WhyReef - Lifestyle
A large marine turtle, reaching up to 1,200 mm in carapace length; largest Egyptian specimen is 1,190 mm. Carapace depressed, rounded, smooth; scutes juxtaposed; posterior edge without indentations; 4 coastal scutes; first marginal scute in contact with first vertebral scute. Head relatively small with a single pair of prefrontals. C. mydas differs from all other marine turtles in possessing serrations on the lower jaw, which facilitate grazing on marine grasses. Forelimbs and hind limbs have a single claw each. Males smaller, with longer tails and larger claws. Color of carapace light brown with dark streaks radiating out from a point at the posterior margin of each scute. Dorsal sides of limbs and head brown, each scale edged yellowish. All ventral sides whitish yellow.
WhyReef - Fun Facts
Green turtles are found in tropical and portions of subtropical oceans worldwide. They are found in the Atlantic Ocean from the eastern United States along coastal South America to South Africa. They are found throughout the Caribbean Sea and portion of the Mediterranean. They are also found throughout the warm waters of the Indian and Pacific Oceans.
Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )
- Ernst, C., R. Barbour, J. Lovich. 1994. TURTLES of the United States and Canada. Washington and London: Smithsonian Institution.
occurs (regularly, as a native taxon) in multiple nations
Global Range: Distribution is pantropical in the Atlantic, Pacific, and Indian oceans. In some areas this species occurs in higher temperate latitudes due to drifting in ocean currents in conjunction with above-normal sea temperatures or as a normal life history event; young turtles regularly range as far north as New England. Major nesting activity occurs on Ascension Island, Aves Island, in Costa Rica (24,000 females nests each year at Tortuguero), and in Surinam (CSTC 1990). See Hirth (1980) for a map of major nesting beaches.
In U.S. Atlantic waters, green sea turtles occur around the U.S. Virgin Islands and Puerto Rico, where small numbers nest (islas Mona, Vieques, and Culebra, and St. Thomas, St. John, St. Croix), and a juvenile population exists in eastern portion of Puerto Rican Bank (Collazo et al. 1992), and from Texas to Massachusetts. Relatively small numbers nest in Florida, particularly in Brevard, Indian River, St. Lucie, Martin, Palm Beach, and Broward counties (CSTC 1990), mostly from Volusia County to Dade County (Ehrhart and Witherington 1992), with rare recent nesting on the Gulf Coast in Santa Rosa County (Ehrhart and Witherington 1992); important feeding areas in Florida include the Indian River, Florida Bay, Homossassa Bay, Crystal River, and Cedar Key (CSTC 1990). Rarely nests in Georgia, North Carolina, and Texas.
Distribution in Egypt
Known from Egyptian waters in both the Mediterranean and Red Sea. The only reliable evidence of nesting on the Mediterranean shores is a nest with eggs found near Zaranik, North Sinai, in the summer of 1998 (Clarke et al. 2000). A dead juvenile (carapace length 85 mm) found at Baltim could have originated from elsewhere. Dead individuals are frequently encountered throughout the Egyptian Mediterranean shoreline. In the Red Sea the species has been recorded from both the Gulfs of Suez and Aqaba, and has been reported to have nested at Ras Sharatib, south of Abu Rudeis (where some 80 females were estimated to nest),Tiran Island, Qulan Islands, Wadi El Gemal Island, Ras Banas, and Zabargad Island. Eggs and embryos from Giftun El Kebir Island referred to this species by Marx (1968), were re-identified as Eretmochelys imbricata by (Frazier and Salas 1984). The species nests sporadically along the mainland shores of the Red Sea south of Marsa Alam, where almost a hundred nests have been found between Ras Baghdadi and Marsa um El Abbas.
Circum-global, largely within the 20°c oceanic isotherms.
Distribution: Atlantic, Pacific, and Indian oceans, chiefly in the tropics. Europe: Adriatic Sea (Croatia ?), Italy (occasional occurence [E. RAZZETTI, pers. comm.]) Turkey [Basoglu 1973], France, Portugal Indian Ocean: Madagascar, Comoro Islands (Grande Comore, Mohélim Anjouan, Mayotte), Chagos Archipelago Pacific: as far north as Alaska and in the Atlantic Ocean: as far north as Great Britain, Gambia Australia (New South Wales?, North Territory, Queensland, West Australia), Nauru? Americas: Canada (British Columbia), USA SE Mexico (Yucatan, Baja California), Belize, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, Panama, Colombia [Castro,F. (pers. comm.)], Argentina Asia: Korea, Andaman Islands, Nicobar Islands mydas: Atlantic Ocean agassizi: eastern Pacific Ocean, Galapagos Islands. Hawaii (USA) and Papua New Guinea;
Type locality: "l'en bouchure du Nagualated, dans le Pacifique (Guatémala)" [Embayment of Río Nagualate, Guatemala]. japonica: Indian and Western Pacific Ocean acording to the 1994 IUCN Red List of Threatened Animals: EC/NE/NW/SE/SW/WC Atlantic, Indian Ocean eastern, Indian Ocean western, Mediterranean and Black Sea, EC/NW/SW/WC Pacific, American Samoa, Angola, Anguilla, Antigua and Barbuda, Australia, Bahamas, Bangladesh, Belize, Benin, Brazil, British Indian Ocean Territory, Cambodia, Cameroon, Cape Verde, Chile, China, Colombia, Comoros, Congo, Cook Islands, Costa Rica, Cote d'Ivoire, Cuba, Cyprus, Djibouti, Dominica, Dominican Republic, Ecuador, Egypt, El Salvador, Equatorial Guinea, Eritrea, Federated States of Micronesia, Fiji, French Guiana, French Polynesia, Gabon, Ghana, Grenada, Guadeloupe, Guam, Guatemala, Guinea, Guinea-Bissau, Guyana, Haiti, Honduras, India, Indonesia, Iran, Israel, Jamaica, Japan, Kenya, Kiribati, Kuwait, Liberia, Madagascar, Malaysia, Maldives, Marshall Islands, Martinique, Mauritania, Mauritius, Mayotte, Mexico, Montserrat, Mozambique, Myanmar (= Burma), Netherlands Antilles, New Caledonia, Nicaragua, Nigeria, Niue, Northern Marianas, Oman, Pakistan, Palau, Panama, Papua New Guinea, Peru, Philippines, Puerto Rico, Qatar, Reunion, Sao Tome & Principe, Saudi Arabia, Senegal, Seychelles, Sierra Leone, Solomon Islands, Somalia, Sri Lanka, St Helena, St Kitts and Nevis, St Lucia, St Vincent, Sudan, Suriname, Taiwan, Tanzania, Thailand, Togo, Tokelau, Tonga, Trinidad and Tobago, Turkey, Turks and Caicos Islands, Tuvalu, US Minor Pacific Islands, USA (Washington; Western Atlantic: Maine, New Hampshire, Massachusetts, Connecticut, New Jersey, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, Florida), United Arab Emirates, Vanuatu, Venezuela, Viet Nam, Virgin Islands (British), Virgin Islands (US), Western Sahara, Western Samoa, Yemen, Zaire
Type locality: “insulas Pelagi: insularum Adscensionis" [The Pelagie Islands and Ascencion Island]; restricted to Ascension Is., see Mertens, R. & Müller, L. (1928)
Circumglobal in tropical and temperate seas and oceans
They are called green turtles because of the color of the flesh. Chelonia mydas are one of the largest turtles ranging from 71 to 153 centimeters. They can weigh up to 205 kilograms. They have limbs that are paddle-like, which are used to swim. Their heads seem small compared to their body size. Males are larger than females and the tail is longer, extending well beyond the shell. The carapace can be olive to brown, or sometimes black, depending on the geographic location of the species. Green turtles cannot pull their heads inside of their shells. There are two sub-species which include Chelonia mydas mydas and Chelonia mydas agassizii. The common name for Chelonia mydas mydas is the Atlantic green turtle, which lives in the Atlantic ocean and has been see off the shores of Europe and North America. Chelonia mydas agassizii, or Eastern Pacific green turtle and sometimes black sea turtle because of its dark colored carapace, has been see off the coasts of Alaska, through California, and to Chile. Some features that distinguish C. m. agassizii from C. m. mydas are that the shell of C. m. agassizii is higher, the shell is narrower, the marginals are more constricted over the hind legs, and the postcentral lamina are longer relative to their width (Ernst 1994). The Pacific and Atlantic populations have been separated for millions of years.
