Mother Nature Is Trying to Kill You (16 page)

As great as they are at hunting, wolverines are even better at finding carcasses of animals that have already died and eating those. In fact, wolverines have been known to track predators like wolves and lynx, wait until those predators make their kill, and then steal the carcass for themselves.

Using a combination of killing and scavenging, wolverines do very well for themselves. An impressive number of different animal species have been found in the stomachs of wolverines:
moose, elk, caribou, deer, foxes, lynx, hares, marmots, ground squirrels, porcupines, beavers, voles, lemmings, shrews, magpies, hawks, ptarmigans, fish . . . even seals, walrus, and whales.
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That’s the flexibility you get by eating meat. Wolverines can eat whatever they get their claws on, dead or alive. But for all the glorious gluttony of
Gulo
, it’s far from being the most gluttonous predator out there. That title goes to an animal that at first might seem much less dangerous, the shrew.

Shrews make their living eating insects, worms, and the carcasses of larger dead animals. They’re small, but don’t underestimate them. Shrews are arguably the biggest gluttons in the animal kingdom. Sure, a 3,750-pound elephant eats far more food than a 0.1-ounce shrew does, but when you take body size into account, the tables turn. The roughly 225 pounds eaten each day by that elephant make up around 6 percent of its body weight. Compare that to a recorded maximum 384 percent of body weight consumed by a shrew in one day and there’s no contest.
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Shrews and elephants are part of a more general trend: as you look across mammals of different sizes, the smaller they are, the more energy they use
per unit mass
. Since shrews are the smallest mammals, they’re the most gluttonous. Incidentally, if you gathered enough shrews to equal the weight of an elephant, those half a million individuals would collectively eat sixty-four times more food than the elephant would.
Pound for pound, nothing’s so gluttonous as a shrew.
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But there’s another way to measure gluttony in a carnivore, and that’s to ask what animal
kills
the most other animals to survive. Something like a wolverine might only make one kill a week, and the shrew might get by on just a few earthworms a day. Who does the most killing in the name of gluttony? For this one, we go
to the other end of the size spectrum, to the largest animal in the world.

Blue whales aren’t just the biggest animals on Earth, they’re the biggest animals to have
ever
lived
on Earth. They’re bigger than dinosaurs. A single animal can weigh more than 360,000 pounds, yet it feeds on shrimplike creatures called krill that weigh less than an ounce.
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As a result of that size mismatch, blue whales have to kill a lot of prey animals to survive. Fortunately for the whale, though, krill routinely swim around in dense clouds of individuals. That makes getting enough krill as easy as swimming to the right place and opening your mouth. To get that krill without drinking too much seawater, though, the whale does something analogous to the way you separate your spaghetti noodles from the water you cooked them in. The whale swims into a cloud of krill, closes its mouth around that cloud, then pushes water out of its closed mouth with its tongue, forcing the water through hairlike baleen it has around the seal of the mouth (where you’d find teeth in most mammals). With the water expelled from the mouth through the strainer-like baleen, the whale swallows the krill, then sets out preparing for the next mouthful.

On average, that strategy lets a blue whale consume roughly 2,500 pounds of krill per day.
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That’s less than 1 percent of its body weight (consistent with the general trend that larger animals consume less food per unit weight than small animals do), but it means more than 500,000 lives are snuffed out each day by a single animal. That’s a lot of death, especially since blue whales are generally portrayed as gentle giants. I suppose, though, that most people don’t worry so much about the suffering of krill the way they do about the slow lorises that orangutans smack around. That’s what makes these kinds of comparisons tricky. How many
krill is a slow loris worth? Are intelligent animals more valuable than stupid ones, or does it just depend how cute they appear to us? Is it body size? Is it something else?

I don’t mean those as rhetorical questions. In fact, those kinds of questions led me to be a vegetarian for several years after undergrad. I avoided meat because I felt that it would be hypocritical to say that some animals, like bats or dolphins, for example, should never be harmed, but then eat cattle and salmon as if they grew on trees. Even though the idea of killing some species
felt
worse to me than the idea of killing other species, that didn’t seem like a good enough reason for me to start separating animals into edible and untouchable groups. I understood that the whole spectrum of animals, from slow lorises to krill, know to move away from things that can hurt them. To me, that seemed to imply that all those animals had some knowledge of pain, suffering, and fear. It just didn’t seem consistent for me to inflict those experiences on some animals but not others. To me, giving up meat altogether seemed like a way to live less hypocritically.

There is a way to eat meat without inflicting suffering on other animals, but that was not a solution I was at all interested in—eating things that died naturally. To humans, nothing’s more repulsive than chowing down on a bloated corpse that’s been ripening for a couple of days. There are plenty of living things out there, though, that enjoy nothing more, and those gluttons are vitally important parts of the living world.

Let’s say a person dies suddenly from a heart attack while they’re on a walk in the woods, and no one finds them for a few days. The instant that person’s body shuts down, the calories inside it are no longer defended. So, less than
four minutes
after death, creatures start taking that person apart.
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Whole colonies
of bacteria that had been living in the gut, helping the human digest their food, suddenly find that the walls of the digestive tract are no longer protected by an immune system. They immediately go to work on the human itself, feeding and reproducing at a feverish pace. The walls of the digestive tract break down, leaking bacteria into other parts of the body, to begin preying on the other internal organs. As they feed, those bacteria release methane and sulfur-rich gases in the process, causing that characteristic dead-mammal smell to emerge from the body. It’s a smell so disgusting to humans it can make them vomit, but that same smell draws in other animals, like foxes, crows, flies, and beetles, that can make a nice little meal from a rotting human corpse. Just how long it takes for a human to be reduced to bones depends on a lot of factors, most notably temperature, but at around 68 degrees Fahrenheit, sixty-five days is a good ballpark estimate.
^X
It takes even less time, though, if the body is in water, if large scavengers have taken the body apart, or if the person died from a large wound that drained blood and allowed microbes easy access to the body.

