I am lying on my stomach in the wet sand, at eye level with the rear end of a giant leatherback turtle. She smells like she is the sea, a stench so overpowering I am holding my breath. My arms are straining to hold a large plastic bag in place to catch the small batches of eggs she heaves out every few minutes.

The turtle apparently is in such a trance that she doesn't know I am here, taking her eggs before they even touch the sand, or that the other volunteers have just measured and tagged her for scientific study. When she finishes we pull the sack of eggs away and count them before moving them and reburying them in the turtle hatchery.

These 87 eggs add up to easy money in the black market here in Gandoca, a remote Costa Rican village on the east coast near the Panamanian border. But instead, the eggs will be safeguarded in the hatchery 24 hours a day by volunteers and staff of Asociación ANAI, a Costa Rican organization dedicated to sea-turtle conservation and other environmental and community projects. When they hatch, the baby turtles, smaller than your palm, will be released into the sea with at least a slim chance at life. Out of 100 eggs, between one and three will reach adulthood and reproduce.

The volunteers come from all over the world to work at the Gandoca Turtle Project. Every night, rain or shine, for four hours, I walk up and down a portion of the nine-kilometre-long beach with a partner, peering blindly in the dark, looking for turtles. For an animal that's on average 1.5 metres long, the leatherbacks are not easy to see. The Caribbean coast of Costa Rica is the wet coast, and the clouds tend to obliterate the stars. Volunteers often trip into the turtle tracks (deep grooves in the sand) before they realize the turtle is there. Turtle patrol shifts are 8 to midnight and midnight to 4 a.m. We tape red cellophane on our flashlights so the beam won't scare the turtles away. And then we don't turn them on anyway because any light is bad light when a turtle is contemplating coming ashore to nest.

My presence here supports the village economy, and subsequently the turtles themselves. I pay US$6 a night to camp at Matute's Farm, home to the 83-year-old patriarch Gerónimo Matute Hernández and several members of his extended family, a herd of cattle, countless kittens, and some chickens. Other volunteers stay in homes with local families, paying US$14 a night for food and lodging. (Prices have since gone up a bit.)

"The volunteers have helped sway the village," says Matute, who was involved in the start-up of the turtle project and the creation of the Gandoca-Manzanillo Wildlife Reserve in 1985. "They see that other people think the turtles are important and the money supports the village. Most of the village used to be against conservation. Now many of the local youth volunteer for the program. They see a future in it."

Gandoca is a smattering of rustic houses at the end of a long dirt road. There is nowhere to go from here. Go south along the beach and you'll hit the Sixaola River and the Panamanian border; go north and you have a long, muddy hike through the wildlife refuge to the resort town of Manzanillo. The Gandoca Lagoon to the south of the village is home to the only surviving red mangrove in Costa Rica, as well as crocodiles and caimans. Wild, haphazard waves make the beach by the town dangerous for swimming.

Almost everyone in the village works with the volunteers, says volunteer project coordinator Edna Lopez. "Everything changed here because the volunteers came. Now, they have a pulperí­a [grocery store], a car for transportation, rooms and cabins, and even tourist guides."

Gandoca resident Roger Briones Ibarra finished high school a few years ago and has been volunteering with the turtle project ever since. "The turtle is more important alive than dead, for the tourists and for the community," he says. "I [also] work as a tourist guide and charge $10 a person for tours: if there are 10 people, that's $100. If I kill the turtle, it is possible to sell it for $60, but only once."

The volunteer project is also good for the turtles. About 500 turtles are known to nest at this beach. When it began in 1985, about 95 percent of the turtle eggs were being poached; now 90 percent are protected.

But volunteering is not just a walk on the beach.

Turtle patrol goes no matter what the weather is like, and on cloudy nights you really can't see a thing. There are sand cliffs to fall down and driftwood to trip over and many bugs to bite you. But when the night is clear and the stars shine, it's a rare kind of beauty. The cacophony of crashing waves, the utter darkness, and the walking make it feel like an endless lucid dream.

In one week of volunteering, I saw only two leatherbacks, mainly because it was still preseason (late March) and most of the turtles come from April to July. But with continued threats from development, industrial fishing, pollution, and poaching, there may be fewer and fewer leatherbacks to see. The leatherback is an endangered species, and although the population has stabilized at this beach, their numbers are dwindling, sometimes drastically, at nesting sites around the world. But for now, I take heart.

The turtle is thrashing around in the sand trying to obscure the tracks to her nest before slowly lumbering down the beach and disappearing into the waves of the roiling sea.

The eggs are safe tonight.

ACCESS: For more information about volunteering for the Gandoca Turtle Project, visit www.anaicr.org/. Volunteers pay a US$30 sign-up fee, plus US$7 a night to camp, US$15 for food and lodging in local homes, or US$30 for meals and lodging in private cabins. ANAI also has bunk-style accommodation in San José, Costa Rica's capital, for US$7 and will pick volunteers up at the airport for US$30.