Quick answer: Olive ridley turtles fitted with satellite tags in Tamil Nadu have been tracked to the Sri Lanka Dome, a seasonal upwelling zone in the south-western Bay of Bengal. In October 2026, a Wildlife Institute of India study added that one Odisha female swam 6,719 km in 271 days to waters east of Sri Lanka.
Why olive ridley turtles and the Sri Lanka Dome are in the news
Tamil Nadu began satellite-tagging olive ridleys in 2025, working with the Wildlife Institute of India (WII). In 2026, early tracking data showed that some of the tagged turtles had already reached the Sri Lanka Dome, as Mongabay-India reported in June 2026. Turtles from Odisha are also expected to reach the same waters, which suggests the dome is a feeding hotspot shared by India’s east-coast populations.
A second set of results came out in early October 2026. As part of a three-year WII study backed by the Odisha wildlife wing, satellite tags on 10 turtles produced 1,748 days of data. One female covered 6,719 km in 271 days and reached waters east of Sri Lanka. The study found that males leave for the open sea earlier, while females stay near the shore for longer.
Key facts about the olive ridley turtle
- Scientific name: Lepidochelys olivacea, the smallest and most abundant sea turtle in the world.
- Name: it is named after its olive-green carapace (upper shell).
- Mass nesting (arribada): large groups of females come ashore together to nest. In 2025, more than 6.5 lakh olive ridleys arrived at Rushikulya in Odisha.
- Main Indian nesting sites: Gahirmatha (Kendrapara), Rushikulya (Ganjam) and the mouths of the Devi river, all in Odisha.
- Protection: Vulnerable on the IUCN Red List, and listed in Schedule I of the Wildlife (Protection) Act, 1972.
- Biology: the sex of the hatchling depends on the temperature at which the egg incubates (temperature-dependent sex determination). Eggs take roughly 45 to 65 days to hatch.
- Survival: only about one in 1,000 hatchlings reaches adulthood.
What is the Sri Lanka Dome?
The Sri Lanka Dome is a patch of the ocean east of Sri Lanka where colder, nutrient-rich water rises towards the surface during the south-west monsoon. Oceanographers describe it as an upwelling recirculation feature within the Southwest Monsoon Current. Here is its seasonal cycle, based on a 20-year satellite record presented at the 2016 Ocean Sciences Meeting.
| Month | What happens |
|---|---|
| May | The dome forms east of Sri Lanka |
| July–August | It strengthens |
| Late season | It drifts north and then west |
| September | It fades off north-east Sri Lanka |
A 2020 modelling study placed the dome region roughly between 5°N–10°N and 82°E–87°E. It found that chlorophyll there peaks from June to September. Chlorophyll rises when local winds push up a shallower thermocline and when the monsoon current carries nutrients in from the Arabian Sea. Water rich in plankton supports a busy food web, and olive ridleys travel long distances in search of food. So conservation has to cover these feeding waters, not just the nesting beaches.
Tamil Nadu’s tagging effort
One of the first Tamil Nadu turtles to be tagged, Kayal, was released from Besant Nagar beach in Chennai on 8 January 2026. She went south towards Marakkanam, then came back to Chennai and nested twice on Marina Beach, laying 272 eggs. In March 2026, the state said 51 hatcheries were looking after 1,788 nests that season.
Exam angle: how NDA, CDS and CAPF can ask this
- Questions on “arribada” and the Odisha nesting sites (Gahirmatha, Rushikulya, Devi) appear often in environment sections.
- Know the protection status: IUCN Vulnerable, Schedule I of the Wildlife (Protection) Act, 1972.
- Upwelling, monsoon currents and why some ocean zones are rich in plankton are core physical geography topics for the NDA and CDS.
Practice MCQs
Q1. The term “arribada” is associated with:
(a) Coral bleaching (b) Mass nesting of olive ridley turtles (c) Monsoon onset (d) Mangrove regeneration
Answer: (b) — Thousands of female olive ridleys nest together on the same beach.
Q2. The Sri Lanka Dome is best described as:
(a) A volcanic seamount (b) A seasonal upwelling zone in the south-west Bay of Bengal (c) A coral atoll (d) A salt dome in the Gulf of Mannar
Answer: (b) — It forms in the Southwest Monsoon Current from about May to September.
Q3. What is the IUCN Red List status of the olive ridley turtle?
(a) Critically Endangered (b) Endangered (c) Vulnerable (d) Least Concern
Answer: (c) — It is listed as Vulnerable, and in India it is in Schedule I of the Wildlife (Protection) Act.
Q4. Which of these olive ridley nesting locations is NOT in Odisha?
(a) Gahirmatha (b) Rushikulya (c) Devi river mouth (d) Besant Nagar
Answer: (d) — Besant Nagar is in Chennai, Tamil Nadu. This is where the tagged turtle Kayal was released in January 2026.
Frequently asked questions
Why are olive ridley turtles going to the Sri Lanka Dome?
The dome is an upwelling zone where nutrient-rich water supports plankton and the animals that feed on it. Tracking suggests it works as a feeding ground for turtles from India’s east coast.
When does the Sri Lanka Dome form?
It usually forms in May, strengthens in July and August, and fades by September, following the south-west monsoon.
How far did the tagged Odisha turtle travel?
The Wildlife Institute of India found that one female travelled 6,719 km in 271 days and reached waters east of Sri Lanka.
Where do olive ridleys nest in India?
The main mass-nesting sites are Gahirmatha, Rushikulya and the Devi river mouth in Odisha. Tamil Nadu beaches such as those in Chennai also see nesting.
Also read on NCA: Kariyachalli Island, Gulf of Mannar | Gangetic river dolphin | Monthly defence current affairs | Online NDA coaching
Sources: Mongabay-India, OdishaBytes (WII study), UNI, The Better India, Cullen and Shroyer, AGU Ocean Sciences 2016, Pramanik et al. 2020 (NASA MODIS), SeaLifeBase. Facts as reported up to 3 November 2026.
Featured image background (representative): Claudio Giovenzana / Wikimedia Commons, CC BY-SA 3.0.
