11 Bloody Facts About Vampire Bats

iStock / through-my-lens
iStock / through-my-lens

Bats are firmly rooted in Western vampire lore, but only three species, out of some 1100 in the order Chiroptera, actually have a taste for blood. The vampire bats are the only mammals in the world that live on blood alone, and the unique challenges of that diet make them some of the most specialized, fascinating and downright weird animals that nature has to offer.

1. The three vampire bat species—the common vampire bat (Desmodus rotundus), the hairy-legged vampire bat (Diphylla ecaudata), and the white-winged vampire bat (Diaemus youngi)—are closely related and grouped together in the subfamily Desmodontinae. Their ranges overlap in parts of Central and South America, so, in what might be an effort to avoid competition with each other, the species specialize in different prey. The common vampire feeds primarily on the blood of mammals —ranging from tapirs to horses to the occasional human—and seems to have a preference for livestock animals. The hairy-legged vampire, meanwhile, lives almost exclusively on bird blood, while the white-winged vampire is more versatile and drinks from both birds and mammals.

2. Other bats with less grisly diets got a bad rap from European explorers in the Americas. The Europeans had heard stories about blood-drinking bats and encountered native people and livestock that had been bitten in the night and, without any real knowledge of the animals’ diets, began labeling different bats as vampires willy nilly, usually applying the term to bigger and/or uglier ones. Bats that lived on insects or even fruit were assumed to be vampires thanks to their appearance, and the association stuck when they were scientifically described and saddled with names like Vampyrum spectrum and Pteropus vampyrus. Meanwhile, when a naturalist finally got his hands on an actual vampire, D. rotundus, no one one believed his assertions that it drank blood, and he made no mention of it in his description.

3. When the bats feed, they use their teeth to shear away hair or feathers from a small spot and then cut into their victim’s flesh with their sharp incisors. (According to zoologists at Chicago’s Field Museum, even the teeth on old, preserved bat skulls in museum collections are sharp enough to cut someone handling them carelessly.) Rather than actively suck the blood from the wound like their namesakes, the bats let the physics of capillary action do the work. They lap at the blood and specialized grooves on their lips, tongues, and/or roof or their mouths suction it up. A protein in the bats’ saliva called a plasminogen activator prevents the blood from clotting and keeps it flowing freely while they drink.

4. White-winged vampires have a few tricks for feeding on domestic chickens without startling the birds. Sometimes, they’ll approach a hen and mimic a chick by nuzzling up to her brood patch. This featherless section of skin on the hen’s underside is densely packed with blood vessels and is used to transfer heat to her eggs or chicks during nesting. The vessels make an easy target for the bat, and if the hen thinks it's her baby cuddling up to her, she’ll sit on the bat to give it access to drink. Other times, the bats will climb up on a hen’s back, mimicking the touch and weight of a mounting rooster and sending the hen into the crouching stance they take before mating. The bat can then shimmy up to the hen’s neck for a bite and she’ll stay in that position until the bat hops off.

5. White-winged vampires will also take their meals in the trees instead of the barnyard. While a bird roosts on a branch, the bat sneaks up on it from below, crawling along the underside of the branch and staying out of sight. Once it’s directly underneath its prey, the bat bites the bird’s big rear-pointing toe and drinks its fill.

6. The hairy-legged vampire also feeds in the trees, but doesn’t bother with subtlety like its cousin. They’ll often land directly on a bird and hang from its body upside-down with their feet while biting around the bird’s cloaca, the all-purpose entrance and exit for the intestinal, reproductive, and urinary tracts. The maneuver is helped by the bat’s calcar, a bony spur that comes off the ankle bone. It’s absent in some bats and underdeveloped in others, but the hairy-legged vampire’s protrudes noticeably and is used by the bat like an extra digit to help it hang on.

7. Unlike its cousins, the common vampire bat eats solely on the ground, and it has evolved to be as nimble there as it is in flight. While most other bats are awkward crawlers, the common vampire can move with a quick run-like gait or hop along the ground, supporting its weight on its hind legs and using its wings and elongated thumbs to steer and push off of the ground. This comes in handy for chasing after prey on the move and for jumping out of the way if it needs to.

Feeding for common vampires is often risky, given that their preferred victim, the domestic cow, is several thousand times larger than they are. They usually bite cows on the area of the leg just above and behind the hoof, since the skin is relatively thin and the blood vessels run close to the surface. One step backwards, and a bat could be squashed if it hadn’t figured out how to run or make impressive three-foot leaps into the air.

8. To meet their energy needs, vampire bats need to drink about an ounce of blood at every meal, meaning they consume half their body weight during each 20 to 30 minute feeding session. Their bodies have adapted to lighten that load, and their stomach lining rapidly absorbs much of the blood’s water content and sends it to the kidneys so it can be excreted. The bats can process their meal so quickly that they may begin disposing of it before they’re even finished with it, and start urinating just a few minutes into the feeding.

9. Vampires are known to share meals with each other. Mother bats regurgitate previously-drunk blood for their offspring until the babies are old enough to hunt on their own. Other related bats and even unrelated ones have also been observed puking blood up for one another in a reciprocal arrangement. If a bat can’t find a meal one night, one of its roost-mates may share some of its meal. In the future, the bat who was fed is highly likely to return the favor. If it cheats, or takes a blood donation without ever giving back, it may find that it gets the cold shoulder the next time it needs help.

