Olive Ridleys: When One in a Thousand Survives

Photo Story Published : Sep 07, 2022 Updated : Sep 30, 2023

The life of an olive ridley sea turtle is fraught with peril. Even before they hatch, they face predators. Once hatchlings emerge, they continue to encounter a never-ending series of human-created dangers and natural obstacles

The night is silent, except for the sound of waves breaking softly against the shore. Though it is a full moon night, a veil of thick dark clouds shrouds the bright light, making it almost impossible to see a dome-shaped creature slowly making its way up the beach. The animal is a female olive ridley turtle who has travelled thousands of kilometres to reach this beach, the very same one where she was born. Her only goal when she was a baby was to head for the open blue sea. Today, she’s here on a different mission. With no time to waste, she makes her way to the soft sand and gets to work. Using her hind flippers, she digs a hole about 45 cm deep and gently drops round, golf-ball-sized eggs into the depression. After hours of toiling and laying between 50-200 eggs, she takes one last look at her nest and covers it with sand. Dragging her exhausted body back to sea, she disappears, hoping that at least some of her hatchlings will survive to adulthood.

Of the seven species of sea turtles found worldwide, the olive ridley turtle (Lepidochelys olivacea) is one of two living species in the genus Lepidochelys; the other is the critically endangered Kemp’s ridley turtle. These two species are the world’s smallest sea turtles. Though they look quite similar, olive ridleys are found only in warmer waters.

Once listed as “Endangered” on the IUCN Red List, olive ridleys are now considered “Vulnerable”, indicating that wild populations still face significant risks. Despite being listed in Appendix 1 of CITES (highest level of protection) and protected under the Migratory Species Convention, these turtles continue to face many natural and human-made threats.

The most abundant sea turtle species, olive ridleys get their name from the olive colour of their heart-shaped shell. Weighing up to 45 kg and growing about 1-1.2m long, their life expectancy is believed to be around 50-60 years. They are estimated to attain sexual maturity around 15 years of age. Females are known to mate with many males and can store sperm for several months. Ergo, when females lay eggs, they will have been fertilised by different males, which helps increase the population’s genetic diversity.

In reptiles, temperature-dependent sex determination is a well-known phenomenon where it’s not chromosomes that determine the sex of the offspring but external environmental factors like temperature after fertilisation. In olive ridleys, eggs incubated at lower temperatures (28 degrees C or lower) are known to produce males, higher temperatures (30 degrees C or higher) produce females, and moderate temperatures (28-30 degrees C), produce a mixed-sex clutch. Incubation lasts about two months, after which the hatchlings emerge and find their way to sea.

Olive ridley turtles exhibit two kinds of nesting behaviours — solitary nesting and mass nesting (also called arribadas). Arribada, which means arrival in Spanish, is a one-of-a-kind mass nesting event during which thousands of female olive ridleys come ashore on the same beach to lay eggs. Like other species of sea turtles, olive ridleys show natal homing, i.e., females return to lay eggs on the same beach where they were born. To achieve this feat, females may travel thousands of kilometres. Scientists believe that mass nesting is a strategy to increase the survival rate of hatchlings as there is safety in numbers. However, the exact reason these nesting events occur is a mystery.

Once the female encloses her nest and leaves, the potential hatchlings are on their own. Unlike young crocodiles that are tenderly taken out of the nest by their mother, the olive ridleys have to do it by themselves. To facilitate breaking open their eggshells, hatchlings are born with a sharp tooth-like extension called a caruncle on their upper jaw, which falls off soon after birth. After digging out of the nest cavity, young turtles orient themselves towards the brightest horizon and make their way for the sea. When they hatch, they are tiny, weighing less than 30 g and measuring about 3.8 cm in length.

As olive ridley turtles do not provide parental care, eggs and hatchlings are always at risk of predation. At times, monitor lizards or dogs dig up turtle nests and feast on most of the eggs, leaving the rest exposed to predators like Brahminy kites (1) or crows (2). Even after hatching, the time taken to reach the sea from the nest is critical for the little hatchlings as they could either die of dehydration or fall prey to other predators like black-headed seagulls (3).

Unfortunately, the hatchlings are not safe once they reach the ocean either. While we do not know much about the olive ridley’s juvenile life, it is believed that they swim several miles offshore, where currents carry them across the oceans for years. During this period, they grow in size and eventually end up in adult feeding grounds. However, their lives at sea are also fraught with danger. Fish bigger than turtles, crustaceans, seabirds etc., like to feed on baby turtles. Added to this are the deaths caused by plastic waste, ghost nets, and human activities. The challenges these young turtles face are so many that it is estimated that only 1 in 1,000 hatchlings survive to adulthood.

Even if a young turtle beats all the odds and survives till adulthood, the obstacles never seem to reduce. Poaching of adult turtles for their shell, meat, and leather, the accidental killing of adult turtles through entanglement in trawl and gill nets (1), and loss of nesting sites due to coastal development projects are some of the main threats to this species.

Global warming and climate change are also threatening this species. As ocean temperatures increase due to global warming, the sex ratio of the hatchlings is affected as warmer temperatures produce only females. If temperatures keep soaring, the conditions will not be favourable to produce male turtles. Recently, increased incidences of cyclones have become a new threat to olive ridleys. For instance, the Gahirmatha Marine Sanctuary in Odisha is the largest known mass nesting rookery for olive ridley sea turtles in the world, but it is an area that is highly susceptible to cyclones.

Despite all these obstacles, all is not lost. Several organisations and NGOs unite with local communities throughout India and across the world to help protect and conserve these marine animals. During the nesting period, involved parties patrol beaches, extract and relocate eggs to secure locations, and then release young hatchlings into the sea. All this gives little turtles a shot at survival, hopefully improving population numbers.

While most of us cannot directly help turtles or hatchlings, we can do a few things for them. Stop littering beaches and try to participate in a beach clean-up. A case in point is that 80 olive ridley turtles hatched on Mumbai’s Versova beach in 2018 after compassionate citizens cleaned the filthy stretch for two years straight! If you get to watch turtles nesting or hatching, respect them and give them their space. With a bit of help and understanding from us, more olive ridleys will surely swim in our waters.

About the contributors

Saloni Sawant

Saloni is a naturalist and an aspiring science communicator who is often spotted lazing on trees and trying to befriend stray cats.

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Dhritiman Mukherjee

is one of India's most prolific wildlife and conservation photographers. His work has been featured in leading publications. He is also a RoundGlass Ambassador, and an RBS Earth Hero awardee.

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About the contributors

Saloni Sawant

Dhritiman Mukherjee

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