Sea turtles can swim hundreds – and sometimes thousands – of miles to reach different areas of marine habitat. Tracking this highly migratory species by satellite is shedding light on sea turtles’ unique feeding locations and pathways of movement.
Sea Turtle Conservation Bonaire (STCB) – in collaboration withthe Wider Caribbean Sea Turtle Network (WIDECAST) – is working to build a trustworthy base of information about sea turtles. According to this organization, it’s imperative to learn about the species’ different marine habitats and their pathways of movement in order to best protect them.
“Research into the behavior and life cycle of sea turtles has taught us that these creatures do not generally nest and feed in the same area,” says Mabel Nava, STCB representative. “Sea turtles are highly migratory, often traveling hundreds or even thousands of kilometers between the beaches where they lay their eggs and the foraging grounds where they spend much of their time at sea.”
Satellite telemetry is helping explain where sea turtles surrounding Bonaire and Klein Bonaire are going and the routes they’re using to get there. “Satellite tracking involves attaching a special device called a Platform Terminal Transmitter (or PTT) to a sea turtle’s carapace (shell),” says Mabel. These highly sophisticated, expensive pieces of technology resemble an oblong-shaped box with an antenna, and they are available in different colors and sizes. “While the battery in the transmitter has a “low power” life expectancy in excess of 2000 hours, the actual life expectancy of the battery is dependent upon many variables. Our experience has been that the transmitter will continue to send signals for up to 4 or 5 months.”
Because satellite telemetry tags are expensive and valuable in contributing migratory data, researchers work hard to ensure these tags are applied correctly to the shell. The process for attaching a transmitter to a sea turtle is as follows: “you must prepare the turtle’s carapace and ensure rough areas are smoothed flat and that all grease attaching the transmitter is removed,” explains Mabel. “First, we remove any barnacles or fouling organisms that might come off later. Sand paper is then used to clean and lightly score the carapace. Next we scrub and wash it to remove all sanding dust and grease so that the glue can stick very well. Finally we wipe the carapace with a chemical called acetone to remove the last traces of all grease. Now we are ready to apply the epoxy which is pasted over a large area in the front half of the turtle’s carapace. The transmitter is then pressed into place and strips of the fiberglass cloth coated with epoxy are placed in a crisscross fashion over the transmitter and the shell of the turtle. The epoxy will be dry in about 30 minutes and the entire process takes about an hour or so. The turtle will have already been tagged, measured and photographed and once the epoxy sets, the turtle can be released to crawl back to the ocean. If applied correctly the transmitter will stay in place for about a year.”
Attaching satellite transmitters to sea turtles is a harmless process, and the tags are designed to mimimize disturbance of the animal’s natural movements. From STCB’s experiences, sea turtles quickly become accustomed to their tag.
Once correctly attached to a sea turtle’s carapace, the satellite transmitter begins to work. “The PTT sends a message to a satellite each time the turtle comes to the surface to breathe,” says Mabel. “A ground station receives data from the satellite regarding the location of the turtle and forwards it to STCB via email. We then plot the data onto a map. There are thousands of satellite transmitters being used around the world today to monitor ocean circulation, natural hazards, water resources, polar currents, fishing vessels, shipping and offshore oil and wildlife such as albatrosses, whales, polar bears and of course, sea turtles! Generally, after about a year the transmitters quit working and fall safely off the turtle.”
STCB are currently following the movements of tagged loggerhead, green and hawksbill sea turtles, and recent results are fascinating: “None of the 17 tracked turtles remained in the waters around Bonaire and Klein Bonaire beyond the breeding season,” reports Mabel. “Turtles moved 149-1820 miles to reach foraging areas encompassing multiple jurisdictions and therefore highlighting the need for concerted international efforts in the management and conservation of marine turtle stocks.” Interested parties can even follow a few of these tagged ocean travelers online, and read all about sea turtle tracking results.