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 worldwide distribution,
with Atlantic and Indo-Pacific subspeciesE. i. imbricata and
E. i. bissa, respectively.
The hawksbill's appearance is similar to that of other marine
turtles. It has a generally flattened body shape, a protective carapace,
and flipper-like arms, 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
Human fishing practices threaten E. imbricata populations with
extinction. The World Conservation Union classifies the hawksbill
as critically endangered. Hawksbill shells were the primary source
of tortoiseshell material used for decorative purposes. The Convention
on International Trade in Endangered Species outlaws the capture
and trade of hawksbill sea turtles and products derived from them.
E. imbricata has the typical appearance of a marine turtle.
Like the other members of its family, it has a depressed body form
and flipper-like limbs adapted for swimming.
Adult hawksbill sea turtles have been known to grow up to 1
m (3 ft) in length, weighing around 80 kg (180 lb) on average. The
heaviest hawksbill ever captured was measured to be 127 kg (280
lb). 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.
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 arms have two visible claws on each flipper.
of the hawksbill's more easily distinguished characteristics 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 has been known to reach almost 1 m (3 ft)
Hawksbill sea turtles' sand tracks are asymmetrical, because
they crawl on land with an alternating gait. By contrast, the green
sea turtle and the leatherback turtle crawl rather symmetrically.
Due to its consumption of venomous cnidarians, hawksbill sea
turtle flesh can become toxic.
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 major subpopulations are acknowledged
to exist, the Atlantic and Indo-Pacific subpopulations.
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)
through southern Florida and the waters off Virginia. The species'
range extends as far north as the Long Island Sound and Massachusetts
in the west Atlantic and the frigid waters of the English Channel
in the east (the species' northernmost sighting to date).
the Caribbean, the main nesting beaches are in the Lesser Antilles,
Barbados, Guadeloupe, Tortuguero in Costa Rica, and in the Yucatan.
They feed in the waters off Cuba and around Mona Island near Puerto
Rico 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, and all along the southern Asian coast,
including the Persian Gulf, the Red Sea, and the coasts of the Indian
Subcontinent and Southeast Asia. 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 down to northern New Zealand.
The Philippines hosts several nesting sites, including the island
of Boracay. A small group of islands in the southwest of the archipelago
has been named the "Turtle Islands" because two species
of sea turtles nest there: the hawksbill and the green sea turtle.
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 has been legally protected since 1994, and the
population is showing some recovery. The Seychelles' inner islands
and islets, such as Aldabra, are popular feeding grounds for immature
Eastern Pacific subpopulation
In the eastern Pacific, hawksbills are known to occur
from the Baja Peninsula in Mexico south along the coast to southern
Peru. Nonetheless, as recently as 2007, the species had been considered
largely extirpated in the region. Important remnant nesting and
foraging sites have since been discovered in Mexico, El Salvador,
Nicaragua, and Ecuador, providing new opportunities for research
and conservation. 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 Eastern Pacific Hawksbill Initiative, are currently
pushing efforts to research and conserve the population, which remains
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 sea turtle young, they are assumed to be completely pelagic,
remaining at sea until they mature.
While they are omnivorous, sea sponges are the principal food of
hawksbill sea turtles. Sponges constitute 7095% of their diets
in the Caribbean. 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, cnidarians, comb jellies and other jellyfish, and sea anemones.
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.
much is known about the life history of hawksbills. Their life history
can be divided into three phases, namely the pelagic phase, from
hatching to about 20 cm, the benthic phase, when the immature turtles
recruit to foraging areas, and the reproductive phase, when they
reach sexual maturity. The pelagic phase possibly lasts 1 to 4 yr.
Hawksbills show a degree of fidelity after recruiting to the benthic
phase, however movement to other similar habitats is possible.
Hawksbills mate biannually in secluded lagoons off
their nesting beaches in remote islands throughout their range.
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 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 normally contain around 140 eggs.
After the hours-long process, the female then returns to the sea.
