Green Tortoise

The green tortoise or frank tortoise is a Tortue marinades and of the Chelonia . It is largest of the Cheloniidae .

Description

It is a Tortue marinades present in tropical water of all the oceans, but more or less rare according to the areas. The carapace measures on average 110 cm and the animal weighs between 80 and 130 kg. Certain specimens can reach a weight of 300 kg for a length of carapace of 1,5 Mr. His carapace oval is flattened for better hydrodynamics, its width is approximately 88% its length. Its head is small and accounts for approximately 20% length of the carapace. It has only one pair of scale préfrontales. The edge of its jaw lower is coarsely notched while the higher is provided with strong peaks on the inner face. Its backing has four side plates, the former pair is noncontiguous with the plate précentrale. The drill plate consists of 4 pairs of plates inframarginales. Contrary to the Eretmochelys and the Caretta , there is only one claw on each fin. This one is very developed in the males.

The backing is brown olive, the brilliant plates with yellow, green and black spots radiate, the drill plate is yellow pale, cream-coloured or blanchâtre.

It is fastest of the marine tortoises: it can reach a speed of almost 35 km/h.

Sexual maturity can be reached between 8 and 15 years.

Food

Until the benthic youthful stage, to surely secure the fastest possible growth, this tortoise is primarily carnivorous, it consumes small invertebrates and eggs of fish. Then it almost exclusively nourishes algae of the marine herbaria. This food mode is supposed to give a greenish color to its flesh. It can also eat some Mollusque S and of the sponge S.

Reproduction

When it reached its sexual maturity, the female comes to lay all the 3 to 6 years on the beach where it was born (or of the sector). It is coupled close to the beaches and the females will lay there up to six times, which will take approximately a month and half to him. It starts by making sure of the safety of the beach since the edge of water. It will go up to be bordered of vegetation, neither too broad, nor too narrow.

Once arrived rather high on the beach, it will dig its cavity body, a hole of once with once and half its thickness. That takes approximately 20 minutes. Then it digs its well of laying with its back legs. This hole is not very broad and is deep of approximately 70 cm. Still about 20 minutes.

Lastly, it lays a hundred eggs (from 20 to 250), soft, size of a table tennis ball is of 5 has 6 kg. It stops its hole after approximately 20 minutes of laying. Then it advances on about three meters in any direction by throwing sand behind it so that it is impossible to know where it laid. The remaining holes on the beach are only one lure. It turns over to the sea approximately an hour and half after having laid. The duration of incubation is from 45 to 70 days following the temperature.

The green tortoise can make hundreds of km to come to lay at the same place. One is unaware of how it is able to be directed in the middle of the oceans, but it is probable that the terrestrial magnetic field plays a considerable part.

A study controlled by Simon Benhamou of the Center of functional and evolutionary Ecology of Montpellier, and associating various organizations (CNRS, IRD, IFREMER, CEDTM, University of Pisa), watch which the marine tortoises use a relatively simple navigation system.

Every 4 years on average, the green tortoises (Chelonia mydas) of the Indian Ocean traverse hundreds of kilometers to go on specific spot of laying where they carry out 4 to 6 successive layings. In order to better include/understand the processes of navigation and the sensory channels implied in this oceanic navigation with large scales, the researchers made a multi-field study associating biology and physical oceanography based on two series of experiments. In the channel of the Mozambique, on the beaches of the French islands Europa and Mayotte, they captured tortoises with the whole beginning of their cycle of laying, so that they are really justified to reconsider the spot to finish their cycle. They on the open sea slackened them, to a few hundred kilometers of the place of laying, after having fixed a beacon Argos on their carapace to record by satellite their displacement of return towards the beach. The first experiment aimed analyzing the navigation system of the marine tortoises and at including/understanding how they feel the oceanic currents: do they undergo them or are able to use them to optimize their displacements? The study showed that the navigation system of the marine tortoises allows them, whatever the place where they are, to preserve their course on the site of laying. A little as if they were equipped with a compass constantly pointed towards the beach in question. They can thus correct displacements which they undergo: transport in boat, currents marine… But they are unable to compensate for the drift of the oceanic currents in adbiaized, as do it the human navigators. The displacements recorded by satellite represent the sum of the action thus, volunteer, of the tortoises and that, undergone, of the currents. The navigation system of these tortoises would be thus relatively simple and could lead them to wander a long time at sea when the geographical conditions are unfavourable for them. A tortoise slackened to 250 km of its site of laying on Europa has " thus; tourné" for 2 months on more 3 500 km before returning there!

