To help endangered turtles, scientists try satellite tracking
Turtles' numbers drop in the Pacific, but more are showing up in the Atlantic. Scientists hope to learn why.
Leatherback sea turtles have survived since a time when dinosaurs roamed the earth. But if current trends in the Pacific spread around the globe, the mild-mannered, ocean-going reptiles may soon follow the triceratops and T-rex into biological oblivion.
Now, researchers are using satellite tracking to find out more about the turtles' habits. Call it GPS for reptiles. And it just might provide the clue that could save the giant turtles from extinction.
The experiment was prompted by a surprising discovery on beaches along Florida's eastern shoreline. Unlike in the Pacific Ocean, where leatherback turtle populations are in a dangerous nosedive, nesting females are showing up in increasing numbers on Florida beaches.
Sea turtle experts Scott Eckert and Llew Ehrhart want to find out why, and they are hoping the answer may help spark a recovery of leatherback populations worldwide.
"The leatherback is the most endangered of the marine turtles," says Mr. Eckert of the Hubbs-SeaWorld Research Institute in San Diego. "The global population has been dropping faster than we have ever seen for any of the sea turtles. It has been quite extreme."
At a crucial leatherback nesting beach in Mexico, for example, the number of nesting females has dropped from more than 75,000 in the early 1980s to fewer than 1,000 today, Eckert says.
Meanwhile on the east coast of Florida and at key nesting beaches in the Caribbean, the number of female leatherbacks is on the upswing. Although the total numbers are still far smaller than in Pacific populations, the trend is at least in the right direction.
"Through the first nine years of the [turtle monitoring] project we averaged about one [leatherback] nest every other year," says Mr. Ehrhart of the University of Central Florida in Orlando. "Now in the past four years we've had 65 leatherback nests, including 30 last year."
In an effort to better understand what is happening in the Atlantic, Eckert is using a satellite-tracking system to follow a female leatherback, who has nested 10 times in recent weeks on the beach at the Archie Carr National Wildlife Refuge. He believes leatherbacks in the Atlantic may make annual migrations to the fish-rich waters off Nova Scotia and Newfoundland, but such theories are difficult to verify without following the giant turtles.
Like other sea turtles, leatherbacks come ashore at night to lay their eggs. But the giants, who can reach 700 pounds, spend most of their time far from land, cruising the world's oceans. They feed primarily on jellyfish and may swim as many as 6,000 miles a year. Until Eckert started following leatherbacks with satellite-tracking devices, no one knew for sure where they went after nesting.
His satellite-aided research in the Pacific suggests that leatherbacks are being killed in large numbers by commercial fishermen from Peru and Chile who use nets and long-line techniques to catch swordfish. The turtles become tangled in the nets and fishing lines and drown.
Similar problems exist in the Atlantic. US-based shrimp trawlers are equipped with a special escape hatch in their nets that allows loggerhead and green turtles to escape. But the much larger leatherbacks are too big to fit through the hatch and are drawn into the nets.
Eckert hopes that his research will provide enough information about migration patterns and habitat to enable scientists to predict leatherbacks' presence in commercial fishing waters.
Such knowledge could lead to warning fishermen of the presence of turtles, or even closing certain areas of ocean to fishing to avoid turtle encounters.
"I don't know a single fisherman out there who wants to catch sea turtles. They are more of a hassle and are very destructive of their gear," Eckert says.
Linda Candler of the National Fisheries Institute in Washington says US commercial fishermen are largely sympathetic to efforts to prevent turtle deaths.
"The shrimpers have sacrificed a great deal of their catch by putting a hole in their nets, and larger holes for leatherbacks would mean even more of their catch lost," Ms. Candler says. So far, she says, the holes are a trade-off the industry has been willing to make. But she adds, "Will consumers be willing to pay higher prices for shrimp, knowing that part of the cost is for saving turtles?"
Ehrhart says knowledge about leatherbacks may make a critical difference. "Maybe we can improve the notice we give to commercial fishermen and improve their scheduling," he says. "A little knowledge is a wonderful thing."
(c) Copyright 2000. The Christian Science Publishing Society