Range mass: 0 to 0 kg.
Average mass: 205 kg.
Other Physical Features: ectothermic ; bilateral symmetry
Length: 122 cm
Weight: 200000 grams
Differs from the hawksbill in having one rather than two pairs of prefrontals and carapace scutes that do not overlap. Differs from the loggerhead and the ridleys in having the first costal not in contact with the nuchal.
Catalog Number: USNM 257183
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: Sex unknown;
Year Collected: 1840
Locality: No Further Locality Data, Fiji Islands, Republic of Fiji, Pacific Ocean
- Holotype: Girard, C. & Baird, S. F. 1858. Herpetology. Prepared under the superintendence of S.F. Baird. United States Exploring Expedition during the years 1838, 1839, 1840, 1841, 1842, under the command of Charles Wilkes, U.S.N. 20: 456, plate 31, figures 1-4.
Green sea turtles live in tropical waters all over the world. The only time they emerge from the water is when they are nesting. The only time males are not at sea is when they were first born. C. m. agassizii are sometimes found with seals and albatrosses basking on the beach (Pritchard 1967). When it is time to mate they migrate from several hundred to over a thousand miles across the ocean to where they hatched. Female green turtles use the same beaches to nest as their mothers and grandmothers.
Aquatic Biomes: coastal
Habitat and Ecology
Comments: Feeding occurs in shallow, low-energy waters with abundant submerged vegetation, and also in convergence zones in the open ocean (NMFS and USFWS 2007). Migrations may traverse open seas. Adults are tropical in distribution, whereas juveniles range into temperate waters (e.g., see Morreale and Standora, no date). Hatchlings often float in masses of marine macroalgae (e.g., Sargassum) in convergence zones. Coral reefs and rocky outcrops near feeding pastures often are used as resting areas. Inactive individuals may rest on the bottom in winter in the northern Gulf of California. Basking on beaches occurs in some areas (e.g., Hawaii).
Nesting occurs on beaches, usually on islands but also on the mainland. Sand may be coarse to fine, has little organic content; physical characteristics vary greatly in different regions. Most nesting occurs on high energy beaches with deep sand. At least in some regions, individuals generally nest at same beach (apparently the natal beach, Meylan et al. 1990, Allard et al. 1994) in successive nestings, though individuals sometimes change to a different nesting beach within a single nesting season (has switched to beach up to several hundred kilometers away) (see Eckert et al. 1989). Beach development and illumination often make beaches unsuitable for successful nesting.
Water temperature and chemistry ranges based on 4162 samples.
Depth range (m): 0 - 3250
Temperature range (°C): 2.498 - 29.497
Nitrate (umol/L): 0.015 - 26.152
Salinity (PPS): 22.907 - 37.161
Oxygen (ml/l): 2.556 - 6.419
Phosphate (umol/l): 0.033 - 1.673
Silicate (umol/l): 0.769 - 27.080
Depth range (m): 0 - 3250
Temperature range (°C): 2.498 - 29.497
Nitrate (umol/L): 0.015 - 26.152
Salinity (PPS): 22.907 - 37.161
Oxygen (ml/l): 2.556 - 6.419
Phosphate (umol/l): 0.033 - 1.673
Silicate (umol/l): 0.769 - 27.080
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
Warm marine waters. Frequently segrass beds, which by nature are in fairly shallow, sandy, inshore habitats. Often near wadi deltas (In the Red Sea), where the fringing reef is broken and suitable sandy substrate in shallow waters is available. Generally, the availability of suitable seagrass beds is limited in the Egyption Red Sea, and apparently so in the Mediterranean as well, given the small number of records in Egyption territory. Nesting in the Red Sea has been recorded in the months of June and July. Sexual maturity reached between 12 and 50 years, depending on location and nutritional history.
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Adults migrate up to about 3,000 km between nesting beaches and feeding areas (e.g., between Ascension Island and the South American coast). See Balazs (1982) for a map of documented migrations between the major nesting area in Hawaii (French Frigate Shoals) and foraging areas elsewhere in the Hawaiian Islands. See Morreale and Standora (no date) for information on movements along the east coast of the United States.
Seminoff et al. (2002) documented migration between nesting area on the coast of Michoacan (Mexico; January 2000) and a feeding ground on the Sonoran coast of the Gulf of California (Mexico; September 2000).
See Mortimer and Porter (1989) for information on internesting movements at Ascension Island.
Neonates migrate far from natal beaches to foraging areas and return to natal beach to breed/nest up to 40+ years later.
Green turtles are mostly herbivorous. They spend most of their time feeding on algae in the sea and the grass that grow in shallow waters. As juveniles, they eat plants and other organisms such as: jellyfish, crabs, sponges, snails, and worms. As adults, they are strictly herbivorous (Ernst 1994).
Comments: Diet includes"seagrass," macroalgae and other marine vegetation, and various invertebrates such as mollusks, sponges, crustaceans, and jellyfish.
WhyReef - Menu
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 81 to >300
Comments: This species is represented by a large number of nesting occurrences (more than 150 major and minor nesting areas in more than 80 nations worldwide).
