Loggerhead sea turtles go the distance

Loggerhead sea turtles travel from their birth place in Japan to their feeding grounds in Baja, Mexico, and back to Japan.

July 19, 1999
Web posted at: 1:27 p.m. EDT (1727 GMT)

Like their cousin the tortoise, sea turtles may take their time, but they are remarkably persistent, according to new evidence from an Earthwatch sponsored researcher. A satellite tag was recovered in Baja, Mexico, from the flipper of a Loggerhead sea turtle that was tagged in Japan. The tag confirms that endangered loggerheads shuttle nearly 7,500 miles (12,000 kilometers) each way across the Pacific Ocean between nesting beaches in Japan and feeding grounds off the coast of Mexico.

"A paucity of tag returns is common in sea turtle research, making this a great find," researcher Dr. Wallace J. Nichols said. "The small turtle, which began its journey as a 6 inch (16 cm), hand-sized juvenile, made the 12,000-plus kilometer trip in the time it has taken me to get my Ph.D. — six years!" he said.

In 1996, Nichols, a Marshall Fellow at the University of Arizona's School of Renewable Natural Resources, had satellite-tagged an adult female Loggerhead turtle named Adelita. Over the course of 11 months in 1996-97, he tracked her from Baja 10,000 kilometers across the Pacific to nesting grounds in Japan. This was the first indication that loggerheads made such a long journey.

But Adelita's signal was lost somewhere off the Japanese coast. Since mature sea turtles like Adelita usually return to the beach where they hatched to lay eggs, Nichols figured that, in turn, juvenile loggerhead turtles hatched in Japan must be migrating across the Pacific, feeding and maturing off Baja before returning to Japan to nest, but he had no proof of the first half of the huge migration loop.

The exciting evidence came from a Mexican fisherman who reported finding a flipper tag on a different loggerhead with a Japanese return address. However, the tag had been on his key chain for five years. The fisherman had initially been afraid to report his capture of an endangered species but over time he began to trust the researchers, Nichols said.

"Because of our work with the fishing communities collecting turtle information over the past several years," Nichols said, "this fellow finally felt comfortable sharing the tag."

"Baja fishermen have provided great support for the project and have a vested interest in sea turtle recovery as turtles are a traditional food source — one that is still used regularly."

Nichols confirmed that the tag is from a turtle hatched on Yakushima Island, where a third of Japan's loggerheads nest, and the exact beach Nichols was visiting. The hatchling was raised for one year at the Okinawa Aquarium by Drs. Teruya and Uchida, tagged with the small metal tag bearing #572, and released in 1988. Six years later it was captured in San Carlos, Baja California by the fisherman.

Nichols said one Japanese researcher, Naoki Kamezaki, estimated the Japanese adult loggerhead population at a few thousand. "It's quite difficult to guess at the total population," he said.

"I hope that this trip marks the beginning of many years of close collaboration between U.S., Mexican and Japanese researchers, fishermen and conservationists in our efforts to recover Pacific Loggerhead populations," Nichols said.

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