Hawksbill turtles often times feed on sponges, causing succession to occur in the reef and freeing up space for settlement of other organisms.
Ecosystem Impact: creates habitat
For years, humans have hunted the hawksbill turtles in order to sell their scutes. Also, humans eat the turtles as well as their eggs.
Positive Impacts: food ; body parts are source of valuable material
There are no known adverse affects of Eretmochelys imbricata imbricata on humans.
Hawksbill turtles hatch out of eggs. As a hawksbill turtle matures, its carapace shifts from heart-shaped to more elongate. Sex determination is thought to be temperature-dependent as is the case with other sea turtles and reptiles, however not enough data is available to be sure this is true.
Development - Life Cycle: temperature sex determination
It is very difficult to classify how endangered hawksbill turtles are because they are found throughout the world and are migratory. In some places, they may be very scarce, and in others they may thrive. Also, since there is little knowledge of their early population levels, it is very hard to know how much the populations have declined.
Currently (throughout the world), it is illegal to trade hawksbill turtle products. This should create the expansion of the turtles because their major predator, humans, will no longer be able to hunt them. In order to succeed in keeping hawksbill turtles in existence, there must be cooperation among all nations that have hawksbill populations in their waters. Free exchange of information on the turtles is needed to ensure that all nations are aware of the best and most efficient ways of keeping hawksbill turtles in existence.
US Federal List: endangered
CITES: appendix i
IUCN Red List of Threatened Species: critically endangered
The mechanisms that aid hawksbill turtles in returning to their nesting beaches are still unknown. It has been thought that these turtles are guided inland by magnetic fields and lunar phases/position.
This species communicates by the use of ritual mating behaviors.
Communication Channels: visual ; tactile
Perception Channels: visual ; tactile ; acoustic ; chemical ; magnetic
Hawksbill turtles feed primarily on sponges. They show a large level of feeding selectivity in the way that they only eat certain species of sponges, some of which are toxic to other animals. Sea jellies and other coelenterates are also common prey items. These turtles are omnivorous and also eat mollusks, fish, marine algae, crustaceans, and other sea plants and animals. A preferred feeding ground of the turtles is in shallow shoals abundant with brown algae.
Animal Foods: fish; mollusks; aquatic or marine worms; aquatic crustaceans; echinoderms; cnidarians; other marine invertebrates
Plant Foods: leaves; wood, bark, or stems; fruit; algae; macroalgae
Primary Diet: omnivore
Eretmochelys imbricata imbricata are found mainly in the tropical regions of the Atlantic and Pacific oceans. However, in the western hemisphere, they have been reported to have nests as far north as Woods Hole, Massachusetts. They are also present in the Long Island Sound. However, between the Carolinas and New Jersey, very few hawksbill turtles have been recorded.
Biogeographic Regions: australian ; oceanic islands ; indian ocean; atlantic ocean ; pacific ocean ; mediterranean sea
Hawksbill turtles are most commonly found in hard-bottomed and reef habitats containing sponges. They also reside in shoals, lagoons of oceanic islands, and continental shelves. In general, they are found in water no deeper than sixty feet (18.3 m). When hawksbill turtles are young, the are unable to dive into deep water, and therefore are forced to live in masses of floating sea plants, such as sargassum.
Range depth: 20 to 0 m.
Average depth: Near Surface m.
Habitat Regions: saltwater or marine
Aquatic Biomes: reef
The normal lifespan of hawksbill turtles is thought to be about 30 to 50 years, however biologists are not sure exactly how long they live.
Range lifespan
Status: captivity: 20+ (high) years.
Young hawksbill turtles have a heart-shaped carapace. As these turtles mature, their carapaces becomes more elongated. In all of the hawksbill turtles, with the exception of very old individuals, the lateral and posterior areas of the carapace are serrated. The heads of hawksbill turtles taper into a V shape, giving them the appearance of birds' beaks.
Eretmochelys imbricata imbricata have 5 features that distinguish them from other sea turtles. Their heads have two pairs of prefrontal scales. They also have two claws on each of their forelimbs. There are thick, overlapping scutes on their carapaces, which also have four pairs of costal scutes. Their elongate mouths resemble a beak, that taper off to a sharp point at the end.
