Once the turtles came by the tens of thousands, water sluicing off their shells as they heaved themselves from the surf and lurched across the dunes. Somewhere above the high-tide mark, the beach looked and felt right. Sand flying, each animal dug a nest, laid her eggs, covered them, and turned once again toward the ocean. Among nature’s spectacular mass movements—the peregrination of the wildebeests, the migration of the monarch butterflies, the quixotic suicide of the lemmings—the arribada, or arrival, of the Kemp’s ridley sea turtles on Gulf of Mexico beaches could hold its own.
Today, though, the arribadas of the ridleys are history. Decimated by decades of nest robbing and threatened by shrimp nets and pollution, Lepidochelys kempii is the most endangered sea turtle in the world. Only five hundred to six hundred nesting females and an unknown number of males and juveniles remain. One ill-timed natural or man-made disaster—a hurricane, an oil spill—and the epitaph of the ridley can be posted beside those of the passenger pigeon and the woolly mammoth.
Efforts to save the ridley have been ongoing for more than two decades, beginning in 1966, when Mexico made it illegal for anyone to disturb the animals’ primary nesting beach. Every year after that, scientists have hoped and waited for the ridleys to rebound. It hasn’t happened. Though no one realized it at the time, the arribada of 1968 proved to be the last of any real size, and its gathering of two thousand animals was a ghost of the grand aggregations of years past. In 1977, prompted by the feeling that time was running out, representatives from Mexico, the United States, and Texas met to collaborate on an unusual project. The first imperative, they decided, was to redouble efforts to protect the eggs in Mexico. The more radical part of the plan was to launch an experimental program to plant a satellite nesting colony of ridleys on Texas’ Padre Island National Seashore. The theory of imprinting, upon which this plan was based, was unproven in turtles. But the three governments felt they had to act.
The ten years allotted for the colonization attempt will be up at the end of 1988. On the one hand, the overall project is a success. Hatching in Mexico has improved tremendously; 40,000 to 70,000 baby turtles a year are released at the species’ nesting site. On the other hand, the project is a continuing frustration. Every year the number of nesting females has declined 3 to 4 percent, and no brave new colony of ridleys has yet claimed Padre Island. Unless the imprinting part of the program is renewed, the transfer of turtle eggs to Texas this summer will be the last in an unprecedented effort to change the ways of a sea turtle.
Two hundred miles south of Brownsville, in the Mexican state of Tamaulipas, lies the sole mass nesting beach of the Kemp’s ridleys. With its fine sand and low dunes, it looks like any South Texas shore. Flat rocks lie here and there, washed up by the tide. A few spiny shrubs punctuate the low tropical vegetation, and behind shallow lagoons, mangrove trees cast a dappled shade. Half the year villagers from nearby Rancho Nuevo swim and fish here. But every spring and summer the beach is declared off limits as a small number of armed Mexican marines and biologists and bureaucrats from both sides of the border await the arrival of the turtles.
Scientists, students, and soldiers arrive at Rancho Nuevo in April, prepared to stay through July or later if necessary. In the days of the vast arribadas (pronounced “ar-ri- bah-das”), the nesting animals would come in two or three enormous waves in April and May. Now whatever force summoned the turtles has weakened, and the females straggle in over a period of weeks. The Mexican group (under the fisheries department) has erected a permanent bivouac. The United States contingent (coordinated by Brownsville’s Gladys Porter Zoo for the U.S. Fish and Wildlife Service) has a barracks. There is also a building to hold the turtle eggs destined to be raised for a year in Texas and then released off Padre Island. Usually two thousand eggs are transferred; this year it will be one thousand each of eggs and hatchlings. About