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GREEN SEA TURTLES
green turtle
Green sea turtles (Scientific name: Chelonia mydas) are the largest hard-shelled sea turtle. They can weigh up to 200 kilograms (440 pounds) and reach a 1.3 meters (four feet) in length. They can stay underwater or 30 minutes and travel 2,000 kilometers (1.250 miles) from its feeding grounds to its nesting sites.
The green sea turtle name is derived from the reptile's greenish-colored fat. They are unique among sea turtles in that they are mostly herbivores, eating mostly seagrasses and algae. This diet is what gives their fat a greenish color (not their shells), which is where their name comes from. A critter cam hooked up to one in 2007 by National Geographic researchers showed that they were omnivores rather than vegetarians as had been previously thought. [Source: NOAA]
The Green turtle lifespan is unknown, but estimated to be 70 years or more There has been very little research regarding the lifespan of green turtles, due to lack of tagging but it is believed that adults routinely live to be older than 50 or 60. Some may live past the age of 100. AnAge reported a maximum green turtle lifespan of 75 years. Green turtles are not often held for long in captivity, so longevity records from aquariums are not so useful. Threats include bycatch in fishing gear, climate change, direct harvest of turtles and eggs, disease, loss and degradation of nesting and foraging habitat, ocean pollution/marine debris, vessel strikes
See Separate Articles: SEA TURTLES: CHARACTERISTICS, BEHAVIOR, REPRODUCTION ioa.factsanddetails.com ; ENDANGERED SEA TURTLES, FISHING, EGG HARVESTING AND POLLUTION ioa.factsanddetails.com SEA TURTLE SPECIES ioa.factsanddetails.com ;
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures
Green Sea Turtle Habitat and Where They Are Found
green turtle range
Green turtles are found throughout the world. They nest in over 80 countries and live in the coastal areas of more than 140 countries. They are found mostly around grassy estuaries. There are relatively large populations of them. Some places have noted increases of them in recent years. In the U.S. they can be found off New England and Mid-Atlantic, Pacific Islands, Southeast and West Coast
Found in tropical and subtropical waters, green sea turtles are native to the Indian Ocean, Atlantic Ocean and Pacific Ocean and the Mediterranean Sea. They are primarily use three types of habitat — beaches for nesting, open ocean convergence zones as juveniles, and coastal areas for benthic feeding as adults.
In the U.S. Atlantic and Gulf of Mexico waters, green turtles are found in inshore and nearshore waters from Texas to Massachusetts, the U.S. Virgin Islands, and Puerto Rico. In the eastern North Pacific, green turtles have been sighted from Baja California to southern Alaska, but most commonly are seen south of San Diego. Also, in the central Pacific, green turtles are found around most tropical islands, including in Hawaii, American Samoa, Guam, and the Northern Mariana Islands. In U.S. Atlantic and Gulf of Mexico waters, green turtles are found in inshore and nearshore waters from Texas to Maine, the U.S. Virgin Islands, and Puerto Rico. Important feeding areas in Florida include the Indian River Lagoon, the Florida Keys, Florida Bay, the Dry Tortugas, Homosassa, Crystal River, Cedar Key, and St. Joseph Bay. [Source: NOAA]
Green sea turtles are common in reefs, other coastal areas and the open sea. You can find them in shallow tropical and subtropical waters as well as coastline beaches. They forage in coastal areas with plentiful of algae and sea grass. Male and female green turtles use major current systems when migrating to nesting beaches.
There are 11 distinct green turtles population segments (DPS) worldwide listed under the U.S. Endangered Species Act. The largest green turtle nesting populations in the world are found at Tortuguero on the Caribbean coast of Costa Rica and Raine Island on the Great Barrier Reef in Australia. See Nesting Sites and Conservation Below.
