 Vampire bats exist. There are over 950 different species of bats, and three of them are vampires: bats which live on blood. They can only be found in Central and South America. Two of the types of vampire bats restrict their eating habits to the blood of birds, and are quite rare; let's look instead at the more common variety of vampire bat, Desmodus rotundus.  Vampire bats, like all bats, are mammals; they are covered in fur and bear their young live. The common vampire is a small bat, measuring only about 20 centimetres wide from wingtip to wingtip; its body is about the size of an adult's thumb. Vampire bats feed on the blood of birds, cattle, horses, and pigs, and the occasional sleeping human. It is the only mammal which is a parasite. But vampire bats don't suck the blood of their victims. In the dark of night, the vampire bat flies about a metre off the ground, looking for a victim. It lands and walks on its wingtips and legs (the only bat which can do this) until it finds a sleeping animal.  Heat sensors in the bat's nose lead it directly to a vein which is near the surface of its victim's skin. Using tiny but very sharp teeth, it makes a cut in the skin of the animal. As the animal bleeds, the bat quietly laps up the flowing blood. Its saliva, like that of the mosquito, contains an anticoagulant chemical which prevents the blood from clotting. It also contains another chemical which keeps the blood cells from sticking together, and which also prevents the veins under the wound from constricting. So effective is the bat's saliva at keeping the blood flowing that vampire bat saliva research has led to a drug, appropriately called Draculin, which is given to heart patients.  Vampire bats need to consume a few tablespoons of blood every day. If a bat doesn't eat for more than a few days, it will starve. The vampire is well-adapted to its diet of blood; it has very few teeth, and its stomach is designed to expand, and to absorb its contents easily. Because the vampire bat often drains blood from cattle, weakening them, and because it spreads diseases like rabies, it is considered a pest. Vampire bats are one of the few types of bats that can jump straight up off the ground and start flying. The legends of vampire humans were around for centuries before vampire bats were discovered in South America. But Bram Stoker himself was so fascinated by the discovery of these bats that drank blood, that he incorporated them into his book 'Dracula'. |