Mother Nature Is Trying to Kill You: A Lively Tour Through the Dark Side of the Natural World

by Riskin, Dan

  You can tell a female cuttlefish from a male cuttlefish by the shape of her fourth pair of arms and by her mottled skin patterns. So “cross-dressing” sneaker males tuck their fourth arms underneath their bodies, change their body colors to look like a female, and then take on the same body posture a female takes when she’s about to lay eggs. Females about to lay eggs aren’t usually receptive to mating advances, so that body posture keeps most other males from trying to mate with the disguised cuttlefish.V

  Pretending to be a female is a sneaker strategy that can pay off. Disguised, a sneaker male can often sidle right up alongside a true female, even while she’s being guarded by a large, aggressive male. When the sneaker male makes his move toward the female, sometimes she rejects him, sometimes he gets chased off by the dominant male, but quite often, mating goes just fine.

  Another male who pretends to be female is the red-cheeked salamander of the southeastern United States. When red-cheeked salamanders mate, a male and female come together and perform ritualized movements, crawling over one another and rubbing their bodies against one another in very specific ways. Being amphibians, like frogs are, male salamanders don’t have penises, so during mating he glues a ball of sperm to the ground. As they move together, the female slides her body over the sperm ball and draws it up into her body.

  If a male red-cheeked salamander comes across a male and female in the middle of a dance, he will sometimes push them apart. Other times, though, he will sneak in between them and then continue the dance as though he were the female. The original male presumably doesn’t realize there’s been a swap, so the dance continues until he deposits his sperm packet. Then the false female turns around and bites him, causing him to run away.23

  To me, sneaker males embody envy even better than thieving predators do. When smaller males within a species bump heads with larger males, little guys usually end up holding the short end of the stick. Whether or not he’s literally envious is a question that might someday be answered by clever experiments, but since this happens in so many kinds of animals, we can never possibly know for all of them. Whether or not it’s envy, those smaller males seem motivated to make the most of what they’ve got to get their genes passed into the next generation. In nature, the game’s not necessarily over for a male who gets sand kicked in his face.

  Now, this is exactly the kind of moment when we’re tempted to look at these animals and say something about what they can teach us. We may want to point to Bill Gates and Mark Zuckerberg as nerds who came out ahead in the game of life, but that’s a dangerous, slippery slope. Let’s say you look at alternative mating strategies in male animals and then say something to a teenage boy like “Listen, even if you’re not on the football team, you’ll eventually meet a woman who loves you for who you are, who sees your sweetness, your intelligence, or your sense of humor.” That’s a lovely thing to say, but that’s not what’s happening out there. You’re not asking the teenager to intercept a female on her way to a date with the football player and force her to copulate with him. You wouldn’t tell that male teenager to sneak into a couple’s bed while they’ve having sex and take the role of the female so that the football player will ejaculate in the wrong place. You can’t pretend nature’s an instruction manual. It’s fine to take inspiration from nature, but you still have to have common sense. Humans should abide by morals, and nature is not a place of morality. The fact that something happens in nature can never be used to justify it in human behavior, no matter how harmless it might seem to do so.

  When my first real girlfriend and I broke up in high school, she sent me a note (this was before text messages) that said “Tell me, Dan. Is ignorance really bliss?” To this day I still have no idea what she was talking about (maybe that was her point), but for some reason, that concept has haunted me ever since. If ignorance is bliss, then could gaining knowledge make you sadder? If you spend your life seeking new information, is it possible that some joy might be lost?

  As a parent, I’m starting to think so.

  Learning about the natural world has made my life richer than it would otherwise be, but I know that learning about evolution has also peeled away some fairy tales that might have made things a little easier. I imagine that a certain bliss might have come from the belief that my great-aunt Claire could look down from heaven on the birth of Sam and smile along with me at the family resemblance. It might also have been helpful to believe in those tense moments before Sam’s first breath that some benign natural force was looking after him. But the time I’ve spent learning about science has led me not to believe those stories.

