Mother Nature Is Trying to Kill You (10 page)

Unlike Dracula, the real vampires don’t clamp on with fangs. Instead, the bat neatly shaves fur with its teeth from the area it wants to bite, then makes a shallow slash in the skin with its upper middle two teeth. The resulting divot is only about a quarter inch deep and a quarter inch wide, but it bleeds, just like a man’s cheek does when he cuts the capillaries in his face while shaving. Thanks to compounds in a vampire bat’s saliva, the divot in the cow’s skin will continue slowly dripping blood for as long as the feeding takes.
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The bat will feed for twenty to forty minutes, urinating all the while to rid itself of excess water, until it’s consumed about a tablespoon of blood, increasing its weight by around 50 percent. Then the bat jumps into flight and goes back to its roost to hang out.

It’s an important point that vampire bats approach their hosts by walking up to them, because walking is super weird for
a bat. Vampires only walk because, unlike all the other bats, they make their living on blood. Most bats never land on the ground at all, and those that fall accidentally typically jump off the ground as soon as they can. Vampire bats, on the other hand, are perfectly comfortable walking on the ground, and they can launch themselves off the forest floor with amazing dexterity. In fact, there’s a very famous biomechanical study on vampire jumping; it shows that a vampire bat can launch itself in less time than it takes for a human to blink (which, as you already know, is about as fast as a duck unfolds its penis) and can jump upward three feet or more. For an animal the size of a mouse, that’s insane.
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Hiking toward a cave in Costa Rica that I knew might have vampire bats in it made me feel like a twelve-year-old going backstage at a Justin Bieber concert. Maarten, who had been in Costa Rica for several months already, said that the vampires had been in the cave each time he’d checked, but when he saw how excited I was getting, he was quick to mention that he hadn’t been to the cave in several weeks, so there was no guarantee. First, we canoed across a small river, tied the boat to a branch, then set off along a path. As we walked, the forest rose up high above me, and every bump on every branch had a very real possibility of revealing itself to be a monkey or sloth. It was muggy and wet and smelled like mud with a hint of spice. There was a constant buzz of cicadas, and I could see insects all over the forest floor, but there were surprisingly few mosquitoes. Colorful birds zipped across the path ahead of us. I’d always wondered what tropical rainforests were like, and now I was in one.

We stopped about thirty feet from the cave, and Maarten explained the layout so that I’d know what to look for before
scaring all the bats away. On the wall near the mouth of the cave I’d find some sac-winged bats. Those are insect-eating bats best known for the way males throw urine, saliva, and semen on females they want to mate with (more about them in the chapter on envy). Beyond those bats, I would need to crouch to enter the main chamber, which was only about four feet high. On the ceiling, I’d see some short-tailed fruit bats—bats that can tell what kinds of nearby fruit species are ripe by smelling the breath of well-fed bats coming into their cave. Past that main chamber, Maarten told me, the cave narrowed to a hole in the back wall at floor level, some eight feet or so from the entrance. That hole had an open shaft above it, almost like a chimney above a fireplace. Maarten told me that if I slid on my back, pushed my head into that hole, and looked up, I might see a few vampire bats three or four feet directly above my face.

I walked to the cave as silently as I could, found the sac-winged bats, and took some photos. Then I crouched to look in the cave. There was movement, but I was still too tall to really see what was going on, so I took off my backpack, turned around, then lay down on my back and slid into the cave. The cave floor was wet and smelled
terrible
. As I slid through the bat droppings, I felt the sludge slide through my hair, down my neck, and into my shirt. Halfway into the cave, I turned on my headlamp and immediately saw the short-tailed fruit bats, huddled together, looking straight down at me. One of them flew away when my light came on, but then it came right back just a few seconds later and landed right where it had been, next to another two. As they hung, they twisted by their toes, pivoting around, with their faces rotating above me. They were really looking at
me
, and
although I couldn’t hear it, I knew they were observing me with their ultrasonic echolocation calls as well. I’d never experienced anything like this. It was the kind of moment I’d dreamed of having ever since I read my first book on bats in high school. I would have preferred not to have insect-laden guano down my neck, but in spite of that, this was the coolest thing I’d ever done.
^V

