She crawls up the beach in the dark to where shrubs meet the sand. Under a shell the size of a coffee table, her two hind flippers flick sand off to the sides, a cup at a stroke. After digging as deep as she can reach, she lays her eggs.
This sea turtle - a greenish tropical variety known as olive ridley - probably doesn't know it, but her life and the lives of millions of other sea turtles will soon be more secure.
Eight nations in the Western Hemisphere - home to six of the world's seven species - are needed to ratify a treaty to prevent harm to sea turtles where they feed, breed, and hatch.
Environmentalists hope the new treaty - the Inter-American Convention for the Protection and Conservation of Sea Turtles - will be the first step toward protecting turtles worldwide. Two of the eight countries - Venezuela and Mexico - have ratified the treaty already.
Some species - the Pacific loggerhead, for example - will swim thousands of miles to the coast of the Americas from Asia and back again. While the new treaty will protect them on one part of the journey, they are still vulnerable to poachers who sell turtle meat in Asia, most notably in China.
The Americas were easiest to tackle first, says Wallace Nichols, a turtle expert at the University of Arizona in Tucson. "There is a seed of conservation interest in all of the countries. They also share a language - and they share the turtles."
Meanwhile, the US this month announced it would not import shrimp from five Latin American countries - Costa Rica, Guyana, Panama, Surinam, and Trinidad and Tobago - because their fishing industries did not adequately protect sea turtles.
"These animals have no boundaries - so they require an international agreement and enforcement," says Frank Paladino of Indiana-Purdue University who heads up conservation efforts here in Las Baulas (Leatherback) National Park on the west coast of Costa Rica.
The titanic leatherback
The olive ridley turtle is not in as much danger as its titanic, more famous cousin, the leatherback, which is already in danger of extinction. In the early 1980s some 200 leatherbacks were nesting here most nights from September to March. This year only 127 of the six-foot-long turtles came to nest in the whole season.
Just down the beach, some leatherback hatchlings are poking their heads out of the sand and crawling toward the surf. Raccoon eyes shine back in a flashlight from the woods, waiting to feast on the bite-sized turtles. Even if they escape natural predators, these babies have a long way to go.
There is still a black market for turtle eggs here in Costa Rica and across Latin America. In many places development too close to the beach confuses the turtles and they head for electric lights instead of the water.
Once they reach the water there is another series of hurdles. Turtles mistakenly eat or become entangled in ocean trash. Shrimp nets, perhaps the biggest threats, kill about 150,000 sea turtles each year, according to the National Wildlife Federation. It estimates that 95 percent of the hatchlings that make it to the water will not live long enough to reproduce, about age 13.
The treaty's main effect will be the requirement of TEDs - turtle-excluder devices - in fishing nets. The TEDs are essentially screens that allow turtles to slip out a trapdoor in the nets. Shrimpers have for the most part been receptive to the idea, says Dr. Paladino at the leatherback park.
US shrimpers in the Gulf of Mexico have been required to use TEDs for a decade because of a US law. Now US Public Law 101-162 has forced an embargo against the five Latin American countries. The US law may be the only enforcement the new treaty has.
The convention has few critics, but Randall Arauz of the Sea Turtle Restoration Project of the Earth Island Institute, a San Francisco-based group, is worried that what's on paper will not become a reality. "It's going to take a lot of activism - otherwise it'll be just another treaty," says Mr. Arauz, who heads the project's Costa Rica office.
Though its laws place it in compliance with the treaty, the US has not yet ratified it. But, with support from environmentalists and the fishing community in the US, the convention is expected to pass the Senate.
"We want to level the playing field for our fishermen," says David Nitchman, a spokesman for the National Fisheries Institute in Virginia. "The convention is more effective than unilateral action and trying to strong-arm other countries."