Green Sea Turtle Physical Characteristics
Green sea turtle Green turtles are the largest of all the hard-shelled sea turtles, as we said before, and are the second largest overall species of sea turtles after leatherback sea turtles. Green sea turtle range in weight from 150 to 200 kilograms (330 to 440 pounds) and range in length from 100 to 120 centimeters (3.3 to four feet). Green sea turtles are (ectothermic (“cold blooded”, use heat from the environment and adapt their behavior to regulate body temperature). Their basal metabolic rate ranges from 47.9 to 73.8 cubic centimeters of oxygen per gram per hour. Females are larger than males. Males and females have different shapes. [Source: Kendalyn Hersh, Animal Diversity Web (ADW) /=]
A typical green sea turtle adult is one meter (three feet) long and weighs 135 to 160 kilograms (300 to 350 pounds) . They have dark brown, grey, or olive colored shells and a much lighter, yellow-to-white underside. Their shells have five scutes running down the middle and four scutes on each side. Other distinct characteristics of the green turtle are their serrated beak on the lower jaws and two large scales located between the eyes. [Source: NOAA]
Green sea turtles have a comparatively small head. According to Animal Diversity Web: They have only one pair of prefrontal scales, although other species of sea turtles that have multiple pairs. The scales are originally black at hatching, but then change color over the course of 27-50 years as the turtle matures. Their skull shape is described as round and smooth. Green turtles have short snouts and strong beaks that cover the bones of the jaw. Their jaws are short and serrated to properly rip and tear plants apart. The carapace is round and consists of four lateral overlapping scutes. The plastron also consists of four scutes. /=\
Sexual Dimorphism (differences between males and females) isn't completely recognized in green sea turtles until early adulthood. Males and females differ morphologically by the length of their tail and cloacal openings. Female green turtles have smaller tails and a cloacal opening between the anus and tip of the tail. Males are slightly smaller in carapace length, have longer claws, and longer tails where their reproductive organs are located. Their cloacal opening is located more posterior on the tail and past the end of their carapace. /=\
Green Sea Turtle Behavior, Swimming, Senses and Communication
Green sea turtles are motile (move around as opposed to being stationary), migratory (make seasonal movements between regions, such as between breeding and wintering grounds) and colonial (living together in groups or in close proximity to each other) during the nesting season. Green turtles, like all sea turtles, are reptiles and must surface to breathe and lay their eggs on land. They maintain home ranges throughout the year. These habitats include coastal feeding areas during the non-breeding season and natal beaches that the females visit during the nesting season. Adult green turtles have a home range that can expand from 3.8 hectares to 642.2 hectares. They are not known to actively defend a territory. [Source: Kendalyn Hersh, Animal Diversity Web (ADW) /=\, NOAA]
Green turtle in Hawaii Green turtles are often solitary but they can travel in large groups that usually originate from the same natal beach. According to Animal Diversity Web: They spend a lot of their time swimming, traveling about 20-90 kilometers per day. They also can be found eating, diving, reproducing, and migrating.Juvenile green turtles are said to be faster swimmers than other sea turtles such as loggerheads and olive ridleys due to the way green turtle hatchlings stroke their foreflippers. /=\
Green turtles sense using vision, vibrations and magnetism and communicate with vision. They . primarily use vision to detect plants and other prey and use visual displays when communicating. Green sea turtles also use a sense of wave propagation direction to help them navigate under water. Magnetic channels are also used to assist the orientation of the turtle in deep waters. In one study, researchers found that the turtles' inner ear can detect the acceleration and direction of the wave which assists their sense of direction. /=\
Green Sea Turtle Food, Eating Behavior and Predators
Green sea turtles begin their lives as omnivores (animals that eat a variety of things, including plants and animals) and gradually shift to a more herbivorous diet. They turtles are the only largely herbivorous species of sea turtle. Their diet mainly consists of algae and seagrasses, though they may also forage on sponges, invertebrates, and discarded fish. The East Pacific green turtle tends to eat more animal prey than other populations. Prior to recruiting to nearshore foraging areas, pelagic juveniles forage on plant and animal life found in oceanic drift communities (such as pelagic Sargassum communities). [Source: NOAA]
According to Animal Diversity Web: As juveniles, green sea turtles will feast on small marine invertebrates and neustonic material like sea serpents (Hydrozoa), moss animals (Bryozoa), and sea hare eggs (Aplysia). They also consume large quantities of wetland plants such as api api (Avicennia schaueriana) and salt-water cord grass (Spartina alterniflora), which are commonly found in salt marshes. Their diet also consists of a variety of red and green algae such as: filamentous red alga (Bostrychia), red moss (Caloglossa), freshwater red algae (Compsopogon), lobster horns (Polysiphonia), sea lettuce (Ulva lactuca), green seaweed (Gayralia), and crinkle grass (Rhizoclonium). Because green sea turtles are highly mobile throughout their lives, their food choices are often opportunistic. [Source: Kendalyn Hersh, Animal Diversity Web (ADW) /=]
green turtle Green sea turtles face three kinds of predators corresponding with stages of their lives. There are: 1) the animals that feed on green sea turtle eggs and hatchlings on the beach; 2) animals that feed on juveniles; and 3) those that feed on adults. Known predators that feed on adults include saltwater crocodiles, whitetip sharks, tiger sharks and humans. These animals also feed on juveniles. Some other large fish do too. A variety of birds and crabs feed on eggs and hatchlings. Among the other animals that have been observed doing so are jaguars, red foxes, golden jackals and feral dogs.
