Kurma mela: The science of the mass nesting of Olive Ridley turtles 

The Olive Ridley turtle (Lepidochelys olivacea), a susceptible sea turtle species, made headlines earlier this yr: a record-breaking seven lakh turtles had nested at Odisha’s Rushikulya seaside alone in March.

These turtles are famend for his or her synchronised mass nesting occasions known as arribada, a Spanish phrase which means “arrival”. For many individuals, the Rushikulya arribada signalled hope — however for conservation biologists, it raised important questions on the way forward for these susceptible animals and whether or not human interventions, even well-meaning ones, may change the course of nature itself.

Whereas some localised populations of Olive Ridley turtles have expanded, the IUCN Purple Record has estimated that the variety of Olive Ridleys worldwide has dropped by 30-50% since 1960. The Olive Ridleys’ main nesting websites are alongside the Pacific coasts of Mexico and Central America, though Odisha can be a very important location.

The State’s 480-km-long shoreline hosts three main nesting seashores: Gahirmatha, between the Brahmani and Baitarani river mouths; Devi, 100 km south of Gahirmatha; and Rushikulya, 320 km additional south.

The the place of it

Analysis has discovered that Olive Ridley turtles that hatch at a nesting website are ‘imprinted’ with a map of the native magnetic area. A long time later they return with exceptional precision to the positioning by following this map. The phenomenon is named philopatry: a mix of reminiscence, environmental elements, and the earth’s geomagnetic cues. Philopatry is strengthened by a multiplier impact: as females with robust philopatric tendencies improve in quantity, they reinforce website constancy throughout generations.

There are different ecological elements too. Research on the Loggerhead sea turtles (Caretta caretta) have additionally revealed that their nesting zones are close to free swirls of chilly water within the seas — known as cold-core eddies — that transfer vitamins up from the deep sea to the floor, together with these wealthy in chlorophyll. Different elements that have an effect on their selection of nesting websites embody salinity, land slope, threat of predation, and rainfall.

Nesting websites are thought-about extra appropriate if extra turtles have nested there earlier than — however as turtle populations swell whereas the scale of probably the most beneficial nesting grounds doesn’t, seashores usually develop into battlegrounds. A inhabitants that arrives after one other has already nested at a seaside would possibly dig up present nests — feminine turtles are guided by olfactory cues and feminine urine — and break the eggs. This occurred earlier this yr throughout the second mass-nesting occasion at Rushikulya.

Eggs which might be damaged and displaced entice predators. Consultants beforehand believed predators used visible cues to detect turtle nests. More moderen analysis has discovered that olfactory cues, particularly the scent of disturbed soil and damaged eggs, are extra important. Thus, a species’ most profitable survival technique can also sow the seeds of its decline.

In sea turtles, temperature determines the intercourse of hatchlings. Research of Loggerhead turtles have discovered that their populations are extra feminine once they nest on hotter seashores. Researchers are nonetheless gathering comparable information pertaining to Olive Ridley turtles. With rising temperatures shifting the intercourse ratio extra in direction of females, the multiplier impact is anticipated to get strengthened as extra females return to mass-nesting seashores within the coming years.

How mass nesting begins

For his or her first arribadas, feminine sea turtles decide their nesting websites with none discernible sample and use them irregularly. If a feminine turtle reaches the reproductive stage of its life earlier than it is ready to attain the seaside the place it hatched, it could set up a brand new nesting website nearer to its foraging grounds. Its hatchlings can be imprinted with this location and they’re going to try and return to it later.

Put one other means, for a sea turtle inhabitants to thrive, it wants strays and wanderers like these turtles, which set up new locations for the arribada. If they’d been compelled to stay to 1 website over tens of millions of years, they’d probably have develop into extinct resulting from overcrowding within the mass nesting seashores.

Trendy conservation has helped increase turtle populations, particularly by artificially incubating eggs and defending seashores. The query naturally arises: may these measures be too profitable? As a result of if weaker people that will have perished within the wild are actually capable of survive and reproduce, the inhabitants’s genetic resilience will drop.

Folks, turtles, reputation

No conservation story is full with out acknowledging the position of native communities. In Odisha, fisherfolk and villagers are important allies: they guard nests, curb egg poaching, and information conservationists. However not all human interactions are benign.

Turtle tourism has surged lately. The inflow of tourists creates alternatives to boost consciousness however it additionally stresses these light creatures. Crowds collect to observe nesting turtles at night time, utilizing vibrant lights, clicking selfies, and — in some disturbing circumstances — scooping sand out of the bottom to observe the egg-laying and even sitting on turtles for images.

Such acts disturb nesting behaviour and will have an enduring influence on the turtles’ reminiscence, discouraging them from returning to the positioning.

Scientists are additionally simply starting to know the cognitive and emotional internal lives of turtles. It’s solely potential that what we consider as harmlessly marvelling at them may very well be disrupting the traditional rhythms of those mariners.

In different phrases, it’s now not about numbers or rescue operations. The precedence is to make sure the longevity of those nesting seashores and to steadiness tourism with moral accountability.

Olive Ridley turtles have endured mass extinctions, shifting continents, and rising seas. Their resilience is exceptional — however not limitless. No matter whether or not turtles proceed to return to nesting websites regardless of these disturbances, people’ moral accountability is obvious: to safeguard the ecological steadiness that retains sea turtles going.

Deyatima Ghosh is an assistant professor on the Centre for City Ecology, Biodiversity, Evolution and Local weather Change, JAIN (Deemed-to-be) College, Bengaluru.