The olive ridley sea turtle (Lepidochelys olivacea), also known commonly as the Pacific ridley sea turtle, is a species of turtle in the familyCheloniidae. The species is the second smallest[3] and most abundant of all sea turtles found in the world. Lepidochelys olivacea
is found in warm and tropical waters, primarily in the Pacific and
Indian Oceans, but also in the warm waters of the Atlantic Ocean.[4]
This turtle and the related Kemps ridley turtle are best known for their unique mass nesting called arribada, where thousands of females come together on the same beach to lay eggs.[3]
Taxonomy
The olive ridley sea turtle may have been first described as Testudo mydas minor by Georg Adolf Suckow in 1798. It was later described and named Chelonia multiscutata by Heinrich Kuhl in 1820. Still later, it was described and named Chelonia olivacea by Johann Friedrich von Eschscholtz in 1829. The species was placed in the subgenusLepidochelys by Leopold Fitzinger in 1843.[5] After Lepidochelys was elevated to full genus status, the species was called Lepidochelys olivacea by Charles Frédéric Girard in 1858. Because Eschscholtz was the first to propose the specific epithetolivacea, he is credited as the binomial authority or taxon author in the valid name Lepidochelys olivacea (Eschscholtz, 1829). The parentheses indicate that the species was
originally described in a different genus.
The generic name, Lepidochelys, is derived from the Greek words lepidos, meaning scale, and chelys,
which translates to turtle. This could possibly be a reference to the
supernumerary costal scute counts characteristic of this genus.[6] The etymology of the English vernacular name "olive" is somewhat easier to resolve, as its carapace is olive green in color.[7] However, the origin of "ridley" is still somewhat unclear, perhaps derived from "riddle".[8]Lepidochelys is the only genus of sea turtles containing more than one extant species: L. olivacea and the closely related L. kempii (Kemp's ridley).[9]
Description
Growing to about 2 ft (61 cm) in carapace
length (measured along the curve), the olive ridley sea turtle gets its
common name from its olive-colored carapace, which is heart-shaped and
rounded. Males and females grow to the same size; however, females have a
slightly more rounded carapace as compared to males.[4] The heart-shaped carapace is characterized by four pairs of pore-bearing inframarginal scutes on the bridge, two pairs of prefrontals, and up to nine lateral scutes per side. L. olivacea
is unique in that it can have variable and asymmetrical lateral scute
counts, ranging from five to nine plates on each side, with six to eight
being most commonly observed.[6] Each side of the carapace has 12–14 marginal scutes.
The carapace is flattened dorsally and highest anterior to the
bridge. it has a medium-sized, broad head that appears triangular from
above. The head's concave sides are most obvious on the upper part of
the short snout. It has paddle-like fore limbs, each having two anterior
claws. The upper parts are grayish green to olive in color, but
sometimes appear reddish due to algae growing on the carapace. The bridge and hingeless plastron
of an adult varies from greenish white in younger individuals to a
creamy yellow in older specimens (maximum age is up to 50 years).[6][10]
Hatchlings are dark gray with a pale yolk scar, but appear all black when wet.[6]
Carapace length of hatchlings ranges from 37 to 50 mm (1.5 to 2.0 in). A
thin, white line borders the carapace, as well as the trailing edge of
the fore and hind flippers.[10]
Both hatchlings and juveniles have serrated posterior marginal scutes,
which become smooth with age. Juveniles also have three dorsal keels;
the central longitudinal keel gives younger turtles a serrated profile,
which remains until sexual maturity is reached.[6]
The olive ridley sea turtle rarely weighs over 50 kg (110 lb). Adults studied in Oaxaca, Mexico,[6]
ranged from 25 to 46 kg (55 to 101 lb); adult females weighed an
average of 35.45 kg (78.2 lb) (n=58), while adult males weighed
significantly less, averaging 33.00 kg (72.75 lb) (n=17). Hatchlings
usually weigh between 12.0 and 23.3 g (0.42 and 0.82 oz).
Adults are sexually dimorphic. The mature male has a longer and thicker tail, which is used for copulation,[6]
and the presence of enlarged and hooked claws on the male's front
flippers allows it to grasp the female's carapace during copulation. The
male also has a longer, more tapered carapace than the female, which
has a rounded, dome-like carapace.[6]
The male also has a more concave plastron, believed to be another
adaptation for mating. The plastron of the male may also be softer than
that of the female.[10]
Distribution
Lepidochelys olivacea distribution map: red circles are major nesting grounds; yellow circles are minor nesting beaches.
The olive ridley turtle has a circumtropical distribution, living in tropical and warm waters of the Pacific and Indian Oceans from India, Arabia, Japan, and Micronesia south to southern Africa, Australia, and New Zealand. In the Atlantic Ocean, it has been observed off the western coast of Africa and the coasts of northern Brazil, Suriname, Guyana, French Guiana, and Venezuela.
Additionally, the olive ridley has been recorded in the Caribbean Sea
as far north as Puerto Rico. A female was found alive on an Irish Sea beach on the Isle of Anglesey, British Isles, in November 2016, giving this species its northernmost appearance. It was taken in by the nearby Anglesey Sea Zoo, while its health was assessed.[11] A juvenile female was found off the coast of Sussex in 2020.[12] The olive ridley is also found in the eastern Pacific Ocean from the Galapagos Islands and Chile north to the Gulf of California, and along the Pacific coast to at least Oregon.
Migratory movements have been studied less intensely in olive ridleys
than other species of marine turtles, but they are believed to use the
coastal waters of over 80 countries.[13] Historically, this species has been widely regarded as the most abundant sea turtle in the world.[6] More than one million olive ridleys were commercially harvested off the coasts of Mexico in 1968 alone.[14]
The population of Pacific Mexico was estimated to be at least 10
million prior to the era of mass exploitation. More recently, the global
population of annual nesting females has been reduced to about two
million by 2004,[15] and was further reduced to 852,550 by 2008.[1][16] This indicated a dramatic decrease of 28 to 32% in the global population within only one generation (i.e., 20 years).[13]
Olive ridley sea turtles are considered the most abundant, yet
globally they have declined by more than 30% from historic levels.[citation needed]
These turtles are considered endangered because of their few remaining
nesting sites in the world. The eastern Pacific turtles have been found
to range from Baja California, Mexico, to Chile. Pacific olive ridleys nest around Costa Rica, Mexico, Nicaragua, and the northern Indian Ocean; the breeding colony in Mexico was listed as endangered in the US on July 28, 1978.[17]
Nesting grounds
Olive ridley hatchling
Nesting
Olive ridley turtles are best known for their behavior of synchronized nesting in mass numbers, termed arribadas.[10]
Females return to the same beach from where they hatched, to lay their
eggs. They lay their eggs in conical nests about one and a half feet
deep, which they laboriously dig with their hind flippers.[4] In the Indian Ocean, the majority of olive ridleys nest in two or three large groups near Gahirmatha in Odisha.
