Honolulu Star-Bulletin Local News

By Susan Scott, Special to the Star-Bulletin

Working hard
for turtles

The Hawaiian green sea turtles
have been hatching in record numbers
at Tern Island

By Susan Scott
Special to the Star-Bulletin

TERN ISLAND, Hawaii - Autumn isn't usually the time of year we expect to see bursts of new life, but it's happening in Hawaii.

Turtles are bustin' out all over.

Hawaii's green sea turtles, called honu in Hawaiian, have been hatching in record numbers this fall at Tern Island, the main biological research station of the Hawaiian Islands National Wildlife Refuge. Tern is one of several small, sandy islands within French Frigate Shoals, an atoll about 500 miles northwest of Honolulu.

The remote sand islands of this atoll are vital to the survival of the Hawaiian green turtle, because they host the last main nesting sites of this threatened species. About 90 percent or more of Hawaii's greens lay their eggs on beaches within this atoll.

On Tern, the atoll's only island inhabited by biologists year round, turtle nests pock the white sand beaches.

Last summer, each time a female turtle laid eggs on the island, workers recorded the date, then marked the spot with a numbered stake. They soon realized that this would be a banner year for turtle nests.

Last year, biologists recorded 152 successful turtle nests on Tern Island; this year 270 nests have hatched so far. The season is drawing to a close but a few late nests will still produce hatchlings.

"This is a big year for turtles on Tern," said on-site refuge manager Steve Barclay.

"We don't know why so many turtles laid eggs here this year, but it follows a general upward trend. Since the U.S. Coast Guard left the island in 1979, the number of turtle nests have increased, probably because the beaches here aren't disturbed any more."

By Susan Scott, Special to the Star-Bulletin
Steve Barclay, U.S. Fish and Wildlife Service refuge manager
for Tern Island, excavates a hatched green sea turtle nest
for research. He counts eggshells and rescues trapped hatchlings.

The number of Tern Island's turtle nests has approximately tripled since 1986.

And since sea turtles gained legal protection in 1978 under the U.S. Endangered Species Act, Hawaii's greens have been slowly but surely increasing in number. Federal researchers know this through systematic monitoring of turtle populations at French Frigate Shoals during the past 24 years.

Another possible cause of Tern Island's large increase in turtle nests this year is extensive natural erosion on Whale-Skate Island, another major turtle nesting site in French Frigate Shoals. Whale-Skate, a small figure-eight island, is sometimes connected by a sand spit. Other times, like now, the area is two islands separated by a channel of water. Occasionally, ocean currents shift sand completely away from the island complex, making it smaller than usual.

"Whale-Skate has really eroded away this year," said Barclay.

"We don't know for sure, but some females who would have nested there may have found their site underwater and moved to Tern to lay eggs."

The nesting season for Hawaii's sea turtles falls mostly in the summer months. The range, however, is wide. Some females dig nests and lay eggs as early as April, and in some years, as late as November.

During the season, sexually mature females dig numerous pits. Most of these are called false pits and don't function as proper nests. Some collapse, a few are full of rocks or roots and others just don't suit the turtle for some unknown reason.

Of these numerous attempts, each mature female digs three to five successful nests. Into each good nest chamber, she lays about 100 eggs.

The energy these marine reptiles need for such intense reproductive activity is extensive. A female must drag herself above the high waterline of beaches, some strewn with rocks or vegetation, to search for suitable nesting sites. When she finds one, she uses her front flippers to scoop out a body pit and then, with rear flippers, digs a deeper egg chamber, usually in crumbly sand. If all goes well, she then lays dozens of eggs into the hole.

Turtles can't exert such huge effort each year. Most migrate to French Frigate Shoals to nest only every second or third summer.

Although the average nest contains about 100 eggs, usually only about 60 to 80 percent of these hatch. Some eggs don't develop at all, some develop only partially and a few hatchlings get trapped in the sand hole.

Sea turtles usually hatch from their eggs 65 to 70 days after they're laid. The earliest hatchlings lie still in the sand nest until later siblings hatch and there are enough of them to dig to the surface. Then, in the dark of night, when it's cool, the youngsters burst from the hole in a group and scurry toward the ocean. This dash often means life or death for a hatchling; predators lurk on land and in the sea.

Ghost crabs, also called sand crabs, chase and grab the little hatchlings, crushing their skulls with powerful pincers. After the kill, the crab ladles out the guts of the beheaded turtle through the hole in its neck.

Although it's rare, other hatchling predators are frigate birds, numerous on Tern Island. These big seabirds sometimes swoop down and grab turtles caught out during the day, either from getting lost, emerging late or being trapped in vegetation.

By Susan Scott, Special to the Star-Bulletin
This turtle was still struggling from its shell when researchers rescued it from the nest four days after its sublings had left.

Occasionally, frigate birds drop their turtle prizes, and hatchlings may fall into bushes and weeds. If wildlife workers see this happening, they can sometimes rescue the young turtles. Frigate birds are masters of the air but aren't good at picking food from foliage.

Hatchlings that do make it to the ocean still aren't home free. They must dodge marine predators and human entanglements - and do so for a long time. Sexual maturity in green sea turtles can take as long as 50 years.

Even though most sea turtle hatchlings from French Frigate Shoals do make it to the water, a shockingly small number make it to adulthood. Estimates range from one in 1,000 to one in 10,000. This means that of the 20,000 or so eggs that likely hatched this year on Tern Island, only from 2 to 20 of those turtles will reach maturity.

All of Hawaii's sea turtles continue to be protected by both state and federal laws. It is illegal to harass a turtle or a turtle nest in any way. This includes chasing or touching the animals either in the water or on land.

Turtles had a good reproductive season this year at Tern Island but it doesn't mean they're out of the woods.

Marine pollution, human-induced impediments such as gill nets and persistent, debilitating illness in the form of tumors, continue to plague Hawaii's gentle ocean greens.

It's been a big year for little turtles, but they still need to grow up.

Biologists dig hard for turtle info

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