Marine Turtles

There are seven species of Marine Turtle and all are considered endangered.

Australian Flatback | Green Sea Turtle | Hawksbill | Kemp's Ridley | Leatherback | Loggerhead | Olive Ridley

Click on the links above for more detailed information om the individual species, a visual description, what marine turtles eat, where they live, information on marine turtle nesting, their current conservatioin status and the main threats to each marine turtle.

Marine Turtles

Marine turtles have been swimming in the oceans for at least 110 million years, but now our activities threaten turtle populations all over the globe. There are seven species of marine turtles. The International Union for Conservation of Nature and Natural Resources lists the Green Sea Turtle, Loggerhead and Olive Ridley turtles as endangered, and the Australian Flatback, Hawksbill, Kemp's Ridley and Leatherback turtles as critically endangered. Urgent conservation action is needed to prevent the extinction of marine turtle populations around the world. Some of the problems are;

All species of turtle are susceptible to accidental capture in fishing gear, a phenomenon known as bycatch, throughout the world's oceans. On the high seas they get caught in massive drift nets, or hooked on pelagic longlines set for tuna and swordfish. Longline fisheries appear to be particularly damaging, and a study estimated that more than 50,000 leatherback turtles and 200,000 loggerhead turtles were taken as longline bycatch throughout the world's oceans in the year 2000 alone. At their inshore foraging grounds and close to their nesting beaches they are caught by trawlers, gill nets or may become entangled in the buoy ropes of static gear such as prawn creels, tangle nets and lobster pots.

Throughout their range, marine turtles are still hunted for their meat, eggs, and shells. For example, marine turtles are still legally harvested for their meat in the Caribbean, where green and Hawksbill turtles are particularly targeted, although the fisheries are generally uncontrolled. It is not known if these harvests are sustainable, but marine turtle nesting populations in the Caribbean are critically low, most likely as a result of this harvest.

In the tropics, wherever turtles lay their eggs there is a demand for them. In Sri Lanka illegal turtle egg collection can result in the removal of 100% of the nests on some unprotected beaches. In Costa Rica they are eaten as an aphrodisiac. In several Caribbean countries, raw turtle eggs are mixed with alcohol and drunk as an aphrodisiac. The eggs are also eaten as a cure for asthma. No scientific evidence exists that turtle eggs have any of these properties. Extensive turtle egg collection is thought to have been a significant factor in the decline of several marine turtle populations around the world, including all of Sri Lanka's turtle nesting populations and the leatherback nesting population in Malaysia.

In many parts of the world, Hawksbill turtles are targeted for the scales (known as scutes) on their shells, which are used to make tortoiseshell. International trade in wild turtle products is banned by all the countries that have signed up to the Convention on International Trade in Endangered Species (CITES).

Marine turtles depend on a variety of habitats at sea, as well as the all important nesting beaches. These same beaches are under pressure from development, particularly from the tourism industry. If beach development is carried out insensitively it can lead to the interruption of nesting female turtles, erosion of sand from the beach, and light pollution. Light pollution disorientates emerging hatchlings, prompting them head inland to artificial light sources rather than out to sea.

Predicted sea-level rise resulting from climate change will lead to the inland movement of beaches, a process known as coastal squeeze. Critical turtle nesting habitat could be lost if nesting beaches are prevented from moving inland by any development or beach armouring behind them.

Marine habitat can also be unbalanced or ruined by development and other human activities. Seagrass beds and coral reefs are particularly vulnerable if exposed to untreated sewage effluent discharged into the sea and can also be damaged by heavy boat traffic and extensive use by bathers, snorkellors and divers. Excessive and unmanaged boat traffic using key turtle habitat can also lead to fatal boat strike, which has become a significant source of mortality for turtles using coastal waters along the eastern seaboard of the USA.

Marine pollution affects marine turtles and their habitat. Chemical pollution, such as oil spills, can kill marine turtles if they are exposed to it directly. It also leads to contamination of feeding grounds and nesting beaches. As described above, various types of feeding grounds can be degraded by exposure to pollution such as untreated sewage effluent.

Turtles can also be killed by entanglement in and ingestion of marine litter, such as discarded fishing gear, balloons and plastic. Turtle species such as leatherbacks and juvenile loggerheads that feed on floating animals such as jellyfish are particularly at risk, as they will also attempt to swallow floating litter. Turtles cannot digest plastic and if they eat enough to block their digestive tract they will die from starvation.

Marine litter can also affect nesting beaches, where accumulation of litter through the sand column and on the sand surface can reduce the availability of suitable nesting habitat. Litter on the nesting beach can also be hazardous to nesting females and emerging hatchlings.