100,000 to >1,000,000 individuals
Comments: At 46 nesting areas worldwide, representing most but not all of the global population, the latest data indicate that approximately 109,000-151,000 females nest each year (NMFS and USFWS 2007). Assuming an average remigration interval of 3 years, this indicates an adult female population size of roughly 327,000-453,000. Assuming an equal number of adult males yields 654,000-906,000 adults for this subset of the global population.
Eggs and hatchlings typically incur high mortality from various terrestrial and aquatic predators, including both vertebrates and invertebrates (e.g., crabs). Many nests are destroyed by tidal inundation and erosion. In Costa Rica, annual survivorship of adult females was 0.61; in various areas egg survivorship was 0.40-0.86 (see Iverson  for a compilation of survivorship data). Humans are the most important predators on adults. See Witherington and Ehrhart (1989) for information on cold stunning in Florida.
Life History and Behavior
Herbivorous, feeding largely on marine grasses and algae when adult; young carnivorous, pelagic.
Comments: Turtles in the northern Gulf of California overwinter in a dormant condition. Nesting occurs generally at night. In Hawaii, green sea turtles may bask on beaches mid-morning to mid-afternoon, especially after a period of rainy weather (Whittow and Balazs 1982).
Status: captivity: 75 years.
Lifespan, longevity, and ageing
Males and females mature between 10 and 24 years. The breeding season depends on the latitude. Internal fertilization takes place when the male and female copulate. This is the only time there is vocalization. Like many species, there is male competition. One male may try to bite another male who is copulating with a female. Mating occurs underwater or on the surface about one kilometer from the shore. Sometimes the female will retain enough sperm to nest several times that year. Nesting occurs every three to six years. When the female is ready to lay her eggs, she leaves the water, crawls onto the sand and starts digging for hour and hours until her flippers will not allow her to dig deeper. She then lays 100 to 200 eggs. This group of eggs is called a clutch. She covers them with sand to protect them from the sun, heat, and predators. Pacific green turtles lay fewer eggs than Atlantic green turtles. The gestation period is 40 to 72 days, depending on the location.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)
Average gestation period: 59 days.
Average number of offspring: 150.
Average age at sexual or reproductive maturity (male)
Sex: male: 3650 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 3650 days.
Individual reproductive females lay 1-8 clutches per season, averaging about 90-140 eggs, at about two-week intervals usually every 2-5 years. Nesting occurs March-October in Caribbean-Gulf of Mexico region, with peak in May-June; nests in Florida May-September (Ehrhart and Witherington 1992). Nesting encompasses April-October, with a peak between mid-June and early August, in Hawaii (Niethammer et al. 1997). Eggs hatch usually in 1.5-3 months. Hatchlings emerged between early July and late December (peak mid-August to early October) in Hawaii (Niethammer et al. 1997). Females mature probably at an average age of 27 years in Florida, but growth rates and hence age of maturity may vary greatly (from perhaps fewer than 20 years to 40+ years) throughout the range (slower growth in Australia, Hawaii, and Galapagos than in Florida and West Indies region).
Evolution and Systematics
The shell of some sea turtles allows for different levels of buoyancy for juveniles and adults by changing shape.
"Sea turtles sometimes swim on the surface; Jeanette Wyneken tells me that the flared, V-shaped bottom is characteristic of buoyant baby sea turtles, which are obligatory surface swimmers. With maturity and the shift to submerged swimming, the hull shape changes to one more characteristic of submarines." (Vogel 2003:116)
Learn more about this functional adaptation.
- Steven Vogel. 2003. Comparative Biomechanics: Life's Physical World. Princeton: Princeton University Press. 580 p.
Molecular Biology and Genetics
Barcode data: Chelonia mydas
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
-- end --
Download FASTA File
Statistics of barcoding coverage: Chelonia mydas
Public Records: 15
Specimens with Barcodes: 38
Species With Barcodes: 1
Green turtles are an endangered species because they have so many predators--including humans. Even though a female can lay over 200 eggs in on clutch, some will not hatch, and many will be eaten. Even if they do hatch, they get eaten on their way to the water, and in the water. So only a few will survive if any. If the they do survive, they can live to be over 100 years old. Sometimes eggs are laid on a public beach. When this happens conservationists come and move them to a safer place. In the United States, green turtles are protected by the Endangered Species Act.
US Federal List: endangered
CITES: appendix i
IUCN Red List of Threatened Species: endangered
IUCN Red List Assessment
Red List Category
Red List Criteria
Assessment Procedure: In accord with the IUCN criterion that Red List Assessments focus on the number of mature individuals (IUCN 2001a), this assessment measures changes in the annual number of nesting females. Because reliable data are not available for all subpopulations, the present report focuses on 32 Index Sites (Figure 1, Table 1; see link to additional information below). These Index Sites include all of the known major nesting areas as well as many of the lesser nesting areas for which quantitative data are available. Despite considerable overlap at some foraging areas, each is presumed to be genetically distinct (Bowen et al. 1992, Bowen 1995) except for the Turtle Islands of Malaysia (Sabah) and Philippines (Moritz et al. 1991). These two Index Sites are, however, treated independently because of the different management practices exercised by the two governments and the resultant differences in subpopulation trends. Selection of the 32 Index Sites was based on two primary assumptions: (1) they represent the overall regional subpopulation trends and (2) the number of individuals among Index Sites in each region is proportional to the actual population size in that region. Any regional inconsistencies in this proportion may result in a biased global population estimate.
It should be noted that a major caveat of using the number of nesting females to assess population trends is that this data type provides information for the proportion of the adult females that nest in any given year, not the total adult female population. However, when monitored over many years, this index can be reliable for assessing long-term population trends (Meylan 1982, Limpus 1996). In the case of green turtles, which display high inter-annual variability in magnitude of nesting (Limpus and Nichols 1987, Broderick et al. 2001a), using short-term or single-season data sets could misrepresent the actual mean number of nesters over a longer timeframe. To alleviate this potential source of error, we used multiple-year data sets whenever available. However, when single-season datasets represented the only quantitative information for a given time period, these data were used as long as they were in accord with qualitative information from other references.
Because data on annual number of nesting females are not always available, we also used data on number of nests per season, annual hatchling production, annual egg production and annual egg harvest. When these proxies were used, we converted units to number of nesting females based on a constant figure of 100 eggs/nest and three nests/season/female, unless otherwise noted. These conversions were based on the assumptions that (1) the mean number of eggs/nest and nests/female/season differ insignificantly through time, and (2) efforts to monitor nesting female activity and egg production are consistent through time. When using egg harvest data, we also assumed that harvest effort was consistent during all years for which data are available and 100% of the eggs were harvested in any given year. We believe these assumptions are accurate, but their absolute validation is very difficult. Qualitative information does, however, suggest that they are reasonable assumptions. For example, in the case of historic egg harvest, the same group of people usually harvested the eggs at a particular nesting beach each year, and they typically took every egg they could find (e.g., Parsons 1962, Pelzer 1972).
