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5 Sep 06
Turtle trackers: Scientists plumb the secrets of elusive leatherbacks
By Emily Saarman Sentinel correspondent
MOSS LANDING Scientists are searching the Monterey Bay for elusive leatherback sea turtles.
The turtles, the heaviest reptiles in the world — weighing as much as 2,000 pounds — swim from their Indonesian nesting grounds to feed on jellyfish in the bay.
But few on the Central Coast have ever seen these shy creatures that move in small numbers and typically feed far from shore.
"When I started the research in 2000 we had an understanding that there were leatherbacks here, but we didn't know where they were coming from," said Scott Benson, a fisheries scientist for the National Marine Fisheries Service.
Now, thanks to satellite transmitters that Benson and his colleagues strap on the backs of the massive sea turtles, they know the turtles plying California's rich waters are long-distance travelers.
They don't come from Mexico, as the scientists first thought, but nest on beaches in Indonesia, and make the 14,000-mile round trip to feed on succulent jellyfish. "Once they find the feast they probably stick with it until they eat it all up," Benson said.
Benson's colleagues search for the sea turtles in a small plane called a Partenuvia Observer specially outfitted with a clear Plexiglas nose, bubble windows and a downward-looking "belly window" to help scientists get a clear view of the ocean 650 feet beneath the plane.
"The visibility in this plane is really critical to the work we do," said Karin Forney, a research biologist, who helps organize the aerial turtle searches. "Occasionally the scientists on the boat find a turtle on their own, but for the most part we find them from the plane."
The turtle team has chartered the plane for all of September from Aspen Helicopters Inc. Whenever clear skies and light winds permit, pilot Ed Saenz piles in the plane with four scientists to search for turtles. They'll stay up for four hours at a stretch, which pushes the limits of their fuel and their bladders.
The turtles are difficult to find and harder to catch.
In the best year, Benson's team — which includes Peter Dutton, head of the National Marine Fisheries Service marine turtle program, and Jim Harvey of the Moss Landing Marine Lab — estimates there are about 300 turtles along the stretch of coast from Monterey to San Francisco Bay.
That year they caught eight turtles and fitted them with satellite transmitters.
When the aerial team spots a turtle, the work begins. Capt. John Douglas of Moss Landing Marine Lab is an expert at sneaking up on unsuspecting turtles. He can usually get the lab's 30-foot research boat, the Sheila B., within a few yards of a turtle without scaring it. This is close enough for the scientists to capture the turtles in a large net or to use a pole to attach a suction-cupped radio tag to its smooth, leathery back.
The radio tracker stays on the turtle for just a few hours, recording information about how deep the turtle dives and how long it stays down. The scientists will follow the turtle and retrieve the sensor from its back at the end of the day.
Although information from the radio trackers is useful, it doesn't help Benson learn about the turtles' long distance wanderings. For that he needs to catch the turtles and fit them with a satellite transmitter "backpack."
Catching a 1,000-pound animal that can dive to depths of 3,000 feet or more and hold its breath for an hour sounds like an impossible task, but team member Harvey says the turtles typically don't even know the boat is there until they find themselves surrounded by a net.
"They have a brain about the size of a walnut, so they're really not all that bright," Harvey said.
Once the turtle's in the net, the scientists haul it up a special slide and into the boat. It takes three strong men to control the turtle's flailing flippers while a vet checks its vital signs, takes blood and tissue samples for DNA analysis, and scientists fit it with the satellite backpack.
"We have padding on the sides of the boat like a nut house," Harvey said. "They can beat themselves up, and us, if we're not careful."
Instruments in the backpacks record information about the turtle's location, how deep it dives, how long it stays down and the temperature of the surrounding water. When the turtle surfaces to breathe, this information is beamed up to a satellite and back down to the scientists' computers.
The backpacks don't hurt the turtles and fall off naturally after a year or two.
The satellite tracking is part of a collaborative research effort called "Tagging of Pacific Pelagics." The data collected by the sensors helps scientists learn about the animals and about the ocean at the same time.
"We're trying to get data to help fishermen not catch the turtles," Benson said.
Endangered leatherbacks have been disappearing from the Pacific during the past 20 years. Scientists aren't sure why, but they hope by understanding them, they can help protect them.
"There aren't a lot of nesting beaches left in the Pacific," said team member Peter Dutton. "But there's still hope, the population hasn't collapsed yet and threats on the beach are declining."
For the time being, the turtles can count on the California coast to provide them with a juicy jellyfish feast each summer. With lots of fat stored up for their journey, the turtles will head across the Pacific to try their luck another year on the nesting beaches in Indonesia.
They are oddballs of the turtle world: They look different, eat different food and grow much faster than other sea turtles. They dive deeper than 3,000 feet, and hold their breath for up to an hour. They can weigh as much as 2,000 pounds, which is larger than other reptilian giants such as the saltwater crocodile and the komodo dragon.
They don't have a hard shell. Instead they're protected by a system of loosely interlocking bony plates covered by a thick leathery skin. They have oversized front flippers to help them swim long distances.
They feed mostly on jellyfish and other gelatinous open-ocean creatures. A yearly bloom of jellyfish attracts the turtles to the Monterey Bay each summer and fall. Sea nettles, brown jellyfish with long trailing tentacles, are their favorite meal.
They are an endangered species threatened by fishermen, who accidentally catch them in nets, and egg harvesters, who raid their nests. Global warming may prove a threat to these gentle giants.
For leatherbacks, sex is determined by how warm the eggs are before they hatch. Warmer eggs turn into females, which means as global temperatures rise, it could become difficult for females to find a male with which to mate.
To learn more about leatherbacks or the turtle lab, visit the Moss Landing Marine Lab open house 10 a.m. to 4 p.m. Saturday and Sunday. For information about the locations of tagged turtles visit www.toppcensus.org.
Oregon Live 17 Sep 06
Satellites shed light on turtles
In July 2005, a female leatherback sea turtle lumbered off a beach in Indonesia, paddled into the Pacific and began a swim that would take her 7,000 miles.
A year later, she arrived off the coast of Oregon, where she remains today, eating her fill of Pacific Northwest jellyfish.
That the leatherbacks forage in Oregon waters isn't news to researchers, but that was about all they knew. Now, thanks to satellite technology, they know where the turtles come from, when they left and how long they might stick around, says Scott Benson, a researcher with the National Marine Fisheries Service.
It could be a crucial tool in saving the endangered species, now numbering anywhere from 26,000 to 43,000 nesting females, down from 115,000 in 1980. The leatherback turtle population has declined dramatically in the past three decades and is on the verge of becoming extinct in the Pacific Ocean, Benson says.
By identifying the routes the turtles swim, researchers can help fishermen avoid accidentally catching the turtles in their gear.
And now that they know where these mammoth sea reptiles come from, they can work to enhance their nesting areas.
As part of the Tagging of Pacific Pelagic Program, Benson has put satellite transmitters on 11 leatherbacks from an Indonesian nesting beach, including the female swimming about 60 miles off the northern Oregon coast.
There are two populations of leatherback turtles in the Pacific Ocean -- one group nesting in Indonesia that forages off the North American coast and the other in Costa Rica and Mexico that forages off the South American coast.
The turtle off Oregon weighs about 1,100 pounds and is about 5 feet long. Benson expects she'll hang around the Pacific Northwest waters for another month or so, then head south to warmer waters.
"This is an ancient mariner," Benson says. "It's been around in its present form for about 70 million years, back to the time of the dinosaur. The purpose is to understand how we might improve the chances for this animal to survive another million years, or at least our lifetime."
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