1993 Turtles date back to long before the Age of the Reptiles, whentheir ancestors shared the world with dinosaurs. Like otherreptiles such as crocodiles, lizards and snakes, turtles are cold blooded and live only in the warmer parts of the world. Marine turtles have a flatter, lighter shell than do tortoises, and their front and rear flippers are used for swimming. The turtles that nest on South African beaches are the loggerhead and leatherback turtle.
TURTLE BREEDINGTurtles spend most of their lives at sea, but must return to land to lay their eggs. Turtles are often highly migratory - nesting beaches may be up to 3 000 km from their feeding grounds. Marine turtles mate in the waters off the nesting beach, after which the female comes ashore, usually in summer and at night:
HATCHING OF THE EGGSAfter 55 - 65 days the turtle hatchlings use an egg tooth on the end of their beaks to cut their way out of the egg. When most of the baby turtles have emerged they scramble at the walls and roof of the egg chamber, dislodging the loose sand which falls amongst the hatchlings and eggs, gradually raising the floor of the chamber and so lifting the turtles out onto the beach, rather like a lift. The turtles will not emerge until after sunset, when they burst out and make a dash to the sea. At night the sea horizon is brighter over the ocean and this light guides the hatchlings to the water.During the dash to the sea up to 12 % of the hatchlings may be attacked by ghost crabs. For the first few months of their life in the sea they are extremely vulnerable to predators. It is estimated that of every 1 000 that enter the sea, only 1 or 2 will reach maturity. Survivors spend up to three years drifting in the open sea, feeding on floating organisms such as small jelly fish. Following the ocean currents they later return to coastal waters where they feed on shellfish such as mussels. It is believed that nesting females return to the beaches where they hatched.
THREATS TO TURTLESThe seven species of marine turtles alive today are all declining in numbers. Turtles face a huge range of threats to their survival, from the moment the eggs are laid in the sand, through to adulthood. Apart from the threats posed by other creatures, marine turtles are increasingly threatened by the actions of people throughout the world. In some areas, the eggs of certain species are dug up and eaten, while adult turtles are killed for food. Other problems include destruction of nesting beaches, disturbance of the nesting females, and accidental catching and killing of turtles in fishing nets. In addition, turtles mistake plastic bags floating in the sea for jellyfish and eat them. This may choke them to death or prevent them from eating properly. An estimated 44% of leatherback turtles have plastic in their digestive systems.
CONSERVATION ACTIONTurtles need to be protected wherever they are found. Their conservation is particularly difficult because they have such varied habits and large ranges.
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