Sea Turtle Information

Green Sea Turtle

Chelonia mydas

Photo: George H. Balazs

General Description

Of the three native Hawaiian species, the most common is the green sea turtle. This is the largest of the hard-shelled turtles weighing up to 440 pounds and measuring up to 4 feet. Hawaiian green turtles are slightly smaller than their Atlantic cousins. The green sea turtle gets its name from the color of its fat. Its shell is mostly dark brown and may be covered with patches of green algae. Sometimes, small groups of fish cluster around green turtles pecking at their shells. This is an example of a symbiotic relationship (a long standing relationship between two species). When both species benefit: the turtle gets its shell cleaned and the fish gets a meal, this special relationship is called mutualism.

Diet

Researchers know so little about sea turtles' early lives that they call the first few years the "lost years." During these lost years, green turtles float in ocean currents in the pelagic zone (open ocean) searching for a carnivorous (animal based) diet. At around 3–5 years of age, they move closer to shore where they forage for limu (algae and seagrass).

Reproduction

Green turtles are slow-growing reptiles and do not reach sexual maturity until somewhere between 10 and 59 years of age. In sexually mature animals, the difference between males and females is easy to see. The males' tails are thick and long. Females have short, stubby tails. Determining the sex of an animal by using external body characteristics is called sexual dimorphism. Green turtles mate in the water, close to shore and generally near their nesting beach. Males use the claws on their fore flippers to cling to the female and may mate on an annual basis.

Nesting

In many places in the world, development has destroyed the green sea turtles' nesting beaches. Fortunately, in Hawaii more than 90% of the nesting activity takes place far from highly populated main islands. Hawaiian green turtles navigate up to 800 miles to nest at a group of small atolls (low islets) called French Frigate Shoals. These isolated islands are part of the Northwestern Hawaiian Islands National Wildlife Refuge. In Hawaii, green turtles breed every two or more years. From late April through September, females haul their heavy bodies across the beach to lay their eggs above the high water line. First, they dig a pit for their own bodies, then a flask-shaped nest for the eggs. They can deposit up to seven clutches of eggs at 12 to 14 day intervals. Using their flippers, they cover the eggs with sand, and return to the sea leaving the nest completely unattended. The clutch of round, leathery eggs incubate in the warm sand until they are ready to hatch. The internal temperature of the nest determines the eventual sex of the turtles. Warmer nest temperatures generally produce female hatchlings. An emergence is an excited, frenzied activity that requires a team effort. All the hatchlings contribute to the job of not being buried alive. Some use their strong front flippers to scrape away sand from the ceiling, others undercut the walls, and the ones on the bottom compact the sand that filters down from above them. It can take several days for all of the hatchlings to emerge.

Worldwide

The green turtle ranges throughout the world in all tropical and sub-tropical oceans. The Hawaiian green sea turtle is listed as "threatened" under the U.S. Endangered Species Act of 1973. This means that the species is likely to become in danger of extinction throughout all or a significant portion of its range in the foreseeable future. In Florida and on the Pacific coast of Mexico it is considered "Endangered."

Hawksbill Turtle

Eretmochelys imbricata

Photo: George H. Balazs

To many people, the most beautiful sea turtle in the world is the hawksbill turtle. Its Hawaiian name is 'ea. The English name, hawksbill, comes from the animal's distinct, hawk-like beak. Historically, Pacific Islanders used the hawksbill's shell to make fish hooks, and the bones to make tools. The eggs supplied food while other parts of the animal provided medicine. Native Hawaiians used hawksbill "tortoise shell" to fabricate hair ornaments, jewelry, and other decorative and practical items. Today, this exploitation continues in some countries. Extinction threatens this extremely rare sea turtle. The hawksbill is listed as endangered under the U.S. Endangered Species Act.

General Description

The hawksbill is a medium sized turtle weighing between 95 and 160 pounds and reaching a length of approximately three feet. The adult turtle's shell is dark brown with faint yellow streaks and blotches. The color of the hawksbill's carapace (shell) varies in different locales.

Diet

For years, researchers thought that hawksbills were omnivorous scavengers, feeding on plants and animals. However, recent studies suggest that they eat sponges almost exclusively. They may ingest other animals accidentally when they are using their sharp beaks to dig in the narrow coral crevices. Sponges are difficult to digest because they have spicules, a skeletal framework of hard mineral rods. A sponge diet could make a turtle's flesh toxic. This may explain why Hawaiians rarely ate hawksbills, preferring the meat of green turtles.

