Hawksbill Sea Turtle

]] Linnaeus described the hawksbill sea turtle as Testudo imbricata in 1766, in the 12th edition of his Systema Naturae. In 1843, Austrian zoologist Leopold Fitzinger moved it into the genus Eretmochelys. In 1857, the species was temporarily misdescribed as Eretmochelys imbricata squamata. Neither the IUCN processes recognize any formal subspecies, but instead recognize one globally distributed species with populations, subpopulations, or regional management units. Fitzinger derived the genus name Eretmochelys from the Ancient Greek roots eretmo and chelys, corresponding to "oar" and "turtle", respectively, in reference to the turtles' oar-like front flippers. The species name imbricata is Latin, corresponding to the English term imbricate, in reference to the turtles' shingle-like, overlapping carapace scutes.

Hawksbill sea turtles have a wide range, found predominantly in tropical reefs of the Indian, Pacific, and Atlantic Oceans. Of all the sea turtle species, E. imbricata is the one most associated with warm, tropical waters. Two significant subpopulations are known, in the Atlantic and Indo-Pacific.

, Netherlands Antilles|alt=Photo of turtle swimming with extended flippers]] In the Atlantic, hawksbill populations range as far west as the Gulf of Mexico and as far southeast as the Cape of Good Hope in South Africa. They live off the Brazilian coast (specifically Bahia, Fernando de Noronha). Along the East Coast of the United States, hawksbill sea turtles range from Virginia to Florida. In Florida, according to the Florida Fish and Wildlife Conservation Commission, hawksbills are found primarily on reefs in the Florida Keys and along the southeastern Atlantic coast. Several major nesting sites are found in coastal Palm Beach, Broward, and Dade Counties. Guadeloupe, Tortuguero in Costa Rica, and the Yucatan. They feed in the waters off Cuba among other places.

, Mozambique]] In the Indian Ocean, hawksbills are a common sight along the east coast of Africa. One can find them in the seas surrounding Madagascar and Mozambique, and island groups such as Primeiras e Segundas, which include the turtle protection island of Ilha do Fogo. Hawksbills are also common along the southern Asian coast, including the Persian Gulf, the Red Sea, and the Indian subcontinental and Southeast Asian coasts. They are present across the Malay Archipelago and northern Australia. Their Pacific range is limited to the ocean's tropical and subtropical regions. In the west, it extends from the southwestern tips of the Korean Peninsula and the Japanese Archipelago south to northern New Zealand. The Philippines hosts several nesting sites, including the island of Boracay and Punta Dumalag in Davao City. Dahican Beach in Mati City, Davao Oriental, hosts one of the essential hatcheries of its kind, along with olive ridley sea turtles in the archipelagic country of the Philippines. A small group of islands in the southwest of the archipelago is named the "Turtle Islands" because two species of sea turtles nest there: the hawksbill and the green sea turtle. In January 2016, a juvenile was seen in Gulf of Thailand. A 2018 article by The Straits Times reported that around 120 hawksbill juvenile turtles recently hatched at Pulau Satumu, Singapore. Commonly found in Singapore waters, hawksbill turtles have returned to areas such East Coast Park and Palau Satumu to nest. In Hawaii, hawksbills mostly nest on the "main" islands of Oahu, Maui, Molokai, and Hawaii. In Australia, hawksbills are known to nest on Milman Island in the Great Barrier Reef. Hawksbill sea turtles nest as far west as Cousine Island in the Seychelles, where the species since 1994 is legally protected, and the population is showing some recovery. The Seychelles' inner islands and islets, such as Aldabra, are popular feeding grounds for immature hawksbills.

In the eastern Pacific, hawksbills are known to occur from the Baja Peninsula in Mexico, south along the coast to southern Peru. Important remnant nesting and foraging sites have since been discovered in Mexico, El Salvador, Nicaragua, and Ecuador, providing new research and conservation opportunities. In contrast to their traditional roles in other parts of the world, where hawksbills primarily inhabit coral reefs and rocky substrate areas, in the eastern Pacific, hawksbills tend to forage and nest principally in mangrove estuaries, such as those present in the Bahia de Jiquilisco (El Salvador), Gulf of Fonseca (Nicaragua, El Salvador, and Honduras), Estero Padre Ramos (Nicaragua), and the Gulf of Guayaquil (Ecuador). Multi-national initiatives, such as the [http://www.hawksbill.org/ Eastern Pacific Hawksbill Initiative] , are currently pushing efforts to research and conserve the population, which remains poorly understood.

===Habitat=== |alt=Photo of swimming turtle]] Adult hawksbill sea turtles are primarily found in tropical coral reefs. They are usually seen resting in caves and ledges in and around these reefs throughout the day. As a highly migratory species, they inhabit a wide range of habitats, from the open ocean to lagoons and even mangrove swamps in estuaries. Little is known about the habitat preferences of early life-stage E. imbricata; like other young sea turtles, they are assumed to be completely pelagic, remaining at sea until they mature. However, they have been known to seek habitats where they are able to camouflage or hide to minimize predator detection.

|alt=Photo of swimming turtle with extended head]] While they are omnivorous, sea sponges are their principal food; they constitute 70–95% of the turtles' diets. However, like many spongivores, they feed only on select species, ignoring many others. Caribbean populations feed primarily on the orders Astrophorida, Spirophorida, and Hadromerida in the class Demospongiae. Aside from sponges, hawksbills feed on algae, marine plants (seagrasses), woody plant remains, mangrove fruits and seeds, cnidarians (jellyfish, hydrozoans, hard corals, corallimorphs, zoanthids, and sea anemones), comb jellies, bryozoans, mollusks (squid, snails, nudibranchs, bivalves, and tusk shells), echinoderms (sea cucumbers and sea urchins), tunicates, fish and their eggs, crustaceans, and arthropods (crabs, lobsters, barnacles, copepods, and beetles). They also feed on the dangerous jellyfish-like hydrozoan, the Portuguese man o' war (Physalia physalis). Hawksbills close their unprotected eyes when they feed on these cnidarians. The man o' war's stinging cells cannot penetrate the turtles' armored heads. Hawksbills are highly resilient and resistant to their prey. Some of the sponges they eat, such as Aaptos aaptos, Chondrilla nucula, Tethya actinia, Spheciospongia vesparium, and Suberites domuncula, are highly (often lethally) toxic to other organisms. In addition, hawksbills choose sponge species with significant numbers of siliceous spicules, such as Ancorina, Geodia (G. gibberosa), Ecionemia, and Placospongia.

, Puerto Rico]] Less is known about the life history of hawksbills by comparison to several other sea turtle species. Their life history may be divided into three phases, the: (i) early life history phase from approximately 4–30 cm straight carapace length, (ii) benthic phase when the immature turtles recruit to foraging areas, and (iii) reproductive phase, when individuals reach sexual maturity and begin periodically migrating to breeding grounds. The early life history phase is not as geographically resolved as other sea turtle species. This phase appears to vary across ocean regions and may occur in both pelagic and nearshore waters, possibly lasting from 0–4 years of age. however, the movement to other similar habitats is possible.

Hawksbills mate biannually in secluded lagoons off their nesting beaches in remote islands throughout their range. The most significant nesting beaches are in Mexico, the Seychelles, Indonesia, Sri Lanka, and Australia. The mating season for Atlantic hawksbills usually spans April to November. Indian Ocean populations, such as the Seychelles hawksbill population, mate from September to February. After the hours-long process, the female returns to the sea. Their nests can be found throughout beaches in about 60 countries. Hatchlings, usually weighing less than , hatch at night after around two months. These newly emergent hatchlings are dark-colored, with heart-shaped carapaces measuring about long. They instinctively crawl into the sea, attracted by the moon's reflection on the water (disrupted by light sources such as street lamps and lights). While they emerge under the cover of darkness, hatchlings that do not reach the water by daybreak are preyed upon by shorebirds, shore crabs, and other predators.