  In those instances, maybe it’s possible that my science-based perspective has robbed me of a little happiness, but I decided long ago to keep my experience of the world rooted as firmly in reality as possible. That said, though, I can’t help wondering what it would be like just to love Sam without that background conversation about meat robots playing in my head. It’s almost enough to make me envious of those parents who don’t think about evolution at all.

  Almost.

  * * *

  I. A doula is a nonmedical person who assists before, during, and after labor and childbirth, acting as an experienced resource for the family. To me, the biggest benefit of having a doula was just having someone there the whole time saying, “This is normal.”

  II. Claire Riskin was my father’s father’s sister. Roughly one-sixteenth of Sam’s DNA is the same as hers.

  III. Theft is really a type of parasitism, since (as you’ll remember from two chapters ago) parasitism describes any relationship between two organisms in which one gets a benefit (the parasite) and the other pays a cost (the host). In the case of parasitism by theft, biologists use the word kleptoparasitism, and talk about animals that are kleptoparasites of other animals. You might recognize the prefix klepto- from the word kleptomania, the disorder that causes people to steal pathologically.

  IV. This frog mating cuddle is called amplexus, which is Latin for “embrace.”

  V. That said, though, the disguised male still frequently gets hit on by other males (some of whom, confusingly, are also disguised as females: it’s like an elaborate Shakespearean play out there).

  6

  WRATH

  Venoms and Extinctions

  Nature is a violent place. Everyone knows that living things are killed by other living things all the time, and yet despite that fact, people cling to the myth that nature is peaceful. There’s a make-believe world where even the predatory animals are gentle, if you just take the time to get to know them. Most of the time, believing in that fictional world is harmless, but in a worst-case scenario it can get someone killed.

  The killer whale is a perfect example of a deadly animal that people underestimate all the time. Most people know what a killer whale looks like, but few have any idea what they do with their time in the wild. Instead, people watch Free Willy, or they go see killer whales do tricks at places like SeaWorld, and they get the overall impression that a killer whale is kind of like a family dog. In fact, at SeaWorld in Orlando, Florida, you can watch a whale named Tilikum do all kinds of tricks, just like a dog does (and it’s much more impressive to see a 12,000-pound animal do what a trainer tells it to). Literally millions of people come to SeaWorld each year—many with their kids. Many of them probably believe that the whale they’re looking at is Willy from the movie, or at least a friendly whale like him. But the very whale they’re looking at has actually killed people. And it’s happened three separate times.1

  The first death happened in 1991, when Tilikum lived at a marine park in Victoria, Canada, with two other whales. One day, a twenty-year-old trainer accidentally fell partway into the pool. Before she could pull herself out, one of the whales snatched her by the leg and dragged her under the water. The three whales ignored the other trainers’ attempts to distract them and took turns pushing the woman under as she tried to swim away, playing with her like a toy, even tearing off her clothes with their tee
th, until she was dead.

  Soon after that tragedy, Tilikum was moved to SeaWorld, where he still lives today. In 2010, almost nineteen years to the day after that first incident, a forty-year-old trainer was lying at the edge of the pool with her head near Tilikum’s when the whale grabbed her in his mouth and pulled her under. She tried to escape but was repeatedly pulled underwater, then allowed to swim up to the surface. Then the whale pushed her around in the pool with his nose. Her jaw was broken, her spinal cord was severed, and she drowned.

  Presumably those two trainers, having spent considerable time with whales, knew just how dangerous they were. The third death, though, wasn’t of a trainer. It involved a member of the public, someone who may well have been living in the fictional world where killer whales are gentle giants. In the summer of 1999, midway between the two trainer incidents, a twenty-nine-year-old man visiting SeaWorld watched Tilikum perform and then hid somewhere on the SeaWorld property until the staff had closed up shop and left for the day. The next morning his naked body was found underwater, draped across Tilikum’s back. His bathing suit lay at the bottom of the pool. There were no video cameras or witnesses, so no one really knows what happened to the man, but the clues hint at a gruesome death.

