LEATHERBACK SEA TURTLES
Leatherback sea turtles (Scientific name: Dermochelys coriacea) are the world’s largest and fastest reptile, and the most ancient and fastest-swimming turtle. Their have been around for 100 million years, surviving the asteroid that wiped out the dinosaurs 65 million years ago. Generally they spend less that two hours on land a year. [Source: Tim Appenzeller, National Geographic, May 2009]
No one known how long leatherbacks live. It has been estimated that their lifespan could be 50 years or more. Leatherback turtles grow faster than hard-shelled turtles. However, there is uncertainty about the age at which they reach sexual maturity. Average estimates range from nine to 20 years of age. Based on growth layers in the bones that encircle their pupils it could be 30 years before they reach maturity. [Source: NOAA]
A leatherback hatchling is smaller than a child's hand when it hatches, yet it grows to a length of two meters (six feet) and can weigh over 900 kilograms (half a ton). It flippers can stretch three to 4.5 meters (10 to 15 feet). A male leatherback found washed up on a beach in Wales in 1988, was 2.87 meters (9 feet, 5½ inches) long and weighed 962 kilograms (2,120 pounds).
Leatherback sea turtles are the only species of sea turtle that lack scales and a hard shell. They are named for their tough rubbery skin. Leatherbacks are highly migratory, some swimming over 16,000 kilometers (10,000 miles) a year between nesting and foraging grounds. They are also accomplished divers with the deepest recorded dive reaching nearly 1,300 meters (4,000 feet) — deeper than most marine mammals. There are Atlantic and Pacific subspecies or species. Killer whales are one of the few creatures that are known to feed on leatherback sea turtles. [Source: NOAA]
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures; Leatherback sea turtle expert: Scott Eckert, Hubbs-Seaworld research Institute, San Diego CA; Book: “Voyage of the Turtle: In Pursuit of the World’s Last Dinosaur” by Carl Safina (McCrae Books, Henry Holt, 2005]
Leatherback Sea Turtle Habitat and Where They Are Found
Leatherback sea turtles have the widest global distribution and are the most migratory of all reptiles. They have adapted to both Arctic and tropical waters. You can find leatherback sea turtles as far north as Canada and the northern Pacific Ocean. They have been seen as far north as the Aleutian Islands and as far south as Tasmania. They tend to nest on tropical or subtropical beaches however. Within the United States, the leatherback is known to nest in southeast Florida, Puerto Rico, Cape Lookout, North Carolina and St. Croix in the U.S. Virgin Islands. [Source: NOAA +]
leatherback range and nesting sites Leatherbacks are primarily pelagic (open ocean) animals. They travel great distances from their nesting beaches to their feeding grounds. They travel further north than any other sea turtle — to waters off of Newfoundland, Nova Scotia, and Labrador in the western Northern Atlantic and Britain and Norway in the eastern North Atlantic. . They also inhabit South Atlantic Waters, as far south as Argentina and South Africa. [Source: Adam Farmer; Annamarie Roszko; Scott Flore; Kevin Hatton; Veronica Combos; Andrea Helton; Fermin Fontanes, Animal Diversity Web (ADW) /=]
Leatherbacks have been satellite tagged at sea on foraging grounds off Nova Scotia, Canada and tracked to nesting beaches in the Caribbean. Western Pacific leatherbacks feed off the Pacific coast of North America, and migrate across the Pacific to nest in Indonesia, Papua New Guinea, and the Solomon Islands. Eastern Pacific leatherbacks, on the other hand, nest along the Pacific coast of Mexico and Costa Rica, and forage in the south-central and eastern tropical Pacific Ocean. +
Most leatherback sea turtles nest on beaches off tropical or sub tropical waters. Major nesting sites for Pacific leatherbacks are found in Costa Rica, Mexico, Malaysia and Indonesia. Major nesting sites for Atlantic leatherbacks are along the northern coast of South America and in the Caribbean. See Nesting Sites Below.