A vampire bat needs to feed pretty much every night or it will starve to death, so if one comes back to the roost without having successfully found a meal, it will beg the other vampire bats to barf up blood for it. The hungry bat does this by going from bat to bat, licking their mouths until one of them pukes a little to help them out. What makes that French-kissing blood-vomit exchange so incredible (besides the fact that it’s a French-kissing blood-vomit exchange) is that bats will even help unrelated individuals this way. In other words, while it wouldn’t be surprising to see a mother feed her baby, or even a brother help a sister, you don’t ever expect animals to help nonfamily members. That would seem to violate the Scrooge-like rules of selfishness that govern all animals. But the food sharing by vampire bats works because the vampire bats are smart enough to remember who has helped in the past and who has not. If a bat keeps on begging but never shares, the group can just stop puking for that one bat. By puking today, a bat ensures that it will get help when it’s down on its luck next time. Other than humans, vampire bats are among the few animals on Earth that will give away food they have already secured just to help out an unrelated member of their own species.
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I turned off my headlamp and slid onward through the dark, until my head went into that hole at the back of the cave. As I slid from a floor covered in pooped-out fruit to a floor pasted with pooped-out blood, the smell got worse. I came to a stop; then I heard the loud screeching noises coming from above me—sounds I’d never heard, but that I could only assume were the voices of vampire bats! I brought my right arm up toward my head to turn my headlamp on, but my knuckles smacked into rock. That’s when I realized that my head was plugging the only exit to the vampire bats’ chamber. It was too dark to really see what was going on.

I tried a different path for my arm, up my chest and against my face, and was finally able to flick on the headlamp.

There were three of them!

I knew those faces instantly: common vampire bats,
Desmodus rotundus
. In the light they got louder and started moving around on their perch above me. They bared their pointy triangular teeth at me and screeched like miniature dragons. I couldn’t get my camera into the hole with my head, so I had to just lie there and soak it all in. I fully admit that it was uncomfortable—even scary—but I think that was part of what made the whole experience so life-changing. I wasn’t in control. My face was exposed to them. The best way I can think of to describe the vulnerability is to say that it was like swimming in the ocean for the first time. You’re scared, but the thrill and the beauty are enough that you’re
willing
to be scared.

These three vampire bats were exotic, but what made them even more beautiful to me was the context—all those scientific facts I’d acquired made them familiar, like celebrities. I knew so many things about vampire bats that set them apart from all the other bats. Feeding only on blood, with no variety in diet at all, has caused vampire bats to lose their ability to discern different
flavors.
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Because they drink up to half their own body weight in one meal, the stomach of a vampire bat has a side pouch that can fill up with blood quickly and then trickle that meal through the digestive system slowly over the ensuing hours.
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That same out-pocket is what makes it possible for bats to easily puke blood up for one another when they share food. By extension, the food-sharing behavior itself is a by-product of the fact that vampire bats have become parasites.

What started to dawn on me that day was that the vampires are strange and charismatic
because
they feed on blood. In other words, being
parasites
is what made vampire bats so wonderful. Lying in that cave was one of the critical moments that set me on the road to becoming a bat biologist, but it was also the first time I really appreciated how incredible parasites could be. That sparked a curiosity in me about whether there might be any other lazy parasites out there worth a second look.

Were. There. Ever.

