by Matt Simon
Thus the cuttlefish, bereft of a protective shell, manages to stay out of stomachs. Some other camouflagers, though, aren’t going through the trouble of deploying such light shows. They pick an outfit and stick with it, and there’s no better-dressed camouflager than the satanic leaf-tailed gecko. Yes, that’s what it’s actually called. And yes, it’s every bit as amazing as its name would imply.
Satanic Leaf-Tailed Gecko
PROBLEM: Like the tenrec, geckos in the forests of Madagascar face predators aplenty.
SOLUTION: The satanic leaf-tailed gecko does a startlingly faithful impression of a leaf, complete with veins and all.
There’s a picture floating around the Internet of what appears to be a tiny dragon holding on to a branch, with wings sprouting from its back and skin that alternates between red and black. Its eyes, too, are a demonic red, and its tail has chunks missing as if burned away. The photo is, as you can imagine, a fake—but not as much as you’d think. The hoaxer just added the wings and maybe took a few liberties with the saturation. The rest of the creature is perfectly real.
The photo is of a satanic leaf-tailed gecko, one of fourteen known species of leaf-tailed gecko that call Madagascar home. For my money, these critters are some of evolution’s greatest triumphs, so well camouflaged that it’s scary. Not scary because they can tend to look like they’d eat your soul, but because they demonstrate what a powerful force natural selection is.
I doubt you’d be able to tell a satanic leaf-tailed gecko from a cluster of leaves if you weren’t looking for it. The ridge of its back is white, from which radiate white lines—the veins of the leaf. Its tail is shaped like its own leaf, frayed at the edges, seemingly rotted away. Twisting its body in on itself, the gecko completes the ruse: If it didn’t have flesh and blood and organs and all that, it’d be an honest-to-goodness dead, curled-up leaf. But how could such camo evolve? Did the gecko have to, like, think about it really hard? It didn’t, and it wasn’t placed on Earth as a gag. The satanic leaf-tailed gecko is an absolute marvel of evolution, and it’s all thanks to sex.
I failed to mention a while back when we were talking about creatures getting laid that there are a lot of animals that don’t get laid at all. They’re asexual, opting to clone themselves instead of finding a partner. For instance, a gelatinous little aquatic creature called a hydra—which looks like a palm tree, only with fronds that are stinging tentacles like a jellyfish’s—will bud little versions of itself that break free and go about their own lives. Asexuality is fantastic if you aren’t able to find a mate to fertilize you, but it does have a very serious downside.
ON THE ORIGIN OF SPECIES
So we’ve been talking about all of these species, and tried and failed to define what a species is (not my fault), but how do we get a species in the first place? Well, typically it’s a matter of isolation. Take the satanic leaf-tailed gecko and the many weird creatures of Madagascar. When the island drifted off, its species found themselves isolated, and in their isolation they diverged from the populations they left behind. Over time, they became genetically distinct enough that they were no longer able to breed with their counterparts. They’d speciated. This can happen on the mainland as well when, say, a river cuts through a habitat or a mountain range grows, splitting a population in two. And voila, a shiny new species.
Beyond feeling good, sex is great because it kicks evolution into overdrive. A hydra’s offspring are clones—that is, they’re genetically identical to their parent—but the offspring of sexual reproducers get a random mixing of genes, which introduces a bit of welcome chaos. You’re beautiful and your siblings aren’t so much (or vice versa, heaven forbid) in part because when you were conceived, your parents’ genes came together in random ways. Such variability between offspring helps ensure that at least a few of the kids have the traits needed to survive in a given environment (not that I’m saying that being good-looking helps humans survive, though it’d certainly help you pass along your genes).
So, for a satanic leaf-tailed gecko in the rough-and-tumble jungles of Madagascar, not looking exactly like its brothers and sisters can make all the difference. The species has set down the evolutionary path to mimic a leaf—not deliberately, of course—so even the most minute variations count. A vein here or a chunk of a tail missing there, a slightly better color to match a dead leaf—every little detail is nothing to sneeze at when the geckos have hungry eyes locked on them. These traits help the geckos survive, so through generation after generation after generation, individuals with subpar camo get knocked off, while those with beneficial variations pass down their genes.
