Turtles are reptiles with a protective shell and a beak-shaped, curved and hard mouth.
Besides providing protection against predators, aggressions or adverse weather conditions, the shell also provides the animal with camouflage – because of its colours, shape and texture, it usually resembles elements from the surrounding environment (such as leaves or rocks). Some species have particular joints that allow the turtle to take shelter inside the shell in case of danger.
They are oviparous and have a diversified diet. According to the species and to their habitat, turtles may feed on vegetables, jellyfish, fish, seaweed, molluscs, crustaceans or even small mammals and birds.
Like the other reptiles, turtles are ectothermic animals, which means that they do not have any metabolic process for regulating body temperature -it varies according to the environmental conditions. In order to adjust their inner temperature, these animals may adopt different strategies. When temperatures are high, they can take refuge in cool hiding places (such as a lair or a hole). They can also hibernate and thus lower their metabolism (if the temperatures are low).
Sea, freahwater and terrestrial turtles
One can informally distinguish three groups of turtles: sea turtles, freshwater turtles and terrestrial turtles.
Sea turtles live in the ocean (salty water) and only leave the water during breeding season. They lay their eggs on the shore, burying them in the sand. They have a hard time moving on land, but are agile in water, thanks to their fins. They shells are more flattened than those of other turtles – they are more hydrodynamic, which is helpful for their swimming. This flattened shape of the shell does not allow sea turtles to hide inside of the shell. However, and because they are agile swimmers, they can easily escape from predators and do not need to hide from them.
Freshwater turtles can be considered semi-aquatic animals, as they spend time on land and in water. They have paws and have some moving difficulties. This means they cannot run away from predators easily. They depend on other defensive strategies, such as camouflage or hiding their entire body inside the shell.
Terrestrial turtles live only on land, have strong paws and their shells may have some relief.
References
– LEANDRO, P.; GIL, F.; INÁCIO, A. (2009). Guia – Aquário Vasco da Gama. Oeiras: Aquário Vasco da Gama.
– O caso das tartarugas. Available: http://aquariovgama.marinha.pt/PT/profs_alunos/factos/Pages/tartarugas_1.aspx. Last accessed 29-07-2015