  The first clue was that the man’s clothes (other than his bathing suit) were found in a neat pile by Tilikum’s pool, suggesting that he had planned on swimming with the whale. Second, when he was found, the man’s body was covered in cuts and bruises, he had bite marks on his face, and his scrotum had been torn open. Those wounds show that Tilikum had played with him underwater, ripping off his swimsuit, the way he had ripped the clothes off that first trainer eight years earlier. Another clue: the man had especially deep bite wounds in one of his legs. Perhaps he had dangled a foot into the water and been pulled in by the whale, or maybe he jumped in and then tried to get out, only to be pulled back underwater. We’ll never know. What is clear, though, is that Tilikum is not a gentle animal.

  There’s no way to know what that man was thinking when he hatched his plan. It’s been suggested that perhaps he was knowingly committing suicide, but I think the much more likely explanation is that he didn’t see it coming. My guess is that he believed in that imaginary world of friendly whales that theme parks perpetuate to bring in visitors. I’ve even played the scene out in my head a few times. It’s night, and he approaches that pool, believing he’s about to experience something magical. The moment of that first snatch of his leg would have been a disorienting surprise, and then the next few minutes would have been pure hell. That said, all I can really do is speculate.

  In the wild, killer whales have been documented feeding on more than 140 different kinds of animals, from salmon and sharks to seagulls and sea lions.2 Interestingly, each pod of whales will pick one kind of food and stick with it. Some eat only fish. Others, living in the same waters, will eat nothing but mammals, such as porpoises and seals. The fish eaters and the mammal eaters don’t mate with one another, and they don’t seem to interact at all. Perhaps in a few million years they’ll be separate species, but for now they’re like different societies within the whale population.I There’s a lot we don’t know about killer whales, but what we do know about those mammal-eating killer whales offers insights into why Tilikum may have done what he did.

  When a killer whale catches a seal or dolphin, it needs to immobilize it. A whale doesn’t want its meal to swim away after the first bite. Also, having an animal struggle while you try to gulp it down might cause you injuries like tooth breakage. Worse, the defensive bite of an eight-thousand-pound elephant seal can do quite a bit of damage, even to a killer whale weighing ten to twenty thousand pounds. So it’s best for the predatory whale to stop its prey from moving, and one way to do that is to smash it to smithereens.

  For example, killer whales often toss seals or dolphins several feet out of the water with their mouths, then catch them again. Sometimes a killer whale will bat a baby seal with its powerful tail, launching the animal fifty feet or more out of the water. These kinds of games can go on for hours—far longer than is probably necessary. The mammals eaten by killer whales don’t always get a quick death. By the time they’re eaten, they may have open wounds, broken bones, and ruptured organs. It must be a terrible way to die.

  Another killer whale strategy for immobilizing mammals is to drown them. Whales can hold an animal in their teeth underwater, or they can leap out of the water and land on top of the swimming mammal, to prevent it from breathing at the surface. That works on the really big whales—like humpbacks, gray whales, and even blue whales.3 When a pod of killer whales hunts one of those giants, the whales first surround the bigger whale; then the killer whales take turns jumping on its back, over and over, until it becomes exhausted and can be held underwater. Next, the killer whales grab their prey by its flippers and snout and drag it underwater until it drowns. From time to time, killer whales will do this to a full-grown adult, but they usually pick on baby whales separated from their mothers.II

  There’s a striking similarity between the kinds of immobilizing predatory behaviors seen in wild killer whales and the behaviors Tilikum performed when those people got into the water with him. He bumped and poked them until they had broken bodies and drowned. He may have been acting on instincts, or he may have remembered how to hunt from those first two or three years of his life before he was captured near Iceland and put into a pool. He didn’t eat any of those humans, but it’s not hard to understand why he brutalized them. He’s a killer whale. That’s why they’re called killer whales.III

  Killer whales, and other predators like them, hurt their prey because there’s a benefit to immobilizing the prey animal, whereas there’s no benefit to minimizing the prey’s pain or suffering. Because evolution favors the selfish, it has endowed whales, cats, dogs, and many other intelligent predators with the instinctive desire to “play” with their prey while they kill. Because of predators like the killer whale, nature has become a place where animals wreak unimaginable pain and suffering on one another.

