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.

11 Things You Might Not Know About Reindeer

Mats Lindberg/iStock via Getty Images
Mats Lindberg/iStock via Getty Images

Beyond their sled-pulling capabilities and discrimination against those with red noses, what do you really know about reindeer?

1. Reindeer and caribou are the same thing.

Historically, the Eurasian reindeer and American caribou were considered to be different species, but they are actually one and the same: Rangifer tarandus. There are two major groups of reindeer, the tundra and the woodland, which are divided according to the type of habitat the animal lives in, not their global location. The animals are further divided into nine to 13 subspecies, depending on who is doing the classification. One subspecies, the Arctic reindeer of eastern Greenland, is extinct.

2. Reindeer have several names.

Reindeer comes from the Old Norse word hreinin, which means "horned animal.” Caribou comes from Canadian French and is based on the Mi'kmaq word caliboo, meaning “pawer” or "scratcher," in reference to the animal’s habit of digging through the snow for food.

3. Santa’s reindeer are most likely R. tarandus platyrhynchus, a subspecies from Svalbard.

Svalbard reindeer
pum_eva/iStock via Getty Images

Clement C. Moore’s poem, "A Visit from Saint Nicholas,” introduced the world to Santa’s reindeer and describes them as "tiny." The only reindeer that could really be considered tiny are the Svalbard subspecies, which weighs about half as much as most reindeer subspecies and are at least a foot shorter in length. That may prove useful when landing on roofs.

Strangely, you’ll almost never see these guys in depictions of Santa. Live-action films usually use full-sized reindeer and animations usually draw the creatures as a cross between a white-tailed deer and a reindeer.

4. It’s not always easy to tell the sex of a reindeer.

In most deer species, only the male grows antlers, but that’s not true for most reindeer. Although the females in certain populations do not have antlers, many do. During certain times of year, you can still tell the sex of a reindeer by checking for antlers. That’s because males lose their antlers in winter or spring, but females shed theirs in the summer.

5. Santa’s reindeer may or may not be female.

Since reindeer shed their antlers at different points of the year based on their sex and age, we know that Santa’s reindeer probably aren't older males, because older male reindeer lose their antlers in December and Christmas reindeer are always depicted with their antlers. Female Svalbard deer begin growing their antlers in summer and keep them all year. That means Santa’s sled either has to be pulled by young reindeer, constantly replaced as they start to age, or Santa’s reindeer are female.

6. Reindeer were originally connected to Santa through poetry.

Before Moore wrote “A Visit from Saint Nicholas” (a.k.a. “The Night Before Christmas”) in 1823, no one thought about reindeer in conjunction with Santa Claus. Moore introduced the world to Dasher, Dancer, Prancer, Vixen, Comet, Cupid, Dunder and Blixem (the last two of which were later changed from Dutch to German, becoming Donner and Blitzen). While the first six names all make sense in English, the last two in German mean “thunder” and “flash,” respectively.

As for little Rudolph, he wasn’t introduced until catalog writer Robert L. May wrote a children’s book in verse for his employer, Montgomery Ward, in 1939 titled “Rudolph the Red-Nosed Reindeer.”

7. Reindeer are the only mammals that can see ultraviolet light.

Humans can see light in a range of wavelengths, from about 700 nanometers (in the red spectrum) to 400 nanometers (in the violet spectrum). Reindeer can see light to 320 nanometers, in the ultraviolet (UV) range. This ability lets reindeer see things in the icy white of the Arctic that they would otherwise miss—kind of like viewing the glow of a white object under a blacklight. Things like white fur and urine are difficult, even impossible, for humans to see in the snow, but for reindeer, they show up in high contrast.

8. Reindeer evolved for life in cold, harsh environments.

Migrating caribou
Geoffrey Reynaud/iStock via Getty Images

Life in the tundra is hard, but reindeer have it easy-ish thanks to their amazing evolutionary enhancements. Their noses are specially adapted to warm the air they breathe before it enters their lungs and to condense water in the air, which keeps their mucous membranes moist. Their fur traps air, which not only helps provide them with excellent insulation, but also keeps them buoyant in water, which is important for traveling across massive rivers and lakes during migration.

Even their hooves are special. In the summer, when the ground is wet, their foot pads are softened, providing them with extra grip. In the winter, though, the pads tighten, revealing the rim of their hooves, which is used to provide traction in the slippery snow and ice.

9. some reindeer migrate longer distances than any other land mammal.

A few populations of North American reindeer travel up to 3100 miles per year, covering around 23 miles per day. At their top speed, these reindeer can run 50 miles per hour and swim at 6.2 miles per hour. During spring, herd size can range from 50,000 to 500,000 individuals, but during the winter the groups are much smaller, when reindeer enter mating season and competition between the bucks begins to split up the crowds. Like many herd animals, the calves learn to walk fast—within only 90 minutes of being born, a baby reindeer can already run.

10. Reindeer play an important role in Indigenous cultures.

In Scandinavia and Canada, reindeer hunting helped keep Indigenous peoples alive, from the Mesolithic and Neolithic periods all the way through modern times. In Norway, it is still common to find reindeer trapping pits, guiding fences, and bow rests dating from the Stone Age. And in Scandinavia, reindeer is still a popular meat, sold in grocery stores in fresh, canned, and dried forms. Almost all of the animal’s organs are edible and many are crucial ingredients of traditional dishes in the area. In North America, Inuit rely on caribou for traditional food, clothing, shelter, and tools.

11. Reindeer used to live farther south.

Reindeer now live exclusively in the northern points of the globe, but when Earth was cooler and humans were less of a threat, their territory was larger. In fact, reindeer used to range as far south as Nevada, Tennessee, and Spain during the Pleistocene area. Its habitat has shrunk considerably in the last few centuries. The last caribou in the contiguous United States was removed to a Canadian conservation breeding program in 2019.

As for how Santa's nine reindeer manage to fly while pulling a sled carrying presents for every child in the whole world, science still hasn’t worked that out.

Why Thousands of 'Penis Fish' Washed Up on a California Beach

Kate Montana, iNaturalist // CC BY-NC 4.0
Kate Montana, iNaturalist // CC BY-NC 4.0

Nature works in mysterious ways. The latest example materialized at Drakes Beach near San Francisco, California, in early December, when visitors strolling along the shore stumbled upon what looked to be the discarded inventory of an adult novelty shop. In fact, it was thousands of Urechis caupo, a marine worm that bears more than a passing resemblance to a human penis.

The engorged pink invertebrate, which is typically 10 inches in length, is native to the Pacific coast and frequently goes by the less salacious name of “fat innkeeper worm.” Burrowing in sand, the worm produces mucus from its front end to ensnare plankton and other snacks, then pumps water to create a vacuum where the food is directed into their tunnel. Since it builds up a small nest of discarded food, other creatures like crabs will stop by to feed, hence the “innkeeper” label.

You can see the worm in "action" here:

Because the worms enjoy a reclusive life in their burrows, it’s unusual to see thousands stranded on the beach. It’s likely that a strong storm broke up the intertidal sand, decimating their homes and leaving them exposed. The event is likely to thrill otters, as they enjoy dining on the worm. So do humans: Penis fish are served both raw and cooked in Korea and China.

[h/t Live Science]

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