Hawksbill turtles are relatively small sea turtles. Nesting females average a length of 87 centimeters in curved carapace length and weigh 80 kilograms. The average hatchling Eretmochelys imbricata imbricata in the parts of the Caribbean owned by the United States is about 42 millimeters in straight carapace length and weighs 13.5 to 19.5 grams. Male turtles are distinguished by a brighter pigmentation, a concave plastron, long claws, and a thicker tail.
Range mass: 35.7 to 127 kg.
Average mass: 80 kg.
Range length: 62.5 to 114 cm.
Average length: 87 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: male more colorful; sexes shaped differently
Hawksbill turtles, like all turtles, have a hard shell that discourages predators from trying to eat them. Adult turtles are still consumed by humans, sharks, crocodiles, large fish, and octopi. Nests are commonly robbed by terrestrial predators such as dogs, raccoons, rats, and humans.
Directly after hatching, hawksbill turtles face the most dangerous time of their lives: the journey to water. Although this scramble only lasts a few minutes, countless hatchlings are preyed on by flocks of gulls and large crabs.
Known Predators:
Mating occurs roughly every 2 to 3 years. It occurs mainly in shallow waters. No information is available as to whether or not these turtles have life-long partners or are promiscuous.
Copulation usually begins in shallow water near the shore. Males lie and wait in the shallow water for the females to return. At times, males have been seen following the females on shore. However, this behavior is rarely observed.
The entire nesting process takes roughly one to three hours. It involves similar steps as most other species of sea turtles. The turtles come out of the sea and select a site in which to lay their eggs. They then clear the area and dig a pit in the sand. Next they lay their eggs and then proceed to fill in the pit in with their hind limbs. After the site is disguised, the turtles return to the sea.
Breeding interval: The females lay three clutches a year at an interval of roughly thirteen to fifteen days.
Breeding season: Nesting generally occurs between July and October.
Average number of offspring: 140.
Average gestation period: 60 days.
Average age at sexual or reproductive maturity (female): 3 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Average age at sexual or reproductive maturity (male)
Sex: male: 1277 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 1277 days.
After laying the eggs on the beach, the females retreat into the water. After about 60 days, the eggs hatch, and the newborn turtles make a perilous dash for the water where they will mature.
Parental Investment: no parental involvement
Carnivorous, feeding largely on sessile marine invertebrates, such as sponges and soft corals.
Critically Endangered
A moderately sized marine turtle; largest Egyptian specimen has a carapace length of 835 mm. Carapace depressed, elongate, smooth; scutes imbricate in younger animals, increasingly less so in older specimens; posterior edge strongly serrate; 4 cosatal scutes; first marginal scute in contact with first vertebral scute. Head rather small, narrow, with two pairs of prefrontals. Snout is beak-like, elongate. There area 2 claws on each limb. Males smaller, with longer tails and larger claws. Color of carapace yellowish brown, with dark brown and black radiating streaks; dorsal sides of limbs and head brown, scales edged yellowish. All ventral sides yellowish white.
The Red Sea, where it is the commonest marine turtle; not recorded yet from the Egyptian Mediterranean, although Werner (1988) lists the species from Israeli Mediterranean waters. It has been recorded throughout the Red Sea and in both the Gulfs of Aqaba and Suez. Breeding has been recorded throughout the Hurghada Archipelago, Ras Mohamed, Wadi El Gemal Island, Qulan Islands, Ras Banas, and Zabargad Island.
A pan-tropical species, recorded erratically in the Mediterranean, but not known to breed there.
Warm tropical and subtropical marine waters, usually near coral reefs and rocky outcrops in shallow waters.
Fairly common, but declining. The increase in tourist activities and artisanal fishing in the Red Sea is leading to growing disturbance to the nesting sites of these animals on offshore islands. Development on the mainland is reducing available nesting sites. In the past stuffed animals were commonly offered to tourists, but this has subsided to a large extent.