Adult green sea turtles' best form of protection from their predators is their large hard shell. They also have ways they can maneuver away from sharks and fend off attacks from them. When females come on land to lay eggs, their head and limbs are vulnerable and easily attacked by predators. Green turtles are hunted by humans for meat.
Green Sea Turtle Reproduction
Green sea turtles are oviparous (young are hatched from eggs) and engage in seasonal breeding. Female green turtles reach sexual maturity at 25 to 35 years. Every 2 to 5 years they undertake reproductive migrations and return to nest on a beach in the general area where they hatched decades earlier. [Source: NOAA]
The nesting season for green sea turtles in the northern hemisphere usually lasts from June through September. The number of offspring ranges from 75 to 200, with the average number being 136 to 150. The gestation period ranges from 45 to 75 days. Both males and females reach sexual maturity at 27 to 50 years. There is no parental investment by green turtles beyond the mother's egg-laying and camouflaging of the nest. [Source: Kendalyn Hersh, Animal Diversity Web (ADW) /=]
Green turtles migrate hundreds to thousands of kilometers each way between their foraging grounds and nesting beaches. They are solitary, night-time nesters. Green sea turtles mate at sea. Nesting females pull themselves up beaches where they first dig a few holes to fool predators and then lay eggs after sunset. They dig holes with their hind legs, lay their eggs and cover the eggs with sand to protect them from predators. Green sea turtle eggs bounce like ping pong balls. The gender of each baby is determined by the temperature of the sand. The hatchlings (babies) weigh just a few grams at birth.
Green Sea Turtle Mating
Green sea turtles are polygynandrous (promiscuous), with both males and females having multiple partners. According to Animal Diversity Web: Copulation occurs in the shallow waters off the shore of nesting beaches. When females accept a mate, the male will mount her and grab onto her "mating notches" around her shoulders to assist in copulation. Male green turtles also are known to join other mating pairs during copulation by latching onto other males for hours on end in attempts to dislodge the mating male. The reproduction process usually follows a system such as: male searches for a female mate, the male will visually examine and then approach the female, the female will either submit or reject the male,then possible copulation. Copulation can last several hours, with the longest mounting episode lasting 119 hours. Female green turtles average a total of 15 days between initial mounting by a male to the time they attempt to nest on their respective natal beaches. [Source: Kendalyn Hersh, Animal Diversity Web (ADW) /=]
Females use two displays to communicate with males whether or not they wish to mate. They turtles will show approval of a mate by being completely submissive when being mounted by the male. Females will clearly reject a male by either swimming away with their hind legs closed or biting a male if he gets too close. Female green turtles also have a "refusal" position, which consists of floating upward having their plastron facing the male and an extending all limbs. /=\
During the breeding season, actively mating pairs are often approached by several "escort" males that will latch on to the pair during copulation. Sometimes these escort males will attempt to remove the male connected to the female. If the copulating male feels threatened by the escort(s), then he might remove himself from the female briefly to drive off the other males. Even though humans are a predator of green sea turtles, most turtles are not affected by human contact while swimming or during copulation. /=\
Green Sea Turtle Nesting
Nesting green sea turtle females dig holes with their hind legs, lay about 100 to 150 eggs at a time, and cover the eggs with sand. Newborns hatch after about 60 days. In the United States, the breeding season begins in late spring. Males mate with females on foraging grounds, along migratory pathways, and off nesting beaches. Green turtles nest every 2 weeks over several months before leaving the nesting area and returning to their foraging grounds. [Source: NOAA]
Females are known to revisit their natal beaches every two to five years to breed. If they don't return to their natal beach, they will select a beach with similar sand texture, color and accessible beach slope, which they utilize. Females generally follow the same predictable actions when they nest. Although they may not complete every action, the process usually begins with the turtles approaching the beach and selecting a suitable nest site. The females begin clearing the area of debris and digging a hole with their front legs. After laying eggs, the females fill the nest with sand as a way to camouflage and conceal the eggs. Then, the female turtles return to the sea. [Source: Kendalyn Hersh, Animal Diversity Web (ADW) /=]
Female green turtles can lay one to nine clutches in a single nesting season, but tend to average around three. Each of these clutches can include 75-200 eggs. After about two months incubating in the warm sand, the eggs hatch and the hatchlings make their way to the water. Hatchlings orient seaward by moving away from the darkest silhouette of the landward dune or vegetation to crawl towards the brightest horizon. On undeveloped beaches, this is toward the open horizon over the ocean. The hatchings weigh approximately 26 grams on average.
