10 Fascinating Facts About Sea Turtles

Sea turtles are reptiles that live primarily in the ocean. Even though these turtles live in the ocean, they are related to land turtles. Here you can learn about the similarity to land turtles, how many species of sea turtles there are, and other fun facts about sea turtles.

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Sea Turtles Are Reptiles

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 3 or 4-chambered heart.

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Sea Turtles Are Related to Land Turtles

A Russian Tortoise walks through green grass.


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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.​

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Sea Turtles Are Adapted for Swimming

Loggerhead Turtle


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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.

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There Are 7 Species of Sea Turtles

Female, digging in the sand
U.S. Fish and Wildlife Service Southeast Region/Wikimedia Commons/Public Domain

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 2 feet to 6 feet long, depending on the species. The Kemp's ridley turtle is the smallest, and the leatherback is the largest.

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Sea Turtles Lay Eggs on Land

Green sea turtle laying eggs
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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.

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A Sea Turtle's Gender Is Determined by the Temperature of the Nest

Deposition eggs Testudo marginata sarda
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 (sex) 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)

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Sea Turtles Can Migrate Extreme Distances

Green turtle Chelonia mydas is basking on Punaluu Beach Big Island of Hawaii
Brocken Inaglory/Wikimedia Commons/CC BY 3.0

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.

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Sea Turtles Live a Long Time

Loggerhead turtle
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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.

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The First Marine Turtles Lived About 220 Million Years Ago

Odontochelys semitestacea
Nobu Tamura/Wikimedia Commons/CC BY 3.0

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.

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Sea Turtles Are Endangered

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


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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.

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:

  • Sea Turtle Conservancy
  • SeeTurtles.org
  • Spotila, James R. 2004. Sea Turtles: A Complete Guide to Their Biology, Behavior, and Conservation. The Johns Hopkins University Press.
  • Unlocking the Secrets of Sea Turtle Migration (Science Daily)