What a Lovely World of Liars and Frauds
Posted by Richard Conniff on June 18, 2016
by Richard Conniff/The Wall Street Journal
The notion that anything natural must be wholesome and good is, to be honest, idiotic. Polygamy is a natural behavior for some species. Infanticide is natural. Turning your mate into a post-coital snack is not only natural, it’s a strategy for reproductive success.
We are not those species, fortunately, and “Cheats and Deceits” is not a how-to book for humans. The subtitle is “How Animals and Plants Exploit and Mislead.” Martin Stevens is an evolutionary ecologist at the University of Exeter and also a sensory ecologist. He studies disguise and deception as they appear not just to us but to other species, which may rely on chemical signals we can’t perceive or visual signals we can’t see. For instance: Soon after hatching, the caterpillar of the alcon blue butterfly drops to the ground, where one might expect it to be attacked and eaten by foraging ants. But this caterpillar instead gets carried back to the ants’ nest and fed as an honored guest.
This very hungry caterpillar is a fraud: It emits chemicals closely resembling the ones that serve local ants as a means of recognizing nestmates. (Just to be sure, the researchers who demonstrated this applied caterpillar chemicals to tiny glass dummies, and the ants also treated them as newfound friends.) Once inside the nest, the caterpillar adjusts its chemical signal to match the particular ant colony more precisely and ensure continued feeding.
It wants to be very well fed, in fact. So the caterpillar quickly starts mimicking the sounds and vibrations with which the queen of the ant colony communicates her special status. When the caterpillar has finally gotten enough food to pupate and emerge into its adult butterfly form, it does a run for the door. The ants, realizing that they’ve been duped, make a grab for the fleeing intruder but generally come away with nothing more than the scales loosely attached to its body.
The natural world is full of such sophisticated con games, as Mr. Stevens abundantly demonstrates. On Indo-Pacific coral reefs, for instance, certain species, called “cleaner fish,” set up a sort of carwash for other fish species, which duly line up to have the parasites picked off their flanks. No tipping required: For the cleaner fish, the parasites make a meal. But the bluestriped fangblenny is after bigger game. It mimics the appearance of innocent cleaner fish, and when an unsuspecting customer swims up, it darts forward and rips off a chunk of its flesh.
This is naturally bad for business at the carwash, so the fangblennies succeed in part because they are relatively rare. You might think the cleaner fish would do their best to weed out even the occasional imposter, but the fangblennies make this challenging. Their bodies contain chromatophores that “act like packets of pigment,” allowing the fangblennies to switch their mimicry on or off or adjust it to better match the neighbors.
Deception is more than just a curious aspect of animal behavior. Camouflage—particularly the way certain butterfly species disguise themselves as dead leaves—was one of the things that led Alfred Russel Wallace to formulate his ideas about the origin of species, leading to the joint publication by Darwin and Wallace of their theory of evolution by natural selection.
Camouflage, and the case of the peppered moth, also provided the first evidence of evolutionary change observable on a human time scale. As industrial pollution became widespread in mid-19th-century England, the lighter form of these moths, suited to hiding itself against pale or lichen-covered tree trunks, became less common. A darker form, better disguised against soot-blackened trees, proliferated. Then, as antipollution laws went into effect in the mid-20th-century, the pattern began to reverse. Either way, natural selection was a result of hungry birds picking off the less camouflaged form. Creationists have criticized the peppered-moth story as an evolutionary myth. But extensive scientific research has recently vindicated the particulars in painstaking detail. (A study published this month in the journal Nature identified the precise genetic mutation that caused the original color change and dated it to about 1819.)
Mr. Stevens writes as a scientist and does not aim to be particularly colorful or entertaining. But the behaviors he describes take care of that by themselves, and Mr. Stevens makes for a clear, thoughtful, jargon-free guide. He provides plenty of examples to parse out the many varieties of deception, from “sensory exploitation” to “aggressive mimicry” and “motion dazzle.” The book is especially helpful in explaining the details of how scientists over recent decades have refined our understanding of old theories using modern devices “to measure the colours, smells or sounds of animals and to understand and model how animals perceive the world.”
I knew, for instance, about female bolas spiders, which mimic the sex pheromone of certain female moths to attract male moths. Then, when a moth comes in range, the spider flings a sticky ball on a string and hauls it in for dinner. But I didn’t know about recent research on one kind of bolas spider that starts its night’s work by emitting the seductive scent of a moth species common around 10:30 p.m., then shifts to the scent of another species that turns up around 11. It’s a sort of utility femme fatale.
Nor was I aware of recent evidence that leaf mimics have been evolving for at least 126 million years, or that marine brachiopods may have disguised themselves as unpalatable sponges more than 500 million years ago. These delicious, duplicitous details make exploring the natural world seem all the more fascinating. If you want to understand just how thoroughly we live in a realm of intrigue and deception, this book is a fine place to begin.
—Mr. Conniff is the author of “House of Lost Worlds: Dinosaurs, Dynasties, and the Story of Life on Earth.”