Leatherback sea turtles are widely known as pelagic (open ocean) animals but are seen in coastal waters when searching for food. They have been discovered in waters as deep as 1230 meters (4035 feet), well below the photic zone. Leatherbacks lay their eggs in the sand on tropical beaches. Nesting time is the only time they emerge onto land, and only the females do so. /=\
Leatherback Sea Turtle Characteristics
Leatherback sea turtle range in weight from 250 to 900 kilograms (550 to 1982 pounds) and range in length from 1.45 to 1.6 meters (4.75 to 5.2 feet). For adults, the distance from the tip of one front flipper to the tip of the other is around 2.7 meters (nine feet). Females are larger than males. Leatherbacks. [Source: Adam Farmer; Annamarie Roszko; Scott Flore; Kevin Hatton; Veronica Combos; Andrea Helton; Fermin Fontanes, Animal Diversity Web (ADW)]
Leatherback sea turtles are the only reptiles that qualify as warm blooded. They are usually found in warm water but they can range into cold waters in high latitudes because of their ability to generate body heat. This is achieved with a high metabolic rate, two kinds of fat and sophisticated heat-exchange system.
Leatherbacks have rubbery skin with pinkish-white coloring on their underside. Their back is are primarily black or dark brown with white speckles. and They are the only species of sea turtle that lack scales. Their front flippers are proportionally longer than in other sea turtles and their back flippers are paddle-shaped. Both their rigid carapace and their large flippers make the leatherback uniquely equipped for long distance foraging migrations. Leatherback hatchlings are mostly black. Their flippers are margined in white. Rows of white scales give hatchling leatherbacks the white striping that runs down the length of their backs.[Source: NOAA, /=]
Leatherbacks differs from all other turtles in that they are protected by a large leathery sheath of cartilage, with the texture of smooth, hard rubber, rather than a conventional shell. Leatherback have no visible shell (carapace). The shell is present but it consists of bones that are buried into their skin. These small, interlocking dermal bones lie beneath the skin and overlie a supportive layer of connective tissue and fat and the deeper skeleton. The sheath tapers to a blunt point and has seven pronounced, lengthwise-running ridges on the top and five on the underside. The interlocking coin-size plates of bone may compress at extreme depths. The teardrop shape of the sheath and keel-like ridges ease flow across the sheath that merges almost seamlessly from the turtles neck and thick shoulders.
Leatherback sea turtles have large heads, short, thick necks and have a secondary palate, formed by vomer and palatine bones. Leatherback sea turtle ribs and vertebrae are not fused to the cartilage as is the case with normal turtles and their shells. The hundreds of bony plates that are imbedded in the skin and impregnated with oil that helps make them waterproof. Their flippers have no claws.
Leatherback Turtle’s Third Eye
Each leatherback sea turtle turtle has a pinkish spot on its forehead. For a long time no one knew for sure what this spot did. Some have referred to it as a “third eye” because a stalk from the turtle’s brain extends just below the spot, where the skull is at its thinnest. It is thought that the spot receives signals of some sort.
In 2015, Smithsonian magazine reported: New research shows that the turtle has what British biologist John Davenport calls a “skylight” on the top of its skull, an unusually thin area of bone just beneath a spot of unpigmented skin that allows light to impinge directly on the brain’s pineal gland. With changes in long-wave light, Davenport proposes, the brain computes the “equilux,” the day (close to the equinox, but not necessarily coinciding) when sunset and sunrise are exactly 12 hours apart. More reliably than water temperature or light intensity, that’s the signal for turtles feeding in the North Atlantic to head south each fall. [Source: Jerry Adler, Smithsonian magazine, January 2015]
“In most vertebrates, humans included, the pineal regulates sleep and other cyclical activities in response to ambient light. A few species, mostly reptiles and amphibians, actually have a third eye on the top of their head to measure daylight, complete with a lens and retina — similar, but not identical, to the forward-facing eyes. Only leatherbacks, as far as we know, have the skylight.
Leatherback Sea Turtle Behavior
Leatherback sea turtles are the most widely distributed and migratory of all reptiles. They spend nearly all of their time in the open sea. Males spend all of their lives in the open sea and very little is known about them. Females come ashore on average once every three years to lay their eggs.
