Alaska Sea Turtles: Leatherbacks

Sea Turtles: Leatherbacks

Alaska's State Flower is the "Forget-Me-Not. Forget me not flowers are very fragrant in the evening and night time, though there is little or no scent in the daytime. They can be annual or perennial plants. Their seeds are found in small, tulip shaped pods along the stem to the flower.

Only four species of turtles, all marine turtles, have been documented within the state’s borders. Terrestrial and freshwater aquatic species of turtles do not occur in Alaska. Marine turtles are occasional visitors to Alaska’s Gulf Coast waters and are considered a natural part of the state’s marine ecosystem.

Between 1960 and 2007 there were 19 reports of leatherback sea turtles (Dermochelys coriacea), the world’s largest turtle. There have been 15 reports of Green sea turtles (Chelonia mydas). The other two are extremely rare, there have been three reports of Olive ridley sea turtles (Lepidochelys olivacea) and two reports of loggerhead sea turtles (Caretta caretta). Currently, all four species are listed as threatened or endangered under the U.S. Endangered Species Act.

Sea turtles are large, aquatic reptiles with forelimbs specially modified for swimming. These front flippers are significantly larger than the back flippers. Their shell is composed of two pieces, the top, or carapace, and the bottom, or plastron. In most sea turtle species, the shell is made up of bony plates covered with horny shields.

The leatherback sea turtle, unlike other sea turtles, lacks bony plates on its shell. It’s carapace is made up of leathery, oily connective tissue covering loosly interlocking dermal bones. Its shell is mostly black with pinkish white on the underside. This sea turtle also has pink and white spots on its head. It’s back flippers are paddle shaped. A leatherback’s front flippers lack claws and scales and are elongated compared to other sea turtle species. There are seven ridges that run down the turtle’s back. These ridges and the elongated flippers are adaptations to facilitate long distance migrations.

Leatherbacks are the most migratory of all sea turtles. The females migrate to tropical waters to nest then return to temperate waters to forage travelling thousands of kilometers. Some transequatorial migrations have been documented.

Leatherback sea turtles feed almost exclusively on jellyfish. Leatherbacks have a mammal-like ability to maintain a high body temperature (about 80° F), independent of the temperature of the surrounding water. This may account for its relatively common occurrence in cold northern waters where jellyfish are seasonally abundant. Green sea turtles are primarily vegetarian as adults. In contrast to the leatherbacks, the hard shell turtles (green, olive ridley, and loggerhead) are considered warm water species, which rarely stray into cold Alaskan waters.

Leatherback sea turtles feed on soft-bodied pelagic prey including salps and jellyfish. Their mouths are specially adapted to this diet. They have pointed cusps and sharp-edged jaws. They also have backward-pointing spines in their mouth and throat to help retain their prey. It is thought that they may dive to the deep scattering layer to feed on jellyfish or dive to feed on vertically migrating species. They will sometimes eat fish or seaweed.

Leatherbacks mate in waters adjacent to the nesting beach or along migration corridors. Females nest every 2–3 years. A female leatherback will lay several nests during a single nesting season generally 8–12 days apart. Average clutch size is 100 eggs. After 60–65 days, the eggs hatch, and the hatchlings emerge from the nest. The hatchlings are only 2–3 inches long. They will stay in tropical waters until they grow to a carapace length of 100 centimeters.

Leatherbacks are the most wide-ranging sea turtle species. They are found throughout temperate to tropical waters worldwide. They are capable of tolerating much colder temperatures than other species due to counter-current exchange, high oil content, and large body size. 19 leatherbacks have been reported in Alaska between 1960 and 2007. Prior to 1993, they were the most common sea turtle species in Alaskan waters.

Leatherback sea turtles are a highly pelagic species spending most of their time in the open ocean. However, they are known to forage in coastal waters. Females come ashore to nest preferring beaches backed by vegetation near deep water and rough seas. There is no reliable estimate of the global population of leatherback sea turtles. The Pacific leatherback population is known to be smaller than the Atlantic. The species is listed as endangered under the Endangered Species Act (ESA).

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leatherback turtle resting on sand beach

leatherback turtles are rare visitors to Alaska


Leatherbacks	Green Sea Turtle

Olive Ridley	Loggerhead