In the present assessment, population abundance estimates are based on raw data, linear extrapolation functions, and exponential extrapolation functions. In most subpopulations, more than one trajectory was exhibited over the 3–generation interval; changes in subpopulation size are thus often based on a combination of raw data and extrapolations. If no change is believed to have occurred outside the time interval for which published abundance data are available, the raw data were used to determine the change in population size. However, when it is believed that change in subpopulation abundance occurred outside the interval for which raw data were available, extrapolations we performed to determine the overall change. Linear extrapolations were used when it was believed that the same amount of change occurred each year, irrespective of total subpopulation size. Exponential extrapolations were used when it was believed that change was proportional to the subpopulation size. In cases where there is a lack of information on the specific rate of change, both linear and exponential extrapolations were used to derive population estimates. However, if extrapolations resulted in obviously false estimates, their results were discarded (see Table 5; see link to additional information below).
Generation Length. Generation length is based on the age to maturity plus one half the reproductive longevity (Pianka 1974). Although there appears to be considerable variation in generation length among sea turtle species, it is apparent that all are relatively slow maturing and long-lived (Chaloupka and Musick 1997). Green turtles exhibit particularly slow growth rates, and age to maturity for the species appears to be the longest of any sea turtle (Hirth 1997). As a result, this assessment uses the most appropriate age-at-maturity estimates for each index site. At Index Sites for which there are local age-to-maturity data, those data are used to establish generation length. When data are lacking, as they are for a majority of subpopulations, information from the closest subpopulation for which data are available are used to generate age-at-maturity estimates (Table 2; see link to additional information below).
Estimates of reproductive longevity range from 17 y to 23 y (Carr et al. 1978, Fitzsimmons et al. 1995). Data from the apparently pristine Green Turtle stock at Heron Island in Australia’s southern Great Barrier Reef show a mean reproductive life of 19 y (Chaloupka et al. 2004). Because Heron Island is the only undisturbed stock for which reproductive longevity data are available (M. Chaloupka, pers. comm.), this datum is used for all Index Sites (Table 3; follow link to additional information below). Thus, based on the range of ages-at-sexual-maturity (26 yrs to 40 yrs) and reproductive longevity from the undisturbed Australian stock (19 yr), the generation lengths used for this assessment range from 35.5 yrs to 49.5 yrs (Table 3; see link to additional information below).
Uncertainties in assessment process: As with any assessment based on historic data or small datasets, there is a great deal of uncertainty relating to the final results of this report. The sources of uncertainty are rooted in both the procedure itself as well as in the stochastic nature green of turtle biology. Both sources of uncertainty are ultimately related to a lack of information, which can be a common issue when dealing with an animal as long-lived as a Green Turtle.
First and foremost is the uncertainty related to the assumptions invoked for this assessment. For example, if, contrary to our assumption, efforts to monitor nesting female activity and egg production were not consistent through time, then our results may be biased. Similarly, our estimates may be inaccurate if harvest effort or the relative amount of eggs harvested was not consistent through time. In addition, the use of extrapolations may have resulted in erroneous estimates of population change. The potential for this increased when extrapolations were made over long time intervals, when they were based on short-term data sets, or if the start and/or end points of extrapolations were erroneous.
Uncertainty may also be tied to Green Turtle biology. In particular, the substantial variability in the proportion of a population that nests in any given year may result in inaccurate comparisons between past and present data sets. For example, if the proportion of a subpopulation’s adult female cohort nesting each year oscillates over decadal or longer time frames, then it is conceivable that our estimates of annual change in nesting numbers do not correspond to actual changes in the entire subpopulation. Moreover, if our conversion values for eggs/nest and nests/female/season are not accurate for the specific subpopulation being addressed, inaccuracies may result. Lastly, with respect to the migratory behaviour of green turtles, it is expected that each of the Index Sites included in this assessment represent a distinct subpopulation. Indeed, current genetic data support this claim, however, in the absence of complete data for all rookeries, it is possible that turtles moving back and forth between nesting areas in close proximity could have gone undetected. It is thus conceivable that a female could be counted twice. This would, of course, only be a problem when subpopulation size is based on an actual count of individual turtles visiting the beach. Although unlikely, it amounts to an additional source of uncertainty in this assessment.
Population trends. Based on the actual and extrapolated changes in subpopulation size at the 32 Index Sites, it is apparent that the mean annual number of nesting females has declined by 48% to 67% over the last three generations (Table 5; see link to additional information below). In addition, it is apparent that the degree of population change is not consistent among all Index Sites or among all regions (Tables 5 and 6; see link to additional information below). Because many of the threats that have led to these declines are not reversible and have not yet ceased, it is evident that green turtles face a measurable risk of extinction. Based on this assessment, it is apparent that green turtles qualify for Endangered status under Criteria A2bd.
The key supporting documentation is presented in the tables (see link to additional information below), and the full assessment is also available from the Marine Turtle Specialist Group web site.
- 1994Endangered(Groombridge 1994)
- 1990Endangered(IUCN 1990)
- 1988Endangered(IUCN Conservation Monitoring Centre 1988)
- 1986Endangered(IUCN Conservation Monitoring Centre 1986)
National NatureServe Conservation Status
Rounded National Status Rank: N3B,N3N : N3B: Vulnerable - Breeding, N3N: Vulnerable - Nonbreeding
NatureServe Conservation Status
Rounded Global Status Rank: G3 - Vulnerable
Reasons: Distributed worldwide in warm oceans; exploited heavily for meat and eggs and as a component of other products; nesting and feeding habitats are being destroyed or degraded by pollution and development; large decline over the long term, more recently possibly stable or increasing in some areas.
Environmental Specificity: Very narrow to narrow.
Other Considerations: Individuals migrate up to 2,000 km between nesting beaches and feeding areas. Hence local populations may experience negative impacts from distant threats.
Date Listed: 07/28/1978
Lead Region: Southeast Region (Region 4)
Where Listed: FL, Mexico nesting pops.
Date Listed: 07/28/1978
Lead Region: Southeast Region (Region 4)
Where Listed: except where endangered
Population location: Breeding colony populations in FL and on Pacific coast of Mexico
Listing status: E
Population location: Wherever found except where listed as endangered
Listing status: T
For most current information and documents related to the conservation status and management of Chelonia mydas , see its USFWS Species Profile
Status in Egypt
Uncommon, localized and declining. Facing a variety of threats in Egypt, most importantly as a by-catch of commercial fishing vessels. The species along with other marine turtles are consumed in some Egyptian coastal cities. Loss of nesting beaches is also a problem particularly in the Red Sea.
Global Short Term Trend: Decline of 30-70%
Comments: The Marine Turtle Specialist Group of the World Conservation Union analyzed population trends at 32 index nesting sites around the world and found a 48-65% decline in the number of mature females nesting annually over the past 100-150 years (this represents 3 generations).