The coast of Odisha in India is the largest mass nesting site for the
olive ridley, followed by the coasts of Mexico and Costa Rica.[4] In 1991, over 600,000 turtles nested along the coast of Odisha in one week. Nesting occurs elsewhere along the Coromandel Coast and Sri Lanka, but in scattered locations. However, olive ridleys are considered a rarity in most areas of the Indian Ocean.[16]
They are also rare in the western and central Pacific, with known arribadas occurring only within the tropical eastern Pacific, in Central America and Mexico. In Costa Rica, they occur at Nancite and Ostional beaches. Two active arribadas are in Nicaragua, Chacocente and La Flor, with a small nesting ground in Pacific Panama. Historically, several arribadas were in Mexico, yet only one remains at Playa Escobilla in Oaxaca.[16]
Although olive ridleys are famed for their arribadas, many
of the nesting grounds can only support relatively small to
moderate-sized aggregations (about 1,000 nesting females). The overall
contribution and importance of these nesting beaches to the population
may be underestimated by the scientific community.[6]
Foraging grounds
Some
of the olive ridley's foraging grounds near southern California are
contaminated due to sewage, agricultural runoff, pesticides, solvents,
and industrial discharges. These contaminants have been shown to
decrease the productivity of the benthic community, which negatively
affects these turtles, which feed from these communities.[6]
The increasing demand to build marinas and docks near Baja California
and southern California are also negatively affecting the olive ridleys
in these areas, where more oil and gasoline will be released into these
sensitive habitats. Another threat to these turtles is power plants,
which have documented juvenile and subadult turtles becoming entrained
and entrapped within the saltwater cooling intake systems.[6]
Ecology and behavior
An olive ridley sea turtle laying eggs
Reproduction
Mating is often assumed to occur in the vicinity of nesting beaches, but copulating
pairs have been reported over 1,000 km from the nearest beach. Research
from Costa Rica revealed the number of copulating pairs observed near
the beach could not be responsible for the fertilization of the tens of
thousands of gravid females, so a significant amount of mating is believed to have occurred elsewhere at other times of the year.[6]
The Gahirmatha Beach in Kendrapara district of Odisha (India),
which is now a part of the Bhitarkanika Wildlife Sanctuary, is the
largest breeding ground for these turtles. The Gahirmatha Marine
Wildlife Sanctuary, which bounds the Bhitarkanika Wildlife Sanctuary to
the east, was created in September 1997, and encompasses Gahirmatha
Beach and an adjacent portion of the Bay of Bengal. Bhitarkanika
mangroves were designated a Ramsar Wetland of International Importance
in 2002. It is the world's largest known rookery of olive ridley sea
turtles. Apart from Gahirmatha rookery, two other mass nesting beaches
have been located, which are on the mouth of rivers Rushikulya and Devi.
The spectacular site of mass congregation of olive ridley sea turtles
for mating and nesting enthralls both the scientists and the nature
lovers throughout the world.
Olive ridley sea turtles migrate in huge numbers from the
beginning of November, every year, for mating and nesting along the
coast of Orissa. Gahirmatha coast has the annual nesting figure between
100,000 and 500,000 each year. A decline in the population of these
turtles has occurred in the recent past due to mass mortality. The olive
ridley sea turtle has been listed on Schedule – I of the Indian
Wildlife (Protection) Act, 1972 (amended 1991). The species is listed as
vulnerable under IUCN.[1]
The sea turtles are protected under the 'Migratory Species Convention'
and Convention of International Trade on Wildlife Flora and Fauna
(CITES). India is a signatory nation to all these conventions. The
homing characteristics of the ridley sea turtles make them more prone to
mass casualty. The voyage to the natal nesting beaches is the dooming
factor for them. Since Gahirmatha coast serves as the natal nesting
beach for millions of turtles, it has immense importance on turtle
conservation.
Olive ridleys generally begin to aggregate near nesting beaches
about two months before nesting season, although this may vary
throughout their range. In the eastern Pacific, nesting occurs
throughout the year, with peak nesting events (arribadas)
occurring between September and December. Nesting beaches can be
characterized as relatively flat, midbeach zone, and free of debris.[5] Beach fidelity
is common, but not absolute. Nesting events are usually nocturnal, but
diurnal nesting has been reported, especially during large arribadas.[6]
Exact age of sexual maturity is unknown, but this can be somewhat
inferred from data on minimum breeding size. For example, the average
carapace length of nesting females (n = 251) at Playa Nancite, Costa
Rica, was determined to be 63.3 cm, with the smallest recorded at
54.0 cm.[6] Females can lay up to three clutches per season, but most only lay one or two clutches.[10]
The female remains near shore for the internesting period, which is
about one month. Mean clutch size varies throughout its range and
decreases with each nesting attempt.[16]
A mean clutch size of 116 (30–168 eggs) was observed in Surinam, while nesting females from the eastern Pacific were found to have an average of 105 (74–126 eggs).[10]
The incubation period is usually between 45 and 51 days under natural
conditions, but may extend to 70 days in poor weather conditions. Eggs
incubated at temperatures of 31 to 32 °C produce only females; eggs
incubated at 28 °C or less produce solely males; and incubation
temperatures of 29 to 30 °C produce a mixed-sex clutch.[10] Hatching success can vary by beach and year, due to changing environmental conditions and rates of nest predation.
Habitat
Most observations are typically within 15 km of mainland shores in protected, relatively shallow marine waters (22–55 m deep).[10]
Olive ridleys are occasionally found in open waters. The multiple
habitats and geographical localities used by this species vary
throughout its lifecycle.[5] More research is needed to acquire data on and use of pelagic habitats.[6]
Feeding
The olive ridley is predominantly carnivorous,
especially in immature stages of the lifecycle. Animal prey consists of
protochordates or invertebrates, which can be caught in shallow marine
waters or estuarine habitats. Common prey items include jellyfish, tunicates, sea urchins, bryozoans, bivalves, snails, shrimp, crabs, rock lobsters, and sipunculid worms. Additionally, consumption of jellyfish and both adult fish (e.g. Sphoeroides) and fish eggs may be indicative of pelagic (open ocean) feeding.[10]
The olive ridley is also known to feed on filamentous algae in areas
devoid of other food sources. Captive studies have indicated some level
of cannibalistic behavior in this species.[6]
Threats
Olive ridley entangled in a ghost net within the Maldives
Known predators of olive ridley eggs include raccoons, coyotes, feral dogs and pigs, opossums, coatimundi, caimans, ghost crabs, and the sunbeam snake.[10] Hatchlings are preyed upon as they travel across the beach to the water by vultures, frigate birds, crabs, raccoons, coyotes, iguanas, and snakes. In the water, hatchling predators most likely include oceanic fishes, sharks, and crocodiles. Adults have relatively few known predators, other than sharks, and killer whales are responsible for occasional attacks. On land, nesting females may be attacked by jaguars.
