Turtles, the oldest living vertebrates, have graced Earth for a staggering 150 million years, pre-dating even the age of dinosaurs. Ranking as the heaviest reptiles globally, they share the common trait of breathing air, akin to all reptiles and humans. Noteworthy is their remarkable ability to hold their breath for extended durations and navigate impressive depths during dives.
Sea turtles, second only to sea snakes in their seamless adaptation to the aquatic environment, play a crucial role in the marine ecosystem. Their significance is woven into the intricate web of the ocean’s food chain, as they consume jellyfish, sponges, tunicates, algae, sea grasses, and crustaceans. While adult sea turtles face natural predators such as sharks, killer whales, and humans, the extensive laying of high-protein eggs on certain nesting beaches becomes a vital food source for various animals. During their vulnerable hatchling stage, sea turtles contend with predation from a diverse range of marine life, including sharks, groupers, cod, as well as avian predators like herons, egrets, frigate birds, and hawks.
Sea Turtles of India:
India possesses a shoreline spanning over 8000 kilometers, characterized by abundant biodiversity. In addition to supporting fishing areas, the coastal waters and beaches of India serve as essential foraging and nesting locations for various marine species, such as sea turtles. There are five recognized species of sea turtles that inhabit the coastal waters and islands of India, namely the Olive Ridley, Green, Hawksbill, Loggerhead, and Leatherback turtles. Apart from the Loggerhead, all four remaining species engage in nesting activities along the Indian coast.
Olive Ridley Sea Turtle (Lepidochelys olivacea)
IUCN Status: Vulnerable
Geographical Distribution: Occurring in the warmer regions of the Pacific and Indian oceans, this species is prevalent along the coastlines of India specifically during the nesting season.
Description: The typical size of adult Olive Ridley turtles is around 39 kg, featuring a carapace length of 0.76 m. Their carapace exhibits a simple olive-gray hue on the upper side, contrasting with a creamy or white color on the underside. Olive Ridleys undertake extensive migrations covering thousands of miles annually, moving between nesting and feeding areas. While adults primarily travel and rest in surface waters, they have been noted to dive and feed in waters as deep as 200 meters. Olive Ridley turtles spend their entire lifespan in the ocean, with only females venturing ashore for nesting.
Food: Olive Ridley turtles are facultative carnivores, demonstrating the ability to consume a single type of food for extended periods, with red lobsters being a notable example. The diet of adult Olive Ridleys encompasses a variety of items, including lobsters, crustaceans, fish, mollusks, fish eggs, algae, and jellyfish.
Reproduction: The age at maturity for the Olive ridley is, as in the majority of other sea turtles, uncertain. Courtship in this species is not often observed. Mating is performed near the nesting beaches or along the migratory routes and occurs principally at the sea surface. As in other species, the male holds the carapace of the female with the claws of his four flippers, and mating may last for few minutes to several hours.
Nesting: Typically occurring during summer and autumn, the nesting season for Olive Ridley turtles varies across locations. Like other species, Olive Ridleys exhibit nest site fidelity, often returning to the same spot on the beach for nesting, both within a nesting season and in subsequent years. This allows for the tracking of a turtle’s reproductive activity over several years.
Arribada: Olive Ridleys are one of the two species showcasing a remarkable nesting behavior called “arribada” (Spanish for arrival). During arribada, breeding turtles gather in the waters near the nesting beach, and, prompted by an as yet unknown cue (potentially related to the phases of the moon), they emerge en masse from the sea. This synchronized behavior leads them back to lay their eggs on the very beach where they were hatched. Arribada events can involve as many as 610,000 females nesting over several days.
Each nest typically contains around 100 eggs. The incubation period for hatchlings ranges from 45 to 65 days, depending on factors such as sand humidity and the number of eggs in a clutch. Upon hatching, the young turtles are approximately 1.5 inches long and nearly entirely black. Their dark coloration against the light-colored sand during their race to the water makes them vulnerable to predators. It is estimated that only 1 in 3000 eggs laid reaches maturity to nest again.
Leatherback Sea Turtle (Dermochelys coriacea)
IUCN Status: Vulnerable
Geographical Distribution: Leatherback turtles inhabit various regions globally, residing in both tropical and subtropical waters. Due to their extensive migratory patterns, they have been observed as far north as Nova Scotia and as far south as Chile. These turtles can be found in the tropical seas of the Atlantic, Pacific, and Indian Oceans.
