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Night Of The Sea Turtle:
By Joe Haberstroh. STAFF CORRESPONDENT
May 11, 2003
Along the northern shore of this tiny island, Playa Brava was bathed in prehistoric darkness. No artificial light shone near the protected beach. The almost palpable blackness was relieved only by the stars, the Milky Way appearing like a galactic hammock woven with the brightest of diamonds.
On shore, a group of turtle biologists and volunteers settled in for the night. Their leader: Sam Sadove, a Long Island scientist who at dusk had led the party to the beach by way of a jungle trail lined by thick stands of beach grape and mangrove. To the south, clouds massed and a breeze freshened the warm, salty air. Sadove and others spoke in whispers, stayed low on the beach and signaled with flashlights fitted with red filters. They treaded lightly to keep from frightening the extraordinary and reticent animal they hoped to study when it came ashore to nest - the leatherback sea turtle.
The leatherback favors rough ocean beaches such as Playa Brava - Ferocious Beach - to lay eggs before returning to the ocean and swimming north to places such as Long Island Sound, Gardiners Bay and the waters off Montauk. It spends the summer and fall eating jellyfish and other gelatinous creatures. Invisible in the depths, the leatherback is nevertheless as native to Long Island as seasonal songbirds and migrating bluefish.
With some males weighing 2,000 pounds and measuring 8 feet long, leatherbacks are by far the largest turtle in the world. Front flippers extended, some leatherbacks have a wingspan of 15 feet. Starting with its soft, leathery carapace - it does not have a hard shell - the species' physiology is unique among reptiles. Heat exchangers at the shoulder prevent cold water at the flippers from cooling the whole body, which allows the turtle to maintain a fairly constant body temperature whether it is swimming near Greenland or Brazil. On its singularly deep dives - 3,000 feet is routine - it does not rely only on its lungs to stay underwater for an hour. Instead, it stores oxygen for long periods in its blood, not simply in its lungs, which compress under deep-water pressure.
"It's an athlete - that's the only way to put it," said biologist Molly Lutcavage, a senior researcher at the New England Aquarium in Boston, who is studying the Puerto Rican leatherbacks with Sadove. "It does everything to a greater extent than all its fellow sea turtles, and all its fellow reptiles."
Impressive, the turtle also is imperiled. It is listed as endangered by the state of New York and by the federal government. Human settlement has robbed the turtle of many of the nesting beaches it has used for millions of years. Even today, vacation resorts have been approved for two nesting beaches on the main island of Puerto Rico, 17 miles west of Culebra, and scientists fear the developments will drive off the turtles. Historically, island populations from Puerto Rico to Malaysia also have eaten the turtles, and poachers continue to steal leatherback eggs, which are still sold pickled in Caribbean taverns as an aphrodiasic. That practice might be dismissed as a barroom gimmick, but it has its genesis in ancient reverence for turtles.
"In many different cultures, turtles have the same significance - to many people, they mean prosperity, long life and fertility," said Hector Horta, who manages turtle-nesting areas for Puerto Rico's natural resources agency.
Fishermen around the world inadvertently also drown the giants in their nets and on their hooks. Leatherbacks are routinely ensnared in Long Island Sound and in the waters off Montauk in the long ropes that link lobster traps and their surface buoys. No one knows how many leatherbacks are out there, but estimates of the nesting female population in the Atlantic Ocean range from 5,000 to 7,000, down from more than 100,000 in the early 1980s.
If people hope to help the leatherbacks, they need to know more about their mysterious habits. In recent years, a determined group of turtle scientists has begun to deploy battery-powered tags linked to satellites. They have discovered that after nesting in Culebra, the turtles swim to Long Island, but also to Europe and Africa. They are the most widely distributed reptile on Earth.
"The turtles we tag here can be caught in a whelk pot in Wales," Lutcavage said.
People have long described leatherbacks as ocean wanderers. In fact, Lutcavage and Sadove say the tag information suggests that the turtles may move in well-traveled corridors across the seas. If verified over several migratory seasons, such corridors could help fishermen avoid the animals at different times of year.
'Tortuga!" comes the excited whisper from a Spanish-speaking team member crouched closer to the Brava shoreline.
"Turtle!" says another team member.
"What?" asks Sadove.
"A turtle! We have one."
"Oh geez, already? OK, OK, here we go," Sadove says. "Donde?"
A voice in the darkness: "Right here. Right here."
Sadove and Lutcavage have been arranging the equipment needed to attach a satellite tag to the spongy back of one of the turtles. They peer toward the water's edge, where a hulking shape gathers form.
It looks like a boulder.
But it moves.