Distribution

The hawksbill turtle populates fewer areas than any other sea turtle. Their habitat includes tropical reef areas in the Atlantic, Pacific and Indian oceans. Nesting and foraging takes place between the Tropic of Cancer and Tropic of Capricorn. In the U.S. they nest only in Hawaii and Southern Florida. They generally inhabit coastal reefs, bays, estuaries and lagoons.

Reproduction

The nesting season varies with geographical location. Hawksbill nests are difficult to locate and monitor because these rather solitary turtles often choose remote pocket beaches, hiding their nests under vegetation. Females may spend several hours breaking roots and digging in the sand searching for the perfect nesting site. Body size helps determine the number of eggs they lay. Hawksbills will sometimes share a nesting beach with green turtles. In Hawaii, nesting takes place only on the main islands at the southeast end of the chain. Fifty years ago, nesting sites were abundant in Mexico and Ecuador. Today no known nesting beaches remain on the Pacific coast of Mexico. Similar global trends are alarming evidence of their vulnerability.

The most critical problem this species faces is the harvest by humans. Historically, limitations of fishing methods and cultural restrictions controlled subsistence harvesting. Today, modern hunting gear, easy boat access to remote areas, and international trade all contribute to the serious commercial exploitation of the hawksbill turtle. Sea turtle products are the most common products confiscated by Customs agents at ports of entry into the United States.

Leatherback Sea Turtle

Dermochelys coriacea

Photo: Matthew Godfrey

The sea turtle with a real case of wanderlust is also the world's largest species tipping the scale at up to 2000 pounds and measuring 4 to 8 feet in length. Leatherback sea turtles inhabit offshore Hawaiian waters and oceans around the globe. They have the most extensive range of any reptile. Leatherbacks do not have a hard shell like other sea turtles. Their barrel-shaped bodies are divided by keels (ridges) into sections. Thousands of tiny bones, embedded in cartilage, support their leathery skin.

Leatherbacks are highly pelagic creatures. They spend most of their lives in the deep ocean waters eating jellyfish and other marine invertebrates. They eat twice their own weight each day! Unfortunately, in this constant quest for food, they mistake plastic bags and balloons for their natural diet. Ingesting plastic debris obstructs their digestive system and can kill them.

All sea turtles dive, but leatherbacks dive the deepest and stay down the longest. They have been tracked diving 1200 meters (3,937 feet) below sea level. They can stay under water for long periods of time because their bodies have a special adaptation which allows them to eliminate waste gases through their skin. Leatherbacks can withstand cool, deep-water temperatures for several reasons. Adults are large, so their surface area to volume ratio is low, which slows heat loss. Their metabolic rate is higher than that of other reptiles, which contributes to their heat energy. The thick layer of blubber under their leathery skin provides insulation.

Nesting females seem to prefer high energy beaches (beaches immediately adjacent to deep water). Females nest every 2 to 3 years and usually lay 4 to 5 times per season. These giants of the sea have been on Earth 25 times longer than humans. Sadly, we are the cause of their serious decline. Leatherback sea turtles are entangled in longlines, drown in shrimp trawler nets, are killed for their meat, and have lost important nesting beaches to development. Global cooperation in conservation efforts is the only hope for their survival.

For more information on the Leatherback see our Leatherback Sea Turtle Fact Sheet.

Loggerhead Sea Turtle

Caretta caretta

Photo: Michael White

In 1978, the Loggerhead turtle was listed as threatened throughout its range. Since then, its status has stayed the same although recent evidence suggests that the number of nesting turtles in some areas may be declining. Certain subpopulations may require reclassification to endangered. Because loggerheads, like all marine turtles, reach sexual maturity slowly (about 20–30 years) it is difficult to determine the true status of their populations.

Loggerhead turtles are easy to identify because they have an unusually large head. Their heart-shaped carapace is reddish brown on the top and underneath it is yellowish-brown. The hatchlings are dark brown in color. Mature loggerheads can weigh anywhere between 200 and 400 pounds. They typically measure between 32 and 41 inches in length.

Marine invertebrates make up the majority of the Loggerhead's carnivorous diet. Crabs, clams, mollusks, sea urchins, fish and sponges are all part of their bill of fare. Like all sea turtles, they crush their food with strong jaws as they don't have teeth for chewing.

