Buck Island, only one mile long, is an ecologist's haven. Situated off the coast of St Croix, the largest of the three American Virgin Islands, it was declared a national monument by President Kennedy and is now run by the National Park Service. It is easy to see why; Buck's protected coral lagoons, empty beaches and forest-covered hills come as somewhat of a shock after the tarmac and Tex-Mex experience of St Croix, a charming yet wholly urban slice of the US.
"Get down," hisses our guide, Zandi-Marie Hillis. She points to a vast black lump halfway up the beach. I look blankly at my husband; it might as well be a sand dune, for all we know. "Sssshhh," says Zandi. We begin to hear a weird scraping sound coming from the lump; against the stars, a large black flipper is moving up and down, throwing sand about. It is an enormous turtle. "She's about to lay her eggs," whispers Zandi. We are thrilled. We are witnessing an event which has been taking place for more than 140 million years; since the age of the dinosaurs.
Zandi-Marie Hillis is biological technician of research programme on Buck Island. To say that hawksbill turtles are Zandi's passion is an understatement; they are her life. For the past six years in the laying season (March- October); every night, all night, Zandi and a bunch of hardy volunteers patrol Buck Island in order to document the female hawksbills who, every year, swim more than 3,000 miles to lay their eggs at night on this mile-long stretch of coastline.
Zandi waves a clipboard at the turtle: "Hawksbills have been around for 145 million years; and they're dying out. We're going to see the extinction of the species if we don't look after them."
Turtles were once so common here that Christopher Columbus noted he had to ram his boat past thousands to land on St Croix. Now the hawksbill, hunted for its precious mottled shell, is so rare that America has declared it an endangered species. Four hundred years after Columbus only about 20 females return each year to nest on Buck Island.
Zandi inspects the black hillock. It's a green turtle; rare, but not endangered; and one of three different turtle species who nest on the unpolluted, undeveloped beaches of Buck Island.
The turtle is sitting in a "body pit"; a deep hollow she has dug with her flippers and into which she has scooped out an even deeper hole. Eventually, she begins the process of dropping more than 100 eggs into this hole. We are allowed to crawl up and peer into her beaky face. "She's in a trance," says Zandi. "You can do what you like to her now. Nothing will stop those eggs."
Indeed, the eggs drop into the narrow 3ft-deep hole like so many boxes of table-tennis balls. Their leathery shells bounce gently down on to one another, making little dents that trap pockets of warm air between each egg.
Having laid about 120, the turtle will cover over the hole with sand, and lumber off back down the beach, leaving her eggs to incubate. About 60 days later, the hatchlings break out of their shells, run down to the water's edge and swim off. That is, if they have not been eaten by birds, dug up by tourists or sold as aphrodisiacs by locals. Zandi estimates that only 1 per cent of a batch of more than 100 eggs reaches maturity.
Meanwhile, we eat our sandwiches, and continue searching for nesting hawksbills. Rain begins to tip down. Not British drizzle, this is a Caribbean cloud burst, and on Buck Island, with not even a picnic table to hide beneath, rain is no joke.
"Come along. We have to patrol the beaches all night," says Zandi sternly. "Each beach at least once every hour. We might miss a turtle."
My husband is looking as if he wishes he had never heard of hawksbills. It is four in the morning, we are both soaked, and a freezing sea-wind has whipped up. "This is all quite brilliant, though, isn't it?," say I enthusiastically, rain dripping off my hair. "Emphasis on the quite," he says, grumpily looking out to sea. We are not due to leave the island for another four hours.
Until now, we had been staying at the Buccaneer, possibly the most swanky hotel on St Croix. With two swimming pools and three private beaches, it is not exactly a resort for hardy environmentalists. Yet the hotel provides a link between commerce and ecology.
An "eco-package" was launched by the Buccaneer two years ago. Every year this pays for and accommodates two "interns"; volunteer assistants for the National Park Service's Hawksbill Program on Buck Island. In return, "interns" give weekly turtle slide-lectures and take willing guests on to Buck for the all-night experience.
"We have to warn them that it's pretty tough out here," says Zandi. I look at my husband, shivering wetly beneath a rubber poncho, and agree that it's probably not quite the experience that most Gucci-clad guests at the Buccaneer would really welcome. "But I couldn't do without the internships," says Zandi. "There is no sea turtle project in the world that can function without volunteers. The research is highly people-intensive; there is no equipment which can monitor turtles for us."
We troop along another beach. "People always thought the turtles would keep on coming back," says Zandi. "But they're not. They're being devastated by egg harvesting, by the prawn industry which drowns them in its nets, and by the shell trade. Hawksbill shells are being made into cigarette holders and hairclips."
She gestures out over the ocean. "In the British Virgins, only 70 miles away, it's open season on the hawksbill. Thirty-five turtles were reported killed last year. It's a neighbouring, intelligent community and it can't even protect the species. And this is Britain we're talking about!"
Suddenly, in the dark, at the rocky end of the beach, Zandi spots a huge mottled shell. Everyone gets very excited. It's a hawksbill, digging to lay her eggs. Hawksbills have a habit of digging their nests in fearfully unfriendly terrain; this one had already attempted to dig amid rocks, tree roots and pebbles, and is in somewhat of a tiz. Zandi creeps up behind the turtle, and helps her dig the hole. We all wait at a respectful distance. After what seems like several hours, the turtle lays her eggs, and covers the nest over. Expertly, Zandi and the interns muscle in. They pick her up, flip her over and clip an identity tag on to her flipper. The turtle is weighed on a special sling, photographed, measured and generally documented. She is somewhat perturbed, slapping her flippers noisily on her stomach; but with a dearth of data on this rare species, every bit of information is vital.
After about five minutes, Zandi, flushed with success, releases the turtle. Using her huge front flippers as propellers, the hawksbill runs awkwardly down the beach and dives into the sea. Perfectly streamlined for marine travel, she is invisible beneath the waves in seconds. Dawn is breaking over Buck Island; pelicans flap past in the red sky as we stiffly, slowly gather our equipment and prepare to take the boat back to civilisation.