Leatherback sea turtles are strong and fast swimmers, capable of swimming 35 kilometers per hour (22mph) and are large and powerful enough avoid predation. Adult leatherbacks defend themselves aggressively. One 1.5-meter adult was observed chasing a shark that had apparently attacked it, and once the shark fled, the turtle attacked the boat that the observers were in.
Leatherback sea turtles are mostly solitary. They undertake the longest migrations between breeding and feeding areas of any sea turtle, some averaging 600 kilometers (3,700 miles) each way. They spend most of their lives in the ocean, but females leave the water to lay eggs. Leatherbacks are strong swimmers and can dive to depths of over 1300 meters (4,000 feet) — deeper than any other turtle — and can stay down for up to 85 minutes. They seem to be able locate places that have high concentrations of jellyfish, and may dive deep to feed to escape potential predators or seek out high concentrations of prey. [Source: NOAA]
Leatherback Sea Turtle Swimming and Diving
Leatherback sea turtle expert Scott Eckert of Hubbs-Seaworld Research Institute in San Diego says that although leatherbacks look awkward on the land they are excellent swimmers, and are built for long-distance travel: “This one of the finest hydrodynamically designed animals on the planet. They can probably swim as easily as rest,” he said. “They are the most graceful creatures you’ve ever seen. “
The leatherback propels itself with an efficiency no other sea turtle can match, Tim Appenzeller wrote in National Geographic. “All sea turtles can fly through the water by flapping their flippers vertically, generating thrust on both the upstroke and the down. But while other species sometimes shift to less efficient paddling motion, the leatherback uses its longer flippers exclusively as wings.” Jeanette Wynwkwn, who has analyzed leatherback swimming with high speed video said it is “almost pure underwater flight.”
Studies have shown that leatherbacks swim almost constantly, both day and night, at an average speed of 1½ mph. They often dive for jellyfish. In the middle of the day they often swim about two meters below the surface, deep enough to avoid surface wave action and shallow enough to absorb the sun’s rays. Some scientist believe they use the sun to orient themselves when swimming to a new feeding site.
Leatherbacks are the deepest diving of all turtles. They can dive to 1230 meters (4035 feet) — farther than even sperm whales go — and hold their breath for more than an hour. When they dive a sphincter closes off the blood flow to the lungs, conserving energy. The cartilage sheath (its “shell”) compresses under pressure and doesn’t crack as a shell on other sea turtles would.
Cold-Water-Adapted Leatherback Sea Turtles
Leatherback sea turtles feed in waters that are far colder than other sea turtles can tolerate. Leatherbacks can endure long periods of time in water that is 12 degrees F colder than their body temperature. They have a network of blood vessels that work as a counter-current heat exchanger, a thick insulating layer of oils and fats in their skin, and are able to maintain body temperatures much higher than their surroundings.. [Source: Adam Farmer; Annamarie Roszko; Scott Flore; Kevin Hatton; Veronica Combos; Andrea Helton; Fermin Fontanes, Animal Diversity Web (ADW) /=]/=\
Leatherback sea turtleshave the ability to regulate their body temperature. Cold blood returning from the flippers is warmed by outgoing blood before reaching the body core. In very cold water blood flow to and from the flipper surface may shut down intermittently. The leatherback’s large size, thick outer layer of fat, also helps it generate and retain heat. Put you hand on a leatherback’s shoulder and it feels warm to the touch, unusual for a reptile. In an experiment, scientists placed a leatherback in ice and found that it recovered quickly.
Leatherback blood hold large amounts of oxygen because it has more red blood cells than any other reptile. The heart is particularly large with an unusual shutting arrangement which allowed partially oxygenated blood to bypass the lungs, which need to stay compressed in long dives, to deliver more oxygen to the muscles.
Feeding Leatherback Sea Turtles
Leatherback sea turtles are carnivores that roam the open ocean and feed almost exclusively on jellyfish and salps (a free-swimming marine invertebrate related to the sea squirts). Occasionally they eat other kinds of food, including small crustaceans and fish (possibly symbiotes with jellies), cephalopods, sea urchins, and snails. Leatherbacks play an important ecological role by eating jellyfish that feed on the fry of tuna and swordfish and other fish. They usually feed at the surface but are capable of making deep dives.