The Niger Coastal Delta is an enormous classic distributary system located in West Africa, which stretches more than 300 kilometres wide and serves to capture most of the heavy silt load carried by the Niger River. The peak discharge at the mouth is around 21,800 cubic metres per second in mid-October. The Niger Delta coastal region is arguably the wettest place in Africa with an annual rainfall of over 4000 millimetres. Vertebrate species richness is relatively high in the Niger Delta, although vertebrate endemism is quite low. The Niger Delta swamp forests occupy the entire upper coastal delta. Historically the most important timber species of the inner delta was the Abura (Fleroya ledermannii), a Vulnerable swamp-loving West African tree, which has been reduced below populations viable for timber harvesting in the Niger Delta due to recent over-harvesting of this species as well as general habitat destruction of the delta due to the expanding human population here. Other plants prominent in the inner delta flood forest are: the Azobe tree (Lophira alata), the Okhuen tree (Ricinodendron heudelotii ), the Bitter Bark Tree (Sacoglottis gabonensis), the Rough-barked Flat-top Tree (Albizia adianthifolia), and Pycnanthus angolensis. Also present in its native range is the African Oil Palm (Elaeis guineensis)
Five threatened marine turtle species are found in the mangroves of the lower coastal delta: Leatherback Sea Turtle (Dermochelys coricea, EN), Loggerhead Sea Turtle (Caretta caretta, EN), Olive Ridley Turtle (Lepidochelys olivacea, EN), Hawksbill Sea Turtle (Eretmochelys imbricata, CR), and Green Turtle (Chelonia mydas, EN).
There are a number of notable mammals present in the upper (or inner) coastal delta in addition to the Critically Endangered Niger Delta Red Colubus (Procolobus pennantii ssp. epieni), which primate is endemic to the Niger Delta. The near-endemic White-cheeked Guenon (Cercopithecus erythrogaster, VU) is found in the inner delta. The Endangered Chimpanzee (Pan troglodytes) is also found in the inner delta. The limited range Black Duiker (Cephalophus niger) is fournd in the inner delta and is a near-endemic to the Niger River Basin. The restricted distribution Mona Monkey (Cercopithecus mona), a primate often associated with rivers, is found here in the Niger Delta. The Near Threatened Olive Colobus (Procolobus verus) is restricted to coastal forests of West Africa and is found here in the upper delta.
Some of the reptiles found in the upper Coastal Niger Delta are the African Banded Snake (Chamaelycus fasciatus); the West African Dwarf Crocodile (Osteolaemus tetraspis, VU); the African Slender-snouted Crocodile (Mecistops cataphractus); the Benin Agama (Agama gracilimembris); the Owen's Chameleon (Chamaeleo oweni); the limited range Marsh Snake (Natriciteres fuliginoides); the rather widely distributed Black-line Green Snake (Hapsidophrys lineatus); Cross's Beaked Snake (Rhinotyphlops crossii), an endemic to the Niger Basin as a whole; Morquard's File Snake (Mehelya guirali); the Dull Purple-glossed Snake (Amblyodipsas unicolor); the Rhinoceros Viper (Bitis nasicornis). In addition several of the reptiles found in the outer delta are found within this inner delta area.
Other reptiles found in the outer (southernmost) NIger Coastal Delta are the Nile Crocodile (Crocodylus niloticus), African Softshell Turtle (Trionyx triunguis), African Rock Python (Python sebae), Boomslang Snake (Dispholidus typus), Cabinda Lidless Skink (Panaspis cabindae), Neon Blue Tailed Tree Lizard (Holaspis guentheri), Fischer's Dwarf Gecko (Lygodactylus fischeri), Richardson's Leaf-Toed Gecko (Hemidactylus richardsonii), Spotted Night Adder (Causus maculatus), Tholloni's African Water Snake (Grayia tholloni), Smith's African Water Snake (Grayia smythii), Small-eyed File Snake (Mehelya stenophthalmus), Western Forest File Snake (Mehelya poensis), Western Crowned Snake (Meizodon coronatus), Western Green Snake (Philothamnus irregularis), Variable Green Snake (Philothamnus heterodermus), Slender Burrowing Asp (Atractaspis aterrima), Forest Cobra (Naja melanoleuca), Rough-scaled Bush Viper (Atheris squamigera), and Nile Monitor (Varanus niloticus).
There are a limited number of amphibians in the inner coastal delta including the Marble-legged Frog (Hylarana galamensis). At the extreme eastern edge of the upper delta is a part of the lower Niger and Cross River watersheds that drains the Cross-Sanaka Bioko coastal forests, where the near endemic anuran Cameroon Slippery Frog (Conraua robusta) occurs.
The hawksbill sea turtle (Eretmochelys imbricata) is a critically endangered sea turtle belonging to the family Cheloniidae. It is the only extant species in the genus Eretmochelys. The species has a global distribution that is largely limited to tropical and subtropical marine and estuary ecosystems.
