The Hawaiian green sea turtle gets its name from the color of its body fat, which is green as a result of algae it eats. Adults can weigh up to 500 pounds and are usually found near coral reefs and rocky shorelines where the "limu" algae is plentiful. Adult sea turtles eat only plants, while juveniles are carnivores, feeding on jellyfish and other invertebrates.
Known as "honu" in Hawaii, green sea turtles are reptiles whose ancestors were land-dwellers during the time of the dinosaurs. Like other reptiles, the green sea turtle is cold-blooded, breathes air and has scales. And like other turtle species, it has a bony outer shell that covers the turtle's back and belly. However, the green sea turtle cannot retract its head and is specially adapted to ocean life. To keep salt from accumulating in their bodies, green sea turtles have developed a gland behind each eye that allows them to shed large "tears" of excess salt.
Compared to land-dwelling turtles, the green sea turtle has a lighter and more streamlined shell and its front and rear legs have evolved into flippers that enable it to swim long distances. When the sea turtle is awake and active, it must swim to the surface every few minutes to breathe, but when still and sleeping it can remain underwater for upwards of two hours without breathing.
Adult green sea turtles grow very slowly in the wild, reaching sexual maturity at an average age of 25. Immature male and female green sea turtles look very similar, with short, stubby tails. During maturation, however, the male develops a long, thick tail, making adult male and female turtles easy to tell apart.
Despite spending most of their time in the ocean, female green sea turtles must lay their eggs on land. Scientists believe that females return to nest on the same beach where they were born, their natal beach. A female may swim as far as 800 miles from coastal feeding grounds of the central Hawaiian Islands to reach the nesting beaches, which are usually in the northwestern Hawaiian Islands. Males accompany females during the late spring migration period to mate off the shores of the nesting beaches.
Females do not mate every year but when they do mate, they come ashore as often as every 3 days to make nests in the sand and lay their eggs. Although the enormous Hawaiian green sea turtle is graceful in the water, it is clumsy on land. Nesting only at night, the female must use her front flippers to pull herself out of the water and all the way to the dry sand on the upper beach. She uses her front flippers to dig a broad pit in the sand and her rear flippers to carve out a bottle-shaped burrow where she will deposit her clutch of about 100 leathery-skinned eggs. After covering her eggs with sand and completely burying the pit, she returns to the ocean and leaves the young to hatch and fend for themselves.
After two months of incubation, the hatching baby turtles use their egg tooth, a temporary hard knob on their beaks, to break through the eggshell. A few days of digging as a group brings the hatchlings near the surface. If the sand feels hot, they stop digging. Crawling out in the daytime would expose them to the sun and the risk of predatory birds. When the sand feels cool, the tiny turtles resume their digging, emerge from the nest and head toward the brightest horizon, seeking the ocean. Young turtles remain at sea for at least a year before venturing back ashore.
The green sea turtle is now listed as threatened in Hawaii and is already endangered on the Florida coast and the Pacific coast of Mexico. At one time there were several million green sea turtles worldwide but today fewer than 200,000 nesting females remain, with only 100 to 350 females nesting each year in Hawaii.
The green sea turtle population faces many challenges. Coastal development has forced many female sea turtles to stop nesting or nest on beaches other than their natal beach. Few of the hundreds of hatchlings reach adulthood. Some baby turtles lose their way, distracted by artificial lights on the nesting beach. Many are snatched by predators on the way to sea or after reaching the water. Egg clutches are easy to spot because of the trail that the female leaves behind when she struggles back to the water.
More than 10,000 sea turtles are accidentally caught and drowned each year in shrimp fisher nets, longlines, driftnets, coastal gill nets, discarded fishing gear and marine debris. Other threats include damage done by poachers and by disease. Poachers use turtle shells to make jewelry and ornaments, skin to make small leather goods, meat and eggs for food, and fat for oil. Fibropapilloma, an infectious and life-threatening disease that causes the growth of large bulbous tumors on the turtle's soft tissue, affects much of Hawaii's green sea turtle population.
The Hawaiian green sea turtle is protected under the federal Endangered Species Act and under Hawaii state law. These laws prohibit hunting, injuring, harassing, holding, or riding a green sea turtle. A violator can pay as much as $100,000 and serve prison time. In addition, laws prohibiting international trade of sea turtles and their products exist but are violated at a very high rate. Despite laws protecting sea turtles from hunting, poachers continue to kill hundreds of them each year for their eggs, shells, and meat.
Recovery teams are working on continuing and expanding research, management, and enforcement needs to effectively protect and conserve the Hawaiian green sea turtle.
If you would like to help, you can join Sea Turtle Rescue.