Climate change will affect marine turtle populations in several ways. Turtle nesting beaches could be inundated if they are stopped from moving inland as a result of sea-level rise; feeding grounds such as tropical coral reefs and seagrass beds could die off as a result of sea-level rise, water temperature rise and the effects of increased storminess and rainfall.

In addition, marine turtle sex is determined by the temperature at which the eggs are incubated, with hotter temperatures producing female hatchlings and cooler temperatures producing males. If marine turtles do not change their nesting seasons, then increased surface temperatures at the nesting beaches resulting from climate change could lead to increased production of female hatchlings and thereby affect natural sex ratios and reproduction.

A closer look at the seven individual species follows;

Common Name: Australian Flatback - named because its shell is very flat.

Scientific Name: Natator depressus

Description: The head has a single pair of scales in front of its eyes. The flippers have 1 claw. The carapace is bony without ridges and has large, non-overlapping, scutes (scales) present with only 4 lateral scutes. The Flatback turtle is unusual in that its carapace is oval or round and the body is very flat. The edge of carapace is folded and covered by thin, non-overlapping waxy scutes. The carapace is olive-grey with pale brown/yellow tones on margins and the flippers creamy white. The scutes of the hatchlings form a unique dark-grey reticulate pattern, and the centre of each scute is olive coloured.

Size: Adults measure up to 1 metre carapace length.

Weight: Adults weigh an average of 90 kg.

Diet: Australian Flatbacks apparently eat sea cucumbers, jellyfish, mollusks, prawns, bryozoans, other invertebrates and seaweed.

Where do they live? Flatbacks are restricted to the waters of northern and northwest Australia and New Guinea's Gulf of Papua. They prefer turbid inshore waters, bays, coastal coral reef and grassy shallows.

Nesting: They nest only in Australia, primarily on the coast of Queensland. Australian Flatbacks nest 4 times per season. They lay an average of 50 eggs at time, but these are comparatively quite large. The eggs incubate for about 55 days. When the hatchlings emerge, they are larger than most species. Unlike other turtle species, the hatchlings do not swim out into the open ocean when they first enter the sea, but stay close inshore and inhabit coastal lagoons.

Status: - Listed as Endangered (in danger of extinction within the foreseeable future) under the U.S. Federal Endangered Species Act. International - Listed as Critically Endangered (facing an extremely high risk of extinction in the wild in the immediate future) by the International Union for Conservation of Nature and Natural Resources.

Threats to Survival: Flatbacks are threatened with capture, harvesting of eggs, destruction of nesting beaches, ocean pollution, oil spills and entanglement in fishing and shrimp nets.

Common Name: Green Sea Turtle - Once hunted for the trade in turtle soup, the green turtle manages to survive with populations throughout the tropics and the Mediterranean. The name derives from the greenish fat and cartilage, known as calipee, which was the main ingredient of turtle soup. In some areas, the Pacific green turtle is also called the black sea turtle.

Scientific Name: Chelonia mydas

Description: They are easily distinguished from other sea turtles because they have a single pair of prefrontal scales (scales in front of its eyes), rather than two pairs as the other sea turtles have. The head is small and blunt with a serrated jaw. All flippers have 1 visible claw. The carapace is bony without ridges and has large, non-overlapping, scutes (scales) present with only 4 lateral scutes. The body is nearly oval and is more depressed (flattened) compared to Pacific green turtles. The carapace colour varies from pale to very dark green and plain to very brilliant yellow, brown and green tones with radiating stripes. The plastron varies from white, dirty white or yellowish in the Atlantic populations to dark grey-bluish-green in the Pacific populations. Hatchlings are dark-brown or nearly black with a white underneath and white flipper margins. For comparison, the Pacific green turtle (aka Black Sea Turtle) has a body that is strongly elevated or vaulted and looks less round in a frontal view than other Green Sea Turtles. The colour is where you see the biggest difference with Pacific greens having a dark grey to black carapace and the hatchlings are a dark-brown or black with narrow white border with white underneath.

Size: Adults are up to 1.5 m long. The largest green turtle ever found was 1.52m in length and weighed 395 kg.

Weight: Adults can weigh 230 kg and are the second largest turtle.

Diet: Green sea turtle eating habits change significantly during its life. When less than 8 to 10 inches in length they eat worms, young crustaceans, aquatic insects, grasses and algae. Once green turtles reach 8 to 10 inches in length, they mostly eat sea grass and algae, the only sea turtle that is strictly herbivorous as an adult. Their jaws are finely serrated which aids them in tearing vegetation.