In a couple dozen areas for which recent data are available, most populations were stable or increasing (19 or 23) (NMFS and USFWS 2007). These trends should be interpreted with caution because events that affected juvenile recruitment up to several decades ago may continue to affect nesting populations.
Global Long Term Trend: Decline of 30-70%
Comments: Number of subpopulations and especially population size undoubtedly have undergone a major decline over the long term.
Degree of Threat: Very high - high
Comments: Major threats, which vary throughout the range, include degradation of nesting habitat, including beach lighting, which may disorient hatchlings and/or nesting females; human predation on nesting females and turtles in foraging areas (e.g., for meat and use in commericial products); collection of eggs for human consumption; predation on eggs and hatchlings by raccoons, dogs, etc.; mortality in fishing gear and other entangling debris; collisions with power boats; contact with chemical pollutants; and epidemic outbreaks of fibropapilloma or "tumor" infections (Mitchell 1991, Ehrhart and Witherington 1992, Tuato`o-Bartley et al. 1993, Losey et al. 1994, Barrett 1996, NMFS and USFWS 2007). In the north, juveniles experience periodic mortality due to cold-stunning associated with rapid temperature declines in fall. See USFWS (1998) and NMFS and USFWS (2007) for further information on certain threats, including beach erosion, beach armoring, beach nourishment, artificial lighting, beach cleaning, increased human presence, recreational beach equipment, exotic dune and beach vegetation, nest loss to abiotic factors, predation, poaching, and disease.
WhyReef - Threats
As a result of these designations and agreements, many of the intentional impacts directed at sea turtles have been lessened: harvest of eggs and adults has been slowed at several nesting areas through nesting beach conservation efforts and an increasing number of community-based initiatives are in place to slow the take of turtles in foraging areas. In regard to incidental take, the implementation of Turtle Excluder Devices has proved to be beneficial in some areas, primarily in the United States and South and Central America (National Research Council 1990). However, despite these advances, human impacts continue throughout the world. The lack of effective monitoring in pelagic and near-shore fisheries operations still allows substantial direct and indirect mortality, and the uncontrolled development of coastal and marine habitats threatens to destroy the supporting ecosystems of long-lived green turtles.
Restoration Potential: Pattern of nesting on natal beach may inhibit natural recolonization of breeding sites of decimated populations.
Preserve Selection and Design Considerations: Local foraging populations may consist of individuals from widely separated nesting populations. For example, mtDNA data indicate that a foraging population of juveniles from Hutchinson Island, Florida, consisted of individuals from Costa Rica, United States and Mexico, and Aves Island (Venezuela and Surinam; another population of juveniles from the Bahamas represented Costa Rica, United States and Mexico, Aves Island and Suriname, and Ascension Island and Guinea Bissau (Bass and Witzell 2000). Thus the success of preserves for foraging juveniles may depend on cooperative international management (Bass and Witzell 2000).
Management Requirements: Frazer (1992) emphasized the primary need for clean and productive marine and coastal environments; installation of turtle excluder devices in shrimp trawl nets and use of low pressure sodium lighting on beaches were suggested as appropriate sea turtle conservation technologies, whereas headstarting, captive breeding, and hatcheries were regarded as ineffective at best. "Head-starting" and broad-scale nest translocation remain unproven as effective management measures (Ehrhart and Witherington 1992). See Bjorndal (1982) for several papers containing management and research recommendations and discussion of conservation issues.
See NMFS (Federal Register, 19 December 1996, pp. 66933-66947) for recent amendments to regulations pertaining to the use of turtle excluder devices along the Gulf and Atlantic coasts of the southeastern U.S. See NMFS (1993) for recent shrimp trawling regulations for an area off the coast of North Carolina (allow tow-time limits as an interim alternative to the use of turtle excluder devices).
If beach lighting cannot be eliminated, low pressure sodium vapor lights may be the least disruptive to nesting turtles (Witherington 1992).
A recovery plan is available; see Marine Turtle Recovery Team (1984). See also recovery plans for U.S. Pacific and east Pacific populations (NMFS 1998) .
[Move to GPROTNEED: Ehrhart and Witherington (1992) emphasized the need to protect nesting areas in southern Brevard and northern Indian River counties in southeastern Florida.]
Biological Research Needs: Better information is needed on demography, migrations, and developmental requirements.
Needs: Foraging, developmental, and nesting habitat need protection from from any type of human activity. Purchase of turtle products should be discouraged.
See "Recovery plan for U.S. Pacific populations of the green turtle (Chelonia mydas)" and "Recovery plan for U.S. Pacific populations of the east Pacific green turtle (Chelonia mydas)."
Relevance to Humans and Ecosystems
According to "The Official World Wildlife Fund Guide to Endangered Species of North America," in some areas of the world such as the Caribbean, Mexico, and South America, green sea turtles are an important source of food for humans. They are captured and their meat is used for turtle soup (Behler, 1998).
Comments: Adults and eggs are harvested for human consumption in many areas, also for skins and oil for the leather and cosmetics trade. See Mack et al. (1982) for information on commercial exploitation. See Luxmoore and Canin (1985) for information on international trade in shell in the late 1970s and early 1980s.
Galápagos green turtle
The Galápagos green turtle (Chelonia agassizii) used to be classified as a subspecies of the green sea turtle (Chelonia mydas) but was changed for a few reasons. One, caudal dimorphism (vertebrae of the same species changing), means that Chelonia agassizii (or "Chelonia agassizi") has a more domed shell. Another is the colour of the shell – Galápagos green turtles have a darker shell colour. It is endemic to the tropical and subtropical waters of the Pacific Ocean. They are often categorized as one population of the east Pacific green turtle. This title is shared with the other green sea turtle nesting populations inhabiting the Pacific Ocean. More specifically they are referred to as the black sea turtle due to their unique dark pigmentation. The Galápagos green turtle is the only population of green sea turtle to nest on the beaches of the Galápagos Islands and this fact is the derivative of their name.
There have been various debates over the binomial nomenclature of this population due to the distinct morphological characteristics that set them apart from other populations of green sea turtle. It has been difficult for researchers to obtain valid information on the lifestyles of the Galápagos green turtle due to their continuous migrations and submergence in the ocean; most information has been obtained through tagging experimentations. The Galápagos green turtle, along with all other population of green sea turtle, is listed as endangered on the IUCN Red List of threatened species. All populations are still suffering reductions in numbers despite the many conservation efforts being practiced.
