Guided By Earth’s Invisible Map: How Olive Ridley Turtles Find Their Way Back To India’s Shores

Scientists describe it as a built-in biological GPS. Each segment of the Earth’s coastline carries a unique magnetic “signature,” shaped by subtle variations in the planet’s core and crust.

“When Olive Ridley hatchlings break free from their nests and scramble towards the sea for the first time, they imprint this magnetic information. Decades later, as fully grown adults roaming distant feeding grounds, they rely on this invisible map to guide them back to the same region to lay their eggs. This magnetic sensing allows turtles to orient themselves in the open ocean, where visual landmarks are absent and stars are often obscured,” says Dr Prakash Jena, a scientist and leading environmentalist.

“But the journey is not guided by magnetism alone. As Olive Ridleys approach India’s coastline, they fine-tune their route using ocean currents, wave direction and temperature gradients. Nearer to shore, they respond to beach slope, underwater contours and coastal features, instinctively selecting nesting sites less vulnerable to flooding or erosion. The result is a navigation system that is both precise and adaptable—ancient, yet remarkably efficient,” adds Dr Jena.

Nowhere is this phenomenon more dramatically visible than in India, one of the few countries in the world where Olive Ridleys exhibit arribada, or mass nesting. Odisha’s coastline, in particular, offers the right magnetic, geographic and environmental conditions that have drawn generations of turtles back year after year. Even those that nest singly along the shores of Tamil Nadu or Andhra Pradesh are guided by the same magnetic memory system.

In 2025, the power of that instinct was on full display at the Rushikulya river mouth in Odisha’s Ganjam district. Between February 16 and 24, an extraordinary 6,98,718 Olive Ridley turtles emerged from the sea to nest along this scenic stretch of the Bay of Bengal, setting a new record and surpassing the previous high of 6.37 lakh recorded in 2023. The site, along with Gahirmatha beach in Kendrapara district, is recognised globally as one of the most important rookeries for this endangered marine species.

According to Dibya Sankar Behera, Assistant Conservator of Forests at Khallikote, the mass nesting continued uninterrupted until February 24, 2025. “In 2025, the numbers were historic,” he said, noting a steady rise over the past three seasons—from 5.50 lakh turtles in 2022 to over 6.98 lakh 2025.

Behind this success lies a rare convergence of nature, governance and community participation. Local fishing communities, whose livelihoods depend on the sea, cooperated fully with government directives to suspend fishing during the nesting period. Their support ensured a calm, disturbance-free environment for the turtles. Non-governmental organisations, meanwhile, worked on the ground to raise awareness about the significance of protecting these seasonal visitors that travel thousands of kilometres to reach Odisha’s shores.

Favourable climatic conditions also played a role, experts believe. To further safeguard the nesting sites, the forest department fenced newly used beaches from New Podampeta to Prayagi, covering nearly nine kilometres. “The fencing was meant to protect eggs from predators like dogs and jackals. Every possible precaution was taken,” Behera said.

Arribada itself is a spectacle unlike any other. Over successive nights, thousands of female turtles crawl ashore, dig nests, lay their eggs and return to the sea in near-perfect synchrony. About 45 days later, the cycle will continue as hatchlings emerge and instinctively race towards the waves, beginning a journey that may bring them back decades later.

Technology is now offering fresh insights into these ancient migrations. In May 2025, a satellite-tagged Olive Ridley from Gahirmatha travelled nearly 1,000 kilometres in just 51 days, navigating coastal waters past Sri Lanka, Tamil Nadu and Puducherry before reaching Andhra Pradesh. Earlier, another turtle tagged in Odisha astonished researchers by covering over 3,500 kilometres to nest in Maharashtra’s Ratnagiri district.

Since the turtle tagging programme was revived in 2021 by the Zoological Survey of India, around 12,000 turtles have been tracked across Odisha’s major nesting sites. Officials say that tagging on a much larger scale—possibly up to one lakh turtles—could unlock deeper understanding of their biology, growth rates and migratory corridors.

“As Olive Ridleys continue to follow Earth’s invisible magnetic map back to India’s shores, their survival may depend just as much on how well humans learn to protect the destinations they return to, generation after generation,” says Dr Jena.