Leatherbacks lack the crushing, chewing plates characteristic of other sea turtles that feed on hard-bodied prey. Instead, they have pointed tooth-like cusps and sharp-edged jaws that are perfectly adapted for a diet of soft-bodied open ocean prey such as jellyfish and salps. A leatherback's mouth and throat also have backward-pointing spines that help retain gelatinous prey. [Source: NOAA]
Autopsies of dead leatherbacks have revealed they have huge stomachs, often filled with masses of relatively low-calorie and mostly-water jellyfish, stingers and all. Massive salt glands collect excess salt from the jellyfish and excrete it as viscous tears. A favored prey is the lion’s mane. Among the largest jellyfish, it can weigh more than five kilograms. Leatherback sea turtles, sunfish and some other species have backward-pointing pharyngeal "teeth" at the back their throats that prevent slippery prey from sliding back out their mouths. After swallowing a jellyfish they regurgitate it against these teeth, which strains out the water and leaves behind the edible material which is swallowed and digested.
Jellyfish offer little nutrition and sustenance. Like pandas eating bamboo, leatherbacks have to eat a lot of jellyfish and spend a lot of time eating it to get enough calories to power their large bodies. By some estimates leatherbacks need to eat their weight in jellyfish every day to get the nutrition they need. One turtle video taped devoured 60 lion’s mane jellyfish in three hours. Jellyfish consumption estimates vary, one study estimated that adult leatherbacks probably eat about 1000 kilograms of jellyfish per year, another study estimated they eat 2900-3650 kilogram a year.
Leatherback Sea Turtle Reproduction and Mating
Leatherback sea turtles are oviparous (young are hatched from eggs and engage in seasonal breeding. Females reach sexual maturity at five to 21 years. They typically nest once every two or three years and return to the same nesting location every two to three years. They lay about five to seven nests per year, renesting every nine to 10 days. The nesting and breeding season is generally between April and November. In the United States and Caribbean, it lasts from March to July.The number of offspring ranges from 50 to 70, with the average number of offspring being 105. The gestation period ranges from 55 to 75 days[Source: Adam Farmer; Annamarie Roszko; Scott Flore; Kevin Hatton; Veronica Combos; Andrea Helton; Fermin Fontanes, Animal Diversity Web (ADW) /=]
Leatherback turtles They are polygynandrous (promiscuous), with both males and females having multiple partners. Males migrate just offshore to common nesting beaches generally before the nesting season begins. There try and mate with as many females as possible. Studies suggest that the males return to the same nesting beach if they were successful in the previous season. /=\
Leatherback sea turtles mate in the water, just offshore from the nesting beaches. Male leatherback sea turtle sometimes attempt to mate with females just coming from their nesting beaches. Sometimes the females return to their nesting sites 10 days after the eggs are laid. Sometimes females coming ashore and those returning to see after laying their eggs collide on the beach. Each is so purposeful it refuses to give away, with each pushing forwards until enough of an angle emerges to allow them to wedge past each other.
Female Leatherback Sea Turtles Laying Their Eggs
Female swim ashore at night to nest and lay a clutch of usually 50 to 170 eggs, with the average being around 100. A large percentage of those eggs are yolkless and don’t develop any further. Females lay her eggs and then cover the nest with sand to discourage predation and moderate the temperature and humidity around the eggs. Nesting females tamp down the sand over their clutch of eggs, perhaps to obscure the scent of the eggs or make it harder for small predators to dig up the eggs. After the female has completed this process she will returns to the ocean, leaving behind long, circling tracks.. Male leatherback sea turtles never swim to shore and have no part in the nesting process. /=\
Leatherbacks nest several times during a nesting season, typically at 8- to 12-day intervals. They dig a large body pit to lay their eggs in deep egg chambers (nests). Female leatherbacks nest at night on tropical and subtropical beaches. They usually arrive on the beaches on dark, moonless nights to avoid being detected. The eggs incubate approximately two months before leatherback hatchlings emerge from the nest. Hatchlings wait until nightfall to emerge and head for the water as quick as they are able, to avoid predators.
