Introduction to the Olive Ridley Sea Turtle
The Pacific sea turtle, or olive ridley sea turtle (Lepidochelys olivacea), is associated with the Cheloniidae family. The species is the most widespread and second-smallest marine turtle in the world. The warm, tropical waters of the Pacific and Indian Oceans and the warm Atlantic Ocean offer habitat for olive ridley sea turtles. The spectacular synchronized mass nestings known as arribadas, during which thousands of females assemble on the same beach to lay eggs, are the most prominent characteristic of this turtle and its related species Kemp’s ridley sea turtle.
Physical Characteristics of Olive Ridley Turtles
The olive ridley sea turtle gets its name due to its olive-colored, round, heart-shaped carapace (outer shell), which is about 61 cm (2ft) in length (measured along the curve). The carapace of females is a little more rounded compared to that of males, but both sexes attain the same size. Very rarely does a mature olive ridley sea turtle weigh above 50 kg (110 lb). Adult males weighed a lot less, averaging 33.00 kg (72.75 lb) (n=17), while adult females weighed an average of 35.45 kg (78.2 lb) (n=58). Adults ranged in weight from 25 to 46 kg (55 to 101 lb). Usually, hatchlings weigh 12.0 to 23.3 g (0.42 to 0.82 oz).
Habitat and Global Distribution
From southern Africa, Australia, and New Zealand to India, Arabia, Japan, and Micronesia, the olive ridley turtle can be found in the warm, tropical seas of the Pacific and Indian Oceans. It has been seen in the Atlantic Ocean off the shores of northern Brazil, Suriname, Guyana, French Guiana, and Venezuela, as well as off the western coast of Africa. The olive ridley has also been observed as far north as Puerto Rico in the Caribbean Sea. Olive ridleys are thought to use the coastal waters of more than 80 nations, however, their migratory movements have not been as thoroughly investigated as those of other marine turtle species.
This species is widely believed to be the most widely distributed marine turtle globally. In 1968 alone, nearly a million olive ridley were harvested for commercial reasons off the beaches of Mexico. Although being deemed to be the largest group, olive ridley sea turtles have gone down by 30% compared to their original populations worldwide. Due to the limited number of nesting locations left on the globe, these turtles are listed as endangered.
Nesting Behavior and the Arribada Phenomenon
Olive ridley turtles have two distinct nesting habits: coordinated mass nesting, known as arribadas, and solitary nesting, which is the most common. Their most well-known behavior is the latter, which sets them apart from other sea turtle species. To lay their eggs, females return to the seashore where they hatched. Using their hind flippers, they painstakingly dig conical nests that are around 1.5 feet deep, where they lay their eggs.
A large number of Olive Ridleys nest in two or three large colonies adjacent to Gahirmatha in Odisha and the Indian Ocean, Arabian Sea, near Honavar in Karnataka. Alongside the beaches of Mexico and Costa Rica, the Indian state of Odisha is habitat to a few of the Olive Ridley’s largest mass nesting areas. Yet, across the Indian Ocean, olive ridley are viewed as unusual.
Sewage, agricultural runoff, pesticides, solvents, and industrial discharges have polluted some of the olive ridley’s feeding spots in the Southern California zones. Considering these turtles eat the benthic seabed community, it has been found that these contaminants lower their productivity, resulting in a negative impact on the turtles.
Given that more oil and gasoline will be poured into these vulnerable habitats, the growing demand to construct marinas and docks near Baja California and Southern California additionally harms the olive ridleys in these areas. The likelihood of young and subadult turtles getting stuck and entrapped in the saltwater cooling intake systems of power plants is a further threat to these turtles.
Mating and Breeding Patterns
Given that copulating pairs have been spotted over a thousand miles from the closest beach, mating is often believed to happen adjacent to nesting beaches. A significant amount of mating has been believed to have occurred elsewhere over other times of the year, as research from Costa Rica revealed that the number of copulating pairs found near the beach could not be responsible for the fertilization of the tens of thousands of gravid females. The largest turtle breeding place is Gahirmatha Beach in Odisha (India)’s Kendrapara district, which is now a part of the Bhitarnika Wildlife Sanctuary.