Only 50 feet away, it advances directly at the group on shore.
"Everybody, vamos! Now!" Sadove says in a hoarse stage whisper. People stumble in deep sand to grab backpacks and tarps and move aside.
On Brava, it is just after high tide, when the nesting females are programmed to come ashore under the safety of darkness. The volume of water helps carry their massive frames up the beach. Still, at some point, the turtle must walk, and the effort appears supreme. The turtle drags its body forward with its front flippers, which are shaped like paddles and are about 3 feet long. It exhales loudly, sounding like a horse sighing.
The turtle's path to its chosen nesting site depends on the individual. Some plow perpendicular to the shoreline. Others create S-shaped paths. After 10 minutes of progress up the beach, the turtle stops and begins building its nest by flapping its disproportionately large front flippers and sweeping each of its rear flippers back and forth. Then, with its stubby but flexible rear flippers, the turtle begins to dig a protective egg chamber.
The turtle curves one flipper, digs into the sand, and lifts the sand out of the way. Then it rests that flipper to the side and repeats the action with the alternate flipper. In this way, over the course of 45 minutes, a 3-foot hole appears. The cleanly dug chamber looks as if it were excavated with a posthole digger.
Soon the researchers hover at the turtle's rear end and point their flashlights into the hole in the sand.
"She's a big one," Sadove says. "Average. I'd say 600 pounds."
"A few scars." Lutcavage points at creases on the turtle's soft carapace that might be the work of males hanging on to the female during mating in the water.
The rubbery eggs are the size and shape of Ping-Pong balls. The average turtle lays about 100 eggs, including about 20 with no viable yolk. These serve to fool burrowing predators and to maintain the structural integrity of the clutch underground until the 2 1/2-inch-long hatchlings emerge and crawl to the sand's surface in about 60 days.
When 15 eggs have dropped, and the turtle lapses into a sort of hypnotic state, the scientists move in to attach what is known as a pop-up satellite archival tag.
Lutcavage has used the $3,800 tags to track the movements of bluefin tuna. Every hour, the 2.3-ounce tag records depth, water temperature and light levels. The light levels allow the scientists to track the turtle's location using celestial navigation. Sadove and Lutcavage have programmed the tag to separate from the turtle after collecting 180 days' worth of data at sea. The tag is released when, on the preset date, an electrical charge is emitted inside the tag, burning through a wire leading to a detachable nose cone. Then the tag floats to the surface and begins transmitting to a passing satellite. The data arrives at Lutcavage's computer in Boston in the form of an e-mail.
Unlike other species of sea turtles, whose carapaces are considered hard, the leatherback's is not composed of identifiable sections, or scutes. Instead, hundreds of spongy plates, some just a half-inch in diameter, create a protective mosaic. The relatively pliable skin is thought to be one key to how the turtle can withstand the pressure of diving deep.
Dark-green to black and speckled with white spots, the carapace is also keeled with seven distinct ridges. Some scientists say the ridges, much like lapstrake planking on a boat, help the animal maintain a consistent heading through the water on its long journeys.
The tagging operation unfolds like a human surgical procedure. Lutcavage slips on latex gloves and chooses a spot toward the front of the carapace to secure the first of two attachments that will bind the tag to the turtle. The 8-inch-long tag looks like a black microphone with a 4-inch tether attached. She wipes the prospective attachment point with the antiseptic Betadine.
"OK, Charlie, drill," Sadove says.
Charlie Blaney, Lutcavage's partner of 15 years who happily accompanies her on turtle research, leans in with an electric drill. First he dips the drill bit in the Betadine, then bores a hole in the carapace less than 1 inch deep.
Sadove holds up the tether's titanium anchor, which looks like a miniature grappling hook with backward- facing tines. The anchor was made by B&R Industries Inc., a high-tech machine shop in Medford. The tines were provided by Sportswire LLC, an Oklahoma company that manufactures the Terminator line of fishing lures and leader wires.
"Kryo!" Sadove says. A team member sprays the anchor with the anesthetic.
Blaney taps the anchor inside the shell with three quick strikes. Sadove gives it an upward tug to make sure it has set. Then they sink a second anchor to secure the front of the tag. The turtle eventually will expel both anchors.
The researchers stretch measuring tapes across the turtle. She is 3 feet, 8 inches wide and 4 feet, 10 inches long.
As the work goes on, the turtle is motionless. But toward the end of the operation, when she has finished laying her eggs, the turtle nods and occasionally growls. Unique among sea turtles, the leatherback can vocalize.
