Mother Nature Is Trying to Kill You (9 page)

But now he’s a child. When I hold him, Sam feels like a miracle. I love Sam—
love
him—and that’s helped me understand how DNA molecules coerce their meat robots to do their bidding. I’m experiencing the most powerful emotions of my life. If I were a bowerbird, I’d have decorated my nest with blue objects. If I were a bighorn sheep, I’d have smashed my head into anyone I could. But I’m a human, and I instinctively care more about Sammy than anything else in the whole world.

As for Shelby and me, we feel like a team. We look after one another, we support one another, and we’re happy together. Despite the horrible things animals do to one another in the name of sex, we’ve found a way to leave that conflict behind. You can call that natural, but it’s not really. It’s human.

Overall, sex has made me a pretty happy guy. Even if the testosterone that comes with that joy has cut my life shorter by a decade or two, I would say it’s been worth it.

I
. The male builds his “bower” out of twigs. It’s a structure with two parallel walls, about four inches apart, with everything cleared off the ground around it. The male decorates that ground with blue objects, and the number of times females will mate with him depends largely on how many blue objects he can accumulate (Borgia 1985). One of the best places to find blue objects, of course, is the bower of another male bowerbird, so theft is a big part of competition among males (Wojcieszek et al. 2007).

II
. Head-ramming behavior is essential to rams that want to mate (Martin et al. 2013), but collisions tend to be quite bad for mammalian brains. Rams avoid concussions, though, by having heads that are built in a way that mechanically dissipates energy when they ram (Maity and Tekalur 2011).

III
. I’m talking about cortisol. It’s released in high doses by male antechinuses (Naylor et al. 2008), and by people with post-traumatic stress disorder, or PTSD (Steudte et al. 2011).

IV
. A lot of people assume male black widows are always killed by the female after sex, but males usually escape. In fact, male black widows can sometimes inseminate up to three females (Breene and Sweet 1985). The observation that females always kill males probably came from early experiments in closed containers that were so small the male couldn’t escape, which isn’t really how things would work in the wild (Vetter and Isbister 2008).

V
. An example of a spider species that uses nuptial gifts is the nursery web spider (Stålhandske 2001). Sometimes he’ll play dead while he’s holding his gift, and just when the female comes to take it, he’ll spring into action and mate with her (Hansen et al. 2008).

VI
. Maternal mortality per 100,000 births in a few Western countries: USA 21; Canada 12; Australia 7; New Zealand 15; UK 12. And in a few sub-Saharan countries: Chad 1,100; Somalia 1,000; Sierra Leone 890

You can look up other countries using an interactive map of World Health Organization (2012) data here:
http://www.who.int/gho/maternal_health/en/index.html
.

VII
. Thousands of babies have died too. Worldwide every year 3.3 million babies are stillborn and more than 4 million die less than a month after being born. Those babies die for many reasons, but it’s clear that lack of access to medicine is a major factor because those deaths are heavily biased toward less developed countries (World Health Organization 2005).

VIII
. Around 287,000 women died in childbirth in 2010 (World Health Organization 2012).

IX
. The order Carnivora is split into two main groups: the “doglike” canimorphs and the “catlike” felimorphs. Canimorphs include dogs, bears, skunks, and sea lions. Felimorphs include cats, hyenas, fossas, and mongooses (Ignarsson et al. 2010).

X
. For a complete rundown on the mating habits of spotted hyenas, including an adorable picture of a male cuddling with a female after sex, see Szykman et al. (2007).

XI
. What’s truly amazing about the duck’s penis inflation system is that it’s not driven by blood pressure, as it is for humans. Instead, that rapid expansion is driven by the lymphatic system—the same system that slowly drains excess water from your swollen tissues. The wonderful biomechanics paper that explains all this is Brennan et al. (2010). It includes some glorious high-speed videos of duck penises doing their thing, sometimes inside see-through glass vaginas. Those videos are also available on YouTube:
http://www.youtube.com/watch?v=qwjEeI2SmiU
.

XII
. Female waterfowl are especially likely to be killed by marauding males in parks, compared with in the wild, because the sex ratio in parks is often even more biased toward males than usual (McKinney and Evarts 1997).

XIII
. Yes, even Flipper had a dark side (Connor et al. 1992).

XIV
. It’s dark where deep-sea squid live, and it’s hard to tell males from females, so when a male encounters another member of his species, he injects a sperm packet into its skin as quickly as possible. If it’s a female, he’ll probably fertilize some of her eggs. If not, well, no big deal, really. Researchers cleverly named this a “shot in the dark” strategy (Hoving et al. 2011).

XV
. One thing I love about these bats is that they can tell the difference between the calls of poisonous and nonpoisonous frogs, so they can selectively attack nonpoisonous frogs and ignore the calls of poisonous ones (Page and Ryan 2005). Unfortunately for the male túngara frog, he is not poisonous.

XVI
. The most spectacular male birds you could ever possibly see display are the birds of paradise (Scholes 2008). I’m talking about the actual birds, not the flowers with the same name. If you’re not familiar with birds of paradise, spend five minutes on YouTube to see some of the videos Ed Scholes and Tim Laman have taken. Your eyes will explode out of your head in disbelief. Here’s a start:
http://www.youtube.com/watch?v=YTR21os8gTA
.

XVII
. Those red, yellow, and orange pigments are called carotenoids (Hill 2000).

XVIII
. This difference in life history between males and females is part of the reason females can afford to be so big and noticeable, while males need to be small. Their size helps them avoid getting spotted and eaten while they look for females (Vollrath 1998).

