Watching for nesting turtles and saving eggs isn’t easy, according to Eckert, who has studied sea turtles for more than two decades and has spent time in Zihuatanejo researching leatherback turtles, a species rarer than olive ridleys. Most turtles nest at night, so rescuers must stay awake until dawn, always on the move, often while battling insects and the high humidity.
“It’s absolutely hard work,” Eckert says. “You’ve never worked so hard in your life.”
Nesting time coincides with Zihuatanejo’s rainy season, which lasts from late June until early October, so members of Gonzalez’s staff often dig in downpours. Following government standards, the Tides records the number of eggs taken from each nest and the time and date the eggs were transferred. It’s a task that draws attention, both from curious tourists and municipal police, who check anyone digging up eggs to make sure they have government-issued cards that distinguish conservationists from poachers. Gonzalez keeps his in his wallet, next to his driver’s license.
The stakes are high. Once nesting turtles are eliminated from an area, it may take centuries before new turtles colonize it again, says Kenneth Lohmann, a University of North Carolina marine biologist who studies sea turtles. As evidence, he points to a case in Bermuda, where, in the 1960s, conservationists buried thousands of green turtle eggs from Costa Rica with the hopes of re-establishing a nesting population that had been wiped out by hunters and egg gatherers. Not a single turtle has returned to nest, Lohmann says.
Scientists believe that sea turtles learn the distinctive magnetic field that exists at the specific beach where they were born and then use this information to return to their home beach years later. So, while sea turtles are present throughout the world, you can’t remove eggs from, say, a Japanese beach, take them to Florida and establish a nesting population.
“They wouldn’t be able to find their way back to Florida — or Japan, either,” Lohmann says. “Most likely, they would just die.”
Lohmann’s magnetic-field theory was supported by a recent study he and his students conducted, in which they concluded that while a compass made by humans can only point northward, a turtle can determine both longitude and latitude. Essentially, Lohmann says, sea turtles navigate by sensing components of the earth’s magnetic field wherever they might be in the ocean.
“I’m really astounded by how good they are,” he says. “They can perceive the earth’s magnetic field and do much more with it than we can.”
Indeed, the turtles are no slouch when it comes to travel. Using satellite technology, scientists documented one leatherback’s journey of nearly 13,000 miles — from Indonesia to Oregon — from 2003 to 2005 before losing transmission. The Sea Turtle Conservancy based in Gainesville, Fla., has tracked leatherbacks crossing the Atlantic from Portugal to Central America in just five months, and the species, which dines primarily on jellyfish, has also been found in waters off Nova Scotia and the southern tip of Africa. Likewise, an olive ridley tagged in 2009 on an El Salvador beach has wandered more than 4,100 miles and was somewhere near the Galapagos Islands at last report, according to the conservancy. “They are sort of meanderers,” Wallace says.
But batteries wear out and transmitters fall off, so turtles remain enigmas of the sea. Even determining a turtle’s age can be difficult because growth rates are a function of water temperature and food availability. Scientists aren’t sure how long it takes for some species to reach sexual maturity, nor is there any consensus on how long turtles live. And while some populations are thought to be in decline and others are believed to be escalating, there is a substantial amount of guesswork.
“They spend most of their lives underwater and far off the coast,” Lohmann explains. “They’re difficult to study.”