Olive ridley (சிற்றாமை)

சிற்றாமை (Olive ridley)

அனைவருக்கும் வணக்கம்

       ஆலிவ் ரிட்லி என்று அழைக்கப்படும்

சிற்றாமையைப்பற்றிய ஒரு வீடியோவை பார்க்க 

இங்கு கிளிக் செய்யவும்,

இந்த ஆமைகள் இதய வடிவம் கொண்டு ஆலிவ் பச்சை நிறத்தில் இருப்பதால்  ஆலிவ் ரிட்லி என ஆங்கிலத்தில் அழைக்கப்படுகிறது.

ஒவ்வொரு பெண் ஆமையும் ஒரு முறைக்கு 50 முதல் 190 முட்டைகள்வரை இடுகின்றன. முட்டையிட்ட 45  நாட்கள் முதல் 60 நாட்களுக்குள் முட்டைகள் பொரிந்து ஆமைக்குஞ்சுகள் வெளிவருகின்றன.   முட்டைகள் பெரும்பாலும் இரவிலேயே பொரிகின்றன.

தட்ப வெப்பநிலைக்குத் தகுந்தவாறு அவற்றின் பாலினம் அமைவதாக  கருதப்படுகிறது.

இந்த ஆமைகளால் கடலின் சுற்றுச்சூழல் பாதுகாக்கப்படுகிறது. இதன்மூலம் மீன் வளம் அதிகரிக்கிறது. கடலில் காணப்படும் ஜெல்லி மீன்கள் மீனவர்களின் வாழ்வாதாரமான மீன்குஞ்சுகளை உணவாக உட்கொள்கிறது. இந்த ஜெல்லி மீன்களின் இளம் உயிரிகளை ஆமைகள் உணவாக உட்கொண்டு ஜெல்லிமீன்களின் வளர்ச்சியை கட்டுக்குள் வைக்கிறது. இதனால் மீனவர்களின் வாழ்வாதாரமும் அவர்களின் பொருளாதார நிலையும் உயர்கிறது.

எனவே நீங்களும் ஆமையை பாதுகாக்க உதவவேண்டும்.

Olive ridley (Lepidochelys olivacea)
The olive ridley sea turtle (Lepidochelys olivacea), also known as the Pacific ridley sea turtle, are smallest and most abundant of all sea turtles found in the world, species of sea turtle found in warm and tropical waters, primarily in the Pacific and Indian Oceans.
 

Olive ridley turtles are best known for their behavior of synchronized nesting in mass numbers, termed arribadas. Females return to the same beach from where they first hatched, to lay their eggs. They lay their eggs in conical nests about one and a half feet deep which they laboriously dig with their hind flippers. In the Indian Ocean, the majority of olive ridleys nest in two or three large groups near Gahirmatha in Odisha.

Reproduction

Mating is often assumed to occur in the vicinity of nesting beaches, but copulating pairs have been reported over 1,000 km from the nearest beach. Research from Costa Rica revealed the number of copulating pairs observed near the beach could not be responsible for the fertilization of the tens of thousands of gravid females, so a significant amount of mating is believed to have occurred elsewhere at other times of the year.

The Gahirmatha Beach in Kendrapara district of Odisha (India), which is now a part of the Bhitarkanika Wildlife Sanctuary, is the largest breeding ground for these turtles. The Gahirmatha Marine Wildlife Sanctuary, which bounds the Bhitarkanika Wildlife Sanctuary to the east, was created in September 1997, and encompasses Gahirmatha Beach and an adjacent portion of the Bay of Bengal. Bhitarkanika Mangroves were designated a Ramsar Wetland of International Importance in 2002. It is the world's largest known rookery of olive ridley sea turtles.

Olive ridley sea turtles migrate in huge numbers from the beginning of November, every year, for mating and nesting along the coast of Orissa. Gahirmatha coast has the annual nesting figure between one hundred to five hundred thousand, each year. There has been decline in the population of these turtles in the recent past due to mass mortality. The olive ridley sea turtle has been listed on Schedule – I of the Indian Wildlife (Protection) Act, 1972 (amended 1991). Olive Ridley Sea Turtles are listed as vulnerable under IUCN. The sea turtles are protected under the 'Migratory Species Convention' and CITES (Convention of International Trade on Wildlife Flora and Fauna). India is a signatory nation to all these conventions. The 'Homing' characteristics of the Ridley sea turtles make them more prone to mass casualty. The voyage to the natal nesting beaches is the dooming factor for the sea turtles. Since Gahirmatha coast serves as the natal nesting beach for millions of turtles, it has immense importance on turtle conservation.

