Modern science shows that sea turtles have been swimming the Earth's oceans for well over 100 million years--even pre-dating many dinosaurs. In addition, the turtle is an important symbol in the mythologies of many indigenous cultures, usually representing creation, longevity, and wisdom in these belief systems. Turtles are thus truly ancient beings-both in geological and mythological terms. As integral parts of the marine ecosystem, turtles are also useful indicators of the vitality of the overall marine environment.
Sea turtles are gentle reptiles that spend the majority of their lives in the ocean. Females reach reproductive age after 35 to 40 years, and only then return to the beach of their birth to lay their eggs for the next generation. Although a female may lay hundreds of eggs in one season, only a few of the hatchlings will survive to reach maturity.
Hundreds of years ago, there were many millions of sea turtles swimming the Earth's oceans. Today, all seven species of sea turtle are considered either endangered or threatened.
There are three species of sea turtles native to the Hawaiian Islands: the Green, the Hawksbill, and the Leatherback. These fascinating creatures have played important roles in the environment and culture of Hawaii's people. Of the three native sea turtles, the Green Turtle (Honu) is the most common.
These turtles, which can weigh up to 400 pounds, are primarily vegetarians. They eat algae or limu (Hawaiian seaweed) growing underwater on coral reefs and on rocks close to shore. Green turtles prefer to live near large "pastures" of limu that are located in near shore waters around the Hawaiian Islands. The carapaces (upper shells) of adults are dark with olive or gold flecks and receive their name from the color of their body fat rather than their shell color.
Although sea turtles live most of their lives in the ocean, adult females must return to land in order to lay their eggs. Scientists believe that nesting female turtles return to the same beach on which they were born. Hawaii's green turtles migrate up to 800 miles from their feeding areas near the coast of the main islands to nesting beaches in the Northwestern Hawaiian Islands. The males accompany the females in this migration and mate with them offshore from the nesting beaches.
Females often come ashore to nest several times in a season, but wait two to three years before nesting again. Green turtles nest only at night and can be frightened away by lights or movement. It is not easy for these turtles to find a suitable nesting site on land, where they no longer have the buoyancy of water to support their bodies. While on land, these animals shed large, sticky tears that remove excess salt from the body and prevent the eyes from being covered with sand.
When a female finds a suitable nesting site, she uses her flippers to dig a body pit about her. She then digs a flask-shaped egg cavity with her rear flippers. This arduous effort generally lasts all night. After depositing about 100 eggs, the female covers the nest with sand and returns to the sea, leaving the eggs to incubate during the next two months.
After hatching, the tiny, one-ounce turtles take several days to emerge from the nest. A single hatchling would not be able to emerge from the nest by itself. Working as a team, hatchlings scrape sand off the roof of the nest cavity and pack this sand on the floor. In doing so, hatchlings raise their nest toward the surface of the beach. When they are about an inch from the surface, the topmost hatchlings cease their activities if the sand is hot. Cool sand indicates that it is night or an overcast day. The hatchlings then emerge from the nest, thereby avoiding the sun's heat and perhaps predatory birds.
Once out of the nest, the hatchlings race to the water and swim constantly for the next 36 to 48 hours. They are then carried by currents to favorable areas in the open ocean, where they grow for several years until they join adult and juvenile turtles at the coastal feeding grounds. While in the open ocean, young green turtles are probably carnivorous and feed on invertebrates such as jellyfish.
Some hatchlings never reach the oceans and are snatched up by hungry crabs. Hatchlings may also be disoriented or impeded by obstacles and die from the suns heat. Once in the ocean, sharks and other carnivorous fish eat hatchlings. Due to their size and swiftness in the water, adult sea turtles have only two predators: sharks and people. Tiger sharks regularly feed on all sizes of green turtles.
The life span of sea turtles is unknown. Hawaiian green turtles seem to grow very slowly in the wild and may take 40 to 50 years to reach sexual maturity. Male and female green turtles look like they are mature, then the male develops a long tail extending beyond the hind flippers. A female's tail extends only a short distance beyond the end of her shell.
Generally, only female sea turtles leave the ocean after entering it as hatchlings. But in the Northwestern Hawaiian Islands male and female green turtles crawl onto beaches and lie motionless in the sunlight for hours. Turtles may bask in order to increase their body temperature or to avoid tiger sharks.
The Hawaiian island chain is made up of 132 islands, though we generally only think of the eight main islands, Ni'ihau, Kauai, Oahu, Molokai, Lanai, Maui, Kahoolawe and Hawaii. Surrounded by the Pacific Ocean and located over 2400 miles from the nearest continent has created a unique underwater environment, in fact over 25% of marine is endemic to Hawaii.
The four most visited islands are Oahu, Maui, Kauai and Hawaii, they each have their own unique characteristics and dive locations. Lanai, Molokai and Ni'ihau are dived less frequently and offer some unique dives and marine life, although generally recommended for intermediate to advanced divers. If you are interested in diving off Kahoolawe you will need to charter a dive boat.
With mandated protection, Hawaii's reefs have become abundant with these creatures. Look for them resting under ledges or swimming freely. Be especially sensitive to a resting turtle and never grab a turtle as you can literally drown them! These creatures have personalities and moods like you and I. If paid the proper respect the turtles can give you a lifetime memory. There are a couple of subtle signs to watch for when near a sea turtle that signal you may be too close within their comfort zone. "Yawning" type, open mouth movements by the turtle are one. A sign of a more deeply irritated turtle is a "flipper swipe" whereas the turtle swipes his flipper over his forehead area. This is turtle-speak equal to flipping you off! Don't embarrass yourself (or be deemed insensitive) by being flipped off by a turtle, back off if you see that flipper creep up. Other signs of disturbance can include sudden awakening from a sleep-like state on the seafloor, an increase in swimming speed and diving towards deeper water.
[ source: travel-hawaii.com/Hawaii-Sea-Turtles.html ]