10. Vampire bats have a few different tools for finding their food. They have well-developed senses of smell and, despite bats’ reputation, keen eyesight. They’ve also got heat-seeking faces—their wrinkly, leaf shaped noses are loaded with nerves that are, in turn, loaded with proteins that are sensitive to the infrared radiation given off by warm-blooded animals. They also have finely-tuned hearing and specialized neurons that react only to the sound of breathing. They can even distinguish the breathing sounds made by different individuals, and may be able to remember the unique sonic components of an individual animal’s breathing, allowing them to return to the same reliable source of blood night after night.

11. Animals that are adventurous eaters learn to avoid potentially toxic foods through trial and error. They try something new, get sick, and then avoid those flavors in the future. Vampire bats appear to have lost their sense of taste aversion, though. In experiments, biologists have given vampire bats and their fruit- and insect-eating cousins treats seasoned with different, unfamiliar flavors, and then induced vomiting. At their next few meals, the bats were given the choice between normal food and food flavored with the same seasonings from before. While the other bats avoided the flavors they associated with getting sick after the first meal, the vampires dug in to both flavored and unflavored blood. The researchers think that the vampires either lost the ability to make these associations because their diet doesn’t present a variety of flavors and it wasn’t needed, or maybe that they had to lose it early on in their blood-drinking history to make the diet viable.

The Tower of London Welcomes New Baby Ravens for the First Time in 30 Years

Some of the baby ravens born at the Tower of London
Some of the baby ravens born at the Tower of London
Tower of London Twitter (screenshot)

There are some new residents at the Tower of London. They're only about 11 inches tall, are very noisy, and eat rats for breakfast, lunch, and dinner. Fortunately, they're also adorable—not to mention protected by legend.

On May 17, the Tower of London announced that their breeding pair of ravens, Huginn and Muninn, had welcomed four healthy chicks, the first born at the Tower since 1989. The ravens are part of an unkindness that's been located at the Tower for centuries as a sort of protective asset. According to legend, the Tower must always have ravens, or both the Tower and the kingdom will fall. It's not exactly clear when the legend began, but according to the Tower, Charles II decreed there must always be six ravens present.

Huginn and Muninn are newer additions, having arrived at the Tower in late 2018, and they weren't expected to breed this spring. So it was a surprise in mid-April when the devoted Tower Ravenmaster, Yeoman Warder Chris Skaife, noticed something exciting going on. "My suspicions were first piqued that we might have a chance of baby chicks when the parents built a huge nest suddenly overnight and then almost immediately the female bird started to sit on it," Skaife said in a Tower press release. On April 23, Skaife noticed the birds flying to the nest with food, but it was only this week he was able to get close enough to see the four healthy chicks. The sight delighted him: "Having worked with the ravens here at the Tower for the last 13 years and getting to know each of them, I feel like a proud father!"

The chicks have grown quickly, already quadrupling in size since they were born, and eat a diet of quail, rats, and mice the Ravenmaster provides. The raven parents have an egalitarian feeding arrangement: Huginn, the male, preps the food and passes it to Muninn, the female, who feeds it to her tiny chicks.

The plan is for one of the chicks to stay at the Tower and join the rest of the ravens there. "As the ravens started to hatch on the 23 April, St. George’s Day, the raven that will be staying at the Tower will be called George or Georgina in honor of the occasion," the Tower explained in a press release. According to The Telegraph, the breeding program at the Tower kicked off in response to a decline in the number of legal raven breeders in the UK.

The last raven chick born at the Tower was Ronald Raven, born May 1, 1989. In his 2018 book, The Ravenmaster: My Life with the Ravens at the Tower of London, Skaife wrote that "a baby raven looks a bit like a grotesque miniature gargoyle, but then you see them grow and develop ... It really is wonderful."

The baby ravens born at the Tower of London in 2019
The baby ravens born at the Tower of London in 2019 making some noise
Yeoman Warder Chris Skaife

Dozens of Donkeys, Mini-Donkeys, and Baby Donkeys Are Looking for New Homes

iStock.com/huggy1
iStock.com/huggy1

Cats and dogs aren't the only rescue animals that need permanent homes. At the Humane Society of North Texas (HSNT), there are over 60 donkeys, miniature donkeys, baby donkeys, and Thoroughbred horses up for adoption, the Cleburne Times-Review reports.

Many of the equines at HSNT's ranch in Joshua, Texas came from owners who had to give them up, and others were transferred from different animal rescue groups. As part of the ASPCA’s Help A Horse Home Challenge, HSNT is hosting events to help find new homes for its horses and donkeys.

Between April 26 and June 30 this year, the ASPCA is challenging equine organizations to adopt out as many animals as they can. The groups that see the biggest increases in adoptions between this year and last year's Help A Horse Home Challenge will share $150,000 in grant funding. On May 18 and June 8, HSNT is holding open houses at its ranch for anyone interested in adopting an animal. The events will also be used as opportunities to educate the public about the demands of equine ownership.

If you're not free to swing by one of HSNT's open houses, you can still apply to adopt a horse or donkey. Interested owners can fill out and submit this form [PDF] to equine@hsnt.org. And if you'd like to spend time with baby and mini-donkeys without taking one home, HSNT is also looking for volunteers.

[h/t Cleburne Times-Review]

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