Notably, the jaguar is the only cat with a strong enough bite to
penetrate a sea turtle's shell, thought to be an evolutionary adaption
from the Holocene extinction
event. In observations of jaguar attacks, the cats consumed the neck
muscles of the turtle and occasionally the flippers, but left the
remainder of the turtle carcass for scavengers as most likely, despite
the strength of its jaws, a jaguar still cannot easily penetrate an
adult turtle's shell to reach the internal organs or other muscles. In
recent years, increased predation on turtles by jaguars has been noted,
perhaps due to habitat loss and fewer alternative food sources. Sea
turtles are comparatively defenseless in this situation, as they cannot
pull their heads into their shells like freshwater and terrestrial
turtles.[6][18] Females are often plagued by mosquitos during nesting. Humans are still listed as the leading threat to L. olivacea,
responsible for unsustainable egg collection, slaughtering nesting
females on the beach, and direct harvesting adults at sea for commercial
sale of both the meat and hides.[10]
Other major threats include mortality associated with boat collisions, and incidental takes in fisheries. Trawling, gill nets, ghost nests, longline fishing, and pot fishing have significantly affected olive ridley populations, as well as other species of marine turtles.[1][6]
Between 1993 and 2003, more than 100,000 olive ridley turtles were
reported dead in Odisha, India from fishery-related practices.[19] In addition, entanglement and ingestion of marine debris is listed as a major threat for this species. Coastal development, natural disasters, climate change, and other sources of beach erosion have also been cited as potential threats to nesting grounds.[6] Additionally, coastal development also threatens newly hatched turtles through the effects of light pollution.[20]
Hatchlings which use light cues to orient themselves to the sea are now
misled into moving towards land, and die from dehydration or
exhaustion, or are killed on roads.
However, the greatest single cause of olive ridley egg loss results from arribadas,
in which the density of nesting females is so high, previously laid
nests are inadvertently dug up and destroyed by other nesting females.[6] In some cases, nests become cross-contaminated by bacteria
or pathogens of rotting nests. For example, in Playa Nancite, Costa
Rica, only 0.2% of the 11.5 million eggs produced in a single arribada successfully hatched. Although some of this loss resulted from predation and high tides, the majority was attributed to conspecifics unintentionally destroying existing nests. The extent to which arribadas
contribute to the population status of olive ridleys has created debate
among scientists. Many believe the massive reproductive output of these
nesting events is critical to maintaining populations, while others
maintain the traditional arribada beaches fall far short of their reproductive potential and are most likely not sustaining population levels.[6] In some areas, this debate eventually led to legalizing egg collection.
Economic importance
Historically, the olive ridley has been exploited for food, bait, oil, leather, and fertilizer.
The meat is not considered a delicacy; the egg, however, is esteemed
everywhere. Egg collection is illegal in most of the countries where
olive ridleys nest, but these laws are rarely enforced. Harvesting eggs
has the potential to contribute to local economies, so the unique
practice of allowing a sustainable (legal) egg harvest has been
attempted in several localities.[16] Numerous case studies have been conducted in regions of arribadasbeaches
to investigate and understand the socioeconomic, cultural, and
political issues of egg collection. Of these, the legal egg harvest at
Ostional, Costa Rica, has been viewed by many as both biologically
sustainable and economically viable. Since egg collection became legal
in 1987, local villagers have been able to harvest and sell around three
million eggs annually. They are permitted to collect eggs during the
first 36 hours of the nesting period, as many of these eggs would be
destroyed by later nesting females. Over 27 million eggs are left
unharvested, and villagers have played a large role in protecting these
nests from predators, thereby increasing hatching success.[6]
Most participating households reported egg harvesting as their
most important activity, and profits earned were superior to other forms
of available employment, other than tourism. The price of Ostional eggs
was intentionally kept low to discourage illegal collection of eggs
from other beaches. The Ostional project retained more local profits
than similar egg collection projects in Nicaragua,[16]
but evaluating egg-harvesting projects such as this suffers from the
short timeline and site specificity of findings. In most regions,
illegal poaching of eggs is considered a major threat to olive ridley
populations, thus the practice of allowing legal egg harvests continues
to attract criticism from conservationists and sea turtle biologists.
Plotkin's Biology and Conservation of Ridley Sea Turtles,
particularly the chapter by Lisa Campbell titled "Understanding Human
Use of Olive Ridleys", provides further research on the Ostional harvest
(as well as other harvesting projects). Scott Drucker's documentary, Between the Harvest, offers a glimpse into this world and the debate surrounding it.
Conservation status
Two olive ridley hatchlings moving into the ocean after being released from a conservation site in Puerto Vallarta, Mexico.
The olive ridley is classified as vulnerable according to the International Union for Conservation of Nature and Natural Resources (IUCN), and is listed in Appendix I of CITES. These listings were largely responsible for halting the large-scale commercial exploitation and trade of olive ridley skins.[1] The Convention on Migratory Species
and the Inter-American Convention for the Protection and Conservation
of Sea Turtles have also provided olive ridleys with protection, leading
to increased conservation and management for this marine turtle.
National listings for this species range from endangered to threatened,
yet enforcing these sanctions on a global scale has been unsuccessful
for the most part. Conservation successes for the olive ridley have
relied on well-coordinated national programs in combination with local
communities and nongovernment organizations, which focused primarily on
public outreach and education. Arribada management has also played a critical role in conserving olive ridleys.[16] Lastly, enforcing the use of turtle excluder devices in the shrimp-trawling industry has also proved effective in some areas.[1] Globally, the olive ridley continues to receive less conservation attention than its close relative, the Kemp's ridley (L. kempii). Also, many schools arrange trips for students to carry out the conservation project, especially in India.
Several projects worldwide seek to preserve the olive ridley sea
turtle population. For example, in Nuevo Vallarta, Mexico, when the
turtles come to the beach to lay their eggs, some of them are relocated
to a hatchery, where they have a much better chance to survive. If the
eggs were left on the beach, they would face many threats such as
getting washed away with the tide or getting poached. Once the eggs
hatch, the baby turtles are carried to the beach and released.
Another major project, in India involved in preserving the olive
ridley sea turtle population was carried out in Chennai, where the
Chennai wildlife team collected close to 10,000 eggs along the Marina
coast, of which 8,834 hatchlings were successfully released into the sea
in a phased manner.[21]
The green sea turtle (Chelonia mydas), also known as the green turtle, black (sea) turtle or Pacific green turtle,[3] is a species of large sea turtle of the familyCheloniidae. It is the only species in the genusChelonia.[4] Its range extends throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Oceans, but it is also found in the Indian Ocean.[5][6] The common name refers to the usually green fat found beneath its carapace, not to the color of its carapace, which is olive to black.
This sea turtle'sdorsoventrally flattened body is covered by a large, teardrop-shaped carapace; it has a pair of large, paddle-like flippers.
