- Mass hatching of olive ridley turtles has just concluded along the east coast of India, especially in the beaches of Odisha.
- At Rushikulya in Odisha, the turtle traffic is two-way. As the hatchlings are heading out, female turtles are wading in to lay eggs for the second time this year. The first mass nesting happened late February, and the second was last week.
- The forest department claims that this year saw the highest number of turtles since they began recording mass nesting events, or arribadas.
- Despite being an activity that is perhaps older than the dinosaurs, scientists still don’t how such large number of adult female turtles communicate with each other to gather on the same day at the same beach.
The Rushikulya beach on the eastern coast of India is seeing a lot of traffic, some of which is unusually two-way. Millions of baby turtles are emerging from their sandy nests and striking out to try their might against the currents of the Bay of Bengal; and at the same time, thousands of adult female turtles are coming to their home beach to nest.
The eastern coast of India houses some of the largest hatcheries for the olive ridley, a small turtle that circumnavigates the globe in the tropical belt. Females of the species nest together in large numbers at mass nesting sites. The Gahirmatha, Devi and Rushikulya beaches in Odisha are famed for two remarkable events: thousands of female turtles coming in to nest, in February, followed by millions of hatchlings heading out into the sea after exactly 49 days in April.
This April, the Rushikulya beach is witness to both events occurring simultaneously. As the tiny hatchlings, less than 20 g in weight and a couple of inches in length were heading out to the sea, a rare wave of female turtles started wading on to the beach starting from the night of April 17 until April 21. The forest department estimates 36,000 nesting during the second mass nesting event for 2018, following up on the regular first round of nesting between February 21 and 26. According to reports, this rare event was restricted to Rushikulya and not seen in Gahirmatha, Devi or other beaches.
“This is very rare and we haven’t seen this happen since 2006. The following year, in 2007, there was no mass nesting at all,” said Rabindranath Sahu, a local conservationist who runs the Rushikulya Sea Turtle Protection Committee. The committee has more than 50 members – all from the Purunabandha village in Ganjam district near the Rushikulya sea turtle rookery.
Whether the two mass nesting events would impact nesting in 2019 remains to be seen.
A second arribada
Female olive ridleys nest in large numbers at beaches, and such mass nesting events are called arribadas (a Spanish word meaning arrival). Researchers studying olive ridleys and their nesting patterns say there could be a combination of reasons for mass nesting to occur twice in the same year at this site.
“Nesting sites for ridleys tend to be highly dynamic, and the mass nesting in Gahirmatha beach has been on small, not particularly stable sand bars. Perhaps there is a general decline in the nesting habitat, and turtles that usually nest there are nesting in Rushikulya,” said Kartik Shanker, director of the Ashoka Trust for Research in Ecology and the Environment (ATREE), and founder trustee of Dakshin Foundation, which has been monitoring olive ridleys in Rushikulya since 2008.
“The other possible reason for this phenomenon is that there is an actual increase in the population of olive ridleys. Individual turtles usually nest two or three times during the season — when the population has reached a critical mass, a second arribada becomes possible,” added Shanker.
The second arribada has happened quite late in to the nesting season, putting nests at risk, felt Muralidharan Manoharakrishnan, field director, Biodiversity and Resource Monitoring Programme for Dakshin Foundation. “We expect the heat and erosion to have an impact on the nests, but since this is the first time this has happened so late in the season we really would have to wait and watch for the hatchlings to emerge to see what happens,” he added. He is also a member of the Marine Turtle Specialist Group of the International Union for Conservation of Nature.
Another record this year: the sheer number of turtles
The forest department claims that this year saw the highest number of turtles since they began recording arribadas. “Every alternate year is either a bad year or a good year. However, in the last two years we have seen a phenomenal increase in nesting numbers. This year we have estimated that at least 4.75 lakh turtles came on to nest on Rushikulya beach,” said the Berhampur divisional forest officer (DFO), Ashish Kumar Behera.
“In 2011, there were only 1.01 lakh nests. It dropped to 59,000 in 2014. But in 2015, it shot up to 3.09 lakhs. The year 2016, did not see mass nesting. But the following two years caught up – with 2017 having 3.70 lakh nests,” he added.
Field researchers while concurring with the upward trend of nesting population say that these numbers need to be used with caution. “These numbers are highly prone to errors – as much as 50,000 nests per day. It depends on who is doing the sample count on that day,” said Manoharakrishnan.
“What ultimately matters is the trend, and all recent trends show there is an increase in the number of nesting turtles,” he added. He also said that estimating number of hatchlings would be prone to similar errors in estimation.
The mystery of mass nesting
Mass nesting is an extraordinary tactic adopted by olive ridleys – to overcome and overwhelm their natural predators. Instead of fighting against them or developing defense mechanisms, olive ridleys simply nest in large numbers to satiate their predators. Both eggs and hatchlings that emerge out of their nests are eaten by dogs, crows, jackals and even ants.
Thousands of hatchlings strike out to into the Bay of Bengal. Footage provided by Karthikeyan Hemalatha. Editing by Eddie Roquetta / Mongabay.
Apart from Rushikulya and Gahirmatha in Odisha, there are only four mass nesting sites in the world for olive ridleys: Costa Rica, Mexico, Nicaragua and Suriname. Both the beaches in Odisha are ideal mass nesting due to their offshore and onshore properties, say researchers. “The offshore currents in the open ocean aid the migration of turtles from their feeding grounds to the nesting grounds on the eastern coast of the country – and these seem to guide the larger population to the offshore region in around Odisha,” said Manoharakrishnan.
Arribada and the subsequent mass hatching are unique to Odisha and even to India, as they occur in only four other places. Locals, however, remain indifferent to turtles. “We avoid fishing during nesting time as nets can get damaged,” said R Kamraj, a 58-year-old artisanal fisherman from Gokhurkuda village. His village is on the shores of the mass nesting site. Prior to the beach being ‘discovered’ by the forest department, researchers and NGOs working in conservation say that the locals consumed turtle eggs on a regular basis. “We have stopped that now,” Kamraj added.
Not all impacts are positive, observed a report titled ‘Long-term monitoring and community-based conservation of olive ridley turtles in Odisha’, published by Indo-German Biodiversity Programme, GIZ-India. “Resentment grows in them when they witness instances such as the death of a turtle receiving more attention than the death of a fisherman. In a history of coexistence, these feelings were exacerbated by the fishing ban and constant presence of conservation activities,” the report added.
However, man-made threats on the beach are minimal. The beach does not have artificial lights on the landward of the ocean which can disorient hatchlings and make them go towards the land instead of the ocean. With no bottom trawlers, turtles are safe from being accidentally caught by nets. However, trawlers occasionally come from either Andhra Pradesh in the south or from Puri beach in the north. “We have sent proposals to acquire a large vessel that can be used to patrol the nesting beaches. In 2016, we had seized a few trawlers,” said Behera.
Despite being an activity that is perhaps older than the dinosaurs, scientists still don’t how such large number of adult female turtles communicate with each other to gather on the same day at the same beach. “The exact mechanism of communication between the turtles have not yet been deciphered but several theories including the synchronised hormonal release by the female turtles have been hypothesised,” said Manoharakrishnan.
The next time an emerging female hatchling will see the shores of Odisha will be 15 years later – when she comes back to nest again.
[Disclaimer: Karthikeyan Hemalatha is an independent journalist. During the time of the nesting season, he was on a short-term consultancy with the Dakshin Foundation.]