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Introduction
Morphology
Distribution
Vernacular names
Food habits
Nesting
Threats to survival
Arribadas

Introduction
Adult TurtleSea turtles have evolved from land-dwelling reptiles which laid eggs and they have retained this one vital link with life on land. The female turtle comes ashore during the nesting period to dig a pit and lay a nest on a sandy beach above the high tide mark. During incubation many nests are destroyed by predators and the hatching turtles are heavily preyed upon as they enter the sea. Many are lost to predators as they grow , but with each years growth they have fewer enemies, until, when they are adults, only very large sharks can eat them. Less than one in a thousand hatchlings survive to adulthood.
HatchlingsThe Olive Ridley is the most common turtle nesting on the Indian Coast. It is the smallest of all the sea turtles and is named for the color of its olive shaped shell. It forages off-shore in surface waters or dives to depths of atleast 150 meters to feed on bottom dwelling shrimp, crabs, sea urchins and other animals. The Ridley was once thought to be a solitary nester in the 1970's however, it was discovered that, like the kemps Ridley some populations of olive Ridley's synchronize their nesting in mass emergences or Arribadas. Tens of thousands of Olive Ridley's nest during Arribadas which continues for several nights. Today most populations have collapsed as a result of over exploitation.
Chennai on the south Indian coast is a minor nesting ground for the Olive Ridley

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Morphology
Female turtleThe Olive Ridley is the smallest of all sea turtles , adults being about 60 - 70 cm in carapace length and weighing about 40 kg. In shape the adult is very wide-shelled, the carapace having typically sloping sides and a rather flat top. Hatchlings are uniformly charcoal gray , and immature individuals are gray dorsally and white ventrally. Adult turtles differ from hatchlings and sub-adults in their coloration ,having a dark olive or greenish dorsal surface and light yellow on the plastron and ventral aspects of the soft parts.

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Distribution
Foraging areas
The Olive Ridley's are strongly tropical species found within 100 km of the mainland shore. Reasonably large populations exist in eastern Pacific from Mexico to Ecuador ; Philippines, Malaysia , Northern Australia and Britain . In the Indian Ocean the Largest populations occur , especially in the Bay of Bengal .
Nesting areas
The largest known nesting ground for the Olive Ridley in the World is located in Gahirmatha, Orissa . Other major nesting grounds include Oaxaco(Mexico) , and two sites in Pacific Costa Rica and in lesser concentrations in Nicaragua, Panama , French Guyana , Angola and Senegal .

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Vernacular Indian names
Bengali : Buk-chaprano (= chest slapping) , Faikya kossop (= winged turtle) , Faki kochchop (= bird turtle) , Gola kochchop(= round turtle) , Jolpaironger katha (= olive coloured turtle) , Samudrik katha( = sea turtle)
Central Nicobarese : Kap Ngal(= turtle) , Dhivehi Vavoshi Vela(= round frame turtle)
Gujarathi : Daryani Kachbi(= sea turtle)
Hindi : Gadha Kachua(= donkey turtle)
Kannada : Kardelu Aame(= sea turtle)
Lakshadweep : Malaya Mirighan
Oriya : Luni Kachua(= saline turtle) , Samudrik Kachhima(= sea turtle) , Soil Kaichha
South Nicobarese : Karasara
Tamil : Kadal Amai (= sea turtle) , Paingili Amai(= parrot turtle), Pul Amai (= grass turtle), Sith Amai(= small turtle), Thenga Matteyan Amai(= coconut husk turtle)
Telugu : Samudram Tabelu(= sea turtle)
Other English Names : Olive-back Loggerhead , Pacific Ridley Sea Turtle
ANALYSIS OF SCIENTIFIC NAME
Lepidochelys (=scale turtle) , olivacea(= olive colored).

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Food habits
Olive Ridley's are reported to be carnivorous feeding on Shrimp , snails , small crabs fish eggs, pearl oysters , echinoderms , jelly fish , tunicates and so on . Indian ocean Olive Ridley's on the other hand appear to be herbivorous , feeding on marine algae, which features extensively in their diet.