The mature adult Galápagos green turtle is much smaller than those of other Green sea turtle populations; this may be why they are more genetically isolated than other populations. The carapace is dark in color, usually black to dark olive-brown, is oval in shape and tapers toward the tail. The carapace has a distinctive formation that is more sloped or domed than individuals of other populations. There are five vertebral scutes all alike in size with a hexagonal shape and flat edges. The lateral scutes are similar in size but only four run along each side. The carapace is tougher than the plastron, or the underside of the shell, and is also darker in pigmentation. They have been recorded up to 84 cm in length, while other Green sea turtles have been recorded up to 99 cm in length. Their legs are shaped like flippers to aide in swimming; they are broad and generally flattened. The head is rounded and lizard-like with no teeth and does not have the predominantly hooked beak like many other green sea turtles. The sexes are similar in most aspects except size, the females are slightly larger, and the males have a longer tail.
Galápagos green turtles get their name from their specific nesting habitat, the Galápagos Islands. They are the only subpopulation of sea turtle to nest in these islands. The Galápagos straddle the equator off the coast of Ecuador and consist of 17 islands that are volcanic in origin. This is not their only habitat as they are a highly migratory species and spend much of their time cruising the warm waters of the Pacific Ocean. Colonies of green sea turtles have been observed nesting in 80 countries around the globe and they forage along the coasts of approximately 140 countries. There have been recordings the Galápagos green turtle or the black sea turtle from the Baja California peninsula to the Galápagos Islands and Peru and as far west as the Hawaiian and Marshall Islands. Much of their time near shore is spent foraging and resting. Black sea turtles have been recorded to spend much of their time in the bays and lagoons of the Baja California peninsula foraging and resting during the period of maturation. Distances of migration are recorded to range between 1233 and 2143–km and are performed over various time periods. They come to the Galápagos primarily to nest and only the females come ashore and lay eggs, the males stay submerged for most of their lives.
Female Galápagos green turtles most often only lay eggs every 2–3 years and spend the time between resting and foraging. Fertilization occurs underwater with only females emerging for nesting. Mating has not been witnessed outside of the nesting season and usually occurs off shore near the nesting sites. Nesting space can be somewhat limited due to the consistency of the beaches in the Galápagos, being of volcanic origin. There are many rocky areas and cliffs with limited space on sandy beaches. Also, the sandy areas tend to be quite dry and this causes many cave-ins of the nests. Females in the Galápagos have modified their nesting habits due to this factor and usually keep one hind flipper in the nest while depositing the eggs to prevent the unwanted cave-in. Clutch size varies from 50 to 200 eggs per nest and can take up to three hours to accomplish. However, Galápagos sea turtles are known to have smaller clutch sizes than other populations. After the eggs are laid the female will cover them with sand and press down with her plastron for compaction. They have also been noted to make a false nest next to their primary nest to try and fool off predators. When leaving the female turtle will attempt to cover any trace of her presence by flinging sand around in the area of the nest.
Nesting most often occurs at night so there is protection from predators. The prime season for nesting is from December to June, however peak months are January through March. Females are very uneasy when coming up to shore. If they feel threatened they will return to the water and wait until the shore is safer. Approximately two months after nesting the hatchlings emerge. They are approximately 46 mm in length when hatched, smaller than other Chelonian hatchlings.
Green sea turtles have been recorded and observed in the Galápagos over many centuries as far back as the 17th century by William Dampier. There has not been much attention brought to them due to the overwhelming research done on the Galápagos Giant Tortoises. 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. It is the only subpopulation of green sea turtle to be given premise for separate species delineation, proposing Chelonia agassizii as a separate species. At this time no distinctions have been made. This is mainly due to analysis of mitochondrial and nuclear DNA of 15 nesting beaches. This analysis has showed little distinction between the populations of the East Pacific waters and those of other nesting areas.
It is the unique morphological distinctions of the Galápagos green turtle or the black sea turtle that have been giving rise to the debate. The two most notable distinctions are the considerably smaller adult size and the much darker pigmentation of the carapace, plastron, and the extremities. 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. The main argument that separates agassizii from other Chelonians is that with a smaller adult size it would be very difficult for a male of another subpopulation to mate with a female black sea turtle. A male sea turtle must have a fairly strong hold of the females’ carapace during mating in order to successfully copulate; with the female agassizii being much smaller this feat would be impossible. This in turn creates an isolation of agassizii from the genetic variations shared between other populations of green sea turtle in the Pacific.
Three possibilities have arisen from their unique characteristics; agassizii is a separate species from mydas, the Galápagos green turtle is a subspecies of green sea turtle, or it is simply a color mutation. 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.
Galápagos green turtles’ lifestyle is similar to other populations of Chelonians. The behavior of all sea turtles is difficult to track but many tagging experiments have been performed to assess migration patterns as well as feeding habits of Chelonians in the eastern Pacific. The results of this research indicates that the green sea turtles of the eastern Pacific including the Galápagos green turtles are highly migratory and ingest many different variations of forage including some animal matter. The female green turtles are known to nest colonially and to return to the same nesting beach every time they reproduce. This may be a result of comfort from past nesting success or it could be a result of returning to the origin of their own hatching beach. Populations in the eastern Pacific have also shown to return to the same foraging habitat after nesting and these areas are shared with other nesting colonies. Analysis of genetic data shows that populations in the eastern Pacific share the same life history but have developed variations of many details such as size and color. The populations in the Pacific and Indian Oceans are shown to have complete genetic isolation from the populations in the Atlantic and Mediterranean Sea. Black turtles are recorded to spend much of their maturation stage in the coastal areas off the Baja California peninsula in particular in the Bahia Magdalena lagoon and connecting channels. This particular area is rich in mangrove trees that provide forage and protection during this crucial stage of their lives. Another food source for the mature green turtles in the Pacific is marine algae, red alga is common along with green alga and also eelgrasses. This has been observed off the Bahia de los Angeles. In this area they have also been noted to consume many forms of animal matter as well. This may be incidental or intentional in origin, results are unclear. If incidental it may be a repercussion of consuming marine algae near the invertebrates or if intentional it may be to provide important nutrients, minerals, or proteins not obtained from vegetation.
Behaviours of hatchlings differ form that of adults. After a hatchling emerges from the sand it immediately guides itself out to sea. Hatchlings use the light of the night sky to find their way into the ocean. However in many areas with coastal development the hatchlings become confused from the false light and are sometimes guided in the wrong direction to their death, this is not as much of a problem for Galápagos green turtles due to lack of development in the islands. It is important that the hatchlings emerge at night to be protected from predators. They quickly move out to sea and swim for a period of up to 24 hours, this way they are far removed from shore and the predators in that area. They spend many years in the open ocean before entering the coastal habitat for the maturation period as juveniles. This period of maturation last from 10 to 20 years and for populations of black sea turtle is usually spent along the coasts of the Baja California peninsula and the connecting bays, lagoons, and channels that provide excellent forage and protection.
