Sea turtles are survivors of an ancient time with some amazing abilities. They can glide through the water as gracefully as birds fly through the air, using their flippers as wings. They can hold their breath for extended periods of time and dive to incredible depths. They travel hundreds, even a thousand miles or more, to return to their birthplace to nest. They spend nearly their entire lives in the ocean, yet females emerge briefly on sandy beaches only to lay their eggs. Their unique adaptations have allowed them to survive nearly unchanged for many millions of years, yet they are now decreasing in number all over the world and are threatened with extinction throughout their range.

Turtles have existed since the Triassic Period, over 210 million years ago. The first fully sea-adapted turtles emerged 10 to 50 million years later, during the Jurassic Period. Over the course of history, whole families of sea turtles have evolved and disappeared without leaving any species that exist today. Two families that did leave descendants, Cheloniidae and Dermochelyidae, gave rise to all the species of sea turtles that exist in our present day oceans.

There are seven species of sea turtles now in existence: six* of these, the Loggerhead Sea Turtle, Caretta caretta, the Green Sea Turtle, Chelonia mydas, the Hawksbill Sea Turtle, Eretmochelys imbricata, the Olive Ridley Sea Turtle, Lepidochelys olivacea, Kemp's Ridley Sea Turtle, Lepidochelys kempii, and the Flatback Sea Turtle, Natator depressus, are hard-shelled members of the Cheloniidae family. Only one species, the Leatherback Sea Turtle, Dermochelys coriacea, remains from the Dermochelyidae family. This species of sea turtle is distinctive in that it lacks a hard shell, but instead is covered with a thick, leathery skin.

*Some marine biologists would say there are seven species in the Cheloniidae family, adding the Black Sea Turtle, Chelonia agassizi, to the list. However, current DNA evidence does not support categorizing black sea turtles as a separate species, as they are too close genetically to Green Sea Turtles, and are generally considered a black variation of the Green Sea Turtle, Chelonia mydas agassizi. SeaPics.com does, however, reference Black Sea Turtles in the database.

Certain features are common to all species of sea turtles. They all have a shell, the top of which is called the carapace, and the flat bottom of which is called the plastron. They have no teeth, but use their bird-like beaks to tear their food. They have no external ears, but can hear. They possess an excellent sense of smell, and a good sense of sight underwater. They have the ability to hold their breath underwater for hours when at rest, but for only four or five minutes when active. They need only seconds to surface and take a breath. Because they are cold blooded, they prefer warmer waters, and so are most commonly found in the tropics or in the warmest temperate waters.

Sea turtles have many interesting and unique features, and one of the most fascinating is their ability to return without fail to the beach where they were born. Small amounts of magnetite are found in the brain of sea turtles, and some speculate that this may aid them in determining direction. They may also use visual and olfactory cues or perhaps even navigate by the sun and stars.

Sea turtles are protected throughout the world, but all species are still threatened with extinction. Many countries in the sea turtles' range are poor and cannot devote their scant resources to effective wildlife protection. The world's sea turtles suffer from poaching, death by long line fishing, entanglement in fishing nets, habitat destruction, pollution, and animal predators, including domestic animals such as dogs and pigs. While education and conservation measures have shown success in some areas, there is a continual need for greater conservation efforts and increased vigilance in the fight to save these ancient, fascinating sea voyagers.

For more information about sea turtles, click on the links to specific species above, or reference the excellent source books below.

For more information about sea turtles, click on the links to specific species above, or reference the excellent source books below.

Sources:

Perrine, D. Sea Turtles of the World, Voyageur Press, 2003

Ripple, J. Sea Turtles, Voyageur Press, 1996

Witherington, B. Sea Turtles, Voyageur Press, 2006

- Sea turtle information assembled from the sources listed above by Kevin Miller on April 17, 2007 for SeaPics.com.

Adopt A turtle Program (Adopt-A-Turtle)

Marine Conservation Society - http://mcsuk.org

Turtle Conservation Project (TCP) - Sri Lanka - http://www.tcpsrilanka.org/

SeaTurtle.org - http://www.seaturtle.org/tracking/adopt/

Caribbean Conservation Corporation & Sea Turtle Survival League - http://www.cccturtle.org/adoptaturtle.php