Few species have been more misunderstood than the vampire bat (Desmodus rotundus).
Slanderous falsities started with 16th-century New World explorers, who returned to Europe with lurid tales of bloodthirsty beasts that drained their troops as they slept. For a start, vampire bats don’t suck blood, they lap it from an open wound. And being the size of a mouse means their liquid diet amounts to little more than a spoonful. They also rarely attack people – they tend to feed on domesticated cattle or chickens.
How do vampire bats hunt?
Vampire bats approach their victims by stalking them from the ground. They use their exaggerated, winged hands to drag themselves forward while bouncing on stunted rear legs. This sounds awkward, but they move surprisingly fast. One inspired scientist placed bats on a treadmill and they clocked a top speed of more than 2m per second. Vampire bats can also launch themselves vertically, like a Harrier jump jet.
Vampires use infrared sensors in their noses to detect the heat of blood pumping close to the skin (which therefore provides easy access). Favourite hotspots are fur and feather-free: think feet (ticklish), ears (annoying) and anuses (good lord). Bats will return to feed on the same spot several nights in a row, guided by their unique ability to listen out for and memorise a preferred victim’s breathing patterns.
Bloodthirsty bum-biters that stalk their prey by listening to them breathe may sound more evil than Dracula himself. The truth is that female vampire bats are one of the animal kingdom’s most magnanimous animals. Being a flying mammal is an energetically expensive existence, especially for pregnant or nursing mothers. The vampire bat’s exclusively hematophagous diet provides far from ideal fuel, since blood consists of 80 per cent water and absolutely no fat.
Blood-spewing besties
Vampire bats have specially adapted digestive systems that eliminate excess water by urinating as they feed, which enables maximum protein consumption without their stomachs exploding. But with no fat, and no opportunity to build up fat reserves, they must feed at least every 70 hours or die. Up to 30 per cent of bats fly home empty. Two consecutive nights of feeding failure means almost certain starvation.
One of the world’s leading experts on bats, Professor Gerald Wilkinson, discovered how vampires evolved a food-sharing system that sees females vomit up congealed blood for their hungry neighbours. What’s more, they regurgitate for roost-mates that are not even family members. In fact, they are more likely to share with blood-regurgitating buddies than their own relatives. In this caring, sharing, blood-spewing community, female bats form strong and meaningful bonds with each another. ‘You can think of them almost as friends.’ Wilkinson told me.
Vampire bats have an extraordinarily long lifespan for an animal of their size – 30 years compared to two or three years for a similar-sized mouse. They use that time to develop a wide circle of friendships. Bats placed in an enclosure with strangers don’t start sharing food immediately. They test the water by huddling together first, then move on to grooming and finally start sharing food after about two years.
Recent research suggests these bonds extend even beyond the roost. Tracked females demonstrated specialised calls while out foraging. These helped female vampires recognise their besties and invite them over for a life-saving meal: a level of social sophistication rarely seen outside of primates. The world might be a kinder place if humans were a bit more like vampires.
Main image: Vampire bat jumping across the floor/Getty
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