Turtles

HAWAIIAN GREEN SEA TURTLES (Chelonia Mydas) "HONU"

The Hawaiian green turtle was listed as threatened under the U.S. Endangered Species Act of 1973.  Green turtles were a source of food, tools, and ornamentation for early Hawaiians. With the arrival of western culture, however, the level of exploitation of this resource increased dramatically. Large numbers of green turtles were harvested throughout the Hawaiian Islands through the nineteenth and early twentieth centuries. In 1974, the State of Hawaii finally passed a regulation providing some protection, but this was virtually ignored until 1978, when the Hawaiian green turtle was placed on the list of threatened species.

In other parts of the world, green turtles face a serious threat from the destruction and loss of nesting sites.  Fortunately, over 90% of nesting activity for the Hawaiian green turtle population occurs at the French Frigate Shoals, inside a National Wildlife Refuge System administered by the U.S. Fish and Wildlife Service. This, combined with its threatened status under the U.S. Endangered Species Act, has created an environment in which the Hawaiian green turtle should prosper. Unfortunately, the Hawaiian green still faces severe threats, most notably fibropapilloma tumors and degradation of foraging habitat. Current Hawaiian green turtle population levels are still thought to be below pre-western contact, and probably pre-World War II levels as well. 

DESCRIPTION

Green sea turtles get their name from the color of their body fat, which is green from the algae or limu they eat.  Adult green sea turtles are herbivores, meaning that they eat only plants, and therefore do not pose a threat to any other marine animals. Similar to cows, green sea turtles depend on bacteria in their guts for digestion of plant material. Juvenile green sea turtles on the other hand are carnivorous. Their diet consists of jellyfish and other invertebrates. Adult green sea turtles can weigh up to 500 pounds and are often found living near coral reefs and rocky shorelines where limu is plentiful. Although the carapaces of green sea turtles are mostly dark brown in color, they can be covered with patches of algae on which fishes in turn feed. This type of feeding arrangement is an example of symbiosis. Symbiosis occurs when a relationship forms between individuals of two different species for an extended period of time. This particular relationship of the fish eating algae off the turtle's shell would be considered a form of mutualism, a type of symbiosis in which both species benefit from their association. Here, the fish get a free meal, and the sea turtle gets a clean shell.

The life span of sea turtles in not known. Hawaiian green sea turtles seem to grow very slowly in the wild, usually taking between 10 and 50 years to reach sexual maturity - 25 years is the average. Their long period of maturation helps to explain why it takes sea turtles so many years to recover from a substantial population decline. Male and female green sea turtles look virtually alike until they mature. Then, the two sexes are easy to tell apart: the males have long, thick tails, while the females have short, stubby ones. This is an example of sexual dimorphism, or, the ability to differentiate between the sexes of a particular species on the basis of external body characteristics.

Although green sea turtles live most of their lives in the ocean, adult females must return to land in order to lay their eggs. Biologists believe that nesting female turtles return to the same beach where they were born. This beach is referred to as a natal beach. Often sea turtles must travel long distances from their feeding grounds to their natal beach. Just how sea turtles find their natal beaches is not known. Hawaii's green sea turtles migrate as far as 800 miles from their feeding areas along the coasts of the main Hawaiian islands to their nesting beaches in the Northwestern Hawaiian islands. Males accompany the females during the migration, which usually occurs in the late spring, and mate with them off the shores of the nesting beaches. The most popular nesting beaches are on French Frigate Shoals, where an estimated 90% of the Hawaiian population of green sea turtles mate and lay their eggs. Females do not mate every year, but when they do, they come ashore often-as many as five times every 15 days to make nests in the sand and lay eggs.

Green sea turtles nest only at night. The female must pull herself out of the water and all the way to the dry sand of the upper beach using only her front flippers. This is a difficult task as her front limbs have been modified into highly effective swimming flippers, and do not support the bulk of her weight in the sand. Reaching the upper portion of the beach, she uses her front flippers to dig a broad pit in the sand and her rear flippers to delicately carve out a bottle-shaped burrow. She then lays her clutch, which consists of approximately 100 leathery-skinned eggs, in the burrow and covers them carefully with sand. Lastly, she buries the pit entirely to disguise the location of her nest. Her parenting job completed, she returns to the sea, leaving her young to fend for themselves.

Green sea turtle eggs take about two months to incubate. Studies indicate that the temperature of the eggs during incubation influences the sex of baby sea turtles. Lower temperatures tend to produce males, while higher temperatures tend to produce females. The baby turtles are able to break through the eggshell and hatch by chipping away at the shell with a structure called an egg tooth, a temporary hard protuberance on their beaks. After hatching, the tiny one-ounce turtles take a number of days to dig their way out of their nest.  Emerging from the nest must be a group effort as one hatching would not be able to escape by itself. Working together, the hatchings scrape away the roof of the nest until they reach about an inch away from the surface of the beach. The hatchlings nearest to the surface stop their digging if the sand feels hot, indicating that it may be daytime. They wait to resume digging until the sand feels cool, indicating that it is night, and safer to emerge by avoiding the harsh rays of the sun and possibly, predatory birds. Once out of the nest, the hatchlings find their way to the ocean, by heading towards the brightest horizon. Thus, artificial lights on nesting beaches can mean death to

the young turtles as they may confuse them and cause the them to lose their way. When they find their way to the ocean, the hatchlings must swim continuously for the next day and a half to two days. The young turtles remain at sea and do not come inshore until at least one year later.

Unfortunately, not all of the hatchlings reach the ocean. Many are snatched up by hungry crabs and other predators along the way or become lost and die. In addition, some are eaten by sharks and other carnivorous fishes while at sea. Only a few baby turtles from each nest will survive into adulthood. This type of a life history strategy exhibited by the green sea turtle can perhaps be more easily understood by comparing it to other patterns that we see in nature.

HOW TO VIEW TURTLES AND WHERE TO FIND THEM

At Hale Ono Loa all you have to do is to turn left out our door and walk to the end of the building and look down.  One day I counted as many as 20 turtles.  Most often they are present in the early morning or late afternoon.  You can also view them from either of the two sun decks by the water.  Lastly, you can snorkel with them!  Use the swim out steps to enter the reef.  Turtles are protected under state Law and the U.S Endangered species act.  

• Stay back 10 feet from turtles, both on land and in the ocean.

• Do not feed them.

• Do not prevent turtles from exiting or entering the ocean.

• Do not prevent a turtle from surfacing in the water, they need air to breathe.

• Never chase or follow turtles as it causes stress to the animals.

• Allow animals to approach you.

• Never touch the turtles, by doing so you remove protective elements on their skin and shell allowing disease, tumors and parasites to invade them.

• Pick up trash from the ocean and beach so turtles do not become entangle in the debris.  

IF YOU SEE AN INJURED, SICK OR TANGLED TURTLE; SAY SOMETHING!

CALL:  808-286-2549 (Maui Ocean Center Institute)

IF YOU SEE TURTLES BEING HARASSED OR ILLEGAL ACTIVITY INVOLVING SEA TURTLES CALL:  808 643-3567 (Division of Conservation and Resources Enforcement).