Nearly seven lakh Olive ridley turtles laid eggs at the Rushikulya ‘rookery’ or nesting ground in Odisha’s Ganjam district during a mass nesting between February 16 and February 25. The development came after the region did not witness any mass nesting last year. In 2023, around 6.37 lakh Olive ridleys, an endangered marine species, laid eggs at the same spot. What are Olive ridley turtles? Olive ridley turtles (Lepidochelys olivacea) are the smallest and most abundant of all sea turtles in the world. They get their name from the olive green colour of their heart-shaped shell, and inhabit warm waters of the Pacific, Atlantic, and Indian oceans. Olive ridleys can grow about two feet in length, and 50 kg in weight. Scientists do not know exactly how long they live, but like other sea turtles, Olive ridleys are likely long-lived — they reach maturity around 14 years of age. According to the Marine Turtle Specialist Group (MTSG) of the International Union for the Conservation of Nature (IUCN), there has been a 50% reduction in population size of these sea turtles since the 1960s. The main reasons behind their decline include long-term collection of eggs and mass killing of adult females on nesting beaches, and unintended capture in fishing gear which can lead to drowning or cause injuries that result in death. These marine reptiles are best known for their unique mass nesting — also called arribada, Spanish for “arrival” — during which thousands of females come together on the same beach to lay eggs. “Arribada nesting is a behaviour found only in the genus Lepidochelys which includes the Kemp’s ridley and olive ridley sea turtles. Although other turtles have been documented nesting in groups, no other turtles (marine or land) have been observed nesting in such mass numbers and synchrony,” according to a report on the US agency National Oceanic and Atmospheric Administration’s (NOAA’s) website. During nesting, more than 600,000 females emerge from the waters, over a period of five to seven days, to lay eggs. They lay their eggs in conical nests which they dig with their hind flippers and are one and a half feet deep. Where does arribada occur? While solitary nesting by Olive ridleys is known to take place in approximately 40 countries worldwide, arribada nesting occurs on only a few beaches. The coast of Odisha (where Rushikulya and Gahirmatha rookeries are situated) is the largest mass nesting site for the Olive ridley, followed by the coasts of Mexico and Costa Rica. Experts say Rushikulya and Gahirmatha make for an ideal mass nesting site due to favourable weather conditions, warm sandy beaches, and an undisturbed coastal ecosystem. Pratap Mohanty, formerly with the department of marine sciences at Berhampur University (Odisha), told The Indian Express that mass nesting mostly occurs to the north of the river mouth as the conditions in the nearshore water and beach sand are favourable preceding the nesting event and during the nesting. He also said turtles prefer to nest on a beach with a mild slope, medium width and greater percentage of medium sand with low salinity. “Lower wind speed, low to moderate waves and moderate south-westward current before nesting are helpful for Olive ridley turtles to inhabit the coastal waters in large numbers. During the mass nesting, the enhancement in wind speed generates relatively higher wave height, helping the sea turtles to move to the beach for nesting easily,” he said. The coast in Odisha typically witnesses arribada in the first quarter of every year. Why did Odisha see the arrival of so many Olive ridley turtles this year? According to experts, a range of factors could be responsible for a large number of Olive ridleys arriving for nesting at Rushikulya this year. One could be favourable weather conditions. Sunny Khokhar, a divisional forest officer posted in Berhampur, told The Indian Express that the lack of rain in February could have contributed to this. Less rain means that there is no erosion in the beach, which, in turn, provides sufficient space near the river mouth for Olive ridleys to nest in large numbers. “The second reason is the beach gradient, the slope of a beach from the top to the water’s edge, which is less this year compared to previous years,” Khokhar said. Basudev Tripathy, a senior scientist of the Zoological Survey of India (ZSI), also echoed Khokhar’s point, saying that the Rushikulya beach provided enough space for a large number of Olive ridleys to nest this year. He said that Gahirmatha might also witness mass nesting soon. Notably, Tripathy expected more eggs to successfully hatch this year as the nesting had taken place in mid-February and not later. “The Olive ridley turtle eggs will hatch around 50 days from now. This means that fewer eggs will be lost due to high temperatures and coastal erosion. The later the nesting takes place, more eggs are lost to erosion which starts to become an issue in April.” Speaking about the absence of mass nesting in 2024, Tripathy said it was yet to be determined why exactly the arribada did not take place. “Mass nesting is a biological phenomenon, and some years sea turtles skip nesting. We do not know the exact reason for this.”
