After hatching, sea turtles spend a minimum of 1–2 years at sea, but it’s been a mystery as to what they do and where they go during this time. A remarkable new study, published in the Proceedings of the Royal Society B, managed to track 17 tiny loggerhead turtles as they braved the elements and escaped predators, like sharks.
The small turtles were outfitted with lightweight, solar-powered satellite transmitters that gathered data on temperatures and the turtles’ movements. Sun exposure could also be inferred, based on solar-charging rates.
Project leader Katherine Mansfield of the University of Florida’s Marine Turtle Research Group and her colleagues collected tiny turtles along the southeast coast of Florida and reared them until they were at least 3.5 months old. Bryan Wallace, an adjunct professor at Duke University’s School of the Environment, said the high-tech transmitters do not interfere with swimming, and might later be affixed to animals like great white sharks to better determine where they go.
Mansfield told Discovery News that turtles like this, after they go out to sea for at least a couple of years, “start showing up again in near-shore habitats like the Chesapeake Bay, North Carolina’s Sounds, and the Indian River Lagoon on the U.S. East Coast.” This little turtle has a long way to go, however, before hoping to make such destinations.
Turtles aren’t exactly known for being noisy, and Mansfield said that “as far as we know, they don’t socially interact while at sea -- sorry for all those 'Finding Nemo' fans!” She added, however, that “it is possible that turtles may cluster in some areas where currents push certain habitats together, or when certain temperatures are available.”
Many turtles follow what is known as the North Atlantic Subtropical Gyre. It's a circular current system that moves clockwise around the North Atlantic as part of the Gulf Stream, "a fast-moving current -- almost like a river within the ocean -- that runs up the East Coast to about Cape Hatteras, where it then veers to the east or northeast,” Mansfield explained.
Not all turtles follow that pattern, though, to get to places like the Azores. “Some may drop out of the currents of the interior of the circle,” she said. “We think they may be doing this to follow either spin-off currents (like eddies) and/or resource availability, like Sargassum (a type of brown seaweed) habitat that is known to drop out of the Gyre circulation into the Sargasso Sea.”
“I would imagine that life at sea would be very, very dynamic,” Mansfield said. It's no wonder that the little turtles seek out floating seaweed for protection and for clinging on to in choppy water.
“A turtle may find a safe habitat to float with one day, but lose it the next,” she said. “This is very different from what we, as humans, try to create in our societies -- a safe place and access to food and shelter.”
Depending on the species, sea turtles may eat small crustaceans and other organisms typically found floating around in Sargassum seaweed. The researchers also expect that some sea turtles, such as young leatherbacks, feast on jellyfish and other gelatinous items.
The main predators of the turtles are likely larger fish and sharks.
Sea turtles tend to stay close to the surface, a surprising find of the study. This probably helps to keep them warm.
Turtles at sea “might be much warmer than we’d previously guessed,” said Nathan Putnam of Oregon State University’s Department of Fisheries and Wildlife. This suggests higher metabolism rates that, in turn, could mean “some turtles, at least, could grow much more rapidly than we thought.”
“All sea turtle species are considered endangered or threatened throughout their range,” Mansfield said. “In order to effectively conserve and protect a species, it is important to fully understand the animal’s life history -- where they go, how they interact with their environment, when they are found in particular areas or habitats.”
She continued, “Our research provides a few new pieces to the ‘lost years’ puzzle. We are hoping that our data will open up more questions about the turtles early in-water behavior.”