S.O.S. SEA TURTLES

Monday 06 February 2012

S.O.S. SEA TURTLES

Friday 11 December 2009

TAGS: focus news, not only two-legged

S.O.S. Sea turtles – life and peril in the Mediterranean

There are eight species of sea turtle, of which five are found in the Mediterranean. Some of them are sighted frequently (Caretta caretta, Chelonia mydas, Dermochelys coriacea), but others only occasionally (Lepidochelys kempi and Eretmochelys imbricata). The different species are recognised by the shape of the carapace (the back section of the shell), of the cranium (on the basis of the number of scales in the forehead area) and of the fins. Recognition requires experience, and must be carried out by experts. All of these species are large animals: C. caretta can weigh up to 400 pounds and reach a length of over 3½ feet.

In the fascinating world of reptiles, these creatures are among those in danger of extinction. The factor endangering the survival of these gentle giants (Dermochelys coriacea, known as the leatherback turtle, weighing 450 to 1,100 pounds, is the largest living reptile) is the pressure from humans. Although the turtle, one of the four orders of the reptiles class, in many cultures traditionally represents wisdom (for example in Africa), strength (in the Far East the turtle supports the world), continuity and life (among Native Americans the Earth itself was a giant turtle whose back represented the heavenly dome and whose belly was the Earth’s surface), these timid and vulnerable animals have for centuries been hunted and eaten, or butchered to be turned into useless gewgaws or good-luck charms. In more recent years the negative anthropic pressure on the biology of the sea turtle has increased through indiscriminate fishing and the pollution that our activities introduce into the marine environment, as disturbed as the beaches these animals use for nesting. Only one newborn turtle out of a thousand survives to adulthood, and its worst enemy, as things now stand, is mankind.

The Mediterranean sea turtle has at its disposal 10 million square miles of sea with 28,000 miles of coastline, of which 12,000 are island coasts. We can imagine the Mediterranean Sea as divided by the peninsula of Italy into two basins, one to the east (warmer and more saline) and one to the west. Compared to the oceans, this sea does not offer the same richness of nutritional resources. The population of sea turtles living in the Mediterranean, especially C. caretta and C mydas, tend to concentrate in the more eastern regions to reproduce, and in the neritic region (between the surface and a depth of 650 feet) in the north, such as the Adriatic, and the south, such as the Libyan and Tunisian coastal areas, to pass the winter and live their youngest stage, known for this reason as “neritic”. In the western part of the Mediterranean we find the younger specimens coming from the Atlantic, where they will return at the reproductive phase.

Specimens of these species which live in the Mediterranean are smaller than those found in the oceans, and studies suggest they are a genetically isolated population. The leatherback turtle, on the other hand, seems to be a rare but constant presence, although it does not reproduce on the beaches of this basin. Little is known about it, because its huge size makes it complicated to hoist into a boat when it is in difficulty; most studies were carried out by observing the animal at the moment of depositing its eggs (a moment of great vulnerability for the turtle) or by observing stranded specimens, swept either dead or in extreme distress onto the beach.

Caretta caretta and Dermochelys are mainly fish eaters, but can also live from shell-fish, molluscs and jellyfish, whereas Chelonia is mainly vegetarian.

The life-cycles of C. caretta and C. mydas are parallel. The young hatch out of eggs deposited in sand by the female, who returns years later to the very beach where she was hatched to deposit her own eggs. The eggs are laid calmly at dead of night and can number as many as two hundred. After about two months of incubation, the young are hatched, again at night. Once born, the turtles must reach the sea as fast as they can to avoid death in the jaws of numerous predators – birds, dogs, foxes and crabs. Even the sea, however, is not without its perils, and as mentioned above only one turtle out of a thousand reaches maturity.