It is usually lightly colored, although in the eastern Pacific
populations parts of the carapace can be almost black. Unlike other
members of its family, such as the hawksbill sea turtle, C. mydas is mostly herbivorous. The adults usually inhabit shallow lagoons, feeding mostly on various species of seagrasses.[7] The turtles bite off the tips of the blades of seagrass, which keeps the grass healthy.
Like other sea turtles, green sea turtles migrate long distances
between feeding grounds and hatching beaches. Many islands worldwide are
known as Turtle Island
due to green sea turtles nesting on their beaches. Females crawl out on
beaches, dig nests and lay eggs during the night. Later, hatchlings
emerge and scramble into the water. Those that reach maturity may live to 80 years in the wild.[5] C. mydas is listed as endangered by the IUCN and CITES and is protected from exploitation in most countries.[8]
It is illegal to collect, harm or kill them. In addition, many
countries have laws and ordinances to protect nesting areas. However,
turtles are still in danger due to human activity. In some countries,
turtles and their eggs are hunted for food. Pollution indirectly harms turtles at both population and individual scales, as well as light pollution. Many turtles die after being caught in fishing nets. Also, real estate development often causes habitat loss by eliminating nesting beaches.
Taxonomy
The green sea turtle is a member of the tribeChelonini. A 1993 study clarified the status of genusChelonia with respect to the other marine turtles. The carnivorousEretmochelys (hawksbill), Caretta (loggerhead) and Lepidochelys (Ridley) were assigned to the tribe Carettini. HerbivorousChelonia warranted their status as a genus, while Natator (flatback) was further removed from the other genera than previously believed.[9]
The species was originally described by Linnaeus in 1758 as Testudo mydas.[10] In 1868, Marie Firmin Bocourt named a particular species of sea turtle Chelonia agassizii.[11][12] This "species" was referred to as the "black sea turtle".[13] Later research determined Bocourt's "black sea turtle" was not genetically distinct from C. mydas, and thus taxonomically not a separate species.[14] These two "species" were then united as Chelonia mydas and populations were given subspecies status: C. mydas mydas referred to the originally described population, while C. mydas agassizi referred only to the Pacific population known as the Galápagos green turtle.[15][16] This subdivision was later determined to be invalid and all species members were then designated Chelonia mydas.[4] The oft-mentioned name C. agassizi remains an invalid junior synonym of C. mydas.
The species' common name does not derive from any particular green
external coloration of the turtle. Its name comes from the greenish
color of the turtles' fat, which is only found in a layer between their
inner organs and their shell.[17] As a species found worldwide, the green turtle has many local names. In the Hawaiian language it is called honu,[18][19] and it is locally known as a symbol of good luck and longevity.[20]
Its appearance is that of a typical sea turtle. C. mydas has a dorsoventrally flattened body, a beaked head at the end of a short neck, and paddle-like arms well-adapted for swimming.[21] Adult green turtles grow to 1.5 metres (5 ft) long.[22] The average weight of mature individuals is 68–190 kg (150–419 lb) and the average carapace length is 78–112 cm (31–44 in).[23] Exceptional specimens can weigh 315 kg (694 lb) or even more, with the largest known C. mydas having weighed 395 kg (871 lb) and measured 153 cm (60 in) in carapace length.[24]
Anatomically, a few characteristics distinguish the green turtle
from the other members of its family. Unlike its close relative the hawksbill turtle, the green turtle's snout is very short and its beak is unhooked. The neck cannot be pulled into the shell.[25]
The sheath of the turtle's upper jaw possesses a denticulated edge,
while its lower jaw has stronger, serrated, more defined denticulation.
The dorsal surface of the turtle's head has a single pair of prefrontal
scales. Its carapace is composed of five central scutes
flanked by four pairs of lateral scutes. Underneath, the green turtle
has four pairs of inframarginal scutes covering the area between the
turtle's plastron and its shell. Mature C. mydas
front appendages have only a single claw (as opposed to the hawksbill's
two), although a second claw is sometimes prominent in young specimens.[26]
The carapace of the turtle has various color patterns that change over time. Hatchlings of Chelonia mydas,
like those of other marine turtles, have mostly black carapaces and
light-colored plastrons. Carapaces of juveniles turn dark brown to
olive, while those of mature adults are either entirely brown, spotted
or marbled with variegated rays. Underneath, the turtle's plastron is
hued yellow. C. mydas limbs are dark-colored and lined with
yellow, and are usually marked with a large dark brown spot in the
center of each appendage.[5][27]
Distribution
The range of the green sea turtle extends throughout tropical and subtropical oceans worldwide. The two major subpopulations
are the Atlantic and the eastern Pacific subpopulations. Each
population is genetically distinct, with its own set of nesting and
feeding grounds within the population's known range.[5]
One of the genetic differences between the two subpopulations is the
type of mitochondrial DNA found in individual's cells. Individuals from
rookeries in the Atlantic Ocean and Mediterranean Sea have a similar
type of mitochondrial DNA, and individuals from the Pacific and Indian
Oceans have another type of Mitochondrial DNA.[28]
Their native range includes tropical to subtropical waters along
continental coasts and islands between 30°N and 30°S. Since green sea
turtles are a migrating species, their global distribution spans into
the open ocean. The differences in mitochondrial DNA more than likely
stems from the populations being isolated from each other by the
southern tips of both South America and Africa with no warm waters for
the green sea turtles to migrate through. The green sea turtle is
estimated to inhabit coastal areas of more than 140 countries, with
nesting sites in over 80 countries worldwide throughout the year. In the
United States Atlantic coast, green sea turtles can be found from Texas
and north to Massachusetts. In the United States Pacific coast, they
have been found from southern California north to the southernmost tip
of Alaska. The largest populations of green sea turtles within the
United States coastline are in the Hawaiian Islands and Florida.
Globally, the largest populations of sea turtles are in the Great
Barrier Reef in Australia and the Caribbean islands.[29]
Atlantic subpopulation
The green sea turtle can generally be found throughout the Atlantic Ocean. Although the species is most abundant in tropical climates, individuals have been spotted as far north as Canada in the western Atlantic, and the British Isles in the east. The subpopulation's southern range is known until past the southern tip of Africa in the east and Argentina in the western Atlantic. The major nesting sites can be found on various islands in the Caribbean, along the eastern shores of the continental United States, the eastern coast of the South American continent and most notably, on isolated North Atlantic islands.
In the Caribbean, major nesting sites have been identified on Aves Island, the U.S. Virgin Islands, Puerto Rico, and Costa Rica. In recent years there are signs of increased nesting in the Cayman Islands.[30] One of the region's most important nesting grounds is in Tortuguero in Costa Rica.[31] In fact, the majority of the Caribbean region's C. mydas population hails from a few beaches in Tortuguero.[32] Within United States waters, minor nesting sites have been noted in the states of Georgia, North Carolina, South Carolina, and all along the east coast of Florida. Hutchinson Island in particular is a major nesting area in Florida waters. Notable locations in South America include secluded beaches in Suriname and French Guiana.[33] In the Southern Atlantic Ocean, the most notable nesting grounds for Chelonia mydas are found on the island of Ascension,[21] hosts 6,000–13,000 turtle nests.[34][35][36]
In contrast with the sporadic distribution of nesting sites,
feeding grounds are much more widely distributed throughout the region.
