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Online 25 Feb 07
Loggerheads digging fewer nests and no one knows why
By Dinah Voyles Pulver
Moonlight lends an eerie glow to the white-capped breakers as a dark shape begins to emerge. Ever so slowly, a female sea turtle inches her way toward the dune, drawn by some unknown instinct to the same beach year after year. At the foot of the dunes, she begins flinging sand to dig a nest for her eggs.
The mysterious ritual plays out in the warm velvet of summer nights, captivating those who see the rare turtles on Florida beaches.
But a far darker mystery is unfolding for loggerhead turtles. They're digging far fewer nests on Florida beaches and the federal government has put together a task force to figure out why.
Nests have plummeted 40 percent since 1998. The decline could signal a major threat to the species because more than 90 percent of the world's loggerheads nest in only two places: Florida and Oman on the Indian Ocean.
"The falling numbers don't necessarily mean fewer turtles," said Sheryan Epperly, a biologist with the National Marine Fisheries Service, which organized the task force. "There could be a number of explanations that don't involve a change in the population size."
DECREASE IS BAFFLING
The decline is even more mysterious because green turtles and leatherbacks are digging more nests in Florida.
Green and leatherback turtles are considered endangered, in imminent danger of extinction, while loggerheads are threatened, meaning their population is larger but still in danger.
"There are things going on all the time, such as disease and boat strikes," said Anne Meylan, a senior research scientist with the Florida Fish and Wildlife Conservation Commission.
"What's happening with the turtles is probably happening far away from Florida."
But turtles also face threats here. In a November report, Meylan and her colleagues said development and erosion are limiting where turtles can nest. Turtles still nest by the thousands at Canaveral National Seashore but only hundreds do along the urban sections of the beach in Volusia and Flagler.
Turtles spend much of their lives in international waters that the United States can't control, Meylan said.
But nesting habitat is one thing that government officials can protect. Officials restrict beachfront lighting during the summer nesting season to prevent baby turtles from distractions that lead them away from the ocean rather than toward it. But hatchlings still get disoriented and die.
Growing numbers of turtles also are being hit by boats, said Meylan's report, while pollution, trash and chemicals in the water may keep the turtles from nesting.
IS FISHING A FACTOR?
Some experts fear long-line fishing in oceans around the world kills younger turtles before they have a chance to begin nesting.
One 2004 Duke University study concluded 250,000 loggerheads are snared on long-line hooks every year. The hooks, baited with squid and mullet, dangle on lines that stretch up to 40 miles.
Loggerheads are more susceptible than greens and leatherbacks because of their diets, said David Godfrey, director of the Caribbean Conservation Corp., a Gainesville-based turtle advocacy group.
In the past five years, observers traveled on fishing boats, tagging accidentally hooked turtles to track what happens after they're released. Early results showed the turtles survived when caught "lightly" on hooks, said Chris Sasso, a fisheries service biologist in Miami.
Now, the service is following turtles hooked more severely, such as the ones that swallow the hooks.
Meanwhile, the U.S. now requires circle-shaped hooks rather than the more hazardous j-shaped hooks, Epperly said. This country only represents about 10 percent of the commercial fishing in the North Atlantic, she said. However, international fishing bodies have begun encouraging use of circle hooks.
Turtle experts hope they can solve the mystery of the loggerheads' nesting decline, so future generations can experience the thrill of watching a female loggerhead cast the last flipper of sand over her nest and crawl back to the ocean, satisfied her work is done.
Related articles on Global marine issues and sea turtles
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