  The tragedies surrounding Tilikum are a sobering reminder that wild animals don’t treat death and torture with the disdain that humans do. The simple fact is that animals just don’t hesitate to use deadly force when it benefits them, and they don’t have any reason to treat the animals they kill with respect or dignity.

  That kind of carnage isn’t just restricted to whales. It’s all over the animal world. For example, there’s a North American songbird called a loggerhead shrike that impales animals alive on barbed-wire fences like trophies. To look at the bird, you’d never expect such brutal behavior: it’s just a little black-and-white thing, a bit smaller than an American robin, with a tiny, barely perceptible hook at the tip of its beak. But that small size is precisely the reason the shrike has to do such morbid things to the animals it eats.

  For their size, shrikes eat large animals—large insects, lizards and snakes, even birds and mice, some of which weigh half as much as the shrike itself. A prey animal that size is going to put up a fight if you try to eat it, and a shrike doesn’t have powerful raptorlike talons to subdue those animals while they rip them apart. That’s where the barbed-wire fence comes in. By impaling its prey alive on a meat hook, the shrike can leisurely tear into its body with that hooked beak without having to hold the animal in place. Sometimes shrikes use the thorns of plants as hooks, but when barbed-wire fences are available, that seems to be what the shrikes prefer.

  Shrikes of both sexes use impaling behavior to help them feed, but males also use impaled prey to mark their territories and to advertise to females how good they are at hunting.4 I don’t know what’s creepier—that males perform that behavior or that females are turned on by it. Either way, a barbed-wire fence with dead animals spaced out at even intervals on the hooks is reminiscent of severed human heads lining the fence of a medieval fort. If the shrike version weren’t so small, it would be terrifying.

  Killer whales and shrikes could
n’t be less similar in terms of body size, where they live, and what they eat, but as predators they’re united by the need to immobilize their prey, and both accomplish that task by overpowering them. That’s also true of many other kinds of predators, from lions to crocodiles, from eagles to great white sharks, and from mongooses to wolves. Those predators have to be stronger, have better acceleration, or have better stamina than the animals they eat. They feed because they can beat their prey in contests of brute-force physics.

  But not all predators can win those physical contests, so a discussion of wrath in the natural world would be incomplete if I stopped there. Even if a predator isn’t strong enough to overpower its prey with physics, it might still have a chance, using chemistry.

  Venom changes everything.

  Some people use the terms venom and poison interchangeably, but there’s an important difference between them. Poisons are chemicals that animals use to prevent other creatures from eating them. Think of the poisonous skin secretions of a poison dart frog, for example. Venom, on the other hand, is a cocktail of chemicals that is injected into a victim with the specific purpose of harming it. Venom can be used for offense or defense; sometimes it’s used to subdue prey, and other times it’s used for protection from predators. In either case, venom is a chemical weapon. (Next time someone tells you about a poisonous snake, feel free to correct them. Snakes are sometimes venomous but never poisonous.)

  Using chemistry instead of physics to hunt prey means you can eat things that are much stronger than you are, and I can think of no better example than that of a jellyfish killing and eating a fish. It’s only thanks to venom that a boneless blob is able to take down a muscular animal that normally swims circles around it.

  Jellyfish deliver their venom through microscopic harpoons. Hundreds of thousands of them line each tentacle, and when a fish swims into a tentacle, the harpoons fire into its flesh, squirt venom, and then stick into the fish’s skin with back-pointing spikes, just like real harpoons do. This happens unbelievably quickly—the harpoon tips accelerate with a g-force 40,000 times greater than gravity, and once you touch a jellyfish stinger, the whole thing is over in less than three milliseconds—a fortieth of the time it takes you to blink.5 Jellyfish venom quickly immobilizes the small animals that jellyfish eat, but it also works as a defense mechanism, preventing some animals from eating the jellyfish and causing other swimming animals, like us, to simply give the jellyfish all the space it wants.