Loggerheads are circumglobal creatures. They live in tropical, temperate and subtropical waters. Unlike many other sea turtles, they have adapted to a wide variety of habitats. Loggerheads populate continental shelves, bays, estuaries, and lagoons. The primary Atlantic nesting sites are along the east coast of Florida, the Gulf of Mexico, Georgia and the Carolinas. In the eastern Pacific, they range from Alaska in the north, to Chile in the south.

The mating season is from late spring to early summer. In the United States, the main nesting sites are along the east coast of Florida. There are also large nesting colonies off the coast of Oman in the Indian Ocean. Adult females nest at intervals of 2, 3, or more years. Females can nest up to 7 times in each season. They deposit between 100 to 126 eggs in each clutch. If the nest is undisturbed and the weather is favorable, the baby hatchlings will scratch their way to freedom in about 60 days.

Many aspects of human activities contribute to the demise of sea turtles. Shrimp trawlers and gill netting are major concerns for loggerheads living in the Gulf and southwest Atlantic waters. Loggerheads are also vulnerable to the dangers of offshore oil spills and all types of water pollution. In certain areas of the United States, humans still poach sea turtle eggs for food and profit. Because many turtle nesting beaches are also prime beach front property, coastal development has a negative impact on their survival.

General Description

The Kemp's ridley is one of the smallest sea turtles weighing between 75 to 100 pounds. Their shells are heart-shaped, oval or round. Their shells range in color from gray (in young turtles) to shades of olive green in adults. Kemp's ridleys are the most critically endangered species of all sea turtles.

Diet

The Kemp's ridleys are shallow water, benthic (ocean floor) feeders. They eat mostly invertebrates (animals with no backbone). Various types of crab seem to be their favorite food, but they also eat shrimp, mollusks, fish, and sea stars (starfish). They use their slightly hooked, strong beaks to crush their food. Like many other sea turtles, they migrate hundreds of miles from their coastal feeding grounds to their nesting beaches.

Reproduction

In 1947, over 40,000 female Kemp's ridleys nested on just one beach! This remarkable, simultaneous nesting is called arribada or arribazones. The phenomenon is unique to Kemp's and olive ridley sea turtles. At around 7 to 15 years of age, the Kemp's ridley has reached sexual maturity. From April to June, adults mate off the coasts of Tamaulipas and Veracruz, Mexico. Females lay approximately 100 eggs in each clutch every 10 to 28 days each year.

Unfortunately, the world may never see large arribadas of Kemp's ridley again. By the mid 1990s, the number of nesting females had declined from more than 40,000 to only several hundred. One basic problem is that they have only a single primary breeding area. At Padre Island, Texas scientists established a second, experimental site but it has produced limited success. Historically, hunting and overharvesting of eggs have been the major threats to Kemp's ridley populations. Currently, human activities, including population growth and the resulting pressures on coastal habitats, ocean pollution, offshore oil spills, and floating debris pose serious threats to their survival. The Mexican government protects only a portion of the nesting beach. The rest is open to construction and other disturbances. Kemp's ridley are also killed as bycatch (incidental catch) in shrimp trawlers, gill nets, hook and line, and crab traps.

Olive Ridley

Lepidochelys oliveacea

Photo: George H. Balazs

Olive ridleys are the most abundant of all sea turtles. Like the Kemp's ridley, they nest in large groups or arribadas. Formerly, there were large nesting concentrations at several beaches along the Pacific Coast of Mexico. Although these mass nestings continue to take place, studies show that there are disturbing downward trends at several arribada beaches. The Mexican nesting population is endangered under the U.S. Endangered Species Act. The rest of the populations are classified as threatened. Many scientists believe that western Atlantic nesting populations deserve endangered status. Since 1967, the Northern Atlantic population has decreased by 80%.

Olive ridleys have small heads and small, olive gray shells that measure around two feet in length. Their carapace color varies with geographic location. Western Atlantic animals are usually lighter than ones in the Eastern Pacific. They weigh between 70 to 100 pounds.

The olive ridley dines primarily on marine invertebrates including crabs, clams, shrimps and mussels. They crush and grind their food with their strong jaws. Sea urchins, squid and jellyfish are also part of the menu. When feeding, these turtles can dive up to 550 feet.

The olive ridley inhabits tropical regions of the Pacific, Indian and Atlantic Oceans. They migrate thousands of miles in the course of a year between nesting and foraging grounds. In the Indian Ocean, the species is abundant in only a few areas of eastern India and Sri Lanka.