Parasites live everywhere there is life. The squirrel in your backyard is filled with microscopic creatures; the bird at your feeder is covered in teeny parasitic arachnids. Panda bears have parasites, as do the penguins of Antarctica.
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In fact, to my knowledge, biologists have never found an animal species
without
parasites. Those lazy parasitic lifestyles are hugely successful. If a full census of life on Earth could ever be completed, biologists have
argued, the total number of parasite species would likely be even bigger than the number of nonparasite species.
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Humans can get parasites too. You’ve experienced a mosquito bite, I’m sure. Remember the itch? That happened because when that mosquito bit you, she began by spitting into your skin.
^VII
She hawked that loogie into your blood before she started drinking because her spit prevents your blood from clotting. Your immune system went into action to clean up the spit (too slowly to stop the mosquito, but fast enough to make you itchy for a few days), and the inflammation that resulted was itchy.
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In most cases, the mosquito bite has no aftermath, but sometimes a mosquito’s salivary glands are home to parasites called
Plasmodium
. Those are tiny wormlike creatures, even smaller than a single red blood cell. When a
Plasmodium
-infected mosquito bites you, she squirts those parasites into your blood. They float through the bloodstream to the liver, embed there, and breed. After some time, they leave the liver, float back into the blood, and then somehow find their way to the insides of red blood cells—where they reproduce, then burst out, destroying the red blood cells. That process gives the human host horrible fevers, liver damage, and sometimes even inflammation around the brain and spinal cord.

The disease caused by
Plasmodium
is called malaria, and no other parasite (or predator, for that matter) causes as much human pain and suffering as those little wormlike bastards in the salivary glands of mosquitoes. Using those mosquitoes as their delivery system,
Plasmodium
parasites infect hundreds of millions of people each year, killing thousands of them, mostly children.
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If having worms enter your red blood cells isn’t bad enough for you, Mother Nature has a smorgasbord of other human parasites to choose from, each more disgusting than the last. For example, I’m personally quite grossed out by the roundworms that cause that grotesque swelling of the lower body called elephantiasis.
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You get those worms from a mosquito bite, and they quickly set up shop in your lymphatic ducts. (Lymphatic ducts are tubes that drain excess fluid from swollen tissues and put that fluid back into the bloodstream.) Once the worms find those lymphatic ducts, they grow to somewhere between one and four inches in length and hide, undetected by the immune system for up to thirty years.

Thirty years!

Do you realize how long that is? Hiding a four-inch worm inside your body without the immune system going nuts should be impossible, even for a day. If humans could mimic the cloaking ability of those worms, it would be an absolute game changer for organ transplantation, where rejection by the immune system is the major barrier to survival. I’m not saying we should love these worms (I sure don’t), but you’ve got to respect what they can do.

Eventually, the worms will die of old age, and when that finally happens, the cloaking system shuts down and the human immune system, suddenly realizing there are giant worms in the body, goes nuts. Swelling is intense and immediate, but the lymphatic ducts that should drain that excess fluid are blocked by the corpses of the worms. As a result, the limbs swell up to unimaginable dimensions. Voilà. Elephantiasis.

And just in case elephantiasis and malaria aren’t enough to convince you of Mother Nature’s dark side . . . You can get roundworms that burrow through your body, eat your organs, and kill you. There are amoebas that can get behind your contact lens, eat your eyeball,
and make you go blind. There’s even something called a pinworm that lives in your rectum until it’s ready to lay eggs, then waits until you are asleep, sneaks out your anus, and lays eggs so you’ll be itchy in the morning, touch them with your fingers, and accidentally pass them on to other people when you cook breakfast.
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Another noteworthy human parasite is the leech, a blood-sucking animal closely related to the earthworm. A leech has two suckers—one at the mouth and one on the tail—and it uses them in synchrony, to move around like an inchworm. I remember a fellow bat researcher once telling me about the time he was on a bat expedition in the forests of Vietnam and took a moment to squat in some tall grass to poop. As he squatted, the tips of the grass were at eye level, and he could see leeches on those tips, extended upward from their bottom suckers, waving like alien finger puppets all around him. Every time he rustled to adjust his position, the leeches would bend over and inch their way toward him, then pause once more when he got still again.
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Despite his best efforts at stillness, he told me, he had some removals to perform after the job was done. I didn’t ask him for details.