Where do they live? Green turtles are found in all temperate and tropical seas, preferring shallow coastal waters. Nesting occurs throughout their range, with large rookeries found in Costa Rica, Ascension Island, West Africa, Malaysia and Australia. There is a small, highly endangered population in the Mediterranean. They mainly stay near the coastline and around islands and live in bays and protected shores, especially in areas with seagrass beds. Green sea turtles are rarely observed in the open ocean.

Nesting: Green turtles nest at intervals of 2, 3, or more years, with wide year-to-year fluctuations in numbers of nesting females. They nest between 3 to 5 times per season and lay an average of 115 eggs in each nest, with the eggs incubating for about 60 days.

Status: Listed as Endangered (in danger of extinction within the foreseeable future) under the U.S. Federal Endangered Species Act. International - Listed as Endangered (facing a very high risk of extinction in the wild in the near future) by the International Union for Conservation of Nature and Natural Resources.

Threats to Survival: The greatest threat is from the commercial harvest for eggs and food. Other green turtle parts are used for leather and small turtles are sometimes stuffed for curios. Incidental catch in commercial shrimp trawling is an increasing source of mortality. They have been hunted for centuries and used to be so numerous that they were regularly hauled aboard ships for their meat. The popularity of turtle soup increased their value and in the early 20th Century commercial harvesting decimated many populations. Conservation efforts have led to significant recovery at some large nesting populations.

Common Name: Hawksbill - named for its narrow head and hawk-like beak.

Scientific Name: Eretmochelys imbricata

Hunted over the years for their beautiful shells, Hawksbill turtles are considered to be critically endangered. The scutes on their shells are misleadingly known as tortoiseshell and are sought after in some parts of the world to make jewellery and other ornaments. Trade in all wild marine turtles and their parts is currently banned under the Convention on International Trade in Endangered Species (CITES) but some illegal trade continues to endanger the species. Please don't buy genuine tortoiseshell items at home or abroad.

Description: The Hawksbill is one of the smaller sea turtles. The head is narrow and has long, tapered beak, 2 pairs of prefrontal scales (scales in front of its eyes). The jaw is not serrated. The flippers have 2 claws. The carapace is bony without ridges and has large, over-lapping scutes (scales) present and has 4 lateral scutes. It is elliptical in shape. It is orange, brown or yellow and hatchlings are mostly brown with pale blotches on scutes.

Size: Adults can reach 1 metre in length.

Weight: Adults can weigh between 40 and 60 kg.

Diet: The Hawksbill's narrow head and jaws shaped like a beak allows it to get food from crevices in coral reefs. They eat sponges, anemones, squid and shrimp.

Where do they live? Hawksbills are the most tropical of all the marine turtles, living around tropical coral reefs and lagoons in the Atlantic, Pacific and Indian Oceans. Hawksbills nest throughout the tropics with significant rookeries at sites in Australia, the Seychelles, the Caribbean and Mexico. They are typically found around coastal reefs, rocky areas, estuaries and lagoons.

Nesting: Hawksbills nest at intervals of 2, 3, or more years. They nest between 2 to 4 times per season and lay an average 160 eggs in each nest. The eggs incubate for about 60 days.

Status: - Listed as Endangered (in danger of extinction within the foreseeable future) under the U.S. Federal Endangered Species Act. International - Listed as Critically Endangered (facing an extremely high risk of extinction in the wild in the immediate future) by the International Union for Conservation of Nature and Natural Resources.

Threats to Survival: The greatest threat to Hawksbill sea turtle is the harvesting for their prized shell, often referred to as "tortoise shell." In some countries the shell is still used to make hair ornaments, jewellery, and other decorative items.

Common Name: Kemp's Ridley - named Kemp's after Richard Kemp, who helped discover and study the turtle. The name ridley may come from the word "riddler" or "riddle" because this species was once thought be a hybrid of other turtle species. Kemp's ridleys are the most rare of all the marine turtles, and were close to extinction in the 1980's.

Scientific Name: Lepidochelys kempii

Description: The head is moderate and triangular in size with a broad parrot-like beak. The front flippers have 1 claw, while the rear flipper has 1 or 2 claws. The carapace is bony without ridges and has large, non-overlapping scutes (scales) present. It has 5 lateral scutes and is very rounded. Adults have a dark grey green carapace with a white or yellowish plastron, while the hatchlings are jet black.

Size: Kemp's ridleys are the smallest marine turtles. Adult Kemp's ridleys have an almost completely round carapace measuring about 70cm long.

Weight: Adults weigh on average 40kg.

