For 50 years, scientists have attempted to discover where newly hatched green sea turtles go before they reappear as juveniles in the coastal sea grass.
Now, UF researchers have a major clue to what's been dubbed as the mystery of "the green turtles' lost years."
They say their findings, published in the online journal "Biology Letters," could lead to more effective protection of these endangered animals.
Kimberly Reich, a doctoral candidate in zoology and lead author of the study, found a clue to the turtles' whereabouts hidden on the backs of their shells.
Analyzing isotopes of nitrogen and carbon from 44 turtles near the island of Great Inagua in the Bahamas, Reich determined that green turtles spend their formative years living in deep water oceanic habitats and have a carnivorous diet. The turtles dine mostly on jellyfish and other soft-bodied marine organisms at that time.
The result was interesting because green turtles are the only herbivorous adult sea turtle species, Reich said.
Drawing from previous knowledge about another turtle species, Reich estimated that the green turtles go through "approximately a three-to five-year oceanic stage" before returning to shallower waters.
The secret to the turtles' lost years was in their scute, she said.
Scute is the hardened tissue covering a turtle's bony shell and is made of keratin, like human fingernails or hair.
Scute retains the chemical signature of the environment the turtle was living in and the turtle's diet.
Although this research has led to a better understanding of the turtles' habitat and diet during these "lost years," Reich said there is still some mystery about their exact location in the ocean.
"We can't go put our finger on a map and say, 'This is where they are,'" she said.
Karen Bjorndal, director of UF's Archie Carr Center for Sea Turtle Research, hypothesized that the green turtles' particular swimming depth and coloration might have kept them hidden all these years.
Reich said she hopes the discovery of green turtles in deep waters will add weight to the argument for putting more protective measures in place.
All sea turtle species are either threatened or endangered, and green turtles are endangered everywhere they live, Reich said.
She added that the main threats to the turtles in deep sea waters are human-related.
"We know that loggerhead and leatherback turtles, which are oceanic, are significantly impacted by long-line fishing," she said.
"They get hooked by the line, and they drown."
Green sea turtles face similar dangers. Discussion has been under way to develop safer, turtle-friendly hooks, as well as to regulate the depths hooks can descend to and the types of baits used.
Human trash also causes a major problem for sea turtles.
"If you ingest enough debris, you have no room for food," Reich said. "The debris doesn't pass and you die."
Reich, who began the study six years ago, said her research directly links with the work of Archie Carr, the founder of the UF sea turtle research center.
Carr began searching for the green turtles in the 1950s. During all the years he searched, Reich said Carr didn't meet one person who ever spotted a baby green turtle.
"There have been thousands and thousands of hours spent looking for these turtles," she said. "Thousands of hours that Archie Carr spent traveling through the Caribbean and through South America, talking to fishermen, saying 'Do you see them? Do you see them?'"
