Hawksbill Turtle

The hawksbill sea turtle (Eretmochelys imbricata) is a critically endangered species belonging to the family Cheloniidae. It is the only extant species in the genus Eretmochelys. The hawksbill sea turtle is primarily found in tropical and subtropical marine and estuary ecosystems.

In terms of appearance, the hawksbill sea turtle shares similarities with other marine turtles. It has a flattened body shape, a protective carapace, and flipper-like limbs that are adapted for swimming in the open ocean. What distinguishes the hawksbill sea turtle from other species is its sharp, curving beak with a prominent tomium and the saw-like appearance of its shell margins. The color of the hawksbill shell slightly changes depending on water temperature. While this turtle does spend some time in the open ocean, it primarily inhabits shallow lagoons and coral reefs. Unfortunately, due to human fishing practices, the hawksbill sea turtle is classified as critically endangered by the World Conservation Union. In the past, hawksbill shells were sought after for their tortoiseshell material, which was used for decorative purposes. To regulate the international trade of hawksbill sea turtles and their products, the Convention on International Trade in Endangered Species (CITES) has implemented regulations.

Adult hawksbill sea turtles typically reach a length of 1 meter (3 feet) and weigh an average of 80 kilograms (180 pounds). The heaviest hawksbill ever captured weighed 127 kilograms (280 pounds). The shell of the hawksbill sea turtle has an amber background with a pattern of light and dark streaks, predominantly black and mottled-brown colors radiating to the sides. The hawksbill sea turtle possesses certain characteristics that distinguish it from other sea turtle species, such as its elongated, tapered head that ends in a beak-like mouth, which gives it its common name. Its beak is more sharply pronounced and hooked compared to other species. The hawksbill sea turtle's forelimbs have two visible claws on each flipper.

A distinguishing characteristic of the hawksbill sea turtle is its carapace, which is made up of thick scutes. While it has five central scutes and four pairs of lateral scutes like other members of its family, the posterior scutes of E. imbricata overlap in a way that gives the rear margin of its carapace a serrated look, resembling a saw or a steak knife. With a carapace that can reach almost 1 meter (3 feet) in length, the hawksbill sea turtle frequently uses its sturdy shell to access tight spaces in reefs. When crawling, hawksbill sea turtles leave asymmetrical tracks in the sand. In contrast, green sea turtles and leatherback turtles have a more symmetrical gait. It's worth noting that the flesh of hawksbill sea turtles can become toxic due to their consumption of venomous cnidarians. Furthermore, the hawksbill sea turtle exhibits biofluorescence, making it the first reptile recorded with this characteristic. While it is unclear whether this effect is due to the turtle's diet, which includes biofluorescent organisms like the hard coral Physogyra lichtensteini, it is speculated that there may be a behavioral purpose behind the differences in pigmentation between the males and females.

Hawksbill sea turtles have a wide range and are mostly found in tropical reefs of the 🇮🇳 Indian, Pacific, and Atlantic Oceans. Among all sea turtle species, Eretmochelys imbricata is most associated with warm tropical waters. They are known to have significant subpopulations in the Atlantic and Indo-Pacific.

Adult hawksbill sea turtles primarily inhabit tropical coral reefs. They can often be found resting in caves and ledges within these reefs throughout the day. As highly migratory creatures, they occupy a variety of habitats, ranging from the open ocean to lagoons and even estuaries' mangrove swamps. The habitat preferences of early life-stage E. imbricata are not well understood, although it is assumed that, like other young sea turtles, they remain at sea until they reach maturity.

While hawksbill sea turtles are omnivorous, sea sponges make up the majority (70-95%) of their diet. However, they selectively feed on certain species of sponges, ignoring many others. In addition to sponges, hawksbills consume algae, marine plants, cnidarians, comb jellies, jellyfish, sea anemones, molluscs, fish, and crustaceans. They have even been observed eating the venomous hydrozoan known as the Portuguese man o' war (Physalia physalis). To protect themselves from the sting of these cnidarians, hawksbills close their unprotected eyes while feeding. Hawksbills show remarkable resilience to their prey, as some of the sponges they consume, such as Aaptos aaptos, Chondrilla nucula, Tethya actinia, Spheciospongia vesparium, and Suberites domuncula, are highly toxic to other organisms. Additionally, hawksbills prefer sponge species with significant amounts of siliceous spicules, such as Ancorina, Geodia (Geodia gibberosa), Ecionemia, and Placospongia.

Compared to several other sea turtle species, less is known about the life history of hawksbills. Their life history can be divided into three phases: the early life history phase (approximately 4-30 cm straight carapace length), the benthic phase (when immature turtles recruit to foraging areas), and the reproductive phase (when individuals reach sexual maturity and periodically migrate to breeding grounds). The early life history phase is not as well-defined as in other sea turtle species and appears to vary across ocean regions. It may occur in both pelagic and nearshore waters and can last from birth until approximately 4 years of age.

Hawksbills mate every two years in secluded lagoons near their nesting beaches, typically found on remote islands throughout their range. The most significant nesting beaches can be found in 🇲🇽 Mexico, the 🇸🇨 Seychelles, 🇮🇩 Indonesia, 🇱🇰 Sri Lanka, and 🇦🇺 Australia. The mating season for Atlantic hawksbills usually spans from April to November, while 🌊 Indian Ocean populations, like the 🇸🇨 Seychelles hawksbill population, mate from September to February. After mating, females drag their heavy bodies onto the beach during the night. They clear the area of debris, dig a nesting hole using their rear flippers, lay clutches of eggs, and cover them with sand. On average, Caribbean and Florida nests of Eretmochelys imbricata contain around 140 eggs. Once this laborious process is complete, the female returns to the sea. Hawksbill sea turtle nests can be found on beaches in approximately 60 countries.

Hatchlings, usually weighing less than 24 grams (0.85 ounces), emerge from the nests at night after approximately two months. They have a dark-colored appearance, with heart-shaped carapaces measuring around 2.5 cm (0.98 in) in length. Guided by the moon's reflection on the water (but often disoriented by artificial lighting), the hatchlings instinctively crawl towards the sea. However, those that do not reach the water by daybreak become easy prey for shorebirds, shore crabs, and other predators.

Hawksbill sea turtles reach maturity after an estimated 20 years, although their lifespan is still unknown. Like other sea turtles, they are solitary for most of their lives and only come together to mate. They are highly migratory creatures. Due to their tough carapaces, their only natural predators as adults are humans, sharks, estuarine crocodiles, octopuses, and certain pelagic fish species.