Important feeding grounds in Florida include Indian River Lagoon, the Florida Keys, Florida Bay, Homosassa, Crystal River, and Cedar Key.[21][37]
Indo-Pacific subpopulation
About to break the surface for air at Kona, Hawaii
In the Pacific, its range reaches as far north as the southern coast of Alaska and as far south as Chile in the east. The turtle's distribution in the western Pacific reaches north to Japan and southern parts of Russia's Pacific coast, and as far south as the northern tip of New Zealand and a few islands south of Tasmania. The turtles can be found throughout the Indian Ocean.[38]
Significant nesting grounds are scattered throughout the entire Pacific region, including Mexico, the Hawaiian Islands, the South Pacific, the northern coast of Australia, and Southeast Asia. Major Indian Ocean nesting colonies include India, Pakistan, and other coastal countries. The east coast of the African continent hosts a few nesting grounds, including islands in the waters around Madagascar.[38]
Nesting grounds are found all along the Mexican coast. These turtles feed in seagrass pastures in the Gulf of California.[39] Green turtles belonging to the distinct Hawaiian subpopulation nest at the protected French Frigate Shoals some 800 kilometers (500 mi) west of the Hawaiian Islands.[19] In the Philippines, green turtles nest in the Turtle Islands along with closely related hawksbill turtles.[40]Indonesia has a few nesting beaches, one in the Meru Betiri National Reserve in East Java.[41] The Coral Sea has nesting areas of world significance.[42] The Great Barrier Reef has two genetically distinct populations; one north and one south. Within the reef, 20 separate locations consisting of small islands and cays were identified as nesting sites for either population of C. mydas. Of these, the most important is on Raine Island.[43][44]
Major nesting sites are common on either side of the Arabian Sea, both in Ash Sharqiyah, Oman, and along the coast of Karachi, Pakistan. Some specific beaches there, such as Hawke's Bay and Sandspit, are common to both C. mydas and L. olivacea subpopulation. Sandy beaches along Sindh and Balochistan are nesting sites. Some 25 kilometers (16 mi) off the Pakistani coast, Astola island is another nesting beach.[7][45][46]
On 30 December 2007, fishermen using a hulbot-hulbot (a type of fish net) accidentally caught an 80 kg (180 lb), 93 cm (37 in) long and 82 cm (32 in) wide turtle off Barangay Bolong, Zamboanga City, Philippines. December is breeding season near the Bolong beach.[47]
The population that has often been known as the Galápagos green
turtle have been recorded and observed in the Galápagos as far back as
the 17th century by William Dampier.[48] Not much attention has been paid to them due to the overwhelming research done on the Galápagos giant tortoises.[49]
Only over the last 30 years have extensive studies been performed
covering the behaviors of the Galápagos green turtles. Much of the
debate that has surrounded them recently is over the binomial
classification of the species.[50] At one point the name Chelonia agassizii was applied to this population as a separate species.[14] Analysis of mitochondrial and nuclear DNA of 15 nesting beaches.[50]
however has demonstrated that there is not only no significant
distinction of this population but that it would be paraphyletic to
recognise it. As such the species name Chelonia agassizzii is considered a junior synonym of Chelonia mydas[50] as such it is considered as a local cariant of the populations of the East Pacific waters and those of other nesting areas.[50]
The morphological distinctiveness of the Galápagos green turtle has given rise to the debate,[14]
but evidence of taxonomic distinctiveness is best served using the
combination of multiple datasets. The two most notable morphological
distinctions are the considerably smaller adult size and the much darker
pigmentation of the carapace, plastron, and extremities.[14]
Other distinctions are the curving of the carapace above each hind
flipper, the more dome-shaped carapace, and the very long tail of adult
males.[51]
Three possibilities have arisen from their unique characteristics: agassizii is a separate species from C. mydas, it is a subspecies of green sea turtle, or it is simply a color mutation.[51]
These facts have led to the debate over binomial separation however due
to the significance of the DNA testing results there have been no
distinctions made at this time.[50]
At a meeting for sea turtle scientists and their collaborators in 2000,
the evidence for the taxonomic position of the Galápagos green turtle
was reviewed and a majority among the participants supported treating it
as a population or subspecies of the green turtle (instead of a
separate species).[52] However, this is possibly a case of political taxonomy.
As such the three major international checklists that cover turtles of the world Reptile Database[53] the checklist of Fritz and Havas (2007)[2] and the IUCN Checklist (TTWG 2017)[54] all consider this a junior synonym.
Habitat
Green sea turtles move across three habitat types, depending on their life stage.
They lay eggs on beaches. Mature turtles spend most of their time in
shallow, coastal waters with lush seagrass beds. Adults frequent inshore
bays, lagoons, and shoals with lush seagrass meadows. Entire
generations often migrate between one pair of feeding and nesting areas.[21] Green sea turtles, Chelonia mydas,
are classified as an aquatic species and are distributed around the
globe in warm tropical to subtropical waters. The environmental
parameter that limits the distribution of the turtles is ocean
temperatures below 7 to 10 degrees Celsius.<, ref name=":3" />
Within their geographical range, the green sea turtles generally stay
near continental and island coastlines. Near the coastlines, the green
sea turtles live within shallow bays and protected shores. In these
protected shores and bays, the green sea turtle habitats include coral
reefs, salt marshes, and nearshore seagrass beds. The coral reefs
provide red, brown, and green algae for their diet and give protection
from predators and rough storms within the ocean. The salt marshes and
seagrass beds contain seaweed and grass vegetation, allowing ample
habitat for the sea turtles.[29]
Turtles spend most of their first five years in convergence zones within the bare open ocean that surround them.[7][55] These young turtles are rarely seen as they swim in deep, pelagic waters.[56][57] Green sea turtles typically swim at 2.5–3 km/h (1.6–1.9 mph).[58]
Ecology and behavior
Swimming, Hawaii
As one of the first sea turtle species studied, much of what is known
of sea turtle ecology comes from studies of green turtles. The ecology
of C. mydas changes drastically with each stage of its life history. Newly emerged hatchlings are carnivorous, pelagic organisms, part of the open ocean mininekton. In contrast, immature juveniles and adults are commonly found in seagrass meadows closer inshore as herbivorous grazers.