Description: The average weight of an adult leatherback is 300 to 500 kg, accompanied by a length of 4-6 feet (130-183 cm). The largest recorded leatherback reached almost 10 feet (305 cm) from its beak to the tip of its tail and weighed an impressive 2,019 pounds (916 kg). What distinguishes the leatherback from other sea turtles is its lack of a traditional shell. Instead, it is protected by a leathery, scaleless skin composed of tough, oil-saturated tissues, forming seven prominent ridges, giving rise to its name. This unique sea turtle is capable of diving into colder and deeper waters compared to other sea turtles, owing to its remarkable ability to regulate body temperature. Additionally, the leatherback possesses a higher amount of body fat than its counterparts. Adult leatherbacks have been documented diving to depths of up to 1,500 meters.
Food: Leatherbacks are equipped with fragile, scissor-like jaws that are susceptible to damage if used on anything other than soft-bodied prey. Consequently, they primarily consume jellyfish, showcasing a remarkable adaptation. It’s noteworthy that this sizable and active species can sustain itself on a diet primarily consisting of jellyfish, particularly the lion’s mane jellyfish, which is predominantly composed of water and might seem like a less nutrient-rich food source.
Reproduction: Courtship behaviors are indeed observed in leatherback turtles. This process typically lasts for a few minutes, during which the male holds onto the female using its claws while copulation takes place.
Nesting: Leatherback turtles typically nest at intervals of 2 to 3 years, although recent research suggests they may nest every year. The nest is usually constructed just across the high tide mark. Within a nesting season, they may create nests between 4 to 7 times, with an average of 10 days between nesting. Each nest contains an average of 80 fertilized eggs, which are about the size of billiard balls, and 30 smaller, unfertilized eggs. The incubation period for these eggs is approximately 65 days. Unlike some other sea turtle species, leatherback females may alter nesting beaches, although they generally stay within the same region.
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Loggerhead Sea Turtle (Caretta caretta)
IUCN Status: Vulnerable
Geographical Distribution: The loggerhead sea turtle is found in coastal tropical and sub-tropical waters globally, with a wide distribution around the world. Some loggerheads are believed to embark on extensive migrations, utilizing warm ocean currents that take them far from their nesting and feeding areas. This species is prevalent in the Pacific and Indian Oceans, with notable abundance in the Andaman Islands and along the coasts of Sri Lanka. Loggerheads inhabit a variety of environments, including coastal bays, estuaries, lagoons, and open oceans, particularly in warm and temperate waters.
Description: The loggerhead sea turtle is characterized by a substantial head with robust jaws. Its bony carapace lacks ridges and features large, non-overlapping, rough scutes (scales), including five lateral scutes. The carapace is heart-shaped. The front flippers are short and thick, each with two claws, while the rear flippers can have two or three claws. The carapace exhibits a reddish-brown color, complemented by a yellowish-brown plastron. Hatchlings display a dark-brown carapace with pale brown margins on their flippers.
Food: Loggerhead sea turtles exhibit a primarily carnivorous diet, with a focus on shellfish found at the ocean floor. Their menu comprises horseshoe crabs, clams, mussels, and various other invertebrates. The powerful jaw muscles of loggerheads enable them to easily crush the shells of their prey, aiding in efficient consumption. As hatchlings, they source their food from the fauna inhabiting sea grass mats, commonly distributed along drift lines and eddies in their habitat.
Reproduction: The age at which loggerhead sea turtles reach maturity has not been definitively established. Courtship and mating activities typically occur not in proximity to or directly on nesting beaches but along migration routes between feeding and breeding grounds. This species has been observed engaging in underwater copulation. There is a possibility that through the storage of sperm from one or multiple males in the female’s reproductive tract, all clutches laid during a single season can be fertilized without the need for repeated mating. Mating typically takes place several weeks prior to the onset of the nesting season.
Nesting: The primary nesting grounds for loggerhead sea turtles in the Indian Ocean are prominent in South Africa. Nesting activities usually take place during spring and summer, with timing variations based on the latitude and geographical features of the coastline. Loggerhead sea turtles exhibit a nesting pattern occurring at intervals of 2 to 4 years. Within a single nesting season, they may create 3 to 6 nests, each spaced approximately 12 to 14 days apart. Each nest typically contains an average of 100 to 126 eggs, with an incubation period of around 60 days.
