Tracking Sea Turtles

Mote Marine Laboratory, Sarasota, Florida, August 1st, 2005

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The moon casts a gauzy, yellow light along the tops of curling waves. It’s after midnight along Florida’s Gulf Coast. Waves knead the shores, repetitive and predictable. Until she arrives.

Like magic, the sea turtle’s shadowy figure remains on shore as the shimmering tide pulls away. Then she hoists her 250-pound body methodically up the white-sand slope; 30 minutes later she reaches an area on the upper banks to lay her eggs.

She tosses sand gently over her offspring and leaves them to incubate. A gathered group murmurs about how heavy and large she appears, how her head is larger than that of any human there. Yet no one can speak about what happens after she vanishes back into the ocean. It’s simply mysterious — that other 99 percent of a female sea turtle’s life.

“The essential question is ‘where are they going?’ ” said Dr. Tony Tucker as he gazed out to sea. Tucker, manager of Mote’s Sea Turtle Conservation and Research Program, is working with scientists around the world to answer this quintessential turtle question by attaching satellite tags to the turtles so resource managers can understand the animals’ life history and better protect their dwindling numbers.

Sea turtle plight

Since the 1950s, scientists have used flipper tags to identify and study individual sea turtles. They’ve learned a lot about turtle nesting areas, diet and body dimensions — ranging from the average size of an 80 pound, 3-foot-long Kemp’s ridley to a 1-ton, 8-foot-long leatherback. The size differences hint at different sea turtle species’ wide range of prey and habitat but that’s all the information really offers — hints. It doesn’t tell researchers much about the places in the sea that are essential to the turtles’ survival. Today five out of the seven sea turtle species are listed as endangered and loggerheads and olive ridleys are listed as threatened.

One of the most striking examples of a declining population is the story of the Kemp’s ridley. The species is known to nest on only one beach in the world, Rancho Nuevo in the Gulf of Mexico. A historical video once captured about 40,000 females nesting at once — all females of this species nest at the same time. The cluster was so massive that a person could have walked across the beach on the turtles’ backs. But by the 1980s, fewer than 300 Kemp’s ridleys were coming ashore to nest at Rancho Nuevo.

Hundreds of books and papers highlight human activities that contribute to the crash of turtle populations: Hunters capture eggs, females and adults for food, art, jewelry and even for aphrodisiacs; nesting beaches erode each year because of coastal development; artificial lights hinder the ability of adult females and hatchlings to find their way back to the sea. Such land-based impacts are now illegal or closely regulated, but resource managers still don’t fully understand the impacts turtles face at sea. With better technology, scientists like Tucker hope that will soon change.

New tools, new insights

For 20 years, scientists have been experimenting with the use of tags that could transmit a turtle’s whereabouts using the satellites that orbit the earth. The early versions lasted a few months. “The first turtle we tracked went from Mexico to Japan,” said Dr. Wallace J. Nichols, co-director of the Blue Ocean Institute and a research associate at the California Academy of Sciences, who was involved in these early studies.

Although these long treks impressed Nichols and others, today science is trying to look at more localized movements to home in on obstacles to the turtles’ coastal migrations. “The more we know about where and what the sea turtles are doing, the more we can keep nets away from them and keep hooks away from them,” he said.

An estimated 55,000 turtles die each year after being drowned in shrimp trawling nets alone, and oil spills are responsible for an estimated 6 percent of the dead turtles that wash up on U.S. shores. If scientists knew more about where turtles were traveling, managers would have more information to help protect them. “Do their inter-nesting areas overlap with harmful algal blooms? Are they swimming into areas that are dredged for beach renourishment projects? Is boat traffic a potential hazard?” Tucker asked.

Logging the lessons

Female loggerheads come each year to sandy beaches near Mote’s Sarasota campus to lay their eggs. At 3 a.m. on a hot July morning, a female crawled ashore on Casey Key. Tucker and a team of volunteers watched as she finished her nest then started her sand-slide return to the sea. The team moved fast, surrounding the turtle with a portable wooden box.

The turtle let out a few snore-like grunts then quieted as a cool, wet towel was draped over her head. The crew measured her — nearly 3 1/2-feet long and 2 1/2-feet wide — then cleaned off clinging barnacles. The volunteers stepped aside as Tucker used a glue gun to carefully squeeze blobs of gray epoxy onto the turtle’s shell. He then placed a tag the size of a Cracker Jack box with a 6-inch antenna on the turtle.

The crew cat-napped for an hour while the first epoxy layer dried, then watched as Tucker dripped more epoxy over the tag, careful to avoid the screw heads on each end. “Saltwater connects the two screws and then the tag shuts off,” Tucker said. When the screws emerge from the water together as the turtle comes up to take a breath the tag turns back on and sends a signal to a satellite. “It’s a saltwater switch. It’s especially for marine animals as they come out of the water.”

Since the first satellite tags were developed, the technology has improved dramatically, Nichols said. They have smaller batteries, are more compact and stick tightly with new adhesives. The quality and data produced from the tags will probably improve even more over the next 10 years.

But the research has a cost — the tags Tucker uses are $3,000 apiece. Scientists like Nichols hope researchers will share data with each other to maximize resources, combine findings and, in the end, learn more about the turtles. “This is expensive stuff, the more people that share data, the better,” he said.

After a second hour to let the epoxy set, the sun rose and the group lifted the wooden box from around the female loggerhead. Complete with a new nickname, “Squirt,” the turtle and her new tag were on their way.

Logging on

Information from Squirt’s tag is now being picked up by orbiting satellites then relayed to receiving stations. The information is uploaded to the web and the turtle’s location is plotted on a map. Over the next year, researchers will be able to follow the turtle — one of five loggerheads Tony Tucker tagged during the summer of 2005 — on her journeys. Tucker hopes the data will draw international attention to the turtles’ travels and lead to new ways to protect these endangered species. These are the paths of four of the turtles. For updated maps, click here.

How Squirt got her name

In 2004, elementary school science teacher Chris Lener from the New Canaan Country School in Connecticut participated in an Earthwatch expedition focused on Florida’s endangered sea turtles. She worked in Mote’s Sea Turtle Conservation and Research Program capturing, tagging and releasing turtles as part of an ongoing research project.

When it ended, she asked Dr. Tony Tucker how she could stay involved. “I thought it was a great opportunity not just for me, but for our whole school to be involved in,” Lener said. “The project addresses basic marine science as well as environmental and conservation issues that are key to our science curriculum. The project is so exciting and its various components can be used by our science classes across the grade levels.”

Lener applied for a Jeniam Foundation grant to help fund three satellite tags. When she received it, Lener traveled to Sarasota to help with the satellite tagging project, which she will use in lessons for students in grades one through four.

As part of the sponsorship, the students also got to name the three turtles. So now they’re following along as Squirt, Ninja and Yertle travel the oceans. They’ll also be watching two more turtles — sponsored by the Mote Scientific Foundation and a private donor — named Virginia and Casey.