The first life phase of the sea turtle is known as “oceanic”, in that the young swim in deep waters (over 650 feet deep). Then follows a second phase known as “neritic”, in which the turtles shift to a bentonic feeding pattern (eating invertebrates such as shellfish and molluscs), which continues up to sexual maturity. The sub-adults (animals already of a certain size, but not yet full adult size) and the adults which are not in their reproductive phase concentrate in shallow waters along the continental shelf, water of less than 150 feet in depth, in areas used for feeding, migration and passing the winter. Once they reach sexual maturity, which in reptiles depends on their size rather than their age, even though the female sea turtles reach maturity at the age of around 20 years and a length of some 25 inches, during the mating season adults of both sexes move closer to the coast and the nesting sites for mating. The females then swim to the beaches where they deposit the eggs. This requires several hours, while the female digs a trench in the sand with her hind fins. The eggs are spherical and translucent when they are deposited, and turn progressively whiter during the development of the embryo in the following days.

Sea turtles suffer a very high mortality rate during the embryonic and newborn phases, which lessens as the animal develops. This can depend on natural climatic factors (excessive rainfall, sudden changes in temperature), predatory attacks (including by humans), disturbance of the beaches leading to destruction of the nests, light pollution from inhabited areas near the beach which disorientates the newborn and delays their reaching the water, but also environmental pollution from organic or inorganic chemicals which can cause severe intoxication and immediate death, or chronic intoxication leading to progressive weakening and death. The Mediterranean, a semi-closed basin, is an environment of potential build-up of toxic substances. The marine pollution is not caused only by “invisible” chemicals, but also by solid waste such as metal fragments (which appear silvery like the fish on which the turtles feed) and plastics, such as shopping bags which the animals mistake for jellyfish and swallow. The ingestion of foreign bodies of this kind, which cannot be expelled, sentences the unlucky reptiles to a slow and atrocious death by intestinal block or perforation of the gut.

Various fishing techniques are a further threat to the life of the turtle, and it has been estimated that some 30,000 specimens are killed every year by drowning in trawler nets or being caught on fishhooks, which once swallowed are difficult to remove and in most cases lead to the death of the animal before it is seen to be in distress. Not only fishing boats are a danger to them; any kind of boat can collide with the turtle when it surfaces to breathe or when it is floating to enjoy the sunlight. Effects of a collision are devastating and condemn the animal to a slow death: the majority of turtles observed in the Adriatic Sea carry propeller injuries. The decline of the various species over the years has also been hastened by catching the animals, following old habits or legends, to make objects or to eat their meat.

The future conservation of these queens of the sea will depend on a deeper knowledge of their biology and ecology studied by researchers (the assignment of research funds has not always been to the benefit of the most competent researchers), on a greater respect for the environment, which can be promoted by teaching in natural history museums and animal recovery stations, and on thorough information about the protection of wild animals, a true ethical duty of all of us.

If you come across a sea turtle in distress or dead in Italian territory, call the local harbourmaster on 1530 or the State Forestry Corps on 1513, for these are nationally and internationally protected species. It is vital that they are handled by trained personnel in order to avoid injury, not only to the animal but also to persons, because, although they are very gentle creatures, they can bite in self-defence if handled incorrectly. If the turtle is on a beach and alive under the sun, it should be covered with wet cloths to prevent dehydration until help is at hand; the cloths should cover the eyes but not the nostrils. If it is found floating, it should be lifted out of the water by grasping the points where the shield joins the skin (above and behind the head, above the hind flippers) and never by the flippers. Even if seriously weakened, turtles – especially large ones – are extremely strong. If a fishing line is seen protruding from the mouth or anus, it must on no account be pulled, because if a fishing hook is still attached it could cause serious internal lacerations. If the animal has recently suffered injury from a propeller and is still bleeding, a dry cloth should be pressed firmly onto the injury until the haemorrhage is blocked. You should always follow carefully the instructions given by qualified personnel on the telephone, and bear in mind the many other urgent duties they have, such as control of maritime movements by the harbourmaster, or fire-fighting by the Forestry Corps. Actively collaborating in saving a life is not only a thrilling experience but also a moral and civic duty.

Thanks to the Sea Turtle Recovery Unit, Linosa, Province of Agrigento