This is a supplement to an earlier feature on the nesting success of sea turtles.
By Peter Vankevich
Worldwide, there are only seven species of sea turtles and five of them, with varying degrees of frequency, can be found in the waters and nesting onshore on the Outer Banks.
While North Carolina hosts a total of 22 species of turtles, the five sea turtles are different in size and shape from the others and that they spend their entire lives at sea, except for females that go onto land to lay eggs and then return immediately to sea.
Loggerhead (Caretta caretta):
Named for their large head, female loggerheads reach maturity at about 35 years of age. Every two to three years they mate in coastal waters and return to nest on a beach usually in the general area where they hatched themselves decades earlier.
Loggerheads nest at intervals of two to four years and lay between three to six nests per season, approximately 12 to 14 days apart. An average of between 100 to 126 eggs are laid in each nest. Hatchlings emerge in about 60 days.
The successful hatchlings from coastal North America spend years in the Gulf Stream.
Adults vary considerably in size, ranging from 150 to 375 pounds. Loggerheads feed primarily on shellfish. They forage in coastal bays and estuaries as well as in the shallow water along the continental shelves. Carnivores, their powerful jaw muscles enable them to feed on hard-shelled prey such as whelks and conch.
Skeletochronology research in the NOAA lab in Beaufort, North Carolina, has shown that loggerhead sea turtles are likely live to be 70 years or older.
Loggerhead turtles are found worldwide primarily in subtropical and temperate regions of the Atlantic, Pacific, and Indian Oceans, and in the Mediterranean Sea. In the Atlantic, the loggerhead turtle’s range extends from Newfoundland to Argentina.
One study conducted many years ago estimated that worldwide there are between 40,000 and 50,000 nesting females.
Green turtles (Chelonia mydas)
Don’t expect to see green shells on these turtles. They were named for the green color of the fat under their carapaces, i.e., shells. Carapace colors range from brown, olive-and-gray to black.
Females nest at intervals of about every two years and between three to five times per season. They lay an average of 115 eggs in each nest, with the eggs incubating for about 60 days.
Because there are so few nesting females on the Outer Banks, adults are rarely seen, and they are huge — weighing between 240 and 420 pounds — and can be up to four feet in length. Young green sea turtles, weighing in the 10- to 20-pound range, are the most likely species to be seen washed up on shore during cold spells, because many forage in the Pamlico Sound.
Unlike the loggerhead, adult greens are herbivores, feeding on subaquatic vegetation and algae. Young sea turtles will also feed on worms, crustaceans and insects. Their jaws are finely serrated, which aids them in tearing vegetation.
Green turtles are found in all temperate and tropical waters throughout the world near coastlines, islands, bays and protected shores with seagrass beds. Rarely are they observed in the open ocean.
The Sea Turtle Conservancy estimates that worldwide, there are between 85,000 and 90,000 nesting females.
Kemp’s ridley (Lepidochelys kempii)
This sea turtle is named after Richard Kemp, a Florida fisherman and naturalist who discovered this species in 1880 and sent the specimen to Harvard University to be studied.
They nest more often than other sea turtle species — every one to three years on average and two to three times each season. They lay an average of 110 eggs in each nest and the eggs incubate for about 55 days.
Their range is mostly limited to the Gulf of Mexico, which explains why so few nest on the Outer Banks.
Much smaller than loggerheads and greens, adults measure around two feet long and weigh between 70 and 108 pounds. Carnivores, they feed on crabs, clams, mussels, shrimp, fish, sea urchins, squid and jellyfish.
On the brink of extinction in the 1960s, they were listed as “endangered” under the U.S. Endangered Species Conservation Act, the predecessor to the U.S. Endangered Species Act in 1970. Efforts to bring them back included clamping down on illegal harvesting and a successful relocation of more than 20,000 eggs from Mexico to Texas over a period of 10 years.
They remain the rarest of the sea turtles but have made a slow but steady increase. Estimates today are between 7,000 and 9,000 nesting females.
Leatherback (Dermochelys coriacea)
This sea turtle gets its name from its unique carapace, which is composed of a layer of tough, rubbery skin, strengthened by tiny bone plates that gives it a leathery look.
Sightings in the region are highly newsworthy, even if found dead, as was the case in January 2021 when one was found on Hatteras Island.
By far, the leatherback is the largest sea turtle and reptile on earth. Adults are four- to eight-feet in length and most weigh between 500 and 1,000 pounds. The largest leatherback ever recorded, on Wales’ Harlech beach in 1988, weighed 2,019 pounds with a length of nearly 10 feet from head to the tip of the tail.
Leatherbacks nest at intervals of two to three years, and between four to seven times per season. Incubation of an average of 80 eggs is about 60 days.
Unlike the other sea turtle species that return to where they hatched, females may change nesting beaches, though they tend to stay in the same region.
Their primary food source is jellyfish. Strong swimmers, they can dive to depths of approximately 4,000 feet — deeper than any other sea turtle — and can stay down for up to 85 minutes.
Open ocean wanderers, they have the widest distribution of sea turtles because they can tolerate cold temperatures. In the Atlantic, they can be found as far north as Norway and the Arctic Circle and south to the tip of Africa.
In the Pacific, their range extends as far north as Alaska and south beyond the southernmost tip of New Zealand.
They migrate to tropical and subtropical coastal regions to mate and nest, which explains why they are rare nesters in the Carolinas. In the Atlantic, they nest on beaches of the West Indies and Trinidad and Tobago.
Because of their fondness for jellyfish, they are particularly susceptible to harm caused by ingesting plastic bags and other plastics, which can lead to their death.
Estimates are between 34,000 and 36,000 nesting females.
Hawksbill sea turtle (Eretmochelys imbricata)
Named for their narrow, pointed beak, the hawksbills’ beautifully-colored, patterned carapace is the classic “tortoiseshell” that nearly drove them to extinction as hunters sold the shells to those making jewelry and trinkets.
Today, the Convention on International Trade of Endangered Species (CITES) forbids the trade of any turtle products on the international market, including hawksbill tortoise shell, but illegal hunting continues to represent a threat to the species in many parts of the world.
Hawksbills are found mainly throughout the world’s tropical oceans, which accounts for why they are so rare here, with just one known nesting in 2016 and 10 reports of stranded hawksbill sea turtles since records were kept beginning in the mid-1980s; all were small juveniles, and all were observed between 2001 to 2009, according to a published report.
They nest at intervals of two to four years and between three to six times per season, with an average 160 eggs in each nest.
Adults can weigh up to 150 pounds.