Diet
Green sea turtle grazing on seagrass
The diet of green turtles changes with age.[59] Juveniles are carnivorous, but as they mature they become omnivorous.[60] The young eat fish eggs, molluscs, jellyfish, small invertebrates, worms, sponges, algae, and crustaceans.[61][29] Green sea turtles have a relatively slow growth rate because of the low nutritional value of their diet. Body fat turns green because of the consumed vegetation.[60] This diet shift has an effect on the green turtle's skull morphology.[62] Their serrated jaw helps them chew algae and sea grasses.[63] Most adult sea turtles are strictly herbivorous.[60]
Predators and parasites
Only human beings and the larger sharks feed on C. mydas adults. Specifically, tiger sharks (Galeocerdo cuvier) hunt adults in Hawaiian waters.[64] Juveniles and new hatchlings have significantly more predators, including crabs, small marine mammals and shorebirds.[5] Additionally, their eggs are vulnerable to predation by scavengers like red foxes and golden jackals.[65]
Green sea turtles have a variety of parasites including
barnacles, leeches, protozoans, cestodes, and nematodes. Barnacles
attach to the carapace, and leeches to the flippers and skin of the
turtles, causing damage to the soft tissues and leading to blood loss.
Protozoans, cestodes and nematodes lead to many turtle deaths because of
the infections in the liver and intestinal tract they cause. The
greatest disease threat to the turtle population is fibropapilloma,
which produces lethal tumor growth on scales, lungs, stomach, and
kidneys. Fibropapilloma is caused by a herpesvirus that is transmitted
by leeches such as Ozobranchus branchiatus, a species of leech which feeds almost entirely on green sea turtles.[66][67]
Life cycle
Hatchling
Green sea turtles migrate long distances between feeding sites and
nesting sites; some swim more than 2,600 kilometres (1,600 mi) to reach
their spawning grounds. Beaches in Southeast Asia, India, islands in the
western Pacific, and Central America are where Green sea turtles breed.[6]
Mature turtles often return to the exact beach from which they hatched.
Females usually mate every two to four years. Males, on the other hand,
visit the breeding areas every year, attempting to mate.[68] Mating seasons vary between populations. For most C. mydas in the Caribbean, mating season is from June to September.[21] The French Guiana nesting subpopulation nests from March to June.[33] In the tropics, green turtles nest throughout the year, although some subpopulations prefer particular times of the year. In Pakistan, Indian Ocean turtles nest year-round, but prefer the months of July to December.[45]
Sea turtles return to the beaches on which they were born to lay
their own eggs. The reason for returning to native beaches may be that
it guarantees the turtles an environment that has the necessary
components for their nesting to be successful. These include a sandy
beach, easy access for the hatchlings to get to the ocean, the right
incubation temperatures, and low probability of predators that may feed
on their eggs. Over time these turtles have evolved these tendencies to
return to an area that has provided reproductive success for many
generations. Their ability to return to their birthplace is known as
natal homing.[69]
The males also return to their birthplaces in order to mate. These
males that return to their homes know they will be able to find mates
because the females born there also return to breed. By doing this, the
green sea turtles are able to improve their reproductive success and is
why they are willing to expend the energy to travel thousands of miles
across the ocean in order to reproduce.
Mating behaviour is similar to other marine turtles. Female turtles control the process. A few populations practice polyandry, although this does not seem to benefit hatchlings.[70]
After mating in the water, the female moves above the beach's high tide
line, where she digs a hole 11-22 inches in depth with her hind
flippers and deposits her eggs. The hole is then covered up again.[71]
Clutch size ranges between 85 and 200, depending on the age of the
female. This process takes about an hour to an hour and a half. After
the nest is completely covered, she returns to the sea. The female will
do this 3 to 5 times in one season.[6]
The eggs are round and white, and about 45 mm in diameter. The
hatchlings remain buried for days until they all emerge together at
night.[71] The temperature of the nest determines the sex of the turtles at around the 20-40 day mark.[72] At around 50 to 70 days,[73] the eggs hatch during the night, and the hatchlings instinctively head directly into the water. This is the most dangerous time in a turtle's life. As they walk, predators, such as gulls and crabs,
feed on them. A significant percentage never make it to the ocean.
Little is known of the initial life history of newly hatched sea
turtles.[21]
Juveniles spend three to five years in the open ocean before they
settle as still-immature juveniles into their permanent shallow-water
lifestyle.[56][57] It is speculated that they take twenty to fifty years to reach sexual maturity. Individuals live up to eighty years in the wild.[5] It is estimated that only 1% of hatchlings reach sexual maturity.
Each year on Ascension Island in the South Atlantic, C. mydas
females create 6,000 to 25,000 nests. They are among the largest green
turtles in the world; many are more than a metre in length and weigh up
to 300 kilograms (660 lb).[74]
Breathing and sleep
Sea
turtles spend almost all their lives submerged, but must breathe air
for the oxygen needed to meet the demands of vigorous activity. With a
single explosive exhalation and rapid inhalation, sea turtles can
quickly replace the air in their lungs. The lungs permit a rapid
exchange of oxygen and prevent gases from being trapped during deep
dives. Sea turtle blood can deliver oxygen efficiently to body tissues
even at the pressures encountered during diving. During routine
activity, green and loggerhead turtles dive for about four to five
minutes, and surface to breathe for one to three seconds.
Green sea turtle resting under rocks in the Uruguayan Atlantic coast.
Turtles can rest or sleep underwater for several hours at a time, but
submergence time is much shorter while diving for food or to escape
predators. Breath-holding ability is affected by activity and stress,
which is why turtles quickly drown in shrimp trawlers and other fishing gear.[26]
During the night while sleeping and to protect themselves from
potential predators, the adults wedge themselves under rocks below the
surface and under ledges in reefs and coastal rocks. Many green sea
turtles have been observed in returning to the same sleeping location
night after night.[29]
Physiology and sensory modalities
Green
sea turtles tend to have good vision, well adapted to a life at sea.
The turtles can see many colors, but are most sensitive to light from
violet to yellow or wavelengths of 400 to 600 nanometers. They do not
see many colors in the orange to red portion of the light spectrum. On
land, however, the sea turtles are nearsighted because the lenses in the
eyes are spherical and adjusted to refraction underwater.[29]
Sea turtles have no external ear and only one ear bone, called the
columella. With one ear bone, the turtles can only hear low frequency
sounds, from 200 to 700 Hz. Sounds can also be detected through
vibrations of the head, backbone, and shell. The nose of the turtle has
two external openings and connects to the roof of the mouth through
internal openings. The lower surface of the nasal passage has two sets
of sensory cells called the Jacobson's organ. The turtle can use this
organ to smell by pumping water in and out of its nose.[66]
Since green sea turtles migrate long distances during breeding
seasons, they have special adaptive systems in order to navigate. In the
open ocean, the turtles navigate using wave directions, sun light, and
temperatures. The sea turtles also contain an internal magnetic compass.