In the 2nd experiment, the researchers analyzed the influence of the terrestrial magnetic field on the navigation system of the tortoises. They proved for the 1st time in will natura that the marine tortoises make use of the magnetic field emitted by the ground to be directed. Indeed, when they disturb this field while placing a very powerful magnet on their head, their performance of navigation is decreased. But the fact that they can nevertheless reconsider their site of laying of origin shows that the geomagnetic field is not the only information source which they exploit. The researchers think that they could also use their sense of smell like certain marine birds or the carrier pigeons. This assumption remains to be confirmed… This work should make it possible to improve the plans of conservation of the marine tortoises, today threatened and officially protected species, while including/understanding better how they make these long migrations between their sites of laying and food.

Chronology

Ecology

The green Tortoise prefers water not very deep and rich in Zostère S without to circumscribe itself some. The adults traverse very long distances between the herbaria and the zone of nesting. Contrary to the other marine tortoises, one observed green tortoises on the beaches to take the sun like other marine reptiles.

Place of laying

the Comoros (island of Mohéli),
Turkey and Cyprus
the Meeting and Maurice

Predatory and threats

The animal predation acts especially during the blossoming of eggs because the species is threatened by the Crabe S, birds and mammals venturing on the beaches. But, the eggs are also directly threatened by the insects. Once arrived at water, the young green tortoises are not yet in safety, they become the preys of the Pieuvre S and large fish.

Once the benthic youthful stage reached, its predatory becomes the marine sharks and crocodiles off Australia but especially the men who fish it, sometimes by inadvertency but especially for its flesh. Pollution is an unquestionable threat and the multiplication of the diseases such as the Fibropapillomatose seems to testify it. Finally the predation on eggs remains very important in spite of some care taken by the local authorities.

See also: Contenu=Voir also: [[Tortoise marine#Prédateurs]], [[marine Tortoise: Predatory]]

Systematic

Etymology

Their name of " tortoise verte" their comes from the color of their grease, slightly greenish, because of the algae which they consume.

Taxonomy

The taxonomy of this tortoise followed the evolution of knowledge on the phylogenetic one of the tortoises, which defined gradually tax more precise. This species thus was found, in turn, classified in the Testudo by Linné 1758, then Chelonia . In 1868, Bocourt describes another tortoise, the frank tortoise of peaceful or black tortoise which it names syn Chelonia agassizi (. C. Mr. japonica ). These two species, although morphologiquement slightly different, were regarded as belonging to very the species. C. mydas mydas naming the Atlantic population initially described by Linné, C. mydas agassizi naming the population of the black tortoises.

Systematic

The relative evolutionary independent groups are described below by philogénie according to Hirayama, 1997,1998, Lapparent de Broin, 2000, and Parham, 2005:

--O Cheloniidae |--O Caretta L., 1758 |--O… Natator Garman, 1880 `--O Chelonini |--O Eretmochelys `--O |--O Lepidochelys `--O `--O Chelonia L., 1758

The green tortoise and the man

(And sometimes still) pursued a long time for the consumption of its flesh, the consumption of its eggs (sometimes even famous aphrodisiac) or for the use of its carapace, which makes it possible to manufacture objects in scale of tortoise , the green tortoise today is generally protected. The species is also used for the preparation of by-products such as oil, the cartilages ( calipee ) and leather. Moreover like the other marine tortoises, she is threatened by fishing and pollution.

Several countries adopted measures going from protection partial to total protection of eggs and the adult females.

See too

References

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