How OliveRidley Turtles Find Way Back To The Same Beach?
OliveRidley Turtles Return To The Same Beach For Egg Laying Where Once They Were Born
As far as the concept of mass egg laying of OliveRidley Turtles is concerned, the million dollar question in this regard is……
How do these gentle sea creatures navigate thousands of kilometres to find the beach where they were born?
Let’s first learn a little about the different species of sea turtles and their families: – Six species of sea turtles – Green, Hawksville, Lockheed, Olive Ridley (24-28 inches, 75-110 pounds), Kemp Ridley (smallest in size, about 2 feet) and the Flatback – belong to the Chelonida family. The remaining one sea turtle species is known as the Leather Back (the largest in size, about 6 feet) and it belong to a separate family – Dermatochelida.
Rare Happening of the last year
The eastern Indian state of Odisha is known all over the world as the home of the Lepidochelys olivacea(most abundantly seen Olive Ridley). Last year (March 2020), there was surprising and encouraging news for marine biologists and the state forest department as well that, about seven years later, these species of turtles were seen coming ashore for mass egg laying during the daytime . Because usually at night , they come ashore for that.
Most abundant but most vulnerable too
The Olive Ridley Turtle is considered to be the largest visible sea turtle in the world, with about 800,000 breeding turtles annually. Olive Ridley Turtles are usually seen in the tropics of the South Atlantic, the Pacific and the Indian Ocean. They have been listed as endangered species on the IUCN Red List and are covered by the 1972 Wildlife Protection Act in India.
The name of this sea turtle is associated with the color of its shell – an olive green color. Their vulnerability is because of the fact that they nest in very few places, and that is why any disturbance on any of their nesting site can have a major impact on the number of entire Olive Ridley turtles.
According to wildlife experts, a handful of Olive Ridley turtles are nesting on the islands of Maharashtra, Goa and the Andaman Islands in India, while Odisha is the only state in India to have a coastline (specifically in Gahirmatha and the river estuary of Rushikulya and Devi) on the Bay of Bengal where thousands in number of Olive Ridley Turtles come to build nests and lay eggs.
What makes them different?
Both mass spawning grounds (Gahirmatha and Rishikulia estuary) are located near the rich areas of Odisha in terms of varied biodiversity. The Gahirmatha area is adjacent to the Bhitarkanika National Park, while the Rushikulia estuary is located near Asia’s largest brackishwater lagoon, Chilika.
Every year from January to March, thousands of Olive Ridley turtles gather at Gahirmatha Beach in Odisha (declared as the only marine turtle sanctuary in Odisha in 1979) and at the mouth of the Rushikulya to lay eggs. In the moonlight, the turtles slowly move to the beach (one by one, avoiding the sand through their wings) until they find a suitable place to build a nest. The ‘group arrival by sea’ is called “Arribada” (derived from the Spanish language) and it occurs only on a few coast of the world, but not all Olive Ridley habitats have been documented till date.
Digging nest to lay eggs
Source: Hindustan times
The behavior of these turtles nesting and laying eggs during a particular time of the year and at a few particular beaches in the whole world, proves that they are unique and different from other sea turtles.
laying eggs in the self-made nest
source: Telegraph India
Hatching takes place in 45 to 60 days depending on the temp.of the sand and atmosphere
source: Deccan chronicle
hatchling heading for the sea
Two months after the eggs are laid, the babies see the light of the outside world. Each is a matchbox shaped one. After birth, they head straight for the sea, where they spend the rest of their lives swimming, eating, and traveling long distances. Research has shown that if the average temperature on an egg-laying beach exceeds the requirement, the risk of more female turtles being born increases. In the current context of global warming and climate change, there has been a significant change in the proportion of male and female turtles. The turtles reach sexual maturity after about thirteen years and return to their individual birth beach during their advanced stage of pregnancy, traveling for months (and hundreds of kilometers) in the process. Why they do this is a mystery, although some of the possible reasons for this have been revealed.
Possible Reasons behind Arribada
To understand this, let’s first consider how a compass works. All compasses have two basic elements: a dial with beautifully marked directions, and a magnetic needle that points north-south. The Earth also has a magnetic field and has north and south poles. The magnetic pin of your compass reacts to the magnetic field of the earth in the same way as when two magnets are placed together.
Scientists have long known that turtles, like many migratory animals, travel in the sea by sensing the invisible lines of the magnetic field, as sailors use latitude and longitude to determine the course of their sea voyage.
In contrast to humans, the Olive Ridley sea turtles have the innate ability to sense the Earth’s magnetic field, which is observed in almost every nomadic animal species( Migratory birds too change their direction when flying, sensing the magnetic field of the Earth). Everything else prevailing at the birthsite such as light, smell, temperature, and so on, get recorded in the brains of those tiny newly born olive ridley turtles just like by the cockpit voice recorders and blackboxes prior to plane crashes…
Then there is the possibility of another reason. The ocean water is constantly moving in a structure that has been stable for possibly a thousand years. In seawater, these currents travel at high speeds and are used by many migratory marine animals as a way of transportation. Just like birds (like eagles), use less force to keep flying in the same direction as of winds.
Some other researchers believe that turtles rely on their innate instincts and innate knowledge, and some believe that newly conceived turtles only follow older turtles to reach their breeding grounds. An investigation is underway and an unanimous and satisfactory explanation is expected to be settled soon. This is of great interest to marine biologists, especially at this present time when the concept of climate change and global warming have become the buzz words….
As responsible tourists, we too can contribute to the safety of Olive Ridley turtles.
Always look at turtles from a respectable and safe distance.
Organize all your travel related activities through an environmentally friendly tour operator
Do not use flash photography in the presence of turtles
Reduce the use of plastic materials as much as possible.
It is useful to take part in a beach cleaning activity, every time you visit the beach.
Let’s ensure that these gentle, innocent marine creatures never discard the coast of Odisha for the purpose of their mass nesting and egg-laying in future. Please do register your valuable comments in the comment box.
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Dr. Manoj Mishra