On an isolated beach in Bird’s Head Peninsula, Indonesia, a female leatherback turtle shuffles out of the ocean and onto the shore, ready to lay her eggs. Under the cover of night she excavates a hole in the sand, depositing anywhere from 80 to 100 eggs inside. Using her flippers she flicks sand over the eggs, hiding them from potential predators. Then, shuffling away, she returns to the turquoise waters ready to make an 8,500-mile journey across the Pacific Ocean to the California coast.
That incredible migration is now at its peak, as leatherbacks arrive to feed on brown sea nettle jellyfish, abundant in Californian waters. Last year, the leatherback turtle became California’s official marine reptile and October 15th was designated Pacific Leatherback Conservation Day. But even at the height of their presence in Californian waters, the turtles remain largely elusive to the public and to science. It has only been during the past 10 years that researchers have begun to learn more about these rare animals, said Teri Shore, program director at the Turtle Island Restoration Network.
“We didn’t know where these turtles came from and we didn’t know what their status was,” she said. “So this is not only new for Californians, but it’s also new to science.”
One of the reasons for their obscurity is their ability to dive to depths of 4,200 feet—deeper than any other turtle. And unlike on their nesting beaches in Indonesia, leatherbacks rarely venture onto Californian shores.
Hatchling sea turtles. Photo by Jeroen Looye.
“I think the reason people don’t know a lot about them is because they’re out of sight, out of mind,” said Shore. “They live in an ocean environment and only stick their head out to take a breath, so they spend most of their time underwater diving and eating.”
A more sobering reason stems from their critically endangered status. Scientists estimate that there are only 2,000-5,700 nesting female leatherback turtles left in the world. Ricardo Tapilatu, a researcher who studies leatherbacks at their nesting site in Indonesia, said leatherback turtle populations have declined more than 78 percent since 1981.
“We have identified reductions caused by invasive species such as feral pigs and dogs who live in the villages surrounding the beach,” Tapilatu said. “They wander onto the beach, dig up the nest and eat the eggs because they’re looking for an opportunistic hunt.”
Global warming is also changing the temperature of leatherback nests, which need to be around 85 degrees Fahrenheit to produce a mix of male and female hatchlings. Warmer temperatures mean more female hatchlings, while temperatures that are too hot can result in low hatching success.
“We have been monitoring beach temperatures since 2005 and we found that the nest temperatures are exceeding the tolerable temperature for leatherback egg development, resulting in biased sex ratios and low hatching success,” Tapilatu said.
Shore said that closer to California, commercial fisheries are the primary threat to adult leatherback turtles. Because leatherbacks travel such long distances across the ocean they are at risk of being accidentally hooked by longline fishing boats in the Pacific.
“Along our coast we have protections in place that have significantly reduced their capture in the swordfish fishery,” she said. “But the longliners in the Pacific and in Hawaii are still taking their toll.”
Courtesy of NOAA
On Pacific Leatherback Conservation day, Shore stresses the importance of individual action and raising awareness about our seafood consumption. Turtle Island Restoration Network have been promoting such action through their ‘Pacific Conservation Pledge’ asking signatories to refrain from purchasing seafood caught in high-bycatch fisheries such as swordfish or tuna.
“We don’t have a giant event planned but we’re really stressing the importance of individual action through the pledge,” said Shore. “Additionally, California is hosting a leatherback summit, which is not open to the public, but is rather a gathering of scientists who work with leatherback turtles along the coast and at their nesting beaches.”
“This is the first time that we’re bringing them together in California to try and strengthen the international conservation and collaboration between scientists and governments.”
Earlier this year the United States National Oceanographic and Atmospheric Administration (NOAA), designated nearly 42,000 square miles of ocean along the U.S. West Coast as critical habitat for Pacific leatherback turtles. During the leatherback migration both longline and gill-net fishing—also a threat to turtles—are banned along the West Coast.
“Although the state of California has a really good record of protecting these turtles from the fisheries with critical habitat, the turtles are still declining,” Shore said. “Even though in Indonesia they are protecting their nesting beaches and the waters off the beach, the turtles are still declining.
“So what more could we or should we, on either side of the ocean, be doing to protect them?”