Other animals, in other places, decompose more quickly. One of my favorite bat caves in the world is Bracken Cave, near San Antonio, Texas. It’s a particularly hot cave, and there are
millions
of bats in there. Beetles thrive on the floor of the cave, feeding on bat droppings most of the time, but should a baby bat fall to the cave floor before it can fly, its tiny body will be reduced to bones in less than ten minutes. Walking through that cave, you can see that guano (bat droppings) covers the cave floor, but if you look
down carefully at it, you’ll see what look like white pine needles everywhere. But there are no pine trees outside Bracken Cave. Those are the wing bones of bats that have been broken down by scavengers. Bracken Cave is one of the best places to see decomposers at work.

In nature, those decomposers are the last in the chain of energy traders. If you could follow a single calorie of energy out of a cave beetle, back through time, you’d get a convoluted but unbroken chain: the beetle stole energy from the baby bat, who got her energy from her mother’s milk, who got her energy by eating a moth, who as a caterpillar got his energy by eating a corn plant, which got its energy from the sun. If you continued playing the sequence out, like a movie going backward in time, it would end with a ray of light going back on its eight-minute-and-eighteen-second trip between the Earth and the sun. That’s a movie I’d love to see.

In fact, you could do the same with any calorie inside any animal, and the movie would always play through to the same beginning.
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You could watch the energy bounce among organisms, through parasites, predators, and prey, but it would always ultimately have come from the sun. If you could play all those movies backward together at the same time, they’d all converge into a broad beam of light. And if you stopped that movie suddenly, then started playing time in the right direction, you’d suddenly see the flow of energy through the living world as it exists around you right now. Every day, rays of light shower down on our planet. A few of them get harnessed by plants and enter the food web. From there they really might go anywhere. It’s all totally predictable, since we know in what direction the energy will flow, but where any particular sunbeam’s energy will end up is anyone’s guess.

My vegetarianism lasted for three years or so, but around the time I went on that botfly trip to Belize, I started eating meat again. It wasn’t the botfly per se, but that was part of it. My relationship with the living world was changing as I learned more about it, and it was starting to dawn on me that I was still inflicting pain on animals. I’d killed the botfly, after all, but it was much more than that. Whenever I drove my car in the summer, insects got splattered on the windshield. Whenever I ate produce grown on farms, I was reaping the benefits of habitat destruction for the animals that had once lived where the farm now stood. Even a lot of the science I was learning came on the backs of animals, harmed or even sacrificed in the experiments that I was reading about in scientific journals. Sure, I wasn’t eating them directly, but my lifestyle was inflicting pain and suffering on animals. If I was going to live up to what being vegetarian was supposed to be about, I had a long way to go. I was going to have to make sweeping changes to my life well beyond what I ate, and frankly it just seemed like a suite of lifestyle changes I simply didn’t want to make.

I realized that my vegetarianism hadn’t made me any less hypocritical than I’d been before, so I just let it fall away. I went back to eating meat, though much less than before, and with a very different feeling about carnivory than I’d had before. The experience wasn’t a waste of time. It was just part of my education.

As I spent more and more time studying nature, chasing bats through tropical rainforests in Belize and Costa Rica, I started thinking of the food I ate as my connection to their world. Like a bat, I am built to get calories by taking them from other living
things. I don’t get angry at the frog-eating bat for cutting short the lives of frogs, so it was strange to lament my own need for calories. The idea of sparing animals out of sympathy is such a human idea; that doesn’t make it a bad idea at all, but it’s important to realize it’s not an idea that exists in the nonhuman natural world.

Part of the popular image of Prahlad Jani that has emerged from the YouTube interviews and newspaper articles about him is that he’s connected to the world so deeply that he doesn’t need to eat. That’s ironic. Eating is probably the most concrete way in which we participate in nature.

A few thousand years ago, Shelby and I would have needed to find food in the environment around us to feed ourselves and Sam. Now it’s as simple as picking up some chicken breasts on the way home from work, but we’re still part of that flow of energy, from sun to decomposer. The landscape is changing, though. A lot of people are scared about factory farming and genetically modified foods, but I’m still optimistic about Sam’s nutritional future. In the last few thousand years, humans have domesticated more than two hundred different food crops, from agave to watermelon, making some more nutritious, some more resistant to disease, and some better able to grow in the high densities that you’ll typically see on farms.
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Like the acacia plant that has a better life thanks to the security guard ants it domesticated, we thrive because we have manipulated parts of nature too. Humans have been playing by the same rules as the acacia plant for centuries, and it’s the only reason we’ve succeeded like we have. Until recently, those changes came through selective breeding, and now that process also happens through genetic engineering. That doesn’t scare me.
Had Sam been born a hundred years earlier, his life expectancy would have been fifty years, but because he was born in 2011, his life expectancy is closer to eighty, and I wouldn’t be surprised if he made it to one hundred.
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Sam’s access to nutritious food is probably the greatest reason he should expect to live longer than any of his ancestors ever did. (That, plus protection from the kinds of parasites I talked about in the chapter on sloth.)