Economic significance to humans
Now that the Galápagos green turtle is an endangered species it has little positive economic significance for humans. They have in the past been harvested from egg to adult for various human uses. The eggs and meat from all life stages was utilized in many areas as a food source for humans and the meat is still considered a delicacy in some countries of South America. They were also harvested for their hides and for the oils of their fat deposits used in cooking, however the Galápagos green turtle has less body fat than other populations so not as much oil was yielded from their bodies. Now the green turtles have more of a negative impact on human economics due to their status as endangered. They are often involved as bycatch in many ocean fisheries and are protected through many acts of legislation.
As previously noted, the Galápagos green turtle, grouped with all populations of Chelonia mydas, is listed on the IUCN Red List of threatened species. They were placed on the list in the mid 1980s and have remained under protection since. One of the major problems that have led to their decline is the slow growth rate and long period from juvenile to sexual maturity. Chelonians average a period of 26–40 years to maturity; the Galápagos green turtle averages 33 years. The green sea turtle has been shown to have the slowest growth rate of any species of sea turtle and is generally long-lived if left undisturbed. Over all populations of Chelonia mydas have seen a decrease of approximately 48–67% of nesting females, however the population that nests in the Galápagos has remained quite steady with little to no change. The population of nesting females recorded in the Galápagos from 1976–1982 was approximately 1400 individuals and after further evaluation in 1999–2001 they again found around 1400 nesting females.
Reductions in populations of Chelonia mydas are recorded in every ocean ecosystem that they inhabit and the contributing factors that have led to their decline are all anthropogenic. The main threats are harvesting of eggs and individuals, bycatch in marine fisheries, and degradation of the marine and coastal habitats. The most common accidental threat is the entanglement in fishing equipment with the most harmful methods being drift netting, shrimp trawling, long-lining, and dynamite fishing. There are now many pieces of legislation that ban these practices in protected areas.
For Chelonians inhabiting the eastern Pacific, including the Galápagos green turtle, the threats are the same. The main factor leading to decline in this area was the intense and unregulated fishing operations run off the coast of Mexico between 1950 and 1970. In many countries in Central and South America the meat of sea turtles is considered a delicacy and they are to this day poached and hunted directly. The mortality of the sea turtles near their foraging area of the Baja California peninsula is approximately 7800 deaths yearly and this has led many organizations to rally for governmental protection of this area for the species. It was noted that approximately 9 out of 100 individuals will survive a year in the waters of the Baja California peninsula and as previously stated this in an intense foraging ground for all population in the eastern Pacific. Even with the passing of new protective legislation and the many efforts of conservation organizations, populations are continuing to decline, and considering the long generation length of 42.8 years any hit on the population is difficult to recover from.
One of the many conservation efforts being implemented to increase populations at this time is the use of hatcheries for protected egg incubation. The goal of this type of project is to create a protected environment for the hatchlings where they can incubate and emerge from the sand without threat of predators and then be released out to sea safely. Unfortunately this is not the result that has been documented from the practice. Often when hatchlings emerge from the sand in the incubator they remain enclosed inside and expend much of their preserved energy trying to find a way out. They also lose the extremely important dark, night hours used to get far away from shore. When they are released out to sea it is often in the early morning hours of dusk when many predators are about and this limits their chance of survival. In addition to the threat of being released during dusk the hatchlings are also often too weak to gain a swift and long distance movement from shore due to the expended energy lost in the incubator after hatching. These results have led many to believe that hatcheries are ineffective and should only be used as a last resort. There is no extensive research showing the survival rate of the hatchlings after they are released to sea but one study proclaimed a possible 50% loss after release.
|Wikimedia Commons has media related to Chelonia mydas agassizi.|
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Green sea turtle
- "Chelonia" redirects here. It is also the name of the superorder uniting turtles, tortoises and terrapins (Testudines) with the "proto-turtle" Australochelys.
The Green sea turtle (Chelonia mydas), also known as green turtle, black (sea) turtle, or Pacific green turtle, is a large sea turtle of the family Cheloniidae. It is the only species in the genus Chelonia. Its range extends throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Oceans. Their common name derives from the usually green fat found beneath their carapace (upper shell).
The green sea turtle is a sea turtle, possessing a dorsoventrally flattened body covered by a large, teardrop-shaped carapace and a pair of large, paddle-like flippers. It is usually lightly colored, although parts of the carapace can be almost black in the eastern Pacific. Unlike other members of its family, such as the hawksbill sea turtle and loggerhead sea turtle, C. mydas is mostly herbivorous. The adults commonly inhabit shallow lagoons, feeding mostly on various species of seagrasses.
Like other sea turtles, they 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 walk into the water. Those that reach maturity may live to age 80 in the wild.
C. mydas is listed as endangered by the IUCN and CITES and is protected from exploitation in most countries. 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 because of several human practices. In some countries, turtles and their eggs are hunted for food. Pollution indirectly harms turtles at both population and individual scales. Many turtles die caught in fishing nets. Also, real estate development often causes habitat loss by eliminating nesting beaches.
The green sea turtle is a member of the tribe Chelonini. A 1993 study clarified the status of genus Chelonia with respect to the other marine turtles. The carnivorous Eretmochelys (hawksbill), Caretta (loggerhead) and Lepidochelys (Ridley) were assigned to the tribe Carettini. Herbivorous Chelonia warranted their status, while Natator (flatback) was further removed than previously believed.
The species was originally described by Linnaeus in 1758 as Testudo mydas. In 1868, Bocourt named a particular species of sea turtle as Chelonia agassizii (Chelonia agassizi is a commonly cited misspelling of this taxon). This "species" was referred to as the "black sea turtle". Later research determined the "black sea turtle" was not genetically distinct from C. mydas, and thus taxonomically not a separate species. These two "species" were then united as Chelonia mydas and were given subspecies status. C. mydas mydas referred to the originally described population, while C. mydas agassizi referred only to the Pacific population. This subdivision was later determined to be invalid and all species members were then designated Chelonia mydas. 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. As a species found worldwide, the green turtle is called differently in some languages and dialects. In the Hawaiian language, honu is used to refer to this species.
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. Adult green turtles grow to 1.5 metres (5 ft) long. The average weight of mature individuals is 68–190 kg (150–420 lb) and the average carapace length is 78–112 cm (31–44 in). Exceptional specimens can weigh 315 kg (690 lb) or even more, with the largest known C. mydas having weighed 395 kg (870 lb) and measured 153 cm (60 in) in carapace length.
Anatomically, a few characteristics distinguish the green turtle from the other members of its family. Unlike the closely related hawksbill turtle, the green turtle's snout is very short and its beak is unhooked. 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.
The carapace of the turtle has various color patterns that change over time. Hatchlings of C. 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.
The range of C. mydas extends throughout tropical and subtropical oceans worldwide. There are two major subpopulations, the Atlantic and the eastern Pacific subpopulations. Each population is genetically distinct, with their own set of nesting and feeding grounds within the population's known range.