David Attenborough wrote: "With her immense flippers, she heaves herself up the wet sand. Every few seconds she stops and rests. It takes her half an hour or more to climb to the level she seeks, for the nest must be above the reach of the waves yet the sand must be sufficiently moist to remain firm and not cave in as she digs. Then she determinedly starts clearing a wide pit with her front flippers, sweeping a shower soft sand behind her. After a few minutes work, it is deep enough, and with the most delicate movements of her broad back flippers, she scoops out a narrow shaft in the bottom."
"She sheds her eggs quickly, in groups, her back flippers clasped on either side of her ovipositor, guiding the eggs downward. As she lays, she sighs heavily and groans. Mucus trickles from her large lustrous eyes. In less than half an hour, all her eggs are laid and she carefully fills it in, pressing the sand down with her hind flippers. She seldom returns directly to the sea but often moves over to other places on the beach...to confuse her trail. Certainty, by the time she heads back to the waves, the surface of the beach has been so churned up that it is almost impossible to guess just where her eggs lie."
Leatherback Sea Turtle Nesting Sites
Nesting sites have been discovered along the coasts of French Guiana, Suriname, Guyana, Trinidad, Gabon, West Africa, Parque Marino Las Baulas in Guanacaste, Costa Rica, Papua New Guinea, Andaman and Nicobar Islands and Malaysia. Currently, the largest remaining nesting aggregations are found in Trinidad and Tobago, West-Indies in the Caribbean Sea and Atlantic Ocean. and Gabon in Africa in the Southeast Atlantic. In the 1990s, the largest nesting colony was on the coast of French Guiana. More than 7,000 females laid as many as 50,000 eggs there in 1988 and again in 1992. /=\
Perhaps the largest leatherback nesting site is on 10-kilometer-long Matura Beach in Trinidad. Tim Appenzeller wrote in National Geographic, “By day the beach looks as if giant dune buggies have ramped across it. Chevron-pattern tracks five feet wide cover the sand, interrupted by shallow car-size pits. By night the the real earthmovers arrive. Black and gleaming in the moonlight, each female drags herself from the surf, front flippers scouring the sand as she pulls herself along and settles into dig. Scooping with the rear flippers, she excavates a shaft; when she can longer reach the bottom she begins to lay her eggs, a glistening cue ball every few second. Once she has a cache of 80 or so, she fills in the nest, sweeping her front flippers to smooth out the spot. Then she drags herself a feet away and makes another hole — a decoy nest that may serve to confuse predators. After two or three hours in the beach, here throat rosy from exertion, she returns to the sea.”
Young Leatherback Sea Turtles
The shells of leatherback hatchlings are covered with small, pearly scales that disappear after a period of time. As is true with other sea turtle species, the chances of a leatherback sea turtle egg producing a mature adult are very slim. Crabs, herons, birds, racoons and even jaguars feed on eggs and hatchling on land and predator fish wait for the hatchling offshore when they enter the water. People collect the eggs in spite of laws preventing them from doing so.
Nest temperature determines the hatchlings' sex. At 29.5̊ Celsius (85̊ F) hatchlings are equally likely to be male or female, hatchlings incubated at 28.75°C (83.75̊ F) or less will be male, above 29.75°C (85.5̊F) they'll be female. [Source: Adam Farmer; Annamarie Roszko; Scott Flore; Kevin Hatton; Veronica Combos; Andrea Helton; Fermin Fontanes, Animal Diversity Web (ADW) /=]
Baby leatherback Experts estimate that just 1 in 1,000 eggs result in an adult turtle. To begin with many eggs lack a yolk and don't even develop. Hatching success of clutches is about 50 percent in an undisturbed nest. Leatherback turtles eggs and young hatchlings are consumed by a large variety of predators, including ghost crabs land animals such as monitor lizards, raccoons , coatis, genets, dogs, mongooses, pigs, sea animals such as cephalopods and requiem sharks, birds such as turnstones, knots, plovers frigate birds, vultures and hawks.
