Dedicated to Preserving Hawaii's Marine Resource
Green Sea Turtle
Chelonia mydas - (Honu)
Maximum Length: 4 ft (1.22 m)
Maximum Weight: 400 lb (181 kg)
Life Span: 30 - 50 yrs or more
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Chelonia
Family: Cheloniidae
Genus: Chelonia
Species: mydas
The green sea turtle is the most common sea turtle
found in Hawaiian waters. Their name comes from the color of their body fat,
which is green due to all the algae they eat. Hawaiians refer to them as the “honu.”
The carapace of green sea turtles is heart-shaped. It
is mostly dark brown with yellow patches and a white to light yellow plastron.
The shell is often covered with patches of algae. Their head is small, light 
brown in color, with yellow markings. They have a single-clawed flipper. In the
Pacific, they are known as the black sea turtle and are considered by some scientists as a separate species. Hatchlings usually have a black carapace,
white plastron, and white margins on the shell and limbs. Characteristics that
separate them from the other sea turtles include: four pairs of costal scutes,
none of which borders the nuchal scute, and only one pair of prefrontal scales
between the eyes.
Green sea turtles are the most widely distributed of
all the sea turtles found in the oceans of the world. They live in fairly
shallow waters (except when migrating) around sea grass meadows, coral reefs,
bays and estuaries in tropical and subtropical areas. They have been known to
migrate up to 1,400 miles (2,253 km) between their feeding grounds and nesting
sites. Open beaches with a sloping platform and minimal disturbance are needed
for nesting. Females have a strong nesting fidelity, returning to nest on the
same beaches after long distance migrations to the feeding grounds.
Their primary breeding grounds include the Caribbean, North and Central America, the Arabian Peninsula and the Mediterranean. Over 90 percent of Hawaii’s nesting females lay their eggs at French Frigate Shoals, where about 100 to 350 females nest each year.
In the western Pacific, the largest Green turtle nesting aggregation in the world occurs on Raine Island, Australia. On Raine Island, thousands of females nest nightly. 6,000 to 20,000 females are reported to nest annually in Oman of the Indian Ocean.
Adult green sea turtles aggregate around cleaning
stations where small fish live, such as the Hawai’ian cleaner wrass.
Reproductive maturity is not reached until 20-50 years.
Adult females will nest about every two to four years, with a rare few having
clutches in successive years. These adult females will return to the same beach
where they were born (natal beach) to lay their eggs. A female will emerge from
the water at night, crawling up the beach where she digs a burrow in the sand
for her eggs. The process may take only 30 minutes after which she buries the
eggs and returns to the ocean. Adult females can lay up to nine nests per
season, with each nest containing somewhere between 75-200 eggs. After 48-70
days, the eggs will hatch. Baby turtles use a temporary structure on their beak
called an “egg tooth” to help them break through the eggshell. Hatchlings are
between 1.75 to 2.38 inches (4.5 - 6.1 cm), weighing 0.9 ounces (25 gm). They
will emerge from the nest after several days of digging. If the sand near the
surface feels
hot, they will stop digging and wait for nightfall to surface.
Then, they scurry their way towards the brightest horizon, which is usually the
ocean. Bright artificial lights on nesting 
beaches can cause the hatchlings to
become disoriented and lose their way, for many this will mean death. Hungry
crabs and other predators also await the hatchlings, before they reach the
ocean. Once in the ocean, hatchlings will drift with the ocean currents, while
seeking refuge and food in Sargassum rafts and floating debris. Only a few
hatchlings from each nest will actually survive into adulthood.
The nesting season in the Southern U.S. is generally from June through September.
Young sea turtles may feed on jellyfish, small mollusks, and sponges. As they get older, however, they become strict herbivores, feeding mainly on sea grasses and algae.
Like all other species of sea turtles, Green sea turtle
populations are considered either endangered or threatened. On July 28, 1978,
Green sea turtles were listed as threatened/endangered under the U.S. Endangered
Species Act. They are considered endangered in Florida and in the Pacific coast
of Mexico. Hawaii’s Green sea turtle population is listed as threatened. Several
million Green sea turtles once existed worldwide. Fewer than 200,000 nesting
females remain today, with only 100 to 350 nesting in Hawaii.
Green sea turtles are exploited in many countries for their meat, eggs, shells, skin, and fat. The meat and eggs are used for food, the shells for jewelry and ornaments, the skin for leather, and the fat for oil. Fibropapillomatosis, a disease characterized by the development of tumors on the skin and internal organs, is a mortality factor and has seriously impacted populations in Florida, Hawaii, and other parts of the world. Major threats to their survival include large-scale poaching of adult turtles, drowning in shrimp nets, tuna and swordfish longlines and other fishing gear, destruction of nesting beaches from development, pollution, watercraft strikes, channel dredging, commercial exploitation of sea turtle eggs, and commercial fishing operations. Their predictable nesting habits make them easy targets for poachers. Commercial shrimp trawlers trap and drown more than 10,000 sea turtles each year in their nets. Thousands of sea turtles become entangled in longlines, driftnets, coastal gill nets, and other floating fishing debris. Ingestion of trash, particularly plastics, can block the turtle’s ability to digest/pass food, causing them to starve.
Nest protection efforts and beach habitat protection are underway for most of the significant nesting areas. The enforcement of turtle excluder devices on shrimp trawl nets have also reduced mortality. Many coastal communities have developed lighting ordinances to reduce hatchling disorientations.
Because sea turtles take so long to reach sexual
maturity, these
populations are extremely slow to recover. It has taken over 20
years since the implementation of the Endangered Species Act to see any evidence
of recovery. Due to long-range migratory movements between nations,
international cooperation is absolutely essential for the recovery and stability
of these populations. Currently, international trade of sea turtle parts is
illegal under the Convention for International Trade of Endangered Species of
wild fauna and flora (CITES). Violators who enter the U.S. with sea turtle
products from abroad may be fined up to $20,000 and sentenced up to one year in
prison.
Hawaii
In the 1960s, turtles in Hawaii became a favorite and lucrative restaurant dish. Consumption increased from 380 lbs of turtle meat in 1963 to more than 25,000 lbs in 1972. Green sea turtles were becoming scarce. At the time, nobody knew anything about turtles and their biology. In 1973, George Balazs, a University of Hawaii graduate, spent his first season on East Island in the French Frigate Shoals, about 500 miles from the main Hawaiian Islands where the majority of Hawaii’s females migrate to nest and lay their eggs. At the time, he counted only 67 nesting females. By 1978, George Balazs was successful in persuading the U.S. government to place the Hawaiian green sea turtle on the endangered species list. Today, more than 300 females next on East Island.
Green sea turtles in Hawaii are protected federally and under Hawaii state law, which prohibits injuring or harassing them (unless a special permit has been obtained for research or educational purposes). Violations of these laws can result in fines up to $100,000 and possibly time in prison. NMFS, FWS, and the State of Hawaii’s Department of Land and Natural Resources have recently formed a recovery team to help restore Hawaii’s Green sea turtle populations. The recovery plan involves identifying research, management, education, and enforcement needs for proper conservation and protection of green sea turtles.
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