Most, but not all, olive ridley turtles breed in huge groups in the summer or fall. It is common for olive ridleys to nest in successive years. Females lay about 100 eggs in each nest. Eggs hatch in 45–65 days. The number of individuals nesting at one time is very difficult to measure.

According to an article in India's national newspaper, 13,000 olive ridley sea turtles died in fishing trawler's nets during illegal fishing operations along the Orissa coast. The state government's failure to oversee and enforce fishing regulations contributed to this needless slaughter. Many governments worldwide fail to take threats to sea turtles' survival seriously and do not make sincere efforts to protect them. Along with bycatch fatalities, ocean pollution and loss of nesting beach habitats threaten the olive ridleys' long term survival.

Australian Flatback Sea Turtle

Natator depressus

Photo: Kellie Pendoley

This unique turtle gets its name because it has a rather flat shell. The flatback turtle is indigenous to Australian waters and is not found anywhere else in the world. They inhabit the coastal waters of Western, Northern and Eastern Australia. This is one of the only sea turtles that stays close to home.

The flatback's olive gray shell is elliptical in shape with upturned edges. The underneath part of the shell, the plastron, is pale yellow. The shell measures about 40–49 inches long and is very smooth and waxy. The carapace is thin and damages easily. Australian flatbacks are medium size turtles. Adults weigh about 185 pounds.

Like many sea turtles, they have a varied diet including squid, sea cucumbers, soft corals and mollusks. These carnivorous foragers have adapted to a diet that is available close to where they were born.

Flatbacks are unique in many ways including their choice of habitat. Instead of clear, coastal waters, flatbacks live in turbid, inshore waters.

Nesting takes place in November and December (Australia's summer) on steep, sloping beaches and sand dunes. Females lay about four times per season. The eggs hatch in 47–58 days. When the hatchlings emerge, they are larger than most species. They reach sexual maturity earlier than other turtles. This may be a result of their high protein diet.

Australian flatbacks have some interesting predators. Dingos, foxes, rats, and monitor lizards attack hatchlings. Inshore, herons and sea eagles feed on them.

Hawaii's Honu — Sea Turtle Watching in Hawaii

The island of Oahu, in the Hawaiian Islands, is home to the World Turtle Trust. Three species of sea turtles can be found in Hawaiian waters: the green (honu), hawksbill (honuea), and the giant leatherback. Almost all of the turtles seen in the near-shore waters of Hawaii are green sea turtles (honu). Honu primarily eat limu (seaweed) and algae which grow in shallower waters. In some areas, green sea turtles habitually haul themselves out of the water onto rocks and beaches during the day, presumably to rest. It is the plentiful honu that make turtle watching in Hawaii so exceptional. Locals and visitors alike swim year round with honu in the clear tropical waters of Hawaii.

Hawksbills tend to swim in deeper waters further off the coasts of the Hawaiian islands. Again, this behavior is likely determined by their primary food supply—sponges, which are found in deeper waters. Leatherbacks are rarely seen, and when they are seen they are generally in deep ocean waters, as their diet consists mainly of jellyfish.

Have you ever been lucky enough to swim with a sea turtle? Anyone who has experienced this thrill will remember the event in vivid detail. First, there is the heart-stopping moment of seeing a large, dark shadow in the ocean and wondering what it might be. Then, shock, when a prehistoric head pops out of the water. There is no reason to make a mad dash for the shore. Sea turtles are gentle, harmless animals. Tread water for a few moments and marvel at the honu's intricately patterned shell dappled in sunlight.

Swim a little closer and gaze into its dark, gentle eyes. Listen. You will hear a loud "poopf" when it exhales. Watch the strong jaws open for a gulp of air. Now, look inside that beaked mouth. You will not see teeth. Take a whiff…that sour smell is turtle breath. Suddenly, with a swift flip of its flippers the graceful honu will dive under you.

Please resist the temptation to chase it. Honu is a very fast swimmer and you will only frighten it away. Never grab a flipper! Sea turtles, like all reptiles breathe air and can drown. Instead, just hover on the surface and watch. Your reward may be the extraordinary sight of a green sea turtle tearing limu (seaweed) off the rocks with its sharp beak. If you don't intrude, this prehistoric mariner of the sea will let you watch in silent wonderment for a long time.

Even if you can't swim, you might get a close up look at a honu in Hawaii. Unlike other sea turtles, Hawaiian green turtles sometimes bask in the sun. They crawl out of the water along the shoreline and simply rest in the warm sun. Scientists speculate that honu bask to conserve energy, to avoid predators or for thermoregulation (body temperature control).