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May 4, 2006

Hawaiian Honu: The Green Sea Turtle

Shane Swimming With Hawaiian Green Sea Turtle

Hawaiian waters are a haven for four of the remaining seven species of sea turtles in the world: the green sea turtle, the hawksbill, the leatherback and the olive ridley. The green sea turtle is the most common.

Six out of the seven remaining sea turtle species of the world are either endangered and on the verge of extinction or under threat of extinction. Sea turtles have the distinction of being one of the few species on Earth to have witnessed dinosaurs evolving and going extinct. They've lived through ice ages, existing much as they do now, roaming the seas long before the Hawaiian Islands even existed. Some sources even claim that the Marquesas, the first humans to travel to the Hawaiian Islands, were guided by not just the stars, but also sea turtles.

It is unclear, however, if these ancient creatures will be able to survive the age of man.

The cold-blooded, air-breathing Hawaiian Green Sea Turtle is called "Honu" by the locals. We don't know how long the turtles live in the wild, but guestimates project mature adults may reach 80 to 100 years if left alone, reaching sexual maturity at about age 25. Because it takes so long for turtles to mature enough to reproduce, recovering from decline is a long and risky process.

Mother turtles haul out on exposed beaches on which they were born and lay their own clutches of about 100 leathery eggs, burying them in the sand and leaving them to their fates. As the mother turtle drags herself back to the ocean, she leaves an obvious trail leading straight back to her eggs. Nowadays, with beachfront property at a premium, turtle nesting grounds, also called natal beaches, are under threat not just in Hawaii, but also Central America and the Caribbean.

The temperature of the eggs also appears to influence the gender of the resulting hatchlings. Colder eggs tend to result in male hatchlings, while warmer ones tend to become females. As the world warms, we may see a shift in the healthy gender balance of turtle populations.

Sea turtle infant mortality is very high due to egg and hatchling predation from animals like Indian Mongoose, and other human-related impacts have had negative effects as well. For example, lighting near beaches seems to confuse hatchlings, luring them onto roads instead of toward the safety of the sea. Even once the hatchlings reach the water, they face many other threats beyond their natural predators like sharks.

Clumsy by-catch fishing habits result in unnecessary turtle deaths and diseases like fibropapillomatosis have greatly harmed turtle populations for the past century. Sea turtle shells and meat (green turtles are a main turtle soup ingredient) is often seen on the wildlife blackmarket, their fat was once harvested for its oil. Juveniles, who cannot sleep at depth, are forced to rest on the surface and often suffer from watercraft collisions and floating trash like plastic soda can rings.

Turtles are much more agile in the water, moving at speeds up to 35 mph. When we came upon this pair of green sea turtles, they swam up to us from below so quickly, we barely had time to get out of the way. After taking a breath (adults need to breathe about once every two hours when at rest), they returned to their dark overhang in the rocks, deep enough not to be bothered by snorkelers.

At one time, millions of green sea turtles swam the world's oceans. During the past century, their numbers have declined so much that eventually the green turtle was listed as an endangered species in 1978. The Hawaiian green sea turtle has made a partial comeback in the past couple of decades through conservation efforts. Since being listed, the turtle population has grown back up to several hundred thousand.

Current Hawaiian green turtle population levels are still thought to be below pre-western contact, and probably pre-World War II levels as well....Green sea turtles, as well as other sea turtles in Hawaii, are fully protected under both the federal Endangered Species Act and under Hawaii state law. These laws prohibit hunting, injuring or harassing sea turtles or holding them in captivity without first obtaining a special permit for research or educational purposes. Swimmers and divers should be aware that riding sea turtles is illegal as it puts the animals under unnecessary stress. Fines for violating these laws protecting turtles can be as high as $100,000 and may even include some time in prison.

More At: Hawaiian Green Sea Turtle

Still, the rise in the turtle population is a positive sign that conservationalists and wildlife officials are doing something right. It has also helped that in the past decade or so, it has become quite cheap and easy to use GPS tracking of marine creatures. Scientists now gather a lot of important data like migration routes and breeding areas, which helps policymakers protect the animals more effectively.

The first year Hawaii's green sea turtle expert counted the animals in the Northwestern Hawaiian Islands, he found 67 nesting females at East Island, French Frigate Shoals.

Three decades later, on the same island, George Balazs' research team counted 467 nesting females in a season -- a nearly 600 percent increase.

Using additional data from the main Hawaiian Islands and mathematical modeling, Balazs estimates that Hawaii now has as many as 35,000 mature green sea turtles and perhaps 250,000 juveniles age 6 or under.

What a difference 25 years under the protection of the Endangered Species Act can make.

More At: Honolulu Star-Bulletin: Comeback

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Posted by sorsha at May 4, 2006 2:26 PM