Turtle Planet. Yun Rou

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      Turtles are reptiles. That means they are related to snakes and lizards and, more distantly, to crocodilians, but they are far from slimy-skinned amphibians like salamanders and frogs. They reproduce by copulation and internal fertilization, lay eggs, and can have quite elaborate courtship rituals. Most are love-‘em and leave-‘em types, but some stay around to protect their offspring. Like other reptiles, they have lungs, not gills, and possess a bony spinal column and senses that are familiar to us, along with a couple that aren’t. Among the latter are the ability to detect electrical activity in water, to pick up vibrations in the ground using their shells, and perhaps the ability to sense specific airborne chemicals, especially pheromones.

      Turtles are also poikilotherms, meaning that they depend upon external sources for the heat needed by their metabolic processes. They can be cold to touch when that heat is not forthcoming, leading to the misnomer “cold-blooded.” Actually, their blood can be warmer than ours—whilst basking in the desert sun, for example—and in certain situations, some can even generate a little bit of their own body heat. Contrary to folklore, turtles are not particularly slow. Because of the limitations of their physiology, most are not able to sustain fast movement for long periods of time but can get up and move quickly in a short dash or swim. Giant sea turtles can even traverse entire oceans at a clip that only a high-speed submarine could match.

      The turtle’s defining characteristic is its shell. In most turtles—we will meet some exceptions in the fables that follow—the shell’s surface layer is comprised of keratin, the same stuff as human fingernails and hair, and as the horn of a rhinoceros, too. This keratin is divided into sections called scutes, which are basically giant versions of the scales characteristic of all reptiles. The upper shell, the carapace, is joined on each side of the turtle to the lower shell, the plastron, by a bridge. Beneath the scutes lie bony plates that approximate but do not exactly match the scutes above them. One unique feature of the turtle skeleton is that the shoulder girdle is inside the rib cage. If we were built that way, we’d be able to bring our ribs up to our ears when we shrugged.

      Turtle shells range in shape from flat and streamlined to domed and unwieldy, the better to discourage predators such as alligators and wild dogs from crushing them for a meal. Some turtle shells close up so completely that only the most powerful and persistent predator can get inside to the soft parts; others have shells that are quite reduced to facilitate climbing or crawling about in the mud. Turtles with less protective shells typically make up for their deficits with strong jaws, a sharp beak, and a nasty attitude.

      Speaking of attitudes, most turtles get along, at least with each other, and can live in large communities of different species. They have some surprising abilities, too. A few can spend an entire winter under the frozen surface of a lake or pond, reducing their heartbeats to nearly undetectable levels, and extracting what little oxygen they need through skin in their throat folds or urogenital area. The North American red-eared slider, Trachemys scripta elegans, has the most complex color vision system of any vertebrate, with seven different types of color-sensitive cone cells in the eye. Some turtles, while not nearly so eloquent and voluble as the ones we will encounter in the tales that follow, have a significant vocabulary. The Australian northern snake-necked turtle, Chelodina oblonga, uses growls, grunts, chirps, and more to communicate to other members of their species in murky, underwater conditions. Other tortoises vocalize loudly when mating.

      Turtles inhabit Earth’s most intimate spaces. So alien to us and yet so familiar that we routinely take them for granted, turtles remind us that despite our preoccupation with finding intelligent life out in the cosmos, such life is right here beside and below us. They remind us that we are most definitely not alone, though that is something that could also be said of many, many other types of animals. The real reason I chose them is that of all the creatures that crawl, fly, swim, run, slither, burrow, and climb in and through our world, they are the ones closest to my heart and the ones I know best.

Daoism, Meditation, and How a Monk Talks to Turtles