Sea Turtle Facts

Scientific Name: Dermochelys coriacea

Marine turtles photographed on the beautiful Ningaloo Reef of western Australia.

 

Migration Media - Underwater Imaging/Getty Images

Sea turtles are water-inhabiting reptiles, six species of which belong to the Cheloniidae family and one to the Dermochelyidae family. These glorious seaborne relatives of land turtles glide through the coastal and deepwater regions of the Atlantic, Pacific and Indian oceans.

Fast Facts: Sea Turtles

  • Scientific Name: Dermochelys coriacea, Chelonia mydas, Caretta caretta, Eretmochelys imbricate, Lepidochelys kempii, Lepidochelys olivacea, and Natator depressus
  • Common Name(s): Leatherback, green, loggerhead, hawksbill, Kemp’s ridley, olive ridley, flatback
  • Basic Animal Group: Reptile
  • Size: 2–6 feet long 
  • Weight: 100–2,000 pounds
  • Lifespan: 70–80 years
  • Diet: Carnivore, Herbivore, Omnivore
  • Habitat: Temperate, tropical, subtropical waters of the world's oceans
  • Conservation Status: Critically Endangered (hawksbill, Kemp's ridley); Endangered (green); Vulnerable (loggerhead, olive ridley, and leatherback); Data Deficient (flatback)

Description

Green sea turtle swimming
 Westend61 - Gerald Nowak/Brand X Pictures/Getty Images

Sea turtles are animals in the Class Reptilia, meaning they are reptiles. Reptiles are ectothermic (commonly referred to as "cold-blooded"), lay eggs, have scales (or did have them, at some point in their evolutionary history), breathe through lungs and have a three or four-chambered heart.

Sea turtles have a carapace or upper shell that is streamlined to help in swimming. They have a lower shell, called a plastron. In all but one species, the carapace is covered in hard scutes. Unlike land turtles, sea turtles cannot retreat into their shell. They also have paddle-like flippers. While their flippers are great for propelling them through the water, they are poorly-suited for walking on land. They also breathe air, so a sea turtle must come to the water surface when it needs to breathe, which can leave them vulnerable to boats.

Species

There are seven species of sea turtles. Six of them (the hawksbill, green, flatback, loggerhead, Kemp's ridley, and olive ridley turtles) have shells made up of hard scutes, while the aptly-named leatherback turtle is in the Family Dermochelyidae and has a leathery carapace made up of connective tissue. Sea turtles range in size from about two to six feet long, depending on the species; and weigh between 100 and 2,000 pounds. The Kemp's ridley turtle is the smallest, and the leatherback is the largest.

The green and olive ridley sea turtles reside in tropical and subtropical waters around the globe. Leatherbacks nest on tropical beaches but migrate northward to Canada; loggerhead and hawksbill turtles live in temperate and tropical waters in the Atlantic, Pacific, and Indian oceans. Kemp's ridley turtles hang out along the coasts of the western Atlantic and Gulf of Mexico, and flatbacks are found only near the Australian coast.

Diet

Most of the turtles are carnivorous, but each has adapted to specific prey. Loggerheads prefer fish, jellyfish, and hard-shelled lobsters and crustaceans. Leatherbacks feed on jellyfish, salps, crustaceans, squid, and urchins; hawksbills use their bird-like beak to feed on soft corals, anemones and sea sponges. Flatbacks dine on squid, sea cucumbers, soft corals, and mollusks. Green turtles are carnivorous when young but are herbivores as adults, eating seaweeds and seagrass. Kemp's ridley turtles prefer crabs; and olive ridleys are omnivorous, preferring a diet of jellyfish, snails, crabs, and shrimp but also snacking on algae and seaweed.

Behavior

Sea turtles may migrate long distances between feeding and nesting grounds, and also, to stay in warmer waters when the seasons change. One leatherback turtle was tracked for over 12,000 miles as it traveled from Indonesia to Oregon, and loggerheads may migrate between Japan and Baja, California. Young turtles may also spend considerable amounts of time traveling between the time they are hatched and the time they return to their nesting/mating grounds, according to ​long-term research.