Gahirmatha Beach and a nearby area of the Bay of Bengal are part of the Gahirmatha Marine Wildlife Sanctuary, which was established in September 1997 and borders the Bhitarkanika Wildlife Sanctuary to the east. In 2002, the mangroves of Bhitarkanika were named a Ramsar Wetland of International Importance. It is the biggest known olive ridley sea turtle rookery in the world.
Two other mass nesting beaches, on the mouths of the rivers Rushikulya and Devi, have been identified in addition to Gahirmatha Rookery. Scientists and nature enthusiasts from all over the world are captivated by the sight of olive ridley sea turtles congregating in large numbers for mating and breeding.
Conservation Efforts and Legal Protection
The Indian Wildlife (Protection) Act, 1972 (modified in 1991) lists the olive ridley sea turtle on Schedule I. The IUCN has classified the species as vulnerable. The “Migratory Species Convention” and the Convention on International Trade on Wildlife Flora and Fauna (CITES) both protect sea turtles. All of these conventions are ratified by India. The ridley sea turtles are especially vulnerable to mass casualties due to their homing traits. Their downfall is the journey to the natal nesting beaches. The Gahirmatha coast is crucial to turtle protection since it is the natal nesting beach for millions of turtles.
Given that their meat is of little importance, olive ridley has been utilized to produce food, oil, leather, and fertilizer. However, their eggs are very valuable. Because collecting eggs is usually banned, enforcement is lax. A legal egg harvest that has been in place since 1987 in Ostional, Costa Rica, permits residents to gather three million eggs a year within the first 36 hours of nesting, minimizing severe destruction. More than 27 million eggs are still safe, raising the probability that they will hatch. However the idea is still debatable among conservationists, it supports local businesses and hinders illegal poaching. Due to variations in regulations and economic conditions, such projects have not been as successful in Nicaragua.
Diet and Feeding Habits of Olive Ridleys
The olive ridley is mainly carnivorous. Tunicates, such as sea squirts and scallops, starfish, sea urchins, bryozoans, squid, bivalves, snails, barnacles, shrimp, crabs, rock lobsters, and sipunculid worms are examples of common prey items. Furthermore, eating fish eggs and jellyfish as well as adult fish (like Sphoeroides) may be a sign of pelagic (open ocean) feeding. In places where there are no other food sources, the olive ridley is also reported to consume filamentous algae.
Raccoons, coyotes, dogs, pigs, crabs, and snakes prey on Olive Ridley sea turtle eggs, while birds, crabs, and marine predators hunt on hatchlings. Sharks, crocodiles, and even jaguars are the major predators of adults. The biggest threat comes from human activities including hunting, fishing, and egg gathering. Populations are also affected by habitat degradation, boat hits, marine trash, and bycatch. Mass nesting episodes called arribadas cause nest destruction, which leads to a high egg loss rate. Hatchlings are fatally misguided by light pollution. Scientists disagree about whether arribadas help or hurt reproductive success, which affects conservation and egg collection strategies.
Conservation Success Stories and Future Outlook
Large-scale trade has declined given that the olive ridley is listed in Appendix I of CITES and has been classified as vulnerable by the IUCN. The Inter-American Convention and the Convention on Migratory Species both protect it. Conservation efforts have been beneficial due to national programs, NGOs, and public education, however, enforcement is still lacking globally. Fisheries turtle excluder devices and Arribada management have been beneficial. India has seen significant conservation efforts, such as the release of 8,834 hatchlings from Chennai and the discovery of 86 nests in Honnavar in 2023. Even with advancements, Kemp’s ridley continues to garner more attention than the olive ridley. Schools take part in environmental initiatives as well.