Thus something as perfectly camouflaged as the satanic leaf-tailed gecko can appear to be designed. But it’s just a matter of predation pressures. While these are nocturnal hunters, relying on their giant eyes to gather what scant light is available in the rain forest, they still have to be able to make it through the day. So, depending on the species, a leaf-tailed gecko will make use of whatever camouflage evolution has bestowed on it to disappear when the sun comes up, ideally slumbering unperturbed. The more leaflike species curl up among dead leaves, while others lie flat on tree trunks to blend in with the bark, and still another—the mossy leaf-tailed gecko, with its speckled skin and frilly edges—seeks out moss-coated bark. None can modify its camouflage on the fly like the cuttlefish can, but the disguise is so convincing that it doesn’t matter.
Similar-looking species of leaf-tailed gecko roam Australia, but geckos around the world for the most part are comparatively plain Janes, sporting green or brown or yellow skin, sometimes with stripes, other times with polka dots. Yet nothing, not even the Australian varieties, can touch the wonder of the satanic leaf-tailed gecko. But you’d think that if it’s possible to evolve such an outfit, it’d suit geckos around the world to try it on. So what’s so special about the satanic leaf-tailed gecko?
SGT. PEPPER’S LONELY LIGHT-COLORED MOTHS CLUB BAND
You might think creating something as complex as the satanic leaf-tailed gecko would be a drawn-out process that takes thousands or millions of years, and you’d be right. Evolution can take its sweet time with things. But then again, it can also progress with incredible speed.
Take the peppered moth of Britain, a speckled creature adapted to hang tight on lichen-covered trees, thus avoiding birds. But it wasn’t expecting the Industrial Revolution and the consequent pollution, which coated trees in soot. The peppered moth, though, would not fade quietly into extinction. It adapted, developing a darker coloration that was first observed in 1848. Just fifty years later, 98 percent of peppered moths were dark. And when clean-air laws took effect in the twentieth century, the moths went back to being speckled.
The whole saga was evolution gone turbo. Predators were more likely to spot light moths when the environment became coated in soot; thus, the moths’ darker counterparts prevailed and gave rise to soot-colored babies. When the habitat was clean again, dark moths struggled to survive; thus, light moths prevailed. And that, ladies and gentlemen, is an exceedingly rare pollution success story.
No one knows for sure. But it’s worth noting that Madagascar is a very strange place with all manner of goofy creatures found nowhere else on Earth (accordingly, this isn’t the last you’ll be hearing of the island in this book). Islands are fascinating like that. When Madagascar went independent 90 million years ago, its ecosystem reset. The species that rode it out to sea and managed to cope with the isolation evolved uniquely in the new order. And other species, like birds that could manage the expanding oceanic gap, joined them from time to time. Species came, and species went. In their isolation, these creatures evolved like nowhere else on the planet. So maybe there’s something about the predators in Madagascar—maybe they’re that much more menacing—that made the satanic leaf-tailed gecko get so carried away with its camouflage. Or maybe, just maybe, a higher power got drunk and decided to hide some geckos in the forest.
Pangolin
PROBLEM: Ever heard of something called a lion?
SOLUTION: A mammal known as the pangolin has developed gnarly-looking keratinized armor that’s impervious to lions, not to mention the ants it eats.
Jump a few hundred miles from the island of Madagascar across the Mozambique Channel and if you’re lucky you’ll find an African critter that’s stumbled upon a different solution to the problem of predation. The pangolin is a mammal, but you’d be forgiven for mistaking it for a lizard. It’s a streamlined critter covered head to toe with overlapping scales that give it the look of a walking roof, or maybe an artichoke. The thing has shingles—actual shingles, not the rash.