XIX
. Well, he might get the benefit of having an enjoyable time, but he doesn’t make any babies this way. From his DNA’s perspective it’s a waste of energy and a waste of sperm. To get any real advantage from mating, he needs to mate with a member of his own species.

XX
. The link to that video is here:
http://www.youtube.com/watch?v=4-94JhLEiN0
. Last time I checked, it had more than 80 million hits.

XXI
. Shelby’s PhD was mostly about what happens to the quality of water and soil when you convert native Amazonian rainforest to a giant soy field (Riskin et al. 2013).

XXII
. The
Giardia
parasite is one you can also get in North America. You might have heard of it by its nickname, “beaver fever.” It can cause intense (and I mean
intense
) abdominal pain, diarrhea, blood in the feces, and sometimes even blood in the urine. Humans get
Giardia
by ingesting water tainted by the feces of animals (beavers, humans, whatever) that are already infected by the parasite. In other words it’s completely preventable so long as people have access to clean water. Despite that preventability, hundreds of millions of people worldwide have that parasite right now.

Sloth, or laziness, seems at
first like something that only affects humans. After all, we invented TVs, recliners, and video games. We work at desks, we drive cars, and we take the elevator when it’s only one floor. Obesity is on the rise in almost every country now. By 2008, 1.5 billion adults were overweight, 170 million children were overweight or obese, and those numbers continue to climb.
¹

Just as you’d expect with all these big people walking around, experts have been coming out of the woodwork with advice on how to lose weight and stay fit. Many of those antidotes have to do with living “naturally.” Our ancestors weren’t fat slobs (so far as we know), so we’re told that our lost connection with nature is what’s made us so lazy. Nature’s a perfect model of hard work, isn’t it? Survival of the fittest, right?

Nice try.

Sure, I’ll concede that a beaver, for example, epitomizes industriousness and hard work as she builds her dam. But beavers aren’t the only animals out there. The belly of that beaver is home to a whole ecosystem of lazy creatures, stealing mouthfuls of her food for themselves, some even feeding on the beaver’s own flesh. Those freeloading parasites thrive inside that beaver’s body, taking full advantage of all her hard work. And they give absolutely nothing in return.

You cannot possibly get any lazier than that.

If you ask, most people will tell you that they love nature, but many of those same people don’t even want to look at a picture of a parasite. Fact is, though, parasites are as natural as the birds and the bees. In fact, birds and bees are covered with parasites of their own, as is pretty much any other animal you can name. In fact, although it may sound counterintuitive, biologists have even argued that parasites are the sign of a
healthy
ecosystem.
²

Like most people, I didn’t love parasites at first. I was curious about them, but I went into my undergrad program to study bats. The only reason I learned anything at all about parasites was to fulfill my degree requirements. Parasites were confusing to me. I can still remember the agony of trying to memorize their Latin names and life cycles and trying to tell them apart in their specimen jars. They honestly all just looked like overcooked spaghetti. I learned what I needed to pass the courses, but the parasites never really engaged me.

I would have laughed if someone had told me then that in just a few years I’d appear on an internationally broadcast Animal Planet TV show about parasites called
Monsters Inside Me
, or that
I’d become a frequent guest on the
Late Late Show with Craig Ferguson
, talking with him about the very same worms whose names I previously couldn’t even remember. In a few short years, parasites would become a big part of my life, but before all that, I had to somehow realize how incredible they were.

Fortunately, there’s a bat for that.

Within a month of starting my master’s degree, I was sent by my advisor down to Costa Rica to figure out whether a project idea would have any chance of working.
^I
It was my first time in the tropics, and there were so many bats to see. On my second day there, I went with a more senior graduate student named Maarten Vonhof to look for bats in a small cave. That was a very good day—my first encounter with vampires.

Vampire bats drink the blood of other animals, so they are parasites. By definition, a parasite is an animal with a relationship to some other animal, called a host. In that relationship, the parasite gets an overall benefit, and the host pays an overall price. The parasite might get nutrition, protection, or transportation. The host might have some food stolen, or it might get injured, or it might even die. Whatever the exchange, the parasite comes out ahead and the host loses. It doesn’t matter if the parasite is
a worm, a fish, or a bat. So long as it’s mooching off a host, it’s a parasite.
^II

Vampire bats eat blood and nothing else. Although that might seem grotesque, it’s really kind of brilliant. If you think about it, blood is the perfect food. When you eat, your digestive tract pulls nutrients out of your burrito and puts them straight into the bloodstream so that as the blood flows through your body, all your cells can get those nutrients. When a vampire bat drinks a cow’s blood, it taps into a cocktail of molecules that includes everything it needs. That said, getting blood out of a cow that weighs 14,000 times what you do isn’t easy.

Of the more than 1,200 bat species that live in the world, only three drink blood. They don’t turn into well-dressed European men with fangs, but they are called vampire bats nonetheless. All three species live in Central and South America, with two of them feeding on the blood of sleeping birds, by sneaking up on them in trees and biting their toes, and the third, called the common vampire bat, feeding on the blood of mammals. While the common vampire bat usually feeds on cow blood, it can feed on a wide range of animals, and it has been known to feed on sleeping humans.
^III

The common vampire bat is about the size of a mouse.
^IV
To feed, it sneaks up on a sleeping cow by crawling up to it on the ground. When it gets close enough, it uses heat sensors on its nose to find blood vessels close to the cow’s skin. It’s not looking for a big jugular vein or anything, just some capillaries: think of your cheeks, the top of your head, or your fingers and toes. Places that get rosy from blood just below the surface, and that feel warm to the touch. On a cow, capillary beds like that can be found around a hoof, on the neck, around an ear, or right on the sex organs. That’s where vampires bite them.