UF-Led Research Team Finds Sea Turtles Can Travel A Third Of The Planet

August 19, 1996

GAINESVILLE — By using natural genetic “tags,” an international team of scientists has demonstrated that sea turtles migrate further than any other marine animal except seabirds.

Their findings were verified recently after Mexican biologist Antonio Resendiz tagged a sick turtle the old-fashioned way — with a metal clip. The turtle was nursed back to health and released into the waters off Mexico and later was discovered in Japan.

University of Florida biologist Brian Bowen has, for years, been leading a team of researchers studying juvenile loggerhead near Baja California, Mexico, that had traveled to Mexico from nesting beaches in Japan, over 7,000 miles across the Pacific Ocean.

“What we demonstrated with molecular markers was that the Baja turtles were coming from Japan. But we couldn’t verify they were returning,” Bowen said. “This one turtle verified that.”

Finding the birthplace of the sea turtles is important because researchers are finally able to track the turtles across oceanic expanses as the juvenile animals migrate long distances from the nesting colony to feeding areas.

As adults, the turtles instinctively migrate back to the nesting colony where they were born, but these migrations are increasingly dangerous to the turtles as a growing number of man-made hazards block their path. Thousands of sea turtles die every year in nets designed to catch fish and shrimp. In order to understand the impact of these deaths, it’s necessary to know which nesting colonies are producing the turtles killed in fishing nets.

Since sea turtles return to the nesting area where they were born, and do not interbreed with other nesting populations, each nesting colony contains unique DNA segments. These genetic markers can be used to identify the turtles far from the nesting colony.

Juvenile loggerhead turtles were known to feed off Baja California, but for 20 years their origin was a mystery because there are no nesting colonies nearby. The genetic markers link these turtles to the nesting beaches in Japan, and demonstrate that they traverse the entire Pacific Ocean, approximately one third of the planet. This migration puts the turtles in danger from drift nets and longline fisheries, which drown about 4,000 turtles per year in the North Pacific.

“The genetic data have strong conservation implications because they allow wildlife managers to identify the source of animals killed on the high seas,” Bowen said.

Under the United Nations Convention on the Law of the High Seas, nations that host the developmental habitat for migratory marine animals have jurisdiction over these animals as they roam the open ocean. Since the loggerhead turtles hatch in Japan and mature in Mexico, the United Nation Convention gives these countries a legal means to control the slaughter of sea turtles.

Biologists in Mexico and Japan are now lobbying their governments to take action against anyone found killing turtles that inhabited their waters.

The effort is just one aspect of the work that involves Bowen, who works for the Biotechnology Program at UF, which has established a series of labs to apply state-of-the-art biotechnology to conservation problems. The genetic tagging studies are part of a research program begun at UF by the late Professor Archie Carr which continues through the Archie Carr Center for Sea Turtle Research.

“We’re building on the scientific foundation that Archie Carr assembled over three decades,” Bowen said. “He tagged turtles with metal clips originally designed for cattle. We’re still using tags, but we’re reaching into the cells and pulling out naturally inherited tags. Its is unfortunate that Dr. Carr didn’t live long enough to see this extent of his work.”