Green Turtle (Chelonia mydas)
IUCN Status: Endangered
Geographical Distribution: The green turtle is widely distributed in tropical and subtropical waters, commonly found near continental coasts and around islands, but it is rare in temperate waters. Alongside the hawksbill, the green turtle is considered one of the most tropical among marine turtles. This species spans across the Atlantic, Pacific, and Indian Oceans, primarily inhabiting tropical regions. In India, the green turtle typically resides in shallow waters less than 25 meters deep and favors areas protected by reefs, where it feeds on algae. Its distribution extends throughout the Indian and Pacific Oceans, and it is abundant in and around the Krusadai and the Andaman and Nicobar group of Islands in India.
Description: Green turtles can be easily identified from other sea turtles by the presence of a single pair of prefrontal scales (scales in front of their eyes), as opposed to two pairs found in other sea turtles. They have small and blunt head with a serrated jaw. The bony carapace lacks ridges and features large, non-overlapping scutes (scales), with only 4 lateral scutes. The body is nearly oval and more depressed (flattened) compared to Pacific green turtles. All flippers have only one visible claw.
The color of the carapace varies from pale to very dark green, displaying plain to brilliant yellow, brown, and green tones with radiating stripes. The plastron varies from white, dirty white, or yellowish in Atlantic populations to dark grey-bluish-green in Pacific populations. Hatchlings are dark-brown or nearly black with a white underside and white flipper margins.
Food: The diet of green turtles undergoes significant changes throughout their life. When they are less than 8 to 10 inches in length, they primarily consume worms, young crustaceans, aquatic insects, grasses, and algae. However, once they reach a size of 8 to 10 inches, their diet shifts predominantly to sea grass and algae. Notably, green turtles are unique among sea turtles as they are strictly herbivorous as adults. Their finely serrated jaws are adapted to tear through vegetation, facilitating their herbivorous feeding behavior.
Reproduction: The reproductive process of green turtles involves courtship, copulation, and nesting. Typically, several males engage in courtship with a single female near the shore. Copulation commences early in the breeding season and ceases when the nesting period begins. Females generally avoid mating after laying the first clutch of eggs. There is a hypothesis that fertilization of eggs laid in a nesting season may occur several years prior, and the final encounters between males and females likely serve to fertilize eggs for the subsequent season.
Recent studies conducted on turtles in captivity suggest that fertilization occurs early in the season, and excess sperm is potentially stored and utilized for the fertilization of later clutches. In some cases, there might even be enough sperm for clutches in the following season. Although there are no apparent variations in hatch rates among successive clutches within a season, fertility rates do vary, and a few clutches may be infertile.
Nesting: Green turtles follow a nesting pattern, typically laying eggs at intervals of about every 2 years, although there are notable year-to-year variations in the number of nesting females. These females exhibit a remarkable behavior of returning to the exact beach where they were hatched to lay their eggs. The interval between successive seasonal nesting migrations is influenced by factors such as population size, the quality of feeding grounds, and remoteness. During a nesting season, green turtles may create nests between 3 to 5 times, with an average of 115 eggs in each nest. The incubation period for these eggs is around 60 days.
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Hawksbill Sea Turtle (Eretmochelys imbricata)
IUCN Status: Critically Endangered
Description: The hawksbill sea turtle, a smaller species among sea turtles, is characterized by a slender head adorned with two pairs of prefrontal scales (scales in front of its eyes). Unlike certain other sea turtles, its jaw lacks serrations. The bony carapace lacks ridges and features large, overlapping scutes (scales), including four lateral scutes. The carapace is elliptical in shape, and the flippers possess two claws. The carapace displays hues of orange, brown, or yellow, while hatchlings are predominantly brown with pale blotches on the scutes. This species stands out as the most colorful among sea turtles, showcasing a wide range of variations from vibrant colors to heavy melanistic forms in the eastern Pacific. The carapacial coloration is generally dark greenish brown, while the plastral coloration is yellow. The head scales range from black to brown, with lighter margins, and the throat is yellow.
Food: The hawksbill sea turtle’s distinctive narrow head and beak-shaped jaws are well-adapted for obtaining food from crevices in coral reefs. Their diet is diverse and includes sponges, anemones, squid, and shrimp. While they are opportunistic feeders and consume a variety of marine life, hawksbills show a preference for invertebrates such as sponges, jellyfish, sea urchins, mollusks, and crustaceans. Notably, hawksbills are known to occasionally consume poisonous sponges. Interestingly, the toxins from these sponges do not harm the turtles, and they can store the poison in their flesh. As a result, the meat of hawksbill sea turtles can be poisonous, posing a risk to those who consume it.