Olive ridleys generally begin to aggregate near nesting beaches about two months before nesting season, although this may vary throughout its range. In the eastern Pacific, nesting occurs throughout the year, with peak nesting events (arribadas) occurring between September and December. Nesting beaches can be characterized as relatively flat, midbeach zone, and free of debris. Beach fidelity is common, but not absolute. Nesting events are usually nocturnal, but diurnal nesting has been reported, especially during large arribadas. Females can lay up to three clutches per season, but most will only lay one or two clutches. The female will remain near shore for the internesting period, which is about one month. Mean clutch size varies throughout its range and decreases with each nesting attempt.

A mean clutch size of 116 (30–168 eggs) was observed in Surinam, while nesting females from the eastern Pacific were found to have an average of 105 (74–126 eggs). The incubation period is usually between 45 and 51 days under natural conditions, but may extend to 70 days in poor weather conditions. Eggs incubated at temperatures of 31 to 32 °C will produce only females; eggs incubated at 28 °C or less will produce solely males; and incubation temperatures of 29 to 30 °C will produce a mixed sex clutch. Hatching success can vary by beach and year, due to changing environmental conditions and rates of nest predation.

Feeding

The olive ridley is predominantly carnivorous, especially in immature stages of the life cycle. Animal prey consists of protochordates or invertebrates, which can be caught in shallow marine waters or estuarine habitats. Common prey items include jellyfish, tunicates, sea urchins, bryozoans, bivalves, snails, shrimp, crabs, rock lobsters, and sipunculid worms. Additionally, consumption of jellyfish and both adult fish (e.g. Sphoeroides) and fish eggs may be indicative of pelagic (open ocean) feeding. The olive ridley is also known to feed on filamentous algae in areas devoid of other food sources.

Threats
Olive ridley entangled in a ghost net within the Maldives
Taken in a drifting net in the Maldives
Floating in the Arabian Sea, possibly killed by a boat propeller
Known predators of olive ridley eggs include raccoons, coyotes, feral dogs and pigs, opossums, coatimundi, caimans, ghost crabs, and the sunbeam snake. Hatchlings are preyed upon as they travel across the beach to the water by vultures, frigate birds, crabs, raccoons, coyotes, iguanas, and snakes. In the water, hatchling predators most likely include oceanic fishes, sharks, and crocodiles. Adults have relatively few known predators, other than sharks, and killer whales are responsible for occasional attacks. On land, nesting females may be attacked by jaguars. It is notable that the jaguar is the only cat with a strong enough bite to penetrate a sea turtle's shell, thought to be an evolutionary adaption from the Holocene extinction event. In observations of jaguar attacks, it was noted that the cats consumed the neck muscles of the turtle and occasionally the flippers, but left the remainder of the turtle carcass for scavengers as most likely, despite the strength of its jaws, a jaguar still cannot easily penetrate an adult turtle's shell to reach the internal organs or other muscles. In recent years, increased predation on turtles by jaguars has been noted, perhaps due to habitat loss and fewer alternative food sources. Sea turtles are comparatively defenseless in this situation as they cannot pull their head into their shell like freshwater and terrestrial turtles. Females are often plagued by mosquitos during nesting. Humans are still listed as the leading threat to L. olivacea, responsible for unsustainable egg collection, slaughtering nesting females on the beach, and direct harvesting adults at sea for commercial sale of both the meat and hides.

Other major threats include mortality associated with boat collisions, and incidental takes in fisheries. Trawling, gill nets, ghost nests, longline fishing, and pot fishing, have significantly affected olive ridley populations, as well as other species of marine turtles. Between 1993 and 2003, more than 100,000 olive ridley turtles were reported dead in Odisha, India from fishery-related practices. In addition, entanglement and ingestion of marine debris is listed as a major threat for this species. Coastal development, natural disasters, climate change, and other sources of beach erosion have also been cited as potential threats to nesting grounds. Additionally, coastal development also threatens newly hatched turtles through the effects of light pollution. Hatchlings which use light cues to orient themselves to the sea are now misled into moving towards land, and die from dehydration or exhaustion, or are killed on roads.


The olive ridley is classified as vulnerable according to the International Union for Conservation of Nature and Natural Resources (IUCN), and is listed in Appendix I of CITES. These listings were largely responsible for halting the large scale commercial exploitation and trade of olive ridley skins.

Several projects worldwide seek to preserve the olive ridley sea turtle population.

Another major project, in India involved in preserving the olive ridley sea turtle population was carried out in Chennai and other parts (Cuddalore and Marakkanam)