Blood is a natural power drink. It is the bodily fluid found in many animals that carries oxygen and nutrients to the brain and other parts of the body. It is rich in protein and lipids so, from an evolutionary point of view, it’s a great food source for any animal that can get to it. And, since it is Halloween today, what better time to talk about these real life vampires…?
In the realms of human imagination, bats are often little more than creatures of evil, associated with the deepest night. They are linked more intimately with vampires than any other animal and, indeed, many traditional fictional vampires, Dracula included, were able to transform themselves into bats to fly around. But does the bat deserve such bad press?
Most bats do fly around at night, but of the 1,240 or so species of bat in the world, only three of them – the aptly-named vampire bats – feed on blood. The vampire bat prefers stealth and guile to an open attack, sneaking up on its victim (preferably one that is asleep) from the ground. It has specialised thermoreceptors on its nose, which allows it to locate areas where the blood flows close to the skin of its prey. It shaves away the skin with its triangular incisor teeth and starts to feed with rapid flicks of its tongue. Its saliva contains important chemical components that make the job easier: anaesthetics numb the pain receptors of the animal so that it doesn’t feel the bite and attempt to dislodge the bat, and anticoagulants maintain the flow of blood from the wound so that it doesn’t clot until the bat has completed its meal.
As it feeds, a vampire bat may consume up to 50% of its total body mass and this can be a serious problem for a flying animal because it risks becoming temporarily grounded if it gains too much weight. The bat deals with this by processing its meal exceedingly quickly. It manages to avoid gaining too much weight by converting the nutrient-poor blood plasma into a stream of dilute urine within just two minutes of starting a meal.
So should we be wary of vampire bats? Well, unless you live in Central or South America, the answer is a definitive ‘no’, because that’s the only place where they live. And even if you do live there, vampire bats prefer to bite cattle than humans. A bite from a vampire bat tends to bleed a lot, but it isn’t a particularly deep or nasty cut. That being said, a vampire bat can pass on parasitic screw worms and even rabies to the victims they bite, so it might not be such a good idea to go camping in the South American forest with your feet sticking out of your tent…
We must all go to sleep at one point or another. And, when we do, nasty little terrors called bed bugs emerge to feast, unnoticed, on our blood.
Bed bugs probably once fed on bats but several thousand years ago a new type of creature started sharing the bats’ caves with them: early man. Eventually, the bugs made the jump to humans and became primarily nocturnal to avoid being seen. They evolved long, piercing mouthparts to penetrate our much thicker skin.
Before World War II, bed bugs were a fact of life. They were always there, and there was nothing you could do about it, so people rarely gave them much thought. Pesticides developed in the 1940s helped eradicate the bed bug from much of the developed world, but since the mid 1990s they have made a major resurgence. An increase in international travel has helped contribute towards this comeback but it also, quite alarmingly, has much to do with the fact that bed bugs have become largely resistant to chemical controls. Though bed bugs do not transmit diseases, they can cause skin rashes, swelling and secondary infection from constant scratching. The blood loss from a severe infestation can even lead to anaemia.
Getting rid of or controlling bed bugs is no easy feat. They can survive for an entire year without a meal if need be. They move from room to room through cracks in the walls or floor. They produce compounds that they use to communicate with one another and although humans generally cannot detect these smells, trained dogs can. One of the few ways you can help prevent their spread is to resist the urge to buy second-hand furniture, which often have these unwelcome hitchhikers on board.
A bird is probably the least likely blood-sucker you could expect to find, but if you happened to be going on a casual trip to the Galapagos Islands in the Pacific Ocean, off the western side of South America, you might just find one. Living on this archipelago are various finches, each with subtle differences, and each specifically adapted to whatever island they are living on.
The vampire finch is a distinct subspecies of the sharp-beaked ground finch and it lives on arid islands within the Galapagos, where there is very little water. These birds have started to seek moisture-rich food from elsewhere, such as nectar from the Galapagos prickly pear or, more ghoulishly, blood from other birds.
The blue-footed booby and the Nazca booby (which are actually types of seabird for those with rather puerile minds) are the preferred victims of the vampire finch. The small bird pecks at the booby’s skin with its beak until blood is drawn and then it starts to lap it up. Strangely, the boobies seem to offer little to no resistance whatsoever to this behaviour, and so it has been theorised that at one point in their evolutionary history, the vampire finches used to clean parasites from the plumage of the booby before adopting a more gruesome lifestyle. These finches even feed on the eggs of the boobies, stealing them just after they have been laid and then rolling them into rocks until they break.
It’s all pretty ghastly behaviour for such a small, innocent-looking bird, but it seems that getting stranded on a deserted island is enough to turn you into a real-life vampire.