The appearance of the hawksbill is similar to that of other marine turtles. In general, it has a flattened body shape, a protective carapace, and flipper-like limbs, adapted for swimming in the open ocean. E. imbricata is easily distinguished from other sea turtles by its sharp, curving beak with prominent tomium, and the saw-like appearance of its shell margins. Hawksbill shells slightly change colors, depending on water temperature. While this turtle lives part of its life in the open ocean, it spends more time in shallow lagoons and coral reefs. The World Conservation Union, primarily as a result of human fishing practices, classifies E. imbricata as critically endangered.[1] Hawksbill shells were the primary source of tortoiseshell material used for decorative purposes. The Convention on International Trade in Endangered Species (CITES) regulates the international trade of hawksbill sea turtles and products derived from them.[3]
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 Ancient Greek roots eretmo and chelys, corresponding to "oar" and "turtle", respectively, in reference to the turtles' oar-like front flippers. The species name imbricate is Latin, corresponding to the English term imbricate, in reference to the turtles' shingle-like, overlapping carapace scutes.
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 scutes that make up its carapace. While its carapace has five central scutes and four pairs of lateral scutes like several members of its family, E. imbricata's posterior scutes overlap in such a way as to give the rear margin of its carapace a serrated look, similar to the edge of a saw or a steak knife. The turtle's carapace can reach almost 1 m (3 ft) in length.[10] The hawksbill appears to frequently employ its sturdy shell to insert its body into tight spaces in reefs.[11]
Crawling with an alternating gait, hawksbill tracks left in the sand are asymmetrical. In contrast, the green sea turtle and the leatherback turtle have a more symmetrical gait.[12][13]
Due to its consumption of venomous cnidarians, hawksbill sea turtle flesh can become toxic.[14]
The hawksbill is biofluorescent and is the first reptile recorded with this characteristic. It is unknown if the effect is due to the turtle's diet, which includes biofluorescent organisms like the hard coral Physogyra lichtensteini. Males have more intense pigmentation than females, and a behavioral role of these differences is speculated.[15][16]Hawksbill turtles are an endangered species under the protection of the US National Endangered Species Preservation act.
Carapace's serrated margin and overlapping scutes are evident in this individual
A Hawksbill turtle swims past a group of divers on the Great Barrier Reef, Australia
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.[17]
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 Caribbean, the main nesting beaches are in the Lesser Antilles, Barbados,[20] Guadeloupe,[21] Tortuguero in Costa Rica,[22] and the Yucatan. They feed in the waters off Cuba[23] and around Mona Island near Puerto Rico,[24] among other places.
In the Indian Ocean, hawksbills are a common sight along the east coast of Africa, including the seas surrounding Madagascar and nearby island groups. Hawksbills are also common along the southern Asian coast, including the Persian Gulf, the Red Sea, and the Indian subcontinent and Southeast Asia 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.[25] 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.[26] In January 2016, a juvenile was seen in Gulf of Thailand.[27] A 2018 article by The Straits Times reported that around 120 hawksbill juvenile turtles recently hatched at Pulau Satumu, Singapore.[28] Commonly found in Singapore waters, hawksbill turtles have returned to areas such East Coast Park and Palau Satumu to nest.[29] In Hawaii, hawksbills mostly nest on the "main" islands of Oahu, Maui, Molokai, and Hawaii.[30] In Australia, hawksbills are known to nest on Milman Island in the Great Barrier Reef.[31] 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.[32] The Seychelles' inner islands and islets, such as Aldabra, are popular feeding grounds for immature hawksbills.[13][33]
In the eastern Pacific, hawksbills are known to occur from the Baja Peninsula in Mexico south along the coast to southern Peru.[17] Nonetheless, as recently as 2007, the species had been considered extirpated mainly in the region.[34] 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).[35] Multi-national initiatives, such as the Eastern Pacific Hawksbill Initiative, are currently pushing efforts to research and conserve the population, which remains poorly understood.
