Turtles are reptiles, older even than the dinosaurs they have managed to establish themselves on every continent except Antartica and can survive in a wide range of habitat.
There are approximately 300 species, varying in size from the huge marine Leatherback turtle which can be over 900 kg in weight and 2.7 metres long to the tiny terrestrial Speckled Padloper weighing 140g and growing to 8cm in length. Despite differences there are some basic characteristics that all turtles share
Turtles are ectothermic (commonly called cold blooded) their internal temperature varies according to the ambient temperature, so they are more inactive during cold weather..
They lay leathery eggs on land in excavated nests, the eggs incubate and the baby turtles hatch and do not receive any care from their parents. The temperature of the incubating eggs determine the sex of the hatchlings, cooler temperatures create males and warmer temperatures create females.
Turtles have a beak like mouths with horny ridges instead of teeth.
Their most outstanding feature of turtles is their bony, rigid shell – the carapace (upper part) the plastron (lower part), are joined together by bridges. The turtle cannot leave its shell because the shell is part of its skeleton. For most turtles the outside of the shell consists of horny scales called scutes, but some species such as leatherbacks have leathery skin covering their carapace. The hard shell provides protection from predators - box turtles have a hinged “door” on their shells so they are completely enclosed while other species can withdraw or fold their head, limbs and tail into their shell to varying extents.
Turtles shed the outer skin of their bodies and carapace but do so more gradually than other reptiles.
Turtles have good hearing, sensitive colour vision, strong sense of touch (their shell has nerve endings) and good sense of smell.
Turtles are air breathers they can pump air down their throats or use their abdominal muscles as we use our diaphragm to breath. They seem to be able to absorb oxygen through their skin which allows them to remain submerged under water for long periods.
The limbs of a turtle vary according to their habitat – terrestrial turtles or tortoises have heavy blunt feet. Marine turtles have flippers and fly through the water using front flippers for thrust and rear for steering. Freshwater turtles have clawed webbed feet and use dog-paddle swimming style.
Much about turtles remains mysterious - they are silent but it is now thought that they can commincate subsonically, they have amazing navigational skills. Turtles are famous for their logevity captive turtles have survived for over 170 years and one kept in Calcutta died at the age of 250. The secret of their long lives is not understood but they appear to be able to turn their heart off and on, they have low demand for food and water. Unlike other species their vital organs do not appear to deteriorate with age – the organs of ancient and young turtles are almost indistinguishable