Diet: Kemp's ridleys have powerful jaws that help them to crush and grind crabs, calms, mussels, and shrimp. They also like to eat fish, sea urchins, squid and jellyfish and other small sea creatures living on the muddy areas of the seabed where they like to forage.

Where do they live? They are mostly limited to the Gulf of Mexico. Juvenile Kemp's ridleys range between tropical and temperate coastal areas of the northwest Atlantic Ocean and can be found up and down the east coast of the United States. Kemp's ridleys refer shallow areas with sandy and muddy bottoms.

Nesting: The only major breeding site for Kemp's ridleys is on a stretch of beach at Rancho Nuevo in Mexico. Kemp's ridleys nest more often than other species, every 1.5 years on average. They also nest in mass synchronized nestings called arribadas (Spanish for "arrival"). Kemp's ridley nest 2 - 3 times each season. They lay an average of 110 eggs in each nest and the eggs incubate for about 55 days.

Status: - Listed as Endangered (in danger of extinction within the foreseeable future) under the U.S. Federal Endangered Species Act. International - Listed as Critically Endangered (facing an extremely high risk of extinction in the wild in the immediate future) by the International Union for Conservation of Nature and Natural Resources.

Threats to Survival: The population was decimated by egg harvesting, hunting of nesting females and by the accidental drowning of thousands of turtles in shrimp trawl nets in the Gulf of Mexico. The nesting population of female Kemp's Ridleys was down to a few hundred nesting females laying approximately 700 nests in 1985. Since then, successful conservation efforts by the Governments of Mexico and the USA and other conservationist organisations have led to better protection at the nesting beach and the use of Turtle Excluder Devices on shrimp trawlers in the Gulf of Mexico. The Kemp's ridley population is slowly recovering and now approximately 10,000 nests are laid at Rancho Nuevo each year.

Common Name: Leatherback - The Leatherback is the largest of the marine turtles and gets its name from the black, leathery skin that covers its carapace (shell). They are unique amongst reptiles in that they have some internal control of their own body temperature, so can forage in temperatures lower than 5ºC and can dive to depths of over 1km.

Scientific Name: Dermochelys coriacea

Description: The head has a deeply notched upper jaw with 2 cusps. All flippers are without claws. The Leatherback is the only sea turtle that lacks a hard shell. Its carapace is large, elongated and flexible with 7 distinct ridges running the length of the animal. Composed of a layer of thin, tough, rubbery skin, strengthened by thousands of tiny bone plates, the carapace does not have scales, except in hatchlings. It is dark grey or black with white or pale spots, while the plastron is whitish to black and marked by 5 ridges. Hatchlings have white blotches on carapace.

Size: Usually about 2m long. The biggest turtle ever recorded was a male Leatherback known as the Harlech Turtle that washed up dead at Harlech, North Wales in the UK in 1988. It had drowned after entangling in fishing gear and it measured 2.91m in length and weighed 916 kg!

Weight: Around 600kg.

Diet: Leatherbacks have delicate, scissor-like jaws. Their jaws would be damaged by anything other than a diet of soft-bodied animals, so they feed almost exclusively on jellyfish. It is remarkable that this large, active animal can survive on a diet of jellyfish, which are composed mostly of water and appear to be a poor source of nutrients. Leatherbacks often mistake litter, such as plastic bags and balloons, for jellyfish and eat them. Plastic can block a turtle's gut, causing death by starvation. Please dispose of your litter responsibly.

Where do they live? Leatherbacks are the most widely distributed of all sea turtles. Found world wide with the largest north and south range of all the sea turtle species. With its streamlined body shape and the powerful front flippers, a Leatherback can swim thousands of miles over open ocean and against fast currents. They are primarily found in the open ocean, as far north as Alaska and as far south as the southern tip of Africa, though recent satellite tracking research indicates that Leatherbacks feed in areas just offshore. Known to be active in water below 5ºC, the only reptile known to remain active at such a low temperature.

Nesting: Important rookeries are found on the coasts of Central and South America as well as West and South Africa. Leatherbacks nest at intervals of 2 to 3 years, though recent research has indicated they can nest every year. They nest between 6 to 9 times per season, with an average of 10 days between nestings. Leatherbacks lay an average of 80 fertilized eggs, the size of billiard balls, and 30 smaller, unfertilized eggs, in each nest. Eggs incubate for about 65 days. Unlike other species of sea turtles, Leatherback females may change nesting beaches, though they tend to stay in the same region.

