Terrestrial turtles, and their cousins that ventured into the oceans around 130 million years ago, are among the oldest groups of reptiles on Earth. At one time, millions of these creatures roamed the ancient seas, but today, only a tiny fraction remain.

Spending most of their mysterious lives in the ocean, sea turtles come to shore briefly during their egg-laying season. In the Andaman Sea, west of the Malay Peninsula in the Indian Ocean, Koh Phra Thong and neighboring islands are "home" to four species of sea turtle. They are also the site of Naucrates, one of a number of sea-turtle conservation projects along and off the southwest coast of Thailand.

Winter is the nesting season, when females climb ashore at night, lay their eggs in the sand and return to the sea. Sand temperature during the two-month incubation period plays a big part in sex-determination: more males hatch when it's cooler, more females when it's warmer, with a pivotal temperature resulting in equal numbers of each sex.

After laying her eggs, the mother, like many reptiles, takes no further interest in her offspring, whose list of predators is so long -- including crabs, feral dogs, raccoon, birds and fish -- that an individual's chance of surviving to adulthood is about 1:1,000. The ones that do make it to adulthood, though, are impressive: living up to 100 years, reaching up to 1.8 meters in length and weighing in at a hefty 600 kg.

Although most of our knowledge about sea turtles comes from research at nesting beaches, females spend less than 10 percent of their lives there -- and males never go ashore. In particular, conservationists want to learn more about sea turtles' movements. Making journeys along so-called migration corridors to feeding grounds across the oceans, they certainly cover prodigious distances of thousands of kilometers. Females are even found to migrate to nest at the very beach (sometimes on a tiny, remote island) where they hatched.

One theory suggests that turtles achieve their spectacular feats of navigation by geomagneticism, using an internal compass to pick up magnetic signals from the Earth. Traces of a magnetic substance called magnetite have been found in their brains. Now, however, using satellite tracking, researchers have been able to learn more than ever before about the different species' migration patterns.

Researchers at Kyoto University are cooperating with Naucrates and other teams in Southeast Asia to learn more about the routes taken by local species. A transmitter, designed to fall off naturally after a few months, is attached to a turtle's carapace, and sends signals whenever the turtle surfaces to breathe. "We want to know the correlation between fishing grounds and migration patterns, so we can recommend a conservation strategy . . . which we need as quickly as possible," says Sakamoto Wataru, fisheries oceanographer at Kyoto University.

But, predictably, time is running out. On the long beaches of Koh Phra Thong and neighboring islands, the turtles are arriving in sharply reduced numbers, if at all. Researcher Monica Aureggi estimates the number of nests there has fallen about 85 percent in the past 20 years. Reasons for this include the usual assortment of destructive human activities: habitat encroachment, pollution and environmental pressure; as well as beachfront development that creates noise, light and water pollution -- a problem all over tourist-dependent Thailand.

One species, the leatherback, suffocates on plastic bags and other garbage it mistakes for jellyfish, its favorite food. Fishing methods such as shrimp trawling accidentally capture turtles, while illegal poaching and the trade in carapaces and other turtle-parts continue -- with Japan, Taiwan, China and South Korea the biggest consumers. As well, turtle eggs, thought to enhance virility, are poached and sold in local markets.

Although governments have introduced measures -- such as banning trade in body parts, introducing Turtle Escape Devices (TEDs) to reduce drownings in trawling nets, and prohibiting boats from coming within 3 km of shores where turtles are likely to be -- in a region which borders Myanmar and where illegal fishing is rampant, regulations are hard to enforce.

However, conservationists' efforts have had some success. Aureggi realized early in the Naucrates project the importance of education: Volunteers' visits to local schools to give lessons on turtles and conservation have helped create links with villages. As a result, poaching by locals has stopped completely, and some of them now cooperate by monitoring beaches and protecting nests. The remaining poachers are likely to be non-local, and volunteers can usually outsmart them by searching early in the morning for turtle tracks and protecting any eggs.

Meanwhile, a satellite transmitter from Kyoto University may soon be used to increase understanding of migration patterns, as well as nesting places and times. Aureggi cites co-operation between countries as essential. "If we hear about a turtle feeding in, say, Vietnam, that's nesting over here in Thailand, we need to communicate as much as possible."

But in-depth satellite tracking is still too expensive for shoestring conservation projects like Naucrates. "When research is for a human problem, like cancer or other deadly diseases, there's always money to be found. But for an endangered species, forget it," she says.

And for this project, the priorities are much more basic: "Of course, we need to research something scientifically before deciding on a conservation plan, and that takes time -- there is no short-term conservation," she explains.

"But for us, right now, the number of nests is so critically low that we're just trying to protect the eggs we find."