After 2 decades, volunteer efforts to save threatened species pay off
POSTED: Sunday, April 19, 2009
HILO » A surge in new nesting Hawaiian hawksbill sea turtles over the past several years might be evidence that a 20-year-old protection effort is finally producing new baby turtles.
An intensive program has been under way since 1989 to protect the nests of the endangered turtles on more than a dozen remote Big Island beaches.
The local population of the species was seriously in need of help, said Larry Katahira, a Hawaii Volcanoes National Park resource management specialist who ran the program until retiring three years ago. Katahira said fishermen who frequented the coast told him that prior to the program's start, few hatchlings made it to the ocean.
By the numbers
» Volunteers on the Big Island began tagging Hawaiian hawksbill sea turtles in 1991 as a way of keeping track of which turtles were nesting and where.
» Over the next 15 years, the number of newly nesting turtles tagged each year averaged about four.
» Four years ago that number began to grow. In 2005 there were six newly tagged turtles, and then eight each in 2006, 2007 and 2008.
Several dozen volunteers now spend several months each year working to improve those chances. From June to December a crew of mostly college students treks along the windy, sun-baked coast of southern Puna and Kau. Camping at known nesting beaches, they trap and kill mongooses, rats and feral cats that prey on the defenseless hatchlings as they leave the nest.
The volunteers also stay up most of the night watching for females to crawl up from the ocean. The turtle drags itself up above the high-tide mark, digs a nest into which it lays about 150 eggs and then covers it with sand.
But before the turtle can crawl back to her watery home, she is intercepted by the waiting volunteers, who check her flippers for a numbered metal tag that indicates she had been found nesting in the past. If one is present, they record the identifying number. If not, she receives a new tag.
When they reach sexual maturity, hawksbill turtles usually return to the beach of their birth to lay eggs. Although it is not known for sure how long it takes for a hawksbill, or honuea, to mature, it is believed to be around 20 years.
Will Seitz, who took over from Katahira as head of the Hawaii Island Hawksbill Turtle Recovery Project, said there is no way to know for sure whether the jump in numbers of newly tagged females is the result of hatchlings helped by the program returning to nest at the beach of their birth.
"We'd like to think that," Seitz said, "but scientifically we don't have proof."
He said there are other possible explanations for the increase in untagged turtles, including the chance that the volunteers might have previously missed some new nesters. However, the volunteers are now covering more beaches and have more knowledge about potential nesting sites than ever before.
The condition of the newly tagged ones is a hopeful indication.
"A lot of the newly tagged turtles have shells that are not damaged," Seitz said, adding that would likely indicate those turtles are younger, as many of the ones previously tagged have shells showing damage and wear.
The time period seems about right when compared with the green sea turtle, which also is believed to take about 20 years to reach sexual maturity, said veteran researcher George Balazs, a sea turtle biologist with the National Marine Fisheries Service in Honolulu.
Balazs said hawksbills in Hawaii have always been difficult to study because of their low numbers. He credited the efforts of Katahira, Seitz, the volunteers and others for their efforts to reverse that.
"They were the right people to come along for the right species," he said.
The program was honored in 2007 with a Living Reef Award by the Coral Reef Outreach Network.
Hawksbills, which are found in both the Atlantic and Pacific oceans, are protected in U.S. waters under the Endangered Species Act of 1973 and under a variety of international treaties elsewhere.
Worldwide, hawksbill populations have dropped by 80 percent during the past century and continue to decline.
The threats include harvesting of the turtles and their eggs, degradation of coral reefs that provide food and habitat, and the presence of artificial lighting that can deter females from nesting and disorient hatchlings. They have also long suffered from commercial exploitation for such as combs made from their shell, which has been incorrectly called "tortoise shell" and also described as "the first plastic."
Little was known about hawksbills in Hawaii prior to the beginning of the tagging program in 1991, including their numbers. So far 89 have been tagged on Big Island beaches, although three of those are known to have died. That leaves about 100 known nesting females in the state, with the remainder tagged on beaches on Maui, Molokai and Oahu.
Satellite tracking has shown that when they are not nesting along the Big Island's southeastern coast, hawksbills spend most of their time foraging for sponges off the island's Hamakua coast.
According to Seitz, the Big Island program has helped an estimated 75,000 hatchlings to successfully reach the ocean over the past 20 years. Baby turtles hatch after incubating under the sand for about two months, then dig their way out to crawl to the sea. Nearly all the nesting, and most of the hatching, occurs at night.
But even if it makes it to the water, a baby turtle's life is a perilous one. Birds, sharks and other ocean predators take a huge toll on hatchlings, and it is thought that perhaps only one in a thousand might survive to reproduce.
Seitz said intensive monitoring needs to continue in order to better understand Hawaiian hawksbills. He said it is difficult to assess the current population because of the wide range of variables involved in nesting from year to year.
For example, while females often nest every three or four years, the period between nesting can range up to eight years.
The number of nests laid by each turtle during a season also varies from one to five or more.
Such fluctuations have resulted in the number of known nesting turtles in any given year ranging from four to 17, and the number of nests varying from less than 20 to more than 60.