Green Sea Turtle Nesting Sites
There are 11 distinct green turtles population segments (DPS) worldwide listed under the U.S. Endangered Species Act. The largest green turtle nesting populations in the world are found at: Tortuguero on the Caribbean coast of Costa Rica — where 30,000 females on average nest per season — and Raine Island in Australia — where up to 64,000 females nest on this island and the surrounding reef. Raine Island is a vegetated coral cay on the outer edges of the Great Barrier Reef.
Green turtles nest in over 80 countries. In the United States, nesting green turtles are primarily found in the Hawaiian Islands, Guam, the Northern Mariana Islands, American Samoa, Puerto Rico, the Virgin Islands, and Florida. Nesting also occurs annually in Georgia, South Carolina, North Carolina, and Texas. [Source: NOAA]
In the Mediterranean Sea, green sea turtles breed from June through August. They turtles are most frequently found nesting on the coastlines of Cyprus and Turkey. They are also observed nesting on the beaches of Israel, Syria, Egypt and Libya. [Source: Kendalyn Hersh, Animal Diversity Web (ADW) /=]
Raine Island, a 52-acre half-moon of sand on the edge of the Great Barrier Reef, is the biggest nesting island on Earth for green sea turtles. More than 90 percent of the northern Great Barrier Reef’s green turtles deposit eggs here and on nearby Moulter Cay. [Source: National Geographic]
Ras Al Hadd is a nesting site for green sea turtles in Oman on the easternmost point of the Arabian peninsula. The turtles usually arrive around midnight. Judith Miller wrote in the New York Times: “One giant turtle after another inches her way out of water...The turtles dig their holes, and sometimes abandoned a half-dug hole only to dig another a few yards away. The mother turtles sighed and groaned as they began laying their eggs, one by one...About 45 minutes later, the weary turtles, with great difficulty, heave themselves out of the deep trenches, covered the holes with sand, and inched their back to the sea... Baby turtles emerge from eggs in about 50 days. Tourists are on hand to watch the spectacle. Flashlights and flashbulb are forbidden while the turtles come ashore. But once they start laying their eggs lights do not seem to bother them.
Green Turtle Young and Development
The life history of green turtles involves a series of stages of development from hatchling to adult. After emerging from the nest, hatchlings swim to offshore areas, where they live for several years in pelagic habitat. They spend several years drifting in the open ocean as they grow and mature and eventually leave the open sea and travel to nearshore foraging grounds in shallow coastal habitats, where they mature to adulthood and spend the remainder of their lives. Adults return to their natal beach for mating. They migrate every 2 to 5 years from their coastal foraging areas to the waters off the nesting beaches where they originally hatched to reproduce. [Source: NOAA]
Female green sea turtles lay eggs 35-58 millimeters in diameter. As is true with many turtles, before they are born green sea turtle sex is determined by temperature. Eggs that are laid temperature of less than 28.5°C (83.3̊F) tend to produce more males than females, and those laid in temperatures of 30.3°C (86.5̊ F) or more tend to produce more females than males. Both sexes incubate in white, soft shells which can range from for 30to 90 days depending whether or not it is the wet or dry season. Incubation typically takes longer in the wet season. . [Source: Kendalyn Hersh, Animal Diversity Web (ADW) /=]
At birth hatchlings on average weigh 25 grams and are five centimeters long. Their plastrons are white or yellow and carapaces are blue-black. The only defense mechanisms they have are their carapace and swarming in large groups toward the ocean, which means that while some will get picked off by predators. Other will make it the sea. Once the hatchlings reach the water, they face a new group of predators such as sharks and large fish. Juvenile and mature sea turtles also are preyed on by sharks.Juveniles measure to about 40 centimeters in carapace length and subadults will measure between 70 to 100 centimeters. Juvenile green turtles are said to be faster swimmers than other sea turtles such as loggerheads and olive ridleys due to the way green turtle hatchlings stroke their foreflippers. /=\
Green Sea Turtle Migrations
Green sea turtles migrate long distances between feeding sites and nesting sites; some swim more than 2,600 kilometers (1,600 miles) to reach their spawning grounds.Green sea turtles are common in shallow tropical and subtropical waters as well as coastline beaches. They forage in coastal areas with plentiful of algae and sea grass. Male and female green turtles use major current systems when migrating to nesting beaches.