Reproduction: Observations of courtship and mating in hawksbill sea turtles are limited, with reports indicating instances in shallow waters. Mating activities typically take place off the nesting beaches during the nesting period. During the mating process, the male holds the female using its claws and tail, and this interaction can last for several hours. Interestingly, it has been noted that females are more receptive after nesting, and they often receive attention from multiple males without showing a preference for any particular partner. As a result, polygamy is considered the normal mating pattern for hawksbill sea turtles.
Nesting: The hawksbill turtle has traditionally been viewed as a solitary nester, although it does not exhibit the formation of large arribazones, as seen in some other sea turtle species. However, there are a few nesting beaches where hawksbill females arrive in large groups. Similar to other turtles, the hawksbill displays nesting site fidelity, a behavior more commonly observed in older individuals. They nest at intervals of 2 to 4 years and create nests between 3 to 6 times per season. Each nest typically contains an average of 160 eggs, and the incubation period for these eggs is approximately 60 days.
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Threats to Sea Turtles in India
The marine turtles of India face a multitude of threats, creating a complex and challenging conservation landscape. Among the major concerns are unplanned beach development, which includes the construction of ports, extensive lighting, tourism infrastructure, and plantations. These activities disrupt nesting sites, alter critical habitats, and contribute to the loss of crucial nesting grounds.
By-catch mortality is another significant threat, particularly through incidental capture in trawl nets and gill nets used in fisheries. The weak enforcement of fisheries regulations exacerbates the problem, leading to unintentional harm to turtles during fishing operations. Additionally, the inadequate implementation of Protected Area regulations further exposes these species to anthropogenic risks.
Illegal activities, such as the killing of turtles for meat and the poaching of eggs, pose a direct threat to the survival of marine turtles in India. These practices, although limited in extent, contribute to the decline of turtle populations and hinder conservation efforts.
To address these multifaceted challenges, there is a pressing need for enhanced conservation measures, strengthened enforcement of regulations, and community involvement in promoting sustainable practices. By mitigating these threats, we can strive to ensure the continued existence of India’s marine turtles and protect their invaluable contribution to marine ecosystems.
Arribada or Mass Nesting of Sea Turtles in India
The coastal state of Odisha, situated on the eastern coast of India, plays host to one of the world’s most spectacular natural phenomena—the mass nesting, or arribada, of the Olive Ridley turtle. This awe-inspiring event occurs annually from October to April, turning the sandy shores into a bustling nesting ground for these marine turtles. Odisha boasts three of the world’s major mass nesting beaches for Olive Ridleys, making it a crucial conservation area for this species on a global scale.
The sheer magnitude of the nesting population in Odisha is remarkable, with estimates suggesting that more than half a million Olive Ridley turtles participate in this mass nesting spectacle. The significance of this coastal region extends beyond its national borders, as it stands as a cornerstone for the global conservation efforts aimed at protecting and preserving the vulnerable Olive Ridley turtle population.
As the world grapples with the challenges of marine conservation, the mass nesting beaches of Odisha stand as a testament to the delicate balance between human activities and the preservation of critical habitats for endangered species. Continued efforts in research, conservation initiatives, and community engagement are essential to ensure the sustained protection of Olive Ridley turtles in this vital coastal ecosystem.
In conclusion, the sea turtles of India stand as remarkable marine species, contributing to the rich biodiversity along the country’s extensive coastline. This article has highlighted the diverse sea turtle species found in Indian waters, including the Olive Ridley, Green, Loggerhead, Leatherback, and Hawksbill turtles. From their unique nesting behaviors, migratory patterns, to distinctive physical characteristics, each species adds to the fascinating tapestry of marine life.
The nesting grounds in India, play a crucial role in the conservation efforts for these endangered species. Understanding their reproductive habits, feeding behaviors, and the challenges they face in the changing marine environment is paramount for the conservation and protection of these iconic creatures.
While efforts to safeguard sea turtles in India have made significant strides, challenges persist, including habitat degradation, accidental capture in fishing gear, and pollution. Continued research, conservation initiatives, and community engagement are vital components of the ongoing commitment to ensuring the survival of sea turtles in Indian waters.
As we strive to strike a balance between human activities and the preservation of biodiversity, the plight and resilience of India’s sea turtles serve as a poignant reminder of the interconnectedness of marine ecosystems and the urgent need for collective conservation efforts to secure a sustainable future for these captivating marine species.
Sea Turtles Size Comparison Chart
Source: Smithsonian National Museum of Natural History