The pangolin is a living tank. When threatened, it will curl up into a tight, almost spherical ball, wrapping its long armored tail around itself and waiting out the attack. The defense is so effective that even a lion, one of the most powerful predators on Earth, can’t break through. It’ll bat at a pangolin a bit and give it a gnaw here and there, but the lion does so at its own peril: Those scales are crazy sharp and unfriendly to mouths. Sometimes the rest of the lion’s pride will join in, taking turns trying to pry the pangolin open. But it’s all for naught. Inevitably they give up and trot off, and the pangolin uncurls itself and goes about its day.
CHARLES DARWIN DISCOVERS THE VW BUG
Contrary to popular belief, Charles Darwin was not the official naturalist when he boarded the Beagle. That honor went to the ship’s doctor. In reality, he seemed more enthralled with geology than biology during the journey, devoting a great deal of his account, The Voyage of the Beagle, to rocks. His worlds of geology and biology collided, though, when he happened upon the fossilized remains of an enormous armored mammal: Glyptodon. It would have been about as big and heavy as a VW Bug (not Darwin’s comparison, obviously), “with an osseous coat in compartments, very like that of an armadillo.” Unlike the pangolin with its many overlapping scales, Glyptodon had a solid shell of armor, like a mammalian tortoise. It was in fact a relative of modern armadillos and played no small part in shaping Darwin’s theory of evolution by natural selection. He realized a higher power didn’t place species on Earth and wipe them out for the hell of it—there’s a great chain of relatedness among creatures.
Even humans and our many tools have a hard time breaking their defenses. The American naturalist William Beebe (our friend who had a few words to say about the anglerfish) once encountered one in Borneo, noting that the curled-up pangolin’s tail muscles “were as rigid as steel.” William’s guide tried to open up the creature with a shovel, but “even with the spade as leverage, hardly an inch could be pried free.” They left the poor thing alone for five minutes, and then it suddenly raised up its scales, which any self-respecting naturalist would be irresponsible not to tug at. Unfortunately for William, “like the jaws of a steel trap they closed down with such force as to bruise the finger cruelly, or actually to pinch off a fragment of flesh.” That seemed to tickle his guide: “One’s enthusiasm for scientific investigation in this direction was satiated at one trial, which was also sufficient to prove that a Tamil trailmender has a sense of humor and a lack of sympathy.”
These scales are made out of keratin, a wonderfully useful protein in the animal kingdom. Creatures have incorporated the stuff into all kinds of things, from our own hair and nails to a deer’s hooves to the horn of a rhino. It makes up a bird’s beak and the filter-feeding baleen structures in some whales. Keratin is everywhere, and it’s both strong and pliable, as you might notice with your nails. So instead of snapping in half when a lion’s claw (itself made of keratin) snags it, the pangolin’s scales flex, absorbing the energy. Indeed, its strength has not been lost on our species: In India, where the pangolin also roams, warriors once wore armor made of the creature’s scales.
The pangolin’s formidable coat serves another more cryptic purpose. The creature is an insectivore, specifically an insectivore that targets eusocial insects like ants and termites. Using its huge claws, it tears into colonies and laps up the swarming insects with a long, tubular tongue. The thing can be as long as the pangolin’s body minus the tail, but contrary to what you’ll read pretty much everywhere on the Internet, it does not attach near the animal’s pelvis, which, granted, would be kind of awesome. Instead, the tongue is attached near the bottom of the sternum, and it’s coated in mucus from two massive salivary glands. Firing the tongue into ant or termite colonies, the pangolin can get into tunnel after tunnel, snagging the infuriated, panicked insects and reeling them in. The bugs swarm and try to sting and bite but find no purchase on the pangolin, whose scales protect it from the onslaught. The pangolin’s eyelids are also nice and thick to keep out stings and bites to the eyeball. Its ears, too, have special valves that seal to keep out attackers.
But the brutal irony of the pangolin is that the scales that help it survive could well drive it to extinction, all thanks to—drumroll, please—humans. In traditional Chinese medicine, pangolin scales are prized for a wide range of “cures.” Is your kid being difficult? Get some pangolin scales. Are you deaf? Pangolin scales. Have you been possessed by demons? Pangolin scales. Suffering from malaria? Yep, pangolin scales. Just roast them, grind them up, and mix the ash with oil or butter or even a boy’s urine (presumably not that of the bratty kid you’re trying to cure—that would be counterintuitive).
