Kurma mela: The Science Behind Olive Ridley Turtles’ Mass Nesting
The Where of It
Olives Ridley turtles, a vulnerable species, have drawn global attention this year with a record-breaking seven lakh nests at Odisha’s Rushikulya beach. These turtles are known for their synchronized mass nesting events, called arribadas, a Spanish term meaning ‘arrival.’ While this event has sparked hope, it has also raised concerns for conservationists about the future of these animals and the impact of human activities on their natural habitat.
The Olive Ridley’s primary nesting sites are along the Pacific coasts of Mexico and Central America, with Odisha being a critical location. The state’s 480-km-long coastline has three major nesting beaches: Gahirmatha, Devi, and Rushikulya. These beaches are essential for the turtles’ life cycle, as they return to the same sites for nesting, a phenomenon known as philopatry. This behavior is influenced by memory, environmental factors, and the Earth’s geomagnetic cues.
The Factors That Shape Nesting Sites
Research has revealed that Olive Ridley turtles that hatch at a nesting site are imprinted with the local magnetic field. As they grow, they return to the same site with remarkable precision. This philopatry is reinforced by a multiplier effect: as more females return to a site, it becomes more attractive for future generations. Other ecological factors, such as the presence of cold-core eddies, which bring nutrients to the surface, also influence nesting zones. Salinity, land slope, risk of predation, and rainfall play a role in determining the suitability of a nesting site.
Nesting sites are often contested. As turtle populations grow, the size of the most favorable nesting grounds remains the same, leading to competition. A population that arrives after another has already nested may dig up existing nests, breaking the eggs. This happened during the second mass-nesting event at Rushikulya this year. Broken eggs attract predators, and recent studies indicate that olfactory cues, such as the scent of disturbed soil, are more significant in detecting nests than visual cues.
Temperature and Sex Ratio
Temperature plays a crucial role in determining the sex of Olive Ridley hatchlings. Studies on Loggerhead turtles have shown that warmer beaches lead to more female hatchlings. Researchers are still gathering similar data for Olive Ridleys. As global temperatures rise, the sex ratio may shift more towards females, reinforcing the multiplier effect and potentially leading to a decline in genetic diversity.
How Mass Nesting Begins
For their first arribadas, female turtles choose nesting sites without a clear pattern. If a female reaches reproductive maturity before it can return to its hatching beach, it may establish a new nesting site closer to its foraging grounds. This creates a new nesting site for future generations. Without such strays and wanderers, the population might face extinction due to overcrowding.
People, Turtles, and Tourism
Local communities play a vital role in turtle conservation. In Odisha, fisherfolk and villagers help protect nests, prevent egg poaching, and guide conservationists. However, not all human interactions are beneficial. The rise in turtle tourism has created opportunities for awareness but also stress on these gentle creatures. Crowds gathering at night with bright lights, taking selfies, and even sitting on turtles for photos disrupt nesting behavior and may affect the turtles’ memory, discouraging them from returning to the site.
Scientists are beginning to understand the cognitive and emotional inner lives of turtles. What we see as harmless curiosity may actually disrupt the ancient rhythms of these creatures. The priority now is to ensure the longevity of nesting beaches and to balance tourism with ethical responsibility.
Olive Ridley turtles have endured mass extinctions, shifting continents, and rising seas. Their resilience is remarkable, but not limitless. Regardless of whether turtles continue to return to nesting sites, humans have a clear ethical responsibility: to safeguard the ecological balance that keeps sea turtles going.