Turtles are an extremely ancient group of animals, and form one of the four orders of reptiles alive today (Testudinata). Currently there are over 320 known species of turtle on the planet, but only 7 of these are found in the sea. Of these 7 species, 5 species live in the Philippines – the green turtle, the hawksbill turtle, the olive ridley turtle, the loggerhead turtle, and the leatherback turtle.
The shells of most turtles are made of large bones covered by scales called “scutes”. The top shell along the back of the turtle is called the “carapace”, while the bottom shell along the belly is called the “plastron”. Their heads and limbs are also covered in thick scales, which help protect them from predators. The front limbs of sea turtles are formed into flippers, with the back limbs acting as paddles when the turtle swims. Males have a longer tale than females, which extends beyond the shell, and much larger claws used for gripping the female during mating. Many sea turtles grow to well over a meter in length, with leatherback turtles reaching up to 3 meters.
Habitat and Feeding
All sea turtles spend almost all of their lives in the sea, and they are found in almost every ocean in the world. They mostly remain in seas which are above 20°C in temperature. Most turtles live in shallow coastal waters, and feed on sea grass and algae, as well as jellyfish, crayfish and crabs, with many feeding in the same area for several years. The exception to this is the leatherback turtle, which is fully pelagic and lives in the open sea.
Although they live most of their lives underwater, sea turtles still need to breathe air. They therefore have specially adapted lungs which allow an extremely rapid exchange of oxygen, and prevent the trapping of gases when the turtle swims deep. Turtles are able to spend several hours underwater when they are resting or sleeping, but need to breathe much more often when they are foraging or diving.
Nesting and Reproduction
Female turtles return to land around every 2-3 years in order to lay their eggs, a time when their adaptations to living at sea make them slow and vulnerable. Sea turtles bury their eggs in the sand in order to hide them from predators, and green turtles have even been known to create “decoy” nests in order to protect their eggs. Green sea turtles lay between 70 and 130 eggs each time they nest. The eggs remain in these nests for about 2 months before hatchlings emerge, and the ratio of males and females is determined by the temperature of the nest, with warmer temperatures producing more females. Hatchlings emerge at night and must make their way directly to the sea before daybreak to avoid the threat of predation.