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Nesting
Nesting TurtleAdult turtles appear to migrate from long distances to shallow coastal waters to breed and generally do so in large numbers . Mating takes place on the surface of water , with males holding onto the carapaces of the females with the curved claws of their fore-limbs .Copulating pairs are often seen off nesting beaches prior to nesting .The reproductive habits of the Olive Ridley are rather distinct. The small size and Light weight of this species facilitates its utilization of flat wide beaches which are generally avoided by the heavier ones. They usually come to nest only at night , but are also seen nesting at dawn and dusk. Nesting females spend usually around 45 minutes to an hour on land.The turtle chooses a part of the beach which is free from the action of the tide and excavates a round hole about six feet in diameter called a Body Pit. It is in the body pit that they start to build their nest. A turtle may dig several body pits before building a nest . Any noise or unfamiliar movements may scare them . Turtle EggsThe nests are shallow and the eggs laid have an average diameter of 3 to 5 cm. After laying the eggs and filling up the nesting cavity , the Olive Ridley usually thumps the sand over the nesting site by means of vigorous , side to side rocking action of the shell. Nesting may occur two to three times in a season and unlike other species of turtles , nesting in successive seasons occurs quite frequently.On the Chennai coast , a clutch comprises of 80 to 160 eggs and incubation periods range between 50 and 63 days. Hatchlings measure between 3.5 centimeters to 6 centimeters.

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Threats to survival
The survival of the Olive Ridley and its offspring's is diminished by a variety of natural environmental conditions . But the greatest threat comes from the ones that are induced by man - made activities. The most important threats that sea turtles face are listed below.
Disruption caused by lighting
Artificial lightsThe greatest and most obvious threat facing the Ridley's on the Chennai coast is the presence of unnatural beach lighting either onshore or off-shore. Artificial lights affect both Nesting females as well as hatchlings . There is evidence to show that females may be discouraged from nesting on heavily lit beaches. Hatchlings become disoriented and suffer high rates of mortality because of bright lights .
Since Hatchlings are positively photo tropic they are attracted by bright lights located behind the nesting beach ,and head inland rather than towards the sea .Apparently , bright lights appear to be so irresistible that they would even run into the flames of a beach fire.Although hatchlings will eventually be able to reorient themselves towards the sea once the sun rises , they may be too exhausted or desiccated to do so.
Loss of Habitat
The recent spurt in illegal mining for beach sand poses a serious threat to the nesting habitat of the Ridley on the Chennai coast . It can result in lowering of the beach platform to a point that it floods at high tide or during heavy seas, making it an unsuitable medium for incubation.
Chemical Pollution
Industrial EffluenceThe most obvious form of chemical pollution in the nesting habitat is Oil . Fresh crude oil is known to cause significant mortality and morphological changes in the incubating embryos , but weathered oil may not. Untreated Industrial effluence appears to deter nesting turtles in some parts of the Chennai coast . But more research is needed to document the the lethal effects of such chemical pollutants. Eggs , embryos and hatchlings are more vulnerable than adults since volatile and water soluble contaminants can be absorbed into the egg . Both oil spills and resulting clean up operations could have harmful effects at the nesting beach.
Physical Debris
Physical DebrisBeaches around the world are rapidly becoming polluted by man-made debris . This debris includes light bulbs , styrofoam , plastics , tar , wood , glass cloth , fishing gear and organic wastes .Small objects like these , if abundant enough , could become incorporated into the beach sand , and ultimately alter their thermal properties or patterns of gas diffusion within it.
Coastal construction may deter or prevent nesting females from coming ashore.
Incidental Catch
A dead Turtle
Incidental catch results in significant mortality of Adults along the Chennai coast. The absence of Turtle Excluder Devices (TED) can be cited as one of the major causes for this mortality .

Arribadas
The Olive Ridley's are known for their peculiar nesting strategies. Refereed to as Arribada (meaning mass arrival in Spanish), it involves nesting in numbers that may reach many thousands during a single night on a short stretch of beach. One of the largest nesting grounds for the Olive Ridley in the world was discovered in Gahirmatha, Orissa , in Eastern India.

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