They can detect magnetic information by using magnetic forces acting on
the magnetic crystals in their brains. Through these crystals, they can
sense the intensity of Earth's magnetic field and are able to make
their way back to their nesting grounds or preferred feeding grounds.[66]
Natal homing is an animal's ability to return to its birthplace
in order to reproduce. Natal homing is found in all species of sea
turtles and in other animals such as salmon. How these turtles are able
to return to their birthplace is an interesting phenomenon. Many
researchers believe that sea turtles use a process called imprinting,
which is a special type of learning that occurs when turtles first hatch
that allows them to recognize their native beach. There are two types
of imprinting that are thought to be the reason turtles can find these
beaches. The first is the chemical imprinting hypothesis. This
hypothesis states that much like salmon, sea turtles are able to use
olfactory cues and senses to smell their way home. However, a problem
with this hypothesis is that some turtles travel thousands of miles to
return to their native beaches, and the scents from that area aren't
likely to travel and be distinguishable from that distance.
The second hypothesis is the geomagnetic. This hypothesis states that as
it hatches, a young turtle will imprint on the magnetic field of the
beach they are born on. This hypothesis strongly correlates to the
method which sea turtles use to navigate the earth.[69]
In order to tolerate the constant heat loss in the water, sea
turtles have the ability to shunt blood away from tissues that are
tolerant of low oxygen levels toward the heart, brain, and central
nervous system. Other mechanisms include basking on warm beaches and
producing heat through their activity and movements of their muscles. In
the winter months, turtles living at higher latitudes can hibernate for
a short period in the mud.[75]
Unique characteristics and features
The
green sea turtles exhibit sex differences by their development and
appearance. As adult turtles, males are easily distinguishable from the
females by having a longer tail (visibly extending past the shell) and
longer claws on the front flippers. The hatching time and sex of the
turtles are determined by the incubation temperature of the nest.
Hatchings occur more quickly in nests that are warmer than nests that
are in cooler conditions. Warm nesting sites above 30 degrees Celsius
favor the development of females, whereas nesting sites below 30 degrees
Celsius produce males. The position of the egg in the nest also affects
sex-determination. Eggs in the center tend to hatch as females due to
the warmer conditions within the nest.[29]
Green sea turtles play an essential role within the ecosystem in
which they live. In the seagrass beds, the turtles feed on the seagrass
by trimming only the top and leaving the roots of the plant. Through
their feeding technique, the turtles help to improve the health and
growth of the seagrass beds. The healthy seagrass beds that the turtles
provide give habitat and feeding grounds for many species of fish and
crustaceans. On the nesting beaches, the green sea turtles provide key
nutrients for the ecosystem through their hatched egg shells. In their
coral reef habitat, the green sea turtles have a symbiotic interaction
with reef fish, including the yellow tang. The yellow tang fish swims
along with the turtle and feeds on the algae, barnacles, and parasites
on its shell and flippers. This species interaction provides food for
the yellow tang and provides a necessary cleaning and smoothing of the
turtle's shell. This cleaning helps the turtle swim by reducing the
amount of drag and improves their health.[66]
Importance to humans
Harvested green turtles on a wharf at Key West, Florida
Historically, the turtles' skin was tanned and used to make handbags, especially in Hawaii.[19]Ancient Chinese considered the flesh of sea turtles a culinary delicacy, including and especially C. mydas.[76] Particularly for this species, the turtle's fat, cartilage, and flesh, known as calipee, are sought as ingredients for making turtle soup, a popular 19th century American dish.[17]
In Java, Indonesia, sea turtle eggs were a popular delicacy. However, the turtle's flesh is regarded as ḥarām or "unclean" under Islamic law (Islam is Java's primary religion). In Bali, turtle meat was a prominent feature at ceremonial and religious feasts. Turtles were harvested in the remotest parts of the Indonesian archipelago.[77] Bali has been importing sea turtles since the 1950s, as its own turtle supplies became depleted.[78] The mostly Hindu Balinese do not eat the eggs, but sell them instead to local Muslims.
Commercial farms, such as the Cayman Turtle Farm in the West Indies,
once bred them for commercial sale of turtle meat, turtle oil (rendered
from the fat), turtle shell, and turtle leather made from the skin. The
farm's initial stock was in large part from "doomed" eggs removed from
nests threatened by erosion, flooding, or in chemically hostile soil.[79]
The farms held as many as 100,000 turtles at any one time. When the
international markets were closed by regulations that did not allow even
farm-bred turtle products to be exported internationally, the surviving
farm became primarily a tourist attraction, supporting 11,000 turtles.[80]
Initially started as Mariculture Ltd., then Cayman Turtle Farm Ltd and
subsequently branded Boatswain's Beach, in 2010 the farm's brandname was
changed to Cayman Turtle Farm: Island Wildlife Encounter.[81]
Sea turtles are integral to the history and culture of the Cayman Islands. When the islands were first discovered by Christopher Columbus in 1503, he named them "Las Tortugas" because of the abundance of sea turtles in the waters around the islands.[82] Many of the earliest visitors came to the Cayman Islands
to capture the turtles as a source of fresh meat during long voyages.
The Green Turtle is a national symbol displayed as part of the Coat of Arms of the Cayman Islands, which also forms part of the national flag of the Cayman Islands. The country's currency uses a turtle as the watermark in its banknotes.[83] A stylised sea turtle nicknamed "Sir Turtle" is the mascot of the national airline Cayman Airways[84] and is part of the livery of its aircraft.
A ki' pohaku (petroglyph) of a turtle (or honu) can be found on
The Big Island of Hawaii in the Pu'u Loa lava fields. The green sea
turtle (called Honu) has always held a special meaning for Hawaiians and
this petroglyph shows its importance dating to possibly when the
islands first became populated. The turtle symbolizes a navigator that
can find his way home time after time. This symbol mirrors the real life
of the green Hawaiian turtle as it will swim hundreds of miles to lay
its eggs at its own place of birth. Though there are other myths as
well, some Hawaiian legends say the honu were the first to guide the
Polynesians to the Hawaiian Islands. Hawaiians revere the turtle and the
legend of Kailua, a turtle who could take the form of a girl at will.
In human form, she looked after the children playing on Punalu'u beach.[85]
In recent decades,
sea turtles have moved from unrestricted exploitation to global
protection, with individual countries providing additional protection,
although serious threats remain unabated.
Threats
Human
action presents both intentional and unintentional threats to the
species' survival. Intentional threats include continued hunting, poaching and egg harvesting. More dangerous are unintentional threats, including boat strikes, fishermen's nets that lack turtle excluder devices, pollution and habitat destruction. Chemical pollution may create tumors;[86]effluent from harbors near nesting sites may create disturbances; and light pollution
may disorient hatchlings. Habitat loss usually occurs due to human
development of nesting areas. Beach-front construction, land
"reclamation" and increased tourism are examples of such development.[5][7] An infectious tumor-causing disease, fibropapillomatosis,
is also a problem in some populations. The disease kills a sizeable
fraction of those it infects, though some individuals seem to resist the
disease.[19][87][88] In addition, at least in the Southwestern Atlantic (Río de la Plata, Uruguay), exotic invasive species such as the rapa whelk Rapana venosa,
were reported massively bio-fouling immature green turtles, reducing
buoyancy, increasing drag, and causing severe injuries to the carapace.[89] Because of these threats, many populations are in a vulnerable state.