It takes most sea turtle species a long time to mature. Consequently, these animals live a long time. Estimates for the lifespan of sea turtles is 70–80 years.

Reproduction and Offspring

Green sea turtle laying eggs
Peter Wilton/Getty Images/CC BY 2.0

All sea turtles (and all turtles) lay eggs, so they are oviparous. Sea turtles hatch from eggs on shore​ and then spend several years out at sea. It may take 5 to 35 years for them to become sexually mature, depending on the species. At this point, males and females migrate to breeding grounds, which are often near nesting areas. Males and females mate offshore, and females travel to nesting areas to lay their eggs.

Amazingly, females return to the same beach where they were born to lay their eggs, even though it may be 30 years later and the appearance of the beach may have greatly changed. The female crawls up on the beach, digs a pit for her body (which can be more than a foot deep for some species) with her flippers, and then digs a nest for the eggs with her hind flippers. She then lays her eggs, covers her nest with the hind flippers and packs the sand down, then heads for the ocean. A turtle may lay several clutches of eggs during the nesting season.

Turtle laying eggs
Carmen M/Wikimedia Commons/CC BY 3.0

Sea turtle eggs need to incubate for 45 to 70 days before they hatch. The length of incubation time is affected by the temperature of the sand in which the eggs are laid. Eggs hatch more quickly if the temperature of the nest is warm. So if eggs are laid in a sunny spot and there is limited rain, they may hatch in 45 days, while eggs laid in a shady spot or in cooler weather will take longer to hatch.

Temperature also determines the gender of the hatchling. Cooler temperatures favor the development of more males, and warmer temperatures favor the development of more females (think of the potential implications of global warming!). Interestingly, even the position of the egg in the nest could affect the gender of the hatchling. The center of the nest is warmer, therefore eggs in the center are more likely to hatch females, while eggs on the outside are more likely to hatch males. As noted by James R. Spotila in ​Sea Turtles: A Complete Guide to Their Biology, Behavior, and Conservation, "Indeed, which way an egg bounces into the nest might determine its sex." (p.15)

Evolutionary History

Sea turtles have been around for a long time in evolutionary history. The first turtle-like animals are thought to have lived about 260 million years ago, and odontochelys, the first marine turtle, is thought to have lived about 220 million years ago. Unlike modern turtles, odontochelys had teeth. Click for more about leatherback turtle evolution and evolution of turtles and marine turtles.

As you might guess, sea turtles are related to land turtles (such as snapping turtles, pond turtles, and even tortoises). Both land and marine turtles are classified in the Order Testudines. All animals in the Order Testudines have a shell that is basically a modification of the ribs and vertebra, and also incorporates the girdles of the front and back limbs. Turtles and tortoises do not have teeth, but they have a horny covering on their jaws.​

Threats

Man with knife rescuing Critically Endangered Hawksbill Sea Turtle tangled Ghost Net
 

Of the 7 sea turtle species, 6 (all but the flatback) exist in the United States, and all are endangered. Threats to sea turtles include coastal development (which leads to loss of nesting habitat or making previous nesting areas unsuitable), harvesting turtles for eggs or meat, bycatch in fishing gear, entanglement in or ingestion of marine debris, boat traffic, and climate change.

According to the International Union for Conservation of Nature (IUCN), out of the seven species of sea turtles two are classed as Critically Endangered (hawksbill, Kemp's ridley); one as Endangered (green); three are vulnerable (loggerhead, olive ridley, and leatherback), and one is Data Deficient, meaning they need additional study to determine the current status (flatback).
You can help by:

  • Supporting sea turtle research and conservation organizations and projects through volunteering or donating funds.
  • Supporting measures to protect nesting habitats.
  • Choosing seafood that is caught without impacting turtles (e.g., in areas where turtle excluder devices are used, or where bycatch is minimal).
  • Not purchasing sea turtle products, including meat, eggs, oil, or tortoiseshell.
  • Watching out for sea turtles if you are out on a boat in sea turtle habitat.
  • Reducing marine debris. This includes always disposing of your trash properly, using fewer disposable items and plastics, buying locally and purchasing items with less packaging.
  • Reducing your carbon footprint by using less energy.

References and Further Reading: