Hawksbill sea turtle
Hawksbill sea turtle | |
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Hawksbill sea turtle (Eretmochelys imbricata) | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Testudines |
Suborder: | Cryptodira |
Superfamily: | Chelonioidea |
Family: | Cheloniidae |
Subfamily: | Cheloniinae |
Genus: | Eretmochelys Fitzinger, 1843 |
Species: | E. imbricata
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Binomial name | |
Eretmochelys imbricata | |
Expert range map of the hawksbill sea turtle | |
Synonyms | |
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The hawksbill sea turtle (Eretmochelys imbricata) is a
The appearance of the hawksbill is similar to that of other marine turtles. In general, it has a flattened body shape, a protective
Taxonomy
Linnaeus described the hawksbill sea turtle as Testudo imbricata in 1766, in the 12th edition of his Systema Naturae.[4] In 1843, Austrian zoologist Leopold Fitzinger moved it into the genus Eretmochelys.[5] In 1857, the species was temporarily misdescribed as Eretmochelys imbricata squamata.[6]
Neither the IUCN[1] nor the United States Endangered Species Act assessment[7] 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
Description
Adult hawksbill sea turtles typically grow to 1 m (3 ft) in length, weighing around 80 kg (180 lb) on average. The heaviest hawksbill ever captured weighed 127 kg (280 lb).[8] The turtle's shell, or carapace, has an amber background patterned with an irregular combination of light and dark streaks, with predominantly black and mottled-brown colors radiating to the sides.[9]
Several characteristics of the hawksbill sea turtle distinguish it from other sea turtle species. Its elongated, tapered head ends in a beak-like mouth (from which its common name is derived), and its beak is more sharply pronounced and hooked than others. The hawksbill's forelimbs have two visible claws on each flipper.
An readily distinguished characteristic of the hawksbill is the pattern of thick
Crawling with an alternating
Due to its consumption of venomous cnidarians, hawksbill sea turtle flesh can become toxic.[14]
The hawksbill is
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Carapace's serrated margin and overlapping scutes are evident in this individual
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Close-up of the hawksbill's distinctive beak
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Fluorescent markings on Hawksbill sea turtle
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A Hawksbill turtle swims past a group of divers on the Great Barrier Reef, Australia
Distribution
Hawksbill sea turtles have a wide
Atlantic subpopulation
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.[17][18][19] They live off the Brazilian coast (specifically Bahia, Fernando de Noronha).
Along the East Coast of the United States, hawksbill sea turtle 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 County.[8] THE FLORIDA HAWKSBILL PROJECT, is a comprehensive research and conservation Program to study and protect the region’s hawksbill sea turtles and the habitats in which they live. Within the scope of this project, numerous studies have been undertaken to characterize the hawksbill aggregations found in southeast Florida waters, and educational programs have been developed to engage the local dive community in the protection of hawksbill sea turtles and coral reef habitats. This program is hosted by the National Save the Sea Turtle Foundation, located in Fort Lauderdale, Florida.Throughout their global range, hawksbill turtles are known to closely associate with coral reef habitats, mostly due to their preference for eating sponges and corals. Due to the large extent of Florida’s barrier reefs (approx. 350 linear miles), the Hawksbill Project focuses on representative sites in the northern, central, and southern sections of the Southeast Florida Reef Tract. The barrier reefs of northern Palm Beach County, the patch reefs of the northern Keys, and the finger reefs of Key West are the primary locations for their sampling efforts
In the
Indo-Pacific subpopulation
In the
The
Eastern Pacific subpopulation
In the eastern Pacific, hawksbills are known to occur from the
Habitat and feeding
Habitat
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.[10][37] 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.[38]
Feeding
While they are omnivorous,
Hawksbills are highly resilient and resistant to their prey. Some of the sponges they eat, such as
Life history
Less is known about the life history of hawksbills by comparison to several other sea turtle species.[1][42] Their life history may be divided into three phases, the: (i) early life history phase from approximately 4–30 cm straight carapace length,[43] (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.[44][45] 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.[43] One study from the central Pacific Ocean population used bomb radiocarbon (14C) dating and von Bertalanffy growth models to estimate hawksbills reach sexual maturity at ~ 72 cm and 29 years of age (range 23–36 years).[42] Hawksbills show a degree of fidelity after recruiting to the benthic phase[46] however, the movement to other similar habitats is possible.[47]
Breeding
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.[13] After mating, females drag their heavy bodies high onto the beach during the night. They clear an area of debris and dig a nesting hole using their rear flippers, then lay clutches of eggs and cover them with sand. Caribbean and Florida nests of E. imbricata typically contain around 140 eggs. After the hours-long process, the female returns to the sea.[10][18] Their nests can be found throughout beaches in about 60 countries.
Hatchlings, usually weighing less than 24 g (0.85 oz), hatch at night after around two months. These newly emergent
Maturity
Hawksbills evidently reach maturity after 20 years.[18] Their lifespan is unknown.[48] Like other sea turtles, hawksbills are solitary for most of their lives; they meet only to mate. They are highly migratory.[49] Because of their tough carapaces, adults' only predators are humans, sharks, estuarine crocodiles, octopuses, and some pelagic fish[49] species.
A series of biotic and abiotic cues, such as individual genetics, foraging quantity and quality,[50] 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.[51]
Age at maturity has been estimated to occur between 10[52] and 25 years of age[53] for Caribbean hawksbills. Turtles nesting in the Indo-Pacific region may reach maturity at a minimum of 30 to 35 years.[54]
Evolutionary history
Within the sea turtles, E. imbricata has several unique
Exploitation by humans
Throughout the world, hawksbill turtles have been hunted by humans, though it is illegal to capture, kill, and trade hawksbills in many countries today.[3][56] In some parts of the world, hawksbill turtles and their eggs continue to be exploited as food. As far back as the fifth century BCE, sea turtles, including the hawksbill, were eaten as delicacies in China.[57]
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.[58]
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.
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.[1] With the aid of substantial additional trade data, including official trade records from the imperial Japanese archives, the international trade of tortoiseshell was recently updated to have killed approximately 8.98 million hawksbills (range 4.64 to 9.83 million) from 1844-1992.[63] 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).[63]
Conservation
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
The species (along with the entire Cheloniidae family) has been listed in Appendix I of the
The
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.[74]
The
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.[76]
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External links
- hawksbill-turtle/eretmochelys-imbricata Hawksbill sea turtle media from ARKive
- US National Marine Fisheries Service hawksbill sea turtle page
- Seaturtle.org Home to sea turtle conservation efforts such as the Marine Turtle Research Group and publisher of the Marine Turtle Newsletter.
- Hawksbill turtle in Bocas Del Toro
- Australian Government Department of the Environment
- Photos of Hawksbill sea turtle on Sealife Collection