Pacific green turtles' foraging habitats are poorly understood and mostly unknown.[90] These foraging grounds are most likely along the coast of Baja California, Mexico and southern California,[91]
in which these turtles have a high risk of incidental capture by
coastal fisheries. The main mortality factor for these turtles is the
shrimp trawlers in Mexico, in which many of these turtles go
undocumented.[91] The only foraging area that has been identified is the San Diego Bay, but it is heavily polluted with metals and PCBs.[91]
These contaminants have a negative effect on the ocean environment, and
have been shown to cause lesions and sometimes mortality.[91] Green turtles also are threatened by entanglement and ingestion of plastic.[91] In San Diego Bay, an adult green turtle was found dead with monofilament netting tightly packed in its esophagus.[91]
In addition there are indications that global climate change is
affecting the ability of Green Turtle populations in Australia to
produce males due to their temperature-dependent sex determination and the rising temperatures in the northern Great Barrier Reef region.[92]
Green sea turtles are the most commonly traded species along
Java's south coast and are sold in the form of whole, stuffed animals or
turtle oil, locally known as "minyak bulus"[93]
Global initiatives
A confiscated musical instrument made from the shell of a green turtle, on display at Narita International Airport.
The International Union for the Conservation of Nature (IUCN) has repeatedly listed green sea turtles in its Red List under differing criteria. In 1982, they officially classified it as an endangered species.[94] The 1986,[95] 1988,[96] 1990,[97] 1994,[98] and the landmark 1996 edition of the IUCN Red List, retained the listing.[99]
In 2001, Nicholas Mrosovsky filed a delisting petition, claiming
some green turtle populations were large, stable and in some cases,
increasing. At the time, the species was listed under the strict EN
A1abd criteria. The IUCN Standards and Petitions Subcommittee ruled that
visual counts of nesting females could not be considered "direct
observation" and thus downgraded the species' status to EN
A1bd—retaining the turtle's endangered status.[100]
In 2004, the IUCN reclassified C. mydas as endangered under the EN A2bd criteria, which essentially states the wild populations face a high risk of extinction
because of several factors. These factors include a probable population
reduction of more than 50% over the past decade as estimated from
abundance indices and by projecting exploitation levels.[101]
On 3 May 2007, C. mydas was listed on Appendix I of the Convention on International Trade in Endangered Species (CITES) as a member of the family Cheloniidae.[102]
The species was originally listed on Appendix II in 1975. The entire
family was moved to Appendix I in 1977, with the exception of the Australian population of C. mydas.
In 1981, the Australian population joined the rest. It is therefore
illegal to import, export, kill, capture or harass green turtles.[103]
The Mediterranean population is listed as critically endangered.[5][17]
The eastern Pacific, Hawaiian and Southern California subpopulations
are designated threatened. Specific Mexican subpopulations are listed as
endangered. The Florida population is listed as endangered. The World Wide Fund for Nature has labeled populations in Pakistan as "rare and declining".[46]
In the State of Hawaii, specifically on the Island of Hawaii
(Hawaii County), state representative Faye Hanohano, a Native Hawaiian
rights activist, pressed for a measure to delist C. mydas from protected
status so that Native Hawaiians could legally harvest the turtles and
possibly their eggs as well. The bill, HCR14, was largely overlooked by
the media since at that point it was only a local issue. While the bill
was passed in the House, the Senate's Committee on Energy and
Environment refused to hear it, which meant that the bill did not go on
to be heard by the Senate.[104]
Country-specific initiatives
At the Osaka Aquarium, profile photo of turtle resting on bottom
In addition to management by global entities such as the IUCN and
CITES, specific countries around the world have undertaken conservation
efforts.
Bali has traditional uses that were considered sustainable, but
have been questioned considering greater demand from the larger and
wealthier human population. The harvest was the most intensive in the
world.[77]
In 1999, Indonesia restricted turtle trade and consumption because of
the decreasing population and threat of a tourist boycott. It rejected a
request made by Bali Governor I Made Mangku Pastika in November 2009 to set a quota of 1,000 turtles to be killed in Hindu religious ceremonies. While conservationists respect the need for turtles in rituals, they wanted a smaller quota.[105] Ecotourism is one initiative in Sabah, Malaysia. The island of Pulau Selingan is home to a turtle hatchery.
Staff people place some of the eggs laid each night in a hatchery to
protect them from predators. Incubation takes around sixty days. When
the eggs hatch, tourists assist in the release of the baby turtles into the sea.[106]
All populations are listed as "Threatened".[107][108] The Hawaiian subpopulation has made a remarkable comeback and is now one focus of ecotourism and has become something of a state mascot. Students of Hawaii Preparatory Academy on the Big Island have tagged thousands of specimens since the early 1990s.[19]
In the United Kingdom the species is protected by a Biodiversity Action Plan, due to excess harvesting and marine pollution.[109] The Pakistani-branch of the World Wide Fund for Nature has been initiating projects for secure turtle hatching since the 1980s. However, the population has continued to decline.[7]
In the Atlantic, conservation initiatives have centered around Caribbean nesting sites. The Tortuguero nesting beaches in Costa Rica have been the subject of egg-collection limits since the 1950s. The Tortuguero National Park was formally established in 1976, in part, to protect that region's nesting grounds.[31] On Ascension Island, which contains some of the most important nesting beaches, an active conservation program has been implemented.[110] Karumbé has been monitoring foraging and developmental areas of juvenile green turtles in Uruguay since 1999.[111] Cayman Turtle Farm
located in Grand Cayman in the northwest Caribbean Sea is the first
farm to have achieved the second generation of Green Sea turtles bred,
laid, hatched, and raised in captivity.[112] Since its beginning in 1968, the farm has released over 31,000 turtles into the wild,[82] and each year more captive-bred turtles are released into the Caribbean Sea from beaches around the island of Grand Cayman.[113]
Captive-bred turtles released from the farm as hatchlings or yearlings
with "living tags," have now begun to return to nest on Grand Cayman as
adults.[114][115] On February 19, 2012 the farm released the first 2nd-generation captive-bred Green Sea turtle equipped with a Position Tracking Transponder – PTT (also known as a satellite tag).[116]
In addition, the farm provides turtle meat products to the local
population for whom turtle has been part of the traditional cuisine for
centuries. In so doing, the farm curtails the incentive to take turtles
from the wild,[117]
which over the years in addition to the Cayman Turtle Farm's release of
captive-bred turtles has enabled an increase in the number of turtles
sighted in the waters around the island of Grand Cayman and nesting on its beaches.[118]
In the Pacific, green sea turtles nest on the motu (islets) in the Funafuti Conservation Area, a marine conservation area covering 33 square kilometers (12.74 square miles) of reef, lagoon and motu on the western side of Funafuti atoll in Tuvalu.[119]
Genetics
The genome of Chelonia mydas was sequenced in 2013 to examine the development and evolution of the turtle body plan.[120]
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