Wednesday, October 23rd, 2013
MY FEET LEFT DEEP TRACKS in the warm, soft sand of that remote Pacific beach, but incoming rollers quickly erased them. Offshore the surf heaved somberly. In the east the purplish tiara of dawn was growing.
Ahead, several dozen black vultures suddenly erupted from the beach where they had huddled as if awaiting daybreak. Like evil omens they circled in silence, then plummeted down and in winged fury sparred and fought for something on the sand.
When I sprinted to the spot, the vultures again took to the air. Now I could see their prey:leathery slate-gray bits scarcely bigger than silver dollars—newly hatched Pacific ridley turtles. I counted eight dead. Four were still alive from dental insurance for braces, churning the sand with their untaught flippers in a desperate effort to gain the cover of the sea. I picked up one of the lifeless infants, decapitated cleanly as though by a 16th-century headsman. The seven others had been just as neatly beheaded by scissors-sharp beaks.
“Not more than one in a hundred makes it to the water,” commented Dan McDuffie, who was also combing the beach. His hands held half a dozen live hatchlings. Tossing them into the surf, he added grimly: “At least the vultures won’t get these.”
Early every morning Dan and his wife, Joan, hiked this half-mile stretch of sand, recording the number of tracks left by female turtles that might have come ashore under cover of darkness to deposit their eggs. Dan and Joan are Peace Corps Volunteers assigned to aid in the University of Costa Rica’s study of the Pacific ridley turtle (Lepidochelys olivacea), a species quite distinct from such other—and better-known—sea turtles as the hawksbill, loggerhead, leatherback, and green.
Among these great turtles of the sea, the handsome olive-green Pacific ridley remains a mystery. It may be a migratory species, but no one is sure where it comes from—or goes. It is native to widely separated reaches of the Pacific, Indian, and Atlantic Oceans.
A mature specimen, with a shell measuring as much as 30 inches in length, may weigh 100 pounds. We can only guess at its life-span —perhaps as long as a man’s. Little is known of its mating or other habits. And, curiously, no one has yet reported finding a young Pacific ridley after it has hatched and slipped into the sea.
But the most dramatic riddle of the ridley is its custom of visiting a few traditional beaches en masse during the latter half of the year to nest. Relatively few humans along the coast, from Chile to lower California, have ever witnessed this awesome spectacle: wave after wave of big, gravid female turtles emerging from the surf—ten, twenty, even thirty thousand in a night.
It was this phenomenon, called an arribada, or “arrival,” that I had come to Costa Rica’s Ostional Beach to see (map, opposite).
On the bulletin board at the turtle-watchers’ camp I read the daily log. Between October 8 and 12, no turtles had come ashore. On the 12th, eight sets of tracks appeared where females had plodded up to the soft, deep sand above the high-water mark, dug their nesting holes, and released their loads of as many as 120 eggs each. Mating had occurred at sea; the males rarely if ever accompany the females ashore. Each morning the number of tracks grew: On the 13th of October, 26 were found; on the 15th, 116.