Soon, its rear flippers swing into action. One flipper grabs sand, drags it down into the nest and smooths it flat. Same with the opposite flipper. When the turtle finishes filling the hole and tamping the sand, she pumps her front flippers even more aggressively than when she made the nest. Sand flies in a 6-foot ring. She is attempting to disguise where she has buried her eggs. It sounds like someone beating a heavy carpet on a laundry line.
After about 20 minutes, she heaves herself to a second position about 10 feet away. With more violent flipper action, she creates a second structure, which scientists call a "false nest." It's believed these false nests are designed to confuse predators of the eggs.
Even with all this effort, Lutcavage estimates that perhaps one in 100 eggs survives to adulthood. The others are either dug up and eaten as eggs, or, as hatchlings, are plucked by birds from the sand as they scramble for the water after emerging from the nest.
Eventually, the nesting turtle on Brava turned back to the ocean. Leatherbacks are severely nearsighted but are keenly sensitive to light. They detect the difference between the dark line of the coastal forests that line their important nesting beaches, and the lighter surface of the ocean, which at least reflects illumination from stars, or even cloud cover.
Development that could change the nature of the pristine Puerto Rican nesting beaches has raised concerns. One environmental group has sued the government for granting permits to two large projects that would abut the 4-mile nesting areas just west of Fajardo, on the northeastern coast of the main island of Puerto Rico, said Horta, the turtle program coordinator for the local natural resources agency.
The fear is that the projects, which include houses, hotels and a golf course, would thin the woods associated with nesting beaches, erect lighting that would confuse the turtles and, by allowing concrete seawalls to rise, eventually would deplete the beaches of sand.
Horta points out that the single "biological unit" near Fajardo produces more than 300 nests each season. In neighboring Loquillo, where a high-rise, houses and seawall crowd a foreshortened beach, nestings number four annually. Nesting turtles need wide beaches so their eggs won't be washed away. Horta believes that continued nesting success near Fajardo will depend on the developers following through on their assurances to enhance the coastal forest, restrict beach access during nesting season and erect lighting with screens that direct the illumination away from the beach.
"You can observe that when development occurs close to the shoreline," Horta says, "nestings go down."
In the precisely tuned biology of the leatherback, maintaining a variety of nesting beaches is key to the health of the species. Nests made on beaches with darker-colored sand tend to produce more female hatchlings, Horta explained, while white-sand shores tend to produce more males.
Even setting aside development threats, the wide- ranging leatherbacks already have enough to contend with. While large size is any species' best natural defense, leatherbacks often find themselves under attack in the ocean. The turtle researchers routinely tag animals whose flippers have been chomped off by sharks or killer whales, or severed by boat propellers.
On Brava, Sadove, Lutcavage and the others gather around one turtle whose physical condition bespeaks a life in the wild. Her seven ridges are worn down almost flat, suggesting advanced age. Up front on the carapace, a 5-inch wound is scabbed over, and one front flipper also is lacerated.
But the worst wound is on the right rear flipper. It has been severely torn, perhaps crushed. Blood oozes. Still, the turtle digs its nest, using both flippers. Sadove and Lutcavage surmise the old turtle has been struck by a boat.
Although no one knows for certain, scientists believe leatherbacks live 50 to 100 years. If the injured turtle is even only 50 years old and has used Brava as her lifelong nesting beach - as many sea turtles apparently do - this is probably at least the 20th season she has nested here. At a minimum, she would have buried 10,000 eggs on this very beach.
Over the course of the four-month nesting season, female leatherbacks come ashore five to 13 times to lay their eggs. After each nesting, they rendezvous with males waiting offshore.
Sea turtles are not highly intelligent. As with some dinosaurs, the brain of the massive leatherback would fit on the end of a pencil. You could never train a leatherback to balance a beach ball on its nose. But it would be hard to argue that any other animal could be trained to be as profoundly steadfast.
The old turtle at Brava continues to dig its nest. Even with the surf's roar, Sadove, Lutcavage and the others can hear her growl and noisily exhale. Soon the eggs plop one by one and wet into the carefully excavated chamber, and she begins to cover them. In the prehistoric darkness, blood threads from her broken flipper and drips into the sand.
TURTLES BEGIN JOURNEY
Take a virtual trip to Puerto Rico to see the leatherback sea turtles begin migrating north. Visit www.linature.com
The Leatherback Migration
Much of the Atlantic Ocean population of leatherbacks sea turtles nests on the quiet beaches of Culebra and Fajardo, Puerto Rico, in April though July. Many swim north and some stop in Long Island Sound or near Montauk beginning in June. Some will stay in these local waters through November, and some swim onto Canadian waters. Other leatherbacks migrate each summer to Europe or Africa. In early winter, as northern waters cool, the turtles return to the Caribbean.