Status: - Listed as Endangered (in danger of extinction within the foreseeable future) under the U.S. Federal Endangered Species Act. International - Listed as Critically Endangered (facing an extremely high risk of extinction in the wild in the immediate future) by the International Union for Conservation of Nature and Natural Resources.

Threats to Survival: Greatest threat to Leatherback sea turtles is from incidental take in commercial fisheries and marine pollution, such as balloons and plastic bags floating in the water, which are mistaken for jellyfish.

Common Name: Loggerhead - named for its exceptionally large head, which houses powerful jaw muscles and large beak for crushing its crustacean prey.

Scientific Name: Caretta caretta

Description: The head is very large with heavy strong jaws. The front flippers are short and thick with 2 claws, while the rear flippers can have 2 or 3 claws. The carapace is bony without ridges and has large, non-overlapping, rough scutes (scales) present with 5 lateral scutes. It is heart shaped, reddish-brown with a yellowish-brown plastron. Hatchlings have a dark-brown carapace with flippers pale brown on the margins.

Size: Around 1 metre in carapace length.

Weight: Adults can weigh up to 180 kg.

Diet: They are primarily carnivorous and feed mostly on shellfish that live on the bottom of the ocean. They eat horseshoe crabs, clams, mussels, and other invertebrates. Their powerful jaw muscles help them to easily crush the shellfish.

Where do they live? Loggerheads can be found in temperate and subtropical coastal waters worldwide, although they tend not to nest in the tropics. They nest at a few sites in the Mediterranean, and along the coasts of Oman, South Africa, Australia and southeast USA. They prefer to feed in coastal bays and estuaries, as well as in the shallow water along the continental shelves of the Atlantic, Pacific and Indian Oceans.

Nesting: Loggerheads nest at intervals of 2, 3, or more years. They lay 4 to 7 nests per season, approximately 12 to 14 days apart. They lay an average of between 100 to 126 eggs in each nest. The eggs incubate for about 60 days.

Status: - Listed as Threatened (likely to become endangered, in danger of extinction, within the foreseeable future) under the U.S. Federal Endangered Species Act. International - Listed as Endangered (facing a very high risk of extinction in the wild in the near future) by the International Union for Conservation of Nature and Natural Resources.

Threats to Survival: The greatest threat is loss of nesting habitat due to coastal development, predation of nests, and human disturbances, such as coastal lighting and housing developments, that cause disorientations during the emergence of hatchlings. Other major threats include incidental capture in longline fishing, shrimp trawling and pollution. Incidental capture in fisheries is thought to have played a significant role in the recent population declines observed for the Loggerhead.

Common Name: Olive Ridley - The name ridley may come from the word "riddler" or "riddle" because this species was once thought be a hybrid of other turtle species. The Olive Ridley is famous for its spectacular arribadas (Spanish for arrival), where thousands of females nest simultaneously on the same beach.

Scientific Name: Lepidochelys olivaceaf

Description: The head is quite small. Both the front and rear flippers have 1 or 2 visible claws. There is sometimes an extra claw on the front flippers. The carapace is bony without ridges and has large scutes (scales) present. It has 6 or more lateral scutes and is nearly circular and smooth. Its body is deeper than the very similar Kemp's Ridley sea turtle. Juveniles are charcoal grey in colour, while adults are a dark grey green. Hatchlings are black when wet with greenish sides.

Size: Adults measure up to 1m.

Weight: Adults weigh between 35 and 45 kg.

Diet: Olive ridleys have powerful jaws that allow for an omnivore diet of crustaceans, such as shrimp, crabs, molluscs, tunicates, fish.

Where do they live? Olive ridleys are widespread throughout the tropical and subtropical waters of the Pacific, Indian and Atlantic Oceans. They are generally found in coastal bays and estuaries, but can be very oceanic over some parts of its range. They typically forage off shore in surface waters or dive to depths of 150m to feed on bottom dwelling crustaceans.

Nesting: The females nest individually or in arribadas, when large groups of turtles nest together on one rookery. Arribadas occur on a few isolated tropical beaches in Central America. The largest known aribbada occurs twice a year on the coast of Orissa northeast India. They nest every year. An Olive ridleys nests 2 times each season and lays an average of over 105 eggs in each nest. The eggs incubate for about 55 days.

Status: - Listed as Threatened (likely to become endangered, in danger of extinction, within the foreseeable future) under the U.S. Federal Endangered Species Act. International - Listed as Endangered (facing a very high risk of extinction in the wild in the near future) by the International Union for Conservation of Nature and Natural Resources.

Threats to Survival: The direct harvest of adults and eggs, incidental capture in commercial fisheries and loss of nesting habitat are the main threats to this species.