Vampire Bats
Opening:
Welcome everyone to another episode of 8 minutes of Eww! The place where we use curiosity and science to turn fear into fascination and those ewww’s into Oooh’s. Oh! By the way, I’m your host Ms. Mallory, the Curious Conservationist, and self-proclaimed grossologist. Let’s get started.
Intro:
Last week we talked about fruit-eating bats and carnivorous bats, but we ran out of time to chat more about one of my favorite types of bats. I will give you a hint. It got its common name after our favorite bloodsucking Halloween character from Transylvania. Any guesses?
The vampire bat!
How much blood a vampire bat would need to consume if it were the size of Dracula or one of us? Keep that number stored in your memory bank because I will be sharing that little secret at the end.
Background
Although many assume bats are bloodthirsty monsters, very few species strictly feed on blood. Can you guess how many? I will give you a hint. It’s the same number as the number of pigs that wouldn’t let that hairy stranger come in by the hairs on their chinny chin chin. That’s right, just three: the common vampire bat, the hairy-legged vampire bat, and the white-winged vampire bat. Not only are they the only blood-drinking bat, but blood drinking mammals. All of them weigh about as much as a AA battery and won’t be found in the United States. Just wanted to add that in there in case any of my neighbors were worried.
And even if they did live in the United States, these blood drinkers—known as sanguivores— are pretty picky. While the common vampire bats prefer mammal blood— mainly that of livestock like cattle, pigs and horses— the other two species prefer bird blood, especially that from chickens.
And just because I know you are wondering, I will answer your question right now. . Very rarely have vampire bats turned to humans for a meal. On a few occasions, sandal-wearing travelers that decided to camp without a tent in vampire bat habitat have noticed small cuts on their big toes— the telltale sign of a vampire bat feeding. Again, no need to worry if you’re sleeping in a hammock outside the warm regions of southern Mexico, or Central and South America.
Topic 2: Name
Want to hear something crazy, the vampire bat was first named into science in 1810, but it was named after the shape of its tooth and not its love for blood. It wasn’t until many years later that the bat was seen feasting on blood and was given another name after the infamous Dracula character. And to make things even more complicated, there is a bat known as Vampyrum spectrum or the false vampire bat. This bat is the largest bat in North, Central, and South America— a region called the New World—and is much bigger and more impressive than the itty bitty true vampire bat. However, this bat is a carnivorous bat and prefers eating the whole animal, not just the blood. The reason that non-blood-feeding bats have vampire-like names is the result of early zoologists who incorrectly claimed to have captured the mysterious blood-feeding animals reported by European explorers of the New World.
Topic 3 Feeding
Have you ever wondered how vampire bats feed? While casting a spell and plunging its massive fangs into the neck of its prey may be what comes to most of our minds, that approach is merely for the movies. Remember small bats have even smaller bones, so they have to be pretty sneaky and quite careful when it’s time for supper. Like other bats, vampire bats use echolocation, some sight (remember from our last podcast, bats aren’t actually blind), and even scent to find their liquid meals. . .But vampire bat also has some pretty special adaptations that make them the perfect sneaky sippers.
While most bats grab their meal on the wing, vampire bats prefer a more grounded approach—crawling. The tiny Dracula will land on the ground close to this animal of choice, usually when it is sleeping, and slowly creep up from there. But how could a vampire bat tell is an animal is sleeping and not just resting? So glad you asked. The area of the vampire bat’s brain that detects sound has become specialized that it can actually tell the difference between a breath of an animal sleeping and one that is awake. So cool, right!! This tiny, winged crawler was made with a little extra love compared to other bats. It has an extra long, well-developed thumb to help it climb, plus extra strong wings and hind legs. Unlike other bats, vampire bats can walk, run, and even jump using their legs and the thumbs of their folded wings— this can be very handy with a full stomach!
Often times the bat will go for an easy location— like an ankle—but sometimes the bat can’t find a good spot and will climb up the animal’s body to find a better one. And here is where the Vampire bat's second superpower comes in handy. They have highly specialized heat-sensing “pit organs” near their nose— kind of like that of a viper. These heat sensors allow the bat to find an area of the body where the blood flows close to the skin.
Now remember, one kick, flip or lick from a massive cow and that batty becomes a patty, so the vampire bat is going to be VERY careful not to be noticed. Thankfully, the vampire bat’s teeth are so sharp, the massive cow or pig rarely ever knows it’s getting snacked on. Once the perfect picnic spot is found, the bat uses its namesake—those thin, blade-like incisors to make a very small incision, 3 mm long, in the skin of its victim. 3mm, that is the width of two pennies pushed together, a little more than half of a pencil top eraser, and only a quarter of the width of your pinky nail. That’s it. I think I know of papercuts bigger than that.