, Pernambuco, Brazil]] Hawksbills evidently reach maturity after 20 years. Like other sea turtles, hawksbills are solitary for most of their lives; they meet only to mate. They are highly migratory. Because of their tough carapaces, adults' only predators are humans, tiger sharks, requiem sharks (Carcharhinus), estuarine crocodiles, common octopuses, and groupers (Epinephelus). A series of biotic and abiotic cues, such as individual genetics, foraging quantity and quality, or population density, may trigger the maturation of the reproductive organs and the production of gametes and thus determine sexual maturity. Like many reptiles, all marine turtles of the same aggregation are highly unlikely to reach sexual maturity at the same size and thus age. Age at maturity has been estimated to occur between 10 and 25 years of age for Caribbean hawksbills. Turtles nesting in the Indo-Pacific region may reach maturity at a minimum of 30 to 35 years.

Within the sea turtles, E. imbricata has several unique anatomical and ecological traits. It is the only primarily spongivorous reptile. Because of this, its evolutionary position is somewhat unclear. Molecular analyses support Eretmochelys placement within the taxonomic tribe Carettini, including the carnivorous loggerhead and ridley sea turtles, rather than in the tribe Chelonini, which includes the herbivorous green turtle. The hawksbill probably evolved from carnivorous ancestors.

Throughout the world, hawksbill turtles have been hunted by humans, though it is illegal to capture, kill, and trade hawksbills in many countries today. at Orly Airport customs 1995|left]] Beyond direct consumption for food, many cultures have also exploited hawksbill populations for their ornate carapace shells, known variously as tortoiseshell, turtle shell, and bekko. In China, the hawksbill is called dai mei or dai mao ("tortoise-shell turtle"), and was used to make and decorate a variety of small items, as it was in the West. In Japan, the turtles are harvested for their shell scutes, called bekko in Japanese. Bekko is used in various personal implements, such as eyeglass frames and the shamisen (Japanese traditional three-stringed instrument) picks. In Europe, hawksbill sea turtle shells were harvested by the ancient Greeks and ancient Romans for jewellery, such as combs, brushes, and rings. Recently, processed shells were regularly available in large amounts in countries including the Dominican Republic and Colombia. Global estimates of the historical exploitation of hawksbills have received recent attention. From 1950-1992, one pioneering study estimated that as many as 1.37 million adult hawksbills were killed in the international tortoiseshell trade alone. Most of the trade occurred in the Pacific Ocean basin, and the countries of origin and trade routes bore similarity to what is known of illegal, unreported and unregulated fishing (IUU fishing).

|alt=Photo of turtle swimming in shallow, green water]] Consensus has determined sea turtles, including E. imbricata to be at least threatened, because of their slow growth and maturity and low reproductive rates. Humans have killed many adult turtles, both accidentally and deliberately. Their existence is threatened due to pollution and loss of nesting areas because of coastal development. Biologists estimate that the hawksbill population has declined 80 percent in the past 100–135 years. In 1982, the IUCN Red List of Threatened Species first listed E. imbricata as endangered. This endangered status continued through several reassessments in 1986, 1988, 1990, and 1994 until it was upgraded in status to critically endangered in 1996. The species (along with the entire Cheloniidae family) has been listed in Appendix I of the Convention on International Trade in Endangered Species. This means commercial international trade (including in parts and derivatives) is prohibited and non-commercial international trade is regulated. Hawksbill turtles are listed in Annex II of the Protocol Concerning Specially Protected Areas and Wildlife to the Convention for the Protection and Development of the Marine Environment of the Wider Caribbean Region (SPAW), part of the Cartagena Convention. The United States Fish and Wildlife Service and National Marine Fisheries Service have classified hawksbills as endangered under the Endangered Species Act since 1970. for protecting E. imbricata. The Zoological Society of London has inscribed the reptile as an EDGE species, meaning that it is both endangered and highly genetically distinct, and therefore of particular concern for conservation efforts. The World Wildlife Fund Australia (WWF-Australia) has several ongoing projects aiming at protecting the reptile. On Rosemary Island, an island in the Dampier Archipelago off the Pilbara coast of Western Australia, volunteers have been monitoring hawksbill turtles since 1986. In November 2020, a 60-year old turtle first tagged in November 1990 and again in 2011 returned to the same location. ==References==