COMMON SEA TURTLE
Common name: sea turtle or tortoise
HABITAT AND GEOGRAPHICAL DISTRIBUTION
The species Caretta caretta of the family Cheloniidae, is the common saltwater sea turtle, widespread in temperate and tropical seas and oceans all over the world, including the Mediterranean Sea. It is also found in coral reefs, brackish lagoons and even in the mouths of rivers.
CHARACTER, BEHAVIOR AND SOCIAL LIFE
The sea turtle is a reptile that loves the heat therefore it makes real migrations moving towards tropical and subtropical waters during the cold season: temperatures below 10 ° C are lethargic and would cause a sort of "catalepsy" and the turtle would float on the surface; below this temperature it may even die.
An individual can travel up to 5000 km (approximately) to escape the cold winter waters, taking advantage of the ocean currents.
Juveniles and adults are often found along the coasts, preferring rocky rather than sandy bottoms.
The turtles C. caretta they are the largest living turtles on our planet. As we have said, they are found in waters all over the world and it has been observed that those that live in the seas are smaller than those that live in the oceans.
The whole body is protected by a breastplate and the dorsal shield, slightly heart-shaped, is called carapace, formed by five pairs of horny plates (called shields) of red, brown and green color, fused together to form the characteristic furrows.
They are equipped with two pairs of legs transformed into fins that are used for swimming and in the males each front leg is provided with a curved claw that is used during mating.
The head is very large with powerful jaws. The turtles C. caretta they have no teeth but sharp protrusions on their beak which are used to grind food.
Near the eyes there are particular glands that are used to remove the salt from sea water in order to drink it. We often hear people say that, observing C. caretta while it nests, they see it "crying": in reality it is just expelling the excess salt from the water.
They are able to hold their breath for very long periods of time, even hours, even if in general, a typical dive lasts 5-20 minutes.
Males are distinguished from females both because the skin is more brown and the head is more yellow than females and because they have a long tail that develops when they reach sexual maturity.
Some scholars consider two subspecies: the C. caretta gigas of the Pacific and Indian Oceans and the C. Caretta caretta of the Atlantic which differ from each other for the different characteristics of the carapace but many scholars do not agree with this classification.
Not much is known about how these sea turtles communicate with each other. It would seem that courtship depends mainly on sight and touch, although some scholars suggest that it could also depend on some glands that secrete particular odors.
As for the eating habits of the turtles C. caretta they are predominantly carnivorous although they can eat algae and aquatic plants, which makes them practically omnivorous.
Their powerful jaws make them able to easily crush the hard shells of crabs, sea urchins, bivalves but more frequently they eat sponges, jellyfish, insects, cephalopods, shrimps, fish and fish eggs.
REPRODUCTION AND GROWTH OF THE SMALL
Tartarygas lay their eggs in the sand, on the sunny beaches and not too far from the sea as the chicks when they are born must head immediately towards the sea.
Shortly before the reproductive season (beginning of the summer period) the male of the C. caretta migrates towards the beaches where the nesting will take place and stops off to wait for the females. Once the females arrive, the males begin courtship. The females can refuse the male consequently they take shelter towards the bottom of the sea. However, the male waits patiently for them on the surface when they return to the surface to breathe and makes another attempt.
Mating can last for many hours and the male remains attached to the female thanks to the claws of the front legs. During this long period the male tortoise can be chased away by other males to take his place, in fact it is not uncommon that in a single brood there may be eggs fertilized by different males.
The female during the reproductive season alternates several times in the deposition of the eggs in practice it mates, goes to the beach to lay the eggs and then returns to mate and this every 12-14 days during the reproductive season, approximately 2-5 times , which therefore corresponds to 2-5 nests per turtle.
Each turtle nest contains 110 - 130 eggs.
The incubation time of the eggs depends on the temperature in the nest (influenced by the climatic conditions and the position of the egg inside the nest): about 65-70 days at low temperatures (around 25 ° C); about 45 days at higher temperatures (about 35 ° C).
Like many other reptiles in the turtle Caretta caretta the sex of the unborn is determined by the external temperature of the eggs and there is no fixed rule that varies from area to area. For example, it has been observed that in South Africa the temperature at which 50% males and 50% females will be formed must be between 28-30 ° C in fact lower temperatures (24-26 ° C) tend to produce only males while temperatures more high (32-34 ° C) tend to produce only females. In practice, testosterone or estrogen will be produced depending on the temperature. Outside of these thermal fluctuations, eggs are not viable.
Once the eggs hatch, the little turtles head out to sea.
It is not known precisely how the little turtles just born manage to orient themselves (usually the eggs hatch at night) towards the sea: it has been hypothesized that perhaps they distinguish the horizon or the inclination of the beach. Whatever the motivation, it seems certain that once in the water they use chemical and magnetic signals to orient themselves.
They usually tend to return to the same beach they were born on every year.
Adult sea turtles practically have no predators except for sharks that sometimes attack them and man. In reality, those who are preyed on are the small larvae and eggs that have a mortality rate of 80% in the United States while in Australia it has also been calculated of 90-95% due to raccoons and foxes but also by crabs, birds and fish.
STATE OF THE POPULATION
There Caretta caretta it is classified in the IUNC Red list among animals at very high risk of extinction ENDANGERED (EN).
The reasons are different: the accidental capture of these turtles by man with fishing nets; the exploitation of adults and eggs in human nutrition; the destruction of their reproduction habitats by humans both with buildings and indirectly with noise pollution (the noises of boats disturb them during nesting), chemical (pesticides, petroleum products, etc.), light (the lights of cities disorient the little ones in their race towards the sea). Also not to be overlooked is global warming which, by altering temperatures, alters the sex of the unborn with serious imbalances in the population.
All this has led to the common turtles being protected species under various international treaties and agreements, as well as each state having its own national laws.
They are turtles mentioned in Appendix I of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) as endangered species (Cheloniidae spp) and for which all commercial exchanges are prohibited. They are also listed in Annexes I and II of the Convention on Migratory Species (CMS).
SOCIAL, ECONOMIC AND ECOSYSTEM IMPORTANCE
There C. caretta it is a fundamental animal in the ecosystem so much that by many scholars it is called the "keystone" because it feeds on numerous invertebrates whose shells are broken by its powerful jaws which then become nourishment for numerous other animals as a rich source of calcium; its eggs which represent the nourishment of a large number of species; its carapace which represents a den for many species of animals.
For humans too, C. caretta is important for stimulating ecotourism.
Sea turtles are very ancient animals and their appearance has remained unchanged for millions of years.