The baby turtles, 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 around 2.5
cm (0.98 in) long. They instinctively crawl into the sea, attracted
by the reflection of the moon on the water (possibly disrupted by
light sources such as street lamps and lights). While they emerge
under the cover of darkness, baby turtles that do not reach the
water by daybreak are preyed upon by shorebirds, shore crabs, and
The early life history of juvenile hawksbill sea turtles
is unknown. Upon reaching the sea, the hatchlings are assumed to
enter a pelagic life stage (like other marine turtles) for an undetermined
amount of time. While hawksbill sea turtle growth rates are not
known, when juveniles reach around 35 cm (14 in), they switch from
a pelagic lifestyle to living on coral reefs.
Hawksbills evidently reach maturity after 30 years.
They are believed to live from 30 to 50 years in the wild. 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 sharks, estuarine crocodiles,
octopuses, and some species of pelagic fish.
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 a 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.
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 placement of Eretmochelys within the
taxonomic tribe Carettini, which includes 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.
Etymology and taxonomic history
Linnaeus originally 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 genus
Eretmochelys. In 1857, the species was temporarily misdescribed
as Eretmochelys imbricata squamata.
Two subspecies are accepted in E. imbricata's taxon. E. i. bissa
(Rüppell, 1835) refers to populations that reside in the Pacific
Ocean. The Atlantic population is a separate subspecies, E. i. imbricata
(Linnaeus, 1766). The nominate subspecies is the Atlantic taxon,
because Linnaeus' type specimen was from the Atlantic.
Fitzinger derived the genus' name, Eretmochelys, from the Greek
roots eretmo and chelys, corresponding to "oar" and "turtle",
respectively. The name refers to the turtles' oar-like front flippers.
The species' name imbricata is Latin, corresponding to the English
term imbricate. This appropriately describes the turtles' overlapping
posterior scutes. The Pacific hawksbill's subspecies name, bissa,
is Latin for "double". The subspecies was originally described
as Caretta bissa; the term referred to the then-species being the
second species in the genus. Caretta is the genus of the hawksbill's
much larger relative, the loggerhead turtle.
Exploitation by humans
the world, hawksbill sea turtles are taken by humans, though it
is illegal to hunt them in many countries. In some parts of the
world, hawksbill sea turtles are eaten as a delicacy. As far back
as the fifth century BC, sea turtles, including the hawksbill, were
eaten as delicacies in China.
Many cultures also use turtles' shells for decoration. These
turtles have been harvested for their beautiful shell since Egyptian
times, and the material known as tortoiseshell is normally from
the hawksbill. 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 for making and decorating a variety
of small items, as it was in the West. In Japan, the turtles are
also harvested for their shell scutes, which are called bekko in
Japanese. It is used in various personal implements, such as eyeglass
frames and the shamisen (Japanese traditional three-stringed instrument)
picks. 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. In the West, hawksbill
sea turtle shells were harvested by the ancient Greeks and ancient
Romans for jewelry, such as combs, brushes, and rings. The bulk
of the world's hawksbill shell trade originates in the Caribbean.
In 2006, processed shells were regularly available, often in large
amounts, in countries including the Dominican Republic and Colombia.
The hawksbill sea turtle appears on the reverse side of the
Venezuelan 20-bolivar and the Brazilian 2-reais banknotes. A much-beloved
fountain sculpture of a boy riding a hawksbill, affectionately known
as Turtle Boy, stands in Worcester, Massachusetts.
Consensus has determined sea turtles, including E. imbricata to
be, at the very least, threatened species because of their slow
growth and maturity, and slow reproductive rates. Many adult turtles
have been killed by humans, both deliberately and accidentally.
In addition, human and animal encroachment threatens nesting sites,
and small mammals dig up eggs. In the US Virgin Islands, mongooses
raid hawksbill nests (along with those of other sea turtles, such
as Dermochelys coriacea) right after they are laid.
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. 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 analysis of data submitted by the Marine Turtle Specialist
Group (MTSG). The data given by the MTSG showed the worldwide hawksbill
sea turtle population had declined by 80% in the three most recent
generations, and no significant population increase 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% in the future.
The species (along with the entire family Cheloniidae) has been
listed on Appendix I of the Convention on International Trade in
Endangered Species. It is illegal to import or export turtle products,
or to kill, capture, or harass hawksbill sea turtles.
Local involvement in conservation efforts has also increased
in the past few years.
The United States Fish and Wildlife Service and National Marine
Fisheries Service have classified hawksbills as endangered under
the Endangered Species Act since 1970. The US government established
several recovery plans for protecting E. imbricata.