HAVE YOU SEEN MY WIFE AROUND? SHE’S GOT SCALES AND LOVES ANTS
The pangolin holds a special significance among the Shona people of Zimbabwe: Legend goes that long ago, chiefs sent the wife of a spiritual medium, known as a midzimu, to roam the bush, where she became a pangolin. So if you stumble upon such a creature, you’re required, at risk of bad things happening to punish you, to grab it and take it to the midzimu, since it could well be the very same wife. That’s why pangolins curl up into a ball when approached—instead of fleeing, the wife is signaling that she wants her discoverer to pick her up and take her back to her husband. The midzimu then proceeds to cook and eat the pangolin. Not sure how that makes sense, but hey, who am I to judge?
Demand for its scales has made the pangolin the most trafficked mammal on Earth, with all eight species considered endangered or critically endangered. As if the market for the scales weren’t enough, pangolin meat is all the rage in Asia. China’s booming economy in particular has brought with it huge demand. Wild meat like that of the pangolin is a luxury, eaten to celebrate business deals.
Unless something is done soon, the world’s toughest, most wonderfully armored mammal will slip into oblivion. William Beebe saw it coming all along, though interestingly he noted that “their flesh is too infiltrated with formic acid to be palatable.” Maybe William had a particular sense of taste. Regardless, he notes that “until the excessive increase of human dominion and the consequent decrease of anthills comes to pass, the race of Pangolins will continue to flourish on the earth.” We can be confident that the anthills will remain, but whether humans can get their act together certainly isn’t a given.
Crested Rat
PROBLEM: Not all African mammals have the luxury of armor.
SOLUTION: The crested rat deploys special hairs that it slathers with chewed-up poisonous bark. That’ll leave a bad taste in an assaulter’s mouth, and could very well kill it.
There’s a plant that we may as well call the Grim Reaper of East Africa: Acokanthera schimperi. According to one guide to African ethnobotany, it’s also known as the “national poison plant” of Kenya, because anybody who “hunts with a poisoned arrow, poisoned spear, or poisoned trap and uses poisoned weapons against enemies, reaches solely for Acokanthera.” The methods for its preparation differ from community to community, but the end result is always the same: death, and a quick one at that. The poison can even bring down elephants, and indeed certain African peoples have used six-foot bows to rocket three-and-a-half-foot, poison-slathered arrows into the bea
sts, dropping them dead of heart failure.
You’d think, then, that every creature in Africa would go out of its way to avoid the Acokanthera plant, but not a rodent called the crested rat. The beast gnaws on the bark and roots of the thing, gives it a good chew, then applies the poisoned spittle to specialized hairs on its flanks. All it takes is one bite from a predator to get the toxin into a mucous membrane, where it goes to work shutting down the assaulter’s heart.
The crested rat is a perplexingly arranged animal, with fluffy fur and a hairy tail, unlike your average sewer rat. The hair along its flanks is black and white, giving it the appearance of an animal called a zorilla, which looks a lot like a skunk and even comes equipped with that characteristic stinky spray defense. Scientists have suggested that the crested rat evolved to mimic the zorilla, taking advantage of its bad reputation without having to develop a noxious spray. Problem is, the rat only exposes that black and white flank hair when threatened—otherwise the coat is more of a grayish color. So this probably isn’t a matter of mimicry.
No, the crested rat has come up with its own unique defense. To expose that black and white hair, it uses special muscles to both erect the hair up and deflect it down its flanks, parting it so the rat can apply the poison. While these flank hairs may not be hard and sharp like a porcupine’s or hedgehog’s, they’re special in their own way. They’re perforated cylinders that hold many strands, which act like sponges to absorb the creature’s tainted saliva. When the rat is done with the application, it lets the normal hair fall back down, enclosing the specialized black and white hairs, presumably to keep rain from washing out the poison.