The remarkable reptiles known as loggerhead turtles may be in trouble.
These sea turtles live 60 years or longer and can swim across the Atlantic Ocean and back. Females return to the precise Florida beaches where they were born - including some in Pinellas and Hillsborough counties - so they can crawl onto shore and lay eggs in the sand.
But during the past half-dozen years, loggerhead turtle nesting in Florida has dropped sharply. Fewer loggerheads are laying eggs in Florida, even though other Florida sea turtles, such as greens and leatherbacks, actually are nesting more.
David Godfrey, executive director of the Caribbean Conservation Corp., said the dropoff in loggerhead nesting "really represents a drastic decline in the Western Hemisphere population." He worries that a species that has survived since the time of the dinosaurs "could get to a point where extinction is not beyond the realm of possibility within our lifetimes."
The recent decline in Florida's loggerhead nesting concerns researchers and environmentalists, even though they expect some ups and downs in the data. For years, loggerheads were considered a conservation success story, a change from the days of old-time Florida restaurants that specialized in turtle soup.
A downturn in Florida nesting is significant because more than 90 percent of the world's loggerheads nest either in the Middle Eastern nation of Oman, or in Florida.
Scientists and conservationists say they suspect two main causes of the decline. One is commercial fishing - loggerheads sometimes get caught in long-line fishing in the Atlantic Ocean, for example. Another is the increasing number of sea turtle "strandings," cases in which a group of sea turtles is found close to shore, dead or dying, possibly from toxins or disease.
"It certainly is troubling and it means that we ought to pay very close attention to these mortality factors," said Blair Witherington, a research scientist for the Florida Fish and Wildlife Conservation Commission.
Scientists are paying attention, especially to a mysterious series of turtle deaths. At various places around the state, groups of turtles have been found stricken, floating and struggling to stay alive.
"We do know that some toxic element or disease has been affecting adult loggerheads in Florida waters for about five years," Godfrey said.
But a central cause has not been found, and scientists say these episodes deserve more study. In some of these cases, Red Tide is considered a factor.
Such as last summer, when scientists from the Mote Marine Laboratory in Sarasota tagged a loggerhead turtle named Ariel with a satellite-tracking device and released her. She later swam across a stretch of the Gulf of Mexico affected by Red Tide.
"She ventured very close in shore, actually right off St. Pete Beach," said Tony Tucker, Mote's program manager for sea turtle conservation and research.
Afterward, her behavior changed; eventually the satellite device showed she was floating on the surface. Scientists tried, but were unable, to recover her body.
"I can't say Red Tide was absolutely the cause of death, but we have a very strong suspicion," Tucker said.
Fishing also may be a factor. Witherington said long-line fishing kills thousands of sea turtles per year. That's especially true in Atlantic fishing areas where the mileslong fishing lines stay relatively close to the surface, where the loggerheads like to feed.
"Loggerheads are going after the bait and getting hooked on the bait just like the fish would," Godfrey said.
Shrimpers have gone to great lengths to install "turtle excluder devices," or TEDs, in trawling nets, but they're not perfect, Witherington said.
"Although TEDs work, they won't work completely," said Witherington. "Shrimp trawling in U.S. waters probably still kills a lot of loggerheads."
It's worth noting that loggerhead nesting has gone down even as nesting in Florida has increased for green turtles and leatherback turtles. Unlike loggerheads, the green and leatherback turtles are not as likely to be harmed by long-line fishing, he said.
But Bob Jones, executive director of the Southeastern Fisheries Association, said critics condemn commercial fishing without checking the facts.
"From my perspective, the development and the changing of the natural beaches and everything has had more to do with the degradation of Florida's environment than anything else," he said.
Overdevelopment is known to be a factor threatening loggerhead turtles, especially because lights on shore can confuse the hatchlings and stop them from going out to sea. But that is not considered a major reason for the sharp decline. The eight hurricanes that hit Florida in 2004 and 2005 probably are not the cause of the decline either, Godfrey said, because loggerheads take 20 to 30 years to mature, so the impact of those storms would not be evident for decades.