneficial bats that function as the primary seed dispersers and pollinators of the rain forests, without which these forest habitats would no longer be able to function.
If you have found an injured bird of prey (hawk, falcon, owl, etc.), contact the Centre and our experienced staff can assist in determining what steps should be taken to ensure the bird receives the best possible care.
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