Chelonia mydas can generally be found throughout the entire Atlantic Ocean. 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. One of the region's most important nesting grounds is in Tortuguero in Costa Rica. In fact, the majority of the Caribbean region's C. mydas population hails from a few beaches in Tortuguero. 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. In the Southern Atlantic Ocean, the most notable nesting grounds for Chelonia mydas are found on the island of Ascension, hosts 6,000–13,000 turtle nests.
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.
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.
Significant nesting grounds are scattered throughout the entire Pacific region, including Mexico, the Hawaiian Islands including O'ahu's Turtle Bay, 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.
Nesting grounds are found all along the Mexican coast. These turtles feed in seagrass pastures in the Gulf of California. 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. In the Philippines, green turtles nest in the Turtle Islands along with closely related hawksbill turtles. Indonesia has a few nesting beaches, one in the Meru Betiri National Reserve in East Java. The Coral Sea has nesting areas of world significance. The Great Barrier Reef has two genetically distinct populations; one north and one south. Within the reef, twenty 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. 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.
On 30 December 2007, fishermen, using a hulbot-hulbot (a type of fishnet) accidentally caught an 80 kg (180 lb), 93 cm (37 in) and 82 cm (32 in) wide, turtle off Barangay Bolong, Zamboanga City, Philippines. December is breeding season near the Bolong beach.
Ecology and behavior
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.
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.
Turtles spend most of their first five years in convergence zones within the open ocean. These young turtles are rarely seen as they swim in deep, pelagic waters.
Green sea turtles typically swim at 2.5–3 km/h (1.6–1.9 mph).
Only human beings and the larger sharks feed on C. mydas adults. Specifically, tiger sharks (Galeocerdo cuvier) hunt adults in Hawaiian waters. Juveniles and new hatchlings have significantly more predators, including crabs, small marine mammals and shorebirds. In Turkey, their eggs are vulnerable to predation by red foxes and golden jackals.
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. 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. Mating seasons vary between populations. For most C. mydas in the Caribbean, mating season is from June to September. The French Guiana nesting subpopulation nests from March to June. 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.
Green sea turtles mating is similar to other marine turtles. Female turtles control the process. A few populations practice polyandry, although this does not seem to benefit hatchlings. After mating in the water, the female moves above the beach's high tide line, where she digs a hole with her hind flippers and deposits her eggs. Clutch size depends on the age of the female and species, but can range between 100 and 200. She then covers the nest with sand and returns to the sea.
At around 45 to 75 days, 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. Juveniles spend three to five years in the open ocean before they settle as still-immature juveniles into their permanent shallow-water lifestyle. It is speculated that they take twenty to fifty years to reach sexual maturity. Individuals live up to eighty years in the wild. 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 15,000 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).
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.
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.
Importance to humans
Historically, the turtles' skin was tanned and used to make handbags, especially in Hawaii. Ancient Chinese considered the flesh of sea turtles a culinary delicacy, including and especially C. mydas. Particularly for this species, the turtle's calipee, fat and cartilage are sought as ingredients for making turtle soup.
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. Bali has been importing sea turtles since the 1950s, as its own turtle supplies became depleted. 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. 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. Inintially 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.
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. 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. A stylised sea turtle nicknamed "Sir Turtle" is the mascot of the national airline Cayman Airways and is part of the livery of its aircraft.
In recent decades, sea turtles have moved from unrestricted exploitation to global protection, with individual countries providing additional protection, although serious threats remain unabated.
Human action presents both intentional and unintentional threats to the species' survival. Intentional threats include continued hunting 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; 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. 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. Because of these threats, many populations are in a vulnerable state.
Pacific green turtle’s foraging habitats are poorly understood and mostly unknown. These foraging grounds are most likely along the coast of Baja California, Mexico and southern California, in which these turtle’s 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. The only foraging area that has been identified is the San Diego Bay, but it is heavily polluted with metals and PCBs. These contaminants have a negative effect on the ocean environment, and have been shown to cause lesions and sometimes mortality. Green turtles also are threatened by entanglement and ingestion of plastic. In San Diego Bay, an adult green turtle was found dead with monofilament netting tightly packed in its esophagus.
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. The 1986, 1988, 1990, 1994, and the landmark 1996 edition of the IUCN Red List, retained the listing.
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.
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.
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. 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.
The Mediterranean population is listed as critically endangered. 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".
In addition to management by global entities such as the IUCN and CITES, specific countries around the world have undertaken conservation efforts.
The traditional uses of turtle on Bali were once deemed sustainable, but have been questioned considering greater demand from the larger and wealthier human population. The harvest was the most intensive in the world. 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.
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. In the United States, the U.S. Fish and Wildlife Services and National Marine Fisheries Service classify C. mydas as a threatened species under the Endangered Species Act, rendering it a federal offense to capture or kill an individual turtle. 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. In the United Kingdom the species is protected by a Biodiversity Action Plan, due to excess harvesting and marine pollution. 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.
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. On Ascension Island, which contains some of the most important nesting beaches, an active conservation program has been implemented., Karumbé has been monitoring foraging and developmental areas of juvenile green turtles in Uruguay since 1999.
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. Since its beginning in 1968, the farm has released over 31,000 turtles into the wild, and each year more captive-bred turtles are released into the Caribbean Sea from beaches around the island of Grand Cayman. 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.  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). 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, 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.
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.
- Galápagos Green Turtle - a subspecies of the green sea turtle
- Chelonioidea - the sea turtle superfamily.
- Sea Turtle Association of Japan, Kuroshima Research Station
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- Seminoff (2004). Chelonia mydas. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 09 May 2006.
Names and Taxonomy
Comments: Eastern Pacific populations of Chelonia are regarded by some authors as a distinct species, the black turtle, C. agassizii (King and Burke 1989); other authors (e.g., Ernst and Barbour 1989) retain agassizii as a subspecies of C. mydas (Kamezaki and Matsui 1995) or do not recognize it taxonomically at all (Crother et al. 2000). Phylogenetic analyses of mtDNA data by Bowen et al. (1992) yielded no evidence of matrilineal distinctiveness of agassizii. See Karl and Bowen (1999), Pritchard (1999), Grady and Quattro (1999), Shrader-Frechette and McCoy (1999), and Bowen and Karl (1999) for further debate about the taxonomic status of the black turtle.
The Australian flatback turtle, formerly known as Chelonia depressa, has been removed to its own genus, Natator (Zangerl et al. 1988, Limpus et al. 1988). MtDNA data indicate a fundamental phylogenetic split distinguishing all green turtles in the Atlantic-Mediterranean from those in the Indian-Pacific oceans (Bowen et al. 1992).
Most regional populations of Chelonia mydas are genetically distinct (Bowen et al. 1992). Florida population is characterized by unusually high mtDNA diversity (Allard et al. 1994).
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