Predators dig up eggs or take hatchlings as the little turtles race for the sea, Hatchlings wait until nightfall to emerge and head for the water as quick as they are able, to avoid predators. In the ocean, small leatherbacks are attacked by cephalopods, requiem sharks and other large fish.
As time goes on a young turtle's chance of survival presumable increases. Leatherbacks may be the fastest growing reptile in the world, reaching adult size in seven to 13 years. Leatherback hatchlings are smaller than a child's hand when it hatches, They weigh 35-50 grams, and grow very fast.
Migrating Leatherback Sea Turtles
Tagged Leatherback sea turtles have been tracked migrating 11,300 kilometers (7,000) miles to feed, mate and lay eggs. Leatherbacks must lay their eggs in warm sands. They migrate to cold far away waters to feed on jellyfish. In recent years leatherbacks have been showing up more in waters that were regarded as too cold for them such as off Nova Scotia.
Leatherbacks have been satellite tagged at sea on foraging grounds off Nova Scotia, Canada and tracked to nesting beaches in the Caribbean. Western Pacific leatherbacks feed off the Pacific coast of North America, and migrate across the Pacific to nest in Indonesia, Papua New Guinea, and the Solomon Islands. Eastern Pacific leatherbacks, on the other hand, nest along the Pacific coast of Mexico and Costa Rica, and forage in the south-central and eastern tropical Pacific Ocean. [Source: NOAA +]
Satellite tagging studies of leatherbacks from the Western Pacific indicate that turtles that nest during different times of the year have different migration patterns. Summer nesting turtles (July through September) have tropical and temperate northern hemisphere foraging regions, while winter nesters (November through February) traverse to tropical waters and temperate regions of the southern hemisphere. Female leatherbacks return to nest every 2 to 4 years. +
Turtles from Samoa have swum across the Pacific Ocean to California in almost a straight line. Leatherbacks also have been tracked traveling between New Guinea and coastal California and Oregon, perhaps as often once every three years. One leatherback was tracked migrating from nesting sites in the French Guiana and Suriname area in northern South America to the west coast of Africa and then north to the Azores. Another was tracked traveling 10,00 kilometers (6,000 miles) from a feeding site off of Newfoundland to the Mid Atlantic Ridge then to waters off Suriname and north to Trinidad, possibly to nest, and then to feed on jellyfish in the Grand Bank off of New England.
Migration Patterns of Pacific Leatherback Sea Turtles
Two populations of leatherback sea turtles have been observed in the Pacific Ocean: one whose females travel to lay eggs along beaches in the eastern Pacific, another that prefers western Pacific beaches. Cheryl Lyn Dybas wrote in Natural History magazine: Helen Bailey of the University of Maryland Center for Environmental Science placed tracking devices on 135 leatherbacks’ shells. Leatherback turtles in the eastern Pacific were tagged at their nesting sites in Costa Rica and Mexico; western Pacific turtles were tagged at nesting sites in Indonesia and on their foraging grounds off the coast of California. The instruments transmitted satellite signals each time the turtles surfaced.[Source: Cheryl Lyn Dybas, Natural History magazine, September-October 2012]
The results of Bailey’s study were published in the April 2012 issue of Ecological Applications. The western Pacific turtles traveled to feeding sites in the South China Sea, Indonesian seas, southeastern Australia, and the U.S. West Coast. “This wide dispersal,” says Bailey, “allows for a greater likelihood of finding food. It also means that the turtles are more vulnerable to being snagged unintentionally in fishing gear.”
The eastern Pacific leatherbacks have a different migration pattern, traveling south from nesting sites in Mexico and Costa Rica to the southeast Pacific. The turtles feed in offshore upwelling areas where their meals, almost exclusively jellyfish, are easy catches. “The limited feeding grounds of the east Pacific turtlesmake them vulnerable to changes that might occur in the abundance of jellyfish,” says Bailey. “Being caught in fishing gear also poses a greater risk to this population because it has a smaller range than western Pacific leatherbacks.” Entanglement in fishing gear is believed to be a major cause of death in leatherback sea turtles.
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated May 2023