Turtles are long-lived reptiles of the aquatic order Testudines or Chelonia. They are distinguished by a special bony, or plastron, shell evolved from their lower ribs which serves as a protective shield. Turtle shells differ greatly and are referred to as either conch shells or keratin or even osteopteryx. Commonly, the term “Turtles” is usually limited to marine and fresh-water Testudines only. There are actually more than a hundred species of turtles in the world.
Among the most commonly known turtle species are the Planktonic (or sea) turtles, the Coelioxi (or land turtles), which inhabit tropical and subtropical areas of earth; the Dry Tortoise, which are found in the drier tropical areas of the Pacific and Indian Oceans; and the Red Eared Slider, which can be found in the Northern and Southern Hemispheres. Apart from these, there are two other turtle species, which are well-known and widely distributed, such as the Philippine Tapered Snapping, the Manatee, and the Reef Turtle. The Dry Tortoise is the largest of these turtles, which may measure up to twelve inches in length. The Manatee is the smallest among all the species of turtles, which may measure up to eight inches. The other species of turtles generally occur in bodies of only one or two.
In comparison to other terrestrial animals, the marine turtle is one of the rarest. The species generally dwells on the ocean floors, including waters near coral reefs, islands and bays. Most live in cool water, away from predators and with burrows to hide. While a few eat fish, like the Sea Turtles, others simply subsist off vegetation such as algae, plants, and small crabs. Some may even go so far as to subsist on the air and produce shellfish. However, unlike the land turtles, the sea turtles do not usually leave their nests to go to the surface to lay their eggs but instead travel long distances to lay their clutch of eggs.
The most diverse among the turtle species are the terrestrial species, those that spend part of their time below the surface of the water. These mostly live in tropical and subtropical regions, though there are some found in the Arctic and some parts of Australia. Many of them are carnivores, consuming meat such as chicken, beef, sheep and pigs, along with insects. Terrestrial turtles are generally nocturnal, moving around during the night. In fact, they spend most of their time basking under the rocks in their shells.
The aquatic turtle species feed on fish, which they also eat raw. However, they primarily live in fresh and salt water, using rivers, streams and lakes for prey. Most of these turtles are found living in slow moving rivers. They lay eggs in small batches, about half an inch in size, which have a hard covering of grit on them.
These species can live for over half a century. Their lifespan can sometimes be double that of humans, sometimes even more! The females generally reach sexual maturity faster than the males, sometimes reaching it after two years of age. These turtles also differ in terms of their coloration, being yellow, green, gray, brown or even bright red, though they also differ in terms of their size.