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][36] 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.[37]
While they are omnivorous, sea sponges are their principal food; they constitute 70–95% of the turtles' diets.[38] 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.[39] Aside from sponges, hawksbills feed on algae, marine plants, cnidarians, comb jellies and other jellyfish, sea anemones, mollusks, fish and crustaceans.[10][40] 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.[8]
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[8]), Ecionemia, and Placospongia.[39]
Less is known about the life history of hawksbills by comparison to several other sea turtle species.[1][41] Their life history may be divided into three phases, the: (i) early life history phase from approximately 4–30 cm straight carapace length,[42] (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.[43][44] 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.[42] 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).[41] Hawksbills show a degree of fidelity after recruiting to the benthic phase[45] however, the movement to other similar habitats is possible.[46]
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 hatchlings are dark-colored, with heart-shaped carapaces measuring approximately 2.5 cm (0.98 in) 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.[10]
Hawksbills evidently reach maturity after 20 years.[18] Their lifespan is unknown.[47] Like other sea turtles, hawksbills are solitary for most of their lives; they meet only to mate. They are highly migratory.[48] Because of their tough carapaces, adults' only predators are humans, sharks, estuarine crocodiles, octopuses, and some pelagic fish[48] species.
A series of biotic and abiotic cues, such as individual genetics, foraging quantity and quality,[49] 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.[50]
Age at maturity has been estimated to occur between 10[51] and 25 years of age[52] for Caribbean hawksbills. Turtles nesting in the Indo-Pacific region may reach maturity at a minimum of 30 to 35 years.[53]
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.[54]
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][55] 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.[56]
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.[57]
In China, where it was known as tai mei, the hawksbill is called the "tortoise-shell turtle", named primarily for its shell, which was used to make and decorate a variety of small items, as it was in the West.[56] Along the south coast of Java, stuffed hawksbill turtles are sold in souvenir shops, though numbers have decreased in the last two decades.[58] 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.[57] In 1994, Japan stopped importing hawksbill shells from other nations. Prior to this, the Japanese hawksbill shell trade was around 30,000 kg (66,000 lb) of raw shells per year.[23][59] In Europe, hawksbill sea turtle shells were harvested by the ancient Greeks and ancient Romans for jewellery, such as combs, brushes, and rings.[60] Recently, processed shells were regularly available in large amounts in countries including the Dominican Republic and Colombia.[61]
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.[62] 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).[62]
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.[1] Human and animal encroachment threatens nesting sites, and small mammals dig up the eggs to eat.[10] In the US Virgin Islands, mongooses raid hawksbill nests (along with other sea turtles, such as Dermochelys coriacea) right after they are laid.[63]
In 1982, the IUCN Red List of Threatened Species first listed E. imbricata as endangered.[64] This endangered status continued through several reassessments in 1986,[65] 1988,[66] 1990,[67] and 1994[68] until it was upgraded in status to critically endangered in 1996.[1] Two petitions challenged its status as an endangered species prior to this, claiming the turtle (along with three other species) had several significant stable populations worldwide. These petitions were rejected based on their data analysis submitted by the Marine Turtle Specialist Group (MTSG). The MTSG data showed the worldwide hawksbill sea turtle population had declined by 80% in the three most recent generations, and no significant population increase had occurred as of 1996. CR A2 status was denied, however, because the IUCN did not find sufficient data to show the population likely to decrease by a further 80%.[69]
The species (along with the entire Cheloniidae family) has been listed in Appendix I of the Convention on International Trade in Endangered Species.[3] This means commercial international trade (including in parts and derivatives) is prohibited and non-commercial international trade is regulated.[55]
The United States Fish and Wildlife Service and National Marine Fisheries Service have classified hawksbills as endangered under the Endangered Species Act[70] since 1970. The US government established several recovery plans[71] for protecting E. imbricata.[72]
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.[73]
The World Wildlife Fund Australia (WWF-Australia) has several ongoing projects aiming at protecting the reptile.[74]
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.[75]
The hawksbill sea turtle (Eretmochelys imbricata) is a critically endangered sea turtle belonging to the family Cheloniidae. It is the only extant species in the genus Eretmochelys. The species has a global distribution that is largely limited to tropical and subtropical marine and estuary ecosystems.
The appearance of the hawksbill is similar to that of other marine turtles. In general, it has a flattened body shape, a protective carapace, and flipper-like limbs, adapted for swimming in the open ocean. E. imbricata is easily distinguished from other sea turtles by its sharp, curving beak with prominent tomium, and the saw-like appearance of its shell margins. Hawksbill shells slightly change colors, depending on water temperature. While this turtle lives part of its life in the open ocean, it spends more time in shallow lagoons and coral reefs. The World Conservation Union, primarily as a result of human fishing practices, classifies E. imbricata as critically endangered. Hawksbill shells were the primary source of tortoiseshell material used for decorative purposes. The Convention on International Trade in Endangered Species (CITES) regulates the international trade of hawksbill sea turtles and products derived from them.