Reptile: Galápagos Tortoise

When you meet a Galápagos tortoise, as I did recently, it will do one of three things. If annoyed, it will turn and lumber off across the volcanic tuff. If afraid, it will thud onto the lava and pull in its head, like a toddler who thinks she becomes invisible when she covers her eyes. Or, if it is feeling comfortable, it will fix you with Triassic eyes. It can do this for ten minutes without getting bored. Possibly longer. I challenged several to a staring contest, but I always blinked first.

To meet the gaze of a Galápagos tortoise is thrilling and slightly unnerving. True, it has the vacuousness appropriate to an animal with a brain the size of a walnut. And yet in its eye is a quality absent from, say, the stare of its neighbor and distant relation, the marine iguana. The tortoise has a sentience, an alertness and seeming comprehension that marks the line between ignorance and indifference. It’s not that the tortoise doesn’t get it, one feels; it’s that he just doesn’t care.

This attitude is understandable. The giant tortoise can weigh up to 600 lbs. Its carapace, or topshell, can be 4.5 feet across and is thick and heavy. Its scaly skin protects its limbs like a motorcycle jacket. Its ancestors have trod the rugged, lunar landscape of the Galápagos since before chimpanzees split off from protohumans. For three million years, giant tortoises have stumped, peglegged, across the lava, eating whatever plants happened to have evolved recently. Charles Darwin once clocked one at two tenths of a mile per hour. It is believed to be the longest-lived animal on earth, yet no one knows its lifespan. It may live 200 years.

Tortoises float. They have a built-in life jacket made of fat on their backs, under the carapace. Once in a while, a tortoise stumbles off a cliff, is driven offshore by the weather, or simply gets confused, and ends up in the ocean. It can survive for a year or more without water, so its only maritime concern is breathing. The tortoise’s patience is a real virtue at sea. The first colonists tumbled in from the coast of South America, riding the currents some 600 miles west to the Galápagos, which sits sidesaddle on the equator. My Galápagos guide told me that fishermen have reported seeing tortoises floating peacefully in the open ocean.

Thus, tortoises have colonized all the major islands of the Galápagos. Biologists now recognize eleven different kinds of Galápagos tortoise. Some of the farthest-flung varieties are the most closely related. The shells vary from island to island. On moist islands, they tend toward a domeshape. On more arid islands, with less succulent vegetation, one finds the so-called “saddleback” form. The saddleback shell comes to a high ridge just behind the tortoise’s head. Saddleback tortoises also have a long neck and legs, adaptations that give them a greater reach. Tortoises eat leaves, grass, and cactus pads. Their softball-size droppings often contain still-sharp spines....