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Fast-Growing Green Sea Turtles at Maui Ocean Center

An ancient Hawaiian legend tells of a mystical sea turtle named "Kauila" who can transform herself into a human being and watch over children playing along the shoreline. The guardian makes her home on the Big Island at Punaluu Bay, where she shares her spring of pure drinking water.

In many cultures, the sea turtle has long been revered as a spiritual, deistic being. Yet, they continue to be threatened from excessive hunting for food and a variety of commercial uses. Green sea turtles also suffer from a marine disease called fibropapilloma, which causes large tumors. On the island of Maui, however, there are six young green sea turtles that are thriving.

In spring and summer of 1997, Maui Ocean Center, the Hawaiian Aquarium, acquired the young turtles. Their status, so far, has been positive. "They�re doing great, eating well, and are growing four times faster than they would in the ocean because we feed them a well-balanced diet," says Ofer Vardi, aquarist and assistant curator at Maui Ocean Center. Vardi has been monitoring the six turtles, ages two and three, ever since their arrival to the new aquarium.

The young turtles were given to the Maui Ocean Center from Sea Life Park on Oahu, which has created a beach in its turtle facility to encourage turtle hatchlings. The turtle�s parents, who lived for more than two decades at the park on Oahu, mated in captivity. Two of the six turtles were hatched there in summer 1996 and the other four were hatched in summer 1997. After their birth, they were flown to Maui Ocean Center on a "loan" basis to help promote education about the threatened species.

The young turtles have adjusted well to their home in "Turtle Lagoon." Their special home includes a pond with an acrylic window for viewing and a small sandy �beach� where they can bask in the sun and digest their food.

The two, 3-year-olds now weigh about 80 pounds each, and their carapace measure about 24 inches each. The smallest of the 2-year-olds weighs about 40 pounds, and its carapace measures about 16 inches. One reason for their fast growth, says Vardi, is their high-quality diet. "We feed them well twice a day. Their diet consists of squid, fish, shrimp, lettuce, and on occasion sea jellies." Interestingly, it is still too early to distinguish their gender. When they reach sexual maturity at about age 25, the tails on males grow much longer than those of females.

The green turtle is the most common sea turtle in Hawaii. The diet of this omnivorous turtle includes marine plants such as limu (seaweed, algae), and therefore gets its name for its green body fat. It reaches approximately four feet long, and weighs 200 pounds or more. It can dive to depths of 125 feet. Sharks and human beings are its main predators.

Prior to their protection in 1976 (under the U.S. Endangered Species Act), green sea turtles were decimated for their flavorful meat and shell. "After decades of over-exploitation, we�re now seeing a wonderful recovery of the Hawaiian green sea turtles," says George Balazs, head of the marine turtle research program at the National Marine Fisheries Service in Honolulu.

Every two to five years, mature green turtles migrate up to 800 miles from their feeding grounds to French Frigate Shoals in the Northwestern Hawaiian Islands to mate and nest.

Other Sea Turtles

There are seven species of sea turtles in the world and five of the seven can be found in Hawaii. Three are considered to be native to the islands, while two are rare visitors. Native species include the green, hawksbill and leatherback turtles. Rare visitors are the loggerhead and olive Ridley turtles. Sea turtles are members of one of only three groups of marine reptiles. The others are sea snakes and the marine iguanas.

All reptiles breathe air, with the surfacing interval of most governed by their level of activity and other factors, such as water temperature. While submerged, turtles can hold their breath for several hours and can remain out of water for at least 24 hours.

During the summer months, usually on moonless nights around the time of high tide, female turtles will come ashore several times to lay clutches of eggs. Each clutch is usually laid about two weeks apart. The eggs, resembling Ping-Pong balls, will take an average of 60 days to hatch, depending on the temperature of the sand. The sand temperature plays a role in determining the sex of the hatchlings. Above a critical temperature, the majority of the hatchlings will be females. Conversely, below this temperature, the majority will be male.

Over the course of a nesting season, up to a thousand eggs may be laid. Many of these will hatch and leave the nest. The highest hatchling mortality occurs as the animals commence swimming where large fish and sharks eat many. Perhaps only one in a thousand of these hatchlings will live the 20 or so years it takes to reach sexual maturity.

The Native Hawksbill Turtle

"Hawaii�s hawksbills do not migrate away from the main islands but travel within them to nest and forge," says Hannah Bernard, executive director of the Hawaii Wildlife Fund. �So it might be that the hawksbills found around the islands could be indigenous to Hawaii. More research is needed to substantiate this."

The Hawksbill turtle is not typically caught for food because it feeds on toxic sponges, making its flesh poisonous. Instead, they were heavily harvested for "tortoise-shell" products, such as combs and eyeglass frames, buttons, and hairbrush handles. Today they are considered critically endangered.

Unlike the green sea turtle, which nests on unpopulated sand shoals, the hawksbill lays its eggs on Hawaii�s main islands. On North Kihei Road, just east of Maui Ocean Center, you�ll see turtle crossing signs. From June through October, it is nesting season for the hawksbill and many will come ashore to lay eggs. "Coastal development has encroached on nesting habitat, and roads too near the shore have resulted in the deaths of several females attempting to cross the road to lay their eggs," says Bernard. The hawksbill reaches about 30 to 36 inches long, weighs about 90 to 140 pounds at adulthood and is rarely sighted around Maui�s coral reefs.

The Native Leatherback Turtles

You�re unlikely to see leatherback turtles near the beach, but if you�re out whale watching or sport fishing, you may spot one over deep water. The largest sea turtle on earth, the leatherback can be more than eight feet long and weigh more than a ton. It is the only sea turtle without a hard shell. Instead, it is protected by thick, leathery black skin with seven ridges running down its back. Its favorite food are sea jellies, which includes the venomous Portuguese man-of-war. The leatherbacks seen in Hawaii most likely migrated from breeding sites in Mexico, Costa Rica and Malaysia.

While many people are making efforts towards helping endangered sea turtles by preserving and protecting our ecosystem, some are still careless. Turtles often drown when they become entangled in fishing nets. They have also been found dead after ingesting plastic bags that were presumably mistaken for sea jellies. Disturbing or harming sea turtles in any way is illegal. Their grace and beauty, however, can still be admired from a distance.

For more information, contact Lydee Ritchie at the Maui Ocean Center, 192 Ma`alaea Road, Wailuku, Maui, HI 96793, Tel: 808-270-7084, Fax: 808-270-7084, Email: lydee@maui.net

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