Hawaiian green sea turtles.

Sea turtles are graceful saltwater reptiles, well adapted to life in their marine world. With streamlined bodies and flipper-like limbs, they are able to swim long distances in a relatively short time.

When they are active, sea turtles must swim to the ocean surface to breathe every few minutes. When they are resting, they can remain underwater for as long as 2 1/2 hours without breathing. Green turtles often rest in caves or under ledges in deep water.

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. Often, sea turtles must travel long distances from their feeding grounds to their nesting beaches. Just how sea turtles find their nesting beaches is unknown.

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 or 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 heavy bodies. While on land, these animals shed large, sticky tears which 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 nesting 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 their 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, the 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 probably carried by currents to favourable 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.

Hawaiian green sea turtles.