But just in case the cow did seem to notice, the vampire bat’s saliva —or spit— has a gift to give in the form of special, pain-killing proteins. So in case, any discomfort was felt, wouldn’t last long.
Now unlike the movies, true vampire bats don’t just dig in and gulp down blood, they’re a bit more proper than that. With the help of a special ingredient in the saliva that prevents the blood from clotting at the wound site (remember hearing about blood clotting on the scab episode?), the bat can have a meal without any chunky interruptions. Now this special ingredient is known as an anti-coagulant and researchers have given it the nickname—Duraculum, after count Dracula. Because duraculum prevents blood from clotting, researchers hope it could one day help stroke victims by dissolving blood clots that are starving the brain of oxygen.
How long do you think it takes for a vampire bat to get a full meal in? 2 minutes? Maybe 10? The little lapper takes around 20 minutes to get its fill (about 20 grams or 2 tablespoons, or about 1.5 times its pre-feasting weight.
Speaking of meal, we uncovered how the vampire bat gets the meal but how can a creature survive purely on blood?
Most animals need important building blocks to living in the form of protein, fats, and carbohydrates. We need these things too. Proteins build muscles, fats make our skin and hair healthy, and carbohydrates give us energy. We get all of these building blocks with a balanced diet full of lots of different types of nutritious foods. But with a vampire bat, it consumes just one thing and this one thing lacks most of those important building blocks.
Digesting Blood
Thankfully the vampire bat has a lot of tricks on those little wing flaps. Blood is mainly protein and water, not much of anything else. Thanks to special organs and tiny BFFs that break down the blood into vitamins and nutrients in the bat’s gut, the bat can live off a very strange, but simple meal plan.
Unfortunately, blood doesn’t have many calories or energy, so the bat doesn’t have any stored fat to use if it misses a meal. In fact, a vampire bat usually won’t have enough energy to hunt if it misses a few meals. Thankfully, that isn’t the case for humans.
So what happens when a vampire bat has a baby, gets sick, or maybe can’t find a meal for the night? Surprisingly, male vampire bats are quite generous to others in need.
Most vampire bat colonies take up shelter in caves, where up to 250 bats can reside. Within these colonies, small groups of females will come together like neighborhood moms during a playdate. These females are very supportive of one another and will groom, and even umm. . how do I say this. . share a meal with another member in need. If a female bat accepts a meal from a friend, then she will be sure to return the favor in the future. This food sharing and grooming creates strong bonds and makes the colony stronger as a unit. Not bat left behind. Oh. . . Just a thought, if your neighbor is sick, I think getting takeout might be a better choice than trying to feed them like a baby bird, but that’s just my opinion.
Okay every, dig into that memory bank. It’s time to answer that trivia questions. How much blood do you think a vampire bat the size of Dracula would need to drink to fill up during mealtime? Well, we now know the vampire drinks about 2 tablespoons or one and a half times its weight. So to make calculations a bit easier for Ms. Mallory, Let’s say this Dracula-sized vampire bat was tall and weighed 200lbs. He would drink about 300lbs during a meal. If a gallon of water weighs roughly 8 pounds (and I am assuming blood would be a similar weight), he would need to consume almost 36 gallons of liquid to get full! Incredible. I can barely get in my 8 glasses of water a day. (haha). The human body only holds about a gallon to a gallon and a half. Not even worth the time of a man-sized vampire bat. It would need to consume 3.5 cows, two draft horses, or half an African elephant to feel full after a meal. Thank goodness Dracula doesn’t exist lol.
But doesn’t that make you wonder? Drinking more than one and a half times your weight can make it pretty uncomfortable to move, let alone fly. So how does a tiny creature do it? Here comes the vampire bat’s third superpower— quick liquid release. As the bat drinks, a special liner in its stomach quickly absorbs the water from the meal and sends it to the liquid waste department: its kidneys. Within a matter of minutes, the bat pees out the water and is ready for lift-off.
Outro:
Well, my aspiring grossologists, my 8 minutes are up. Thank you for joining me to learn about one of my favorite fear2fascination animals. I used to be terrified of bats growing up and now I just love them. Bats, in total, are so important. Be sure to listen to the other bat podcast if you haven’t already. Lots of good gems in there.
As always, please let me know how you liked this episode. Your comments mean so much to me and will help make this podcast better. For more info, check out the show notes, and don’t forget to subscribe and set those notifications so you don’t miss the next 8 minutes of Eww. Bye.