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November-December 2014

Volume 102, Number 6
Page 469

DOI: 10.1511/2014.111.469

HOW SNAKES WORK: Structure, Function and Behavior of the World’s Snakes. Harvey B. Lillywhite. xiv + 242 pp. Oxford University Press, 2014. $49.95.

Right below our ankles lies a whole—and wholly different—world. Here, with a shift in perspective and scale, grass grows as tall as trees and rocks are as large as boulders. The landscape is so dense that animals can virtually swim in it, wiggling through oceans of grass and debris. Roughly 150 million years ago, a group of four-legged reptiles began to adapt to this rich lower world, evolving increasingly long and slender body plans until they were entirely limbless. From that point, there was no going back. In the switch to life without legs, these creatures also acquired a complete anatomical redesign, inside and out. The result was the animals we know as snakes.

From How Snakes Work.

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Harvey B. Lillywhite’s How Snakes Work explores the ways these animals thrive in the dark, disordered landscape of the forest floor. That emphasis on how sets the book apart, as Lillywhite, a field biologist specializing in snake physiology, focuses on the fantastic tricks and tactics essential to life at ankle level. The result tickles the imagination. Using photographs, detailed explanations, personal stories, and scholarly references, the author convincingly transports the reader into this lower world, introducing a whole cast of strange creatures and their even stranger behaviors.

How Snakes Work will fascinate anyone interested in nature’s innovations. Lillywhite provides a guided tour of ankle-level life’s diverse developments, detailing how one evolutionary change led to another and another. The loss of legs allowed snakes to hide in narrow nooks and concealed crannies, spaces too constricted for most predators to follow. Limblessness also brought the snake’s body into proximity with the ground, providing intimate access to a wonderful array of odors, which, picked up by a snake’s flickering tongue, lead to both prey and mates. Nonetheless, certain tasks, such as feeding, grooming, and reproduction, would at first seem difficult or downright impossible without limbs.

Numerous physiological innovations were necessary for snakes to eat. The mouths of certain snakes evolved fangs to inject venom and, in the cobra, to spit venom at distances of three meters. For the “snail-sucking” snake, such fangs may be either left- or right-handed, adapted to correspond with the spiral of the snail’s shell that the snake is destined to shuck. Now that’s specificity! A snake’s lower jaw is not connected to its upper jaw, enabling it to eat huge items in one gulp; proportionally, the human equivalent would be swallowing a watermelon whole. A photographic sequence of a snake devouring an egg dramatically demonstrates this prodigious feat.

In relating these innovations, Lillywhite weaves an intricate tapestry showing how some have led to multiple ends. Body muscles originally used to drive a snake through the grass evolved to hug, constrict, and suffocate prey. Snakes’ gastrointestinal systems, which can retain digested food in the intestines for days, evolved in concert with novel feeding behaviors. Although the weight of stored food in the gut might seem cumbersome, it may actually aid some species’ ability to strike prey at high speed—a movement so fast that their bodies can actually jump or slide on the ground. For vipers and heavy-bodied pythons and boas, the large weight of digested food in their intestines seems to act as ballast, making the strike more precise.

The fundamental body plan of a snake is similar to that of a human, only greatly elongated, as if drawn on a sheet of rubber and then stretched. The snake’s sinuous locomotion and large intake of food are possible because the skin is highly flexible, like a balloon. Some aquatic species have particularly baggy skin and weak muscle tone; when an aquatic snake is held vertically, blood pools in its tail, which expands as if it were about to explode. Yet many other snakes, especially arboreal species, adopt this posture without trouble. One of the strengths of Lillywhite’s book is the accuracy, even rawness, with which he explains how this body plan works. Such pointedness may be jarring to some nonbiologists: Several pages show snakes sliced open with their organs exposed. Nevertheless, peering into the inside of a snake gives one the same satisfaction as opening a well-packed suitcase, in which items are aligned and arranged to fill up every possible space.

The beauty and diversity of the animals in How Snakes Work can be breathtaking, particularly in the chapter discussing the evolution of skin patterns. Dazzling iridescent scales accompany Lillywhite’s explanations of the “structural color” enabled by a scale’s microstructure. Scales cover and protect every part of the snake’s body except for the tucked-in genitalia, which are protruded and inflated during intercourse. A sidewinder’s scales function as eyebrows, keeping grit out of its eyes when the serpent buries itself in the sand. The book also depicts quite a collection of head shapes: Stunning photos of hog-nosed, leaf-nosed, cottonmouth, tentacled, and even flying snakes make the book worth buying just to adorn one’s living room.

On the broadest level, How Snakes Work is a powerful set of lessons in how to think like a biologist. Each chapter begins with some simple, open-ended questions, which the author answers logically by presenting a series of well-described and well-illustrated snake innovations. In the process, he cites other researchers’ work meticulously, making this book a valuable scholarly reference for anyone interested in understanding snakes—not just biologists but engineers, roboticists, and simply anyone with an active scientific curiosity. This is also clearly a very personal book. Lillywhite regales readers with stories about many contributors to the field, often showing photographs of researchers alongside the snakes with which they work.

Decreasing the average person’s fear of snakes will not be easy, but this book takes a big step forward in fostering greater understanding between the world below the ankles and the one above.


David L. Hu is an associate professor of mechanical engineering and biology at Georgia Institute of Technology in Atlanta. His research focuses on the importance of scales in snake locomotion, a concept he demonstrated by putting a snake into a sock on National Public Radio’s Science Friday.

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