Radio tagging nesting females shows that green turtles are migratory (make seasonal movements between regions, such as between breeding and wintering grounds),, and their non-breeding range includes locations from as far north as 40 degrees north to as far south as 40 degrees south. These areas include parts of the Pacific Ocean, Atlantic Ocean, Mediterranean Sea, and northern Indian Ocean.[Source: Kendalyn Hersh, Animal Diversity Web (ADW)]
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. [Source: Wikipedia]
Humans and Green Sea Turtles
Humans utilize green sea turtles for food; body parts are sources of valuable materials. Historically, green turtles were killed in extraordinarily high numbers for their fat, meat, and eggs. Fishing techniques used to catch green sea turtles have included harpooning, catching by hand, netting, noosing and turning the turtles over on their back. This led to the catastrophic global decline of the species. [Source: NOAA]
Many countries, including the United States, prohibit the killing of sea turtles and collection of their eggs. However, in some areas, the killing of green turtles for their meat or to supply shells to the wildlife trafficking trade remains a threat to their recovery. Bycatch in commercial and recreational fishing gear, vessel strikes, loss of nesting habitat from coastal development, and climate change are the biggest threats facing green turtles. [Source: NOAA]
Although many countries have established laws protecting sea turtles, green sea turtles are still poached for their eggs and meat in certain areas around the world, such as South East Asia. The collecting of eggs remains legal in some countries and this can disrupt regional efforts to recover this species. Shells are also displayed as decoration or used to make jewelry. [Source: Kendalyn Hersh, Animal Diversity Web (ADW) /=]
Green sea turtles are hunted for meat. Simply turning them over makes them helpless. Their meat is said to be the best tasting of all the sea turtle meat. This might have something to do with the fact they eat mostly grass. Sea turtle researcher Archie Carr said, they are “so easy to catch, and comes back to the same place over and over again.”
Green Sea Hunters in Bali
green sea turtle hunting Green sea turtles are greatly prized as delicacies in Bali, where they are served up celebrations, banquets, weddings and special holidays. Because the Balinese have so many celebrations that can add up to a lot turtles. Balinese say the meat of young turtles in the best. The meat is often ground up and mixed with pepper and other spices and made into satay. The Balinese love of turtle meat has been described as cultural and is somewhat similar to the Japanese love of whale meat,
More endangered turtles are killed in Bali than anywhere else in the world. Each year hunters catch and kill 15,000 to 20,000 turtles a year. Most of those caught are green sea turtles even though a law against catching them was passed in 1999. The turtles have also been threatened by the construction of hotels and resorts on the beaches where the turtles lay their eggs. [Source: Los Angeles Times]
The turtles are killed in slaughterhouses, where they are lined up with their flippers tied together so they can no not crawl away. They are cut apart while still alive to make the meat easier to extract from the shells. If the turtles are killed outright the meat sticks to the shells. In most cases the turtles live for about 10 minutes while the flippers are cut off, the chest is cut open and the internal organs are removed. When the heart is taken out it is still beating. One former turtle hunter told the Los Angeles Times, “It’s torture to the sea turtles because they didn’t die right away, even after we have cut them. It’s like killing a human. The sea turtle can cry. Maybe if it could speak, it would ask for mercy.”
The turtle hunters are based mostly in the fishing village of Tanjung Benoa on the southern end of Bali. The hunters often remain at sea of two months and search as far away as Sulawesi and Borneo for turtles. The hunters used nets to catch turtles when they surface for air or shoot them with spears and spears connected to buoys that tire the turtles and it make it possible to pull them aboard the boat. The turtle hunters a well organized. Most are Muslims and Christians not Hindu like most Balinese. The take advantage of loopholes in the laws to catch thousands of turtles and have burnt down the station of police that dared to try and stop them.
Endangered Green Sea Turtles
Green turtles are considered an Endangered species according to the International Union for Conservation of Nature (IUCN) Red List. The Convention on International Trade in Endangered Species (CITES) lists them in Appendix I, which lists species that are the most endangered among CITES-listed animals and plants. This appendix says that trade of this species is prohibited unless the species is being used for research. Exceptions to this prohibition are only valid under approval of import and export permits. Specially Protected Areas and Wildlife (SPAW) Annex II lists green turtles as threatened throughout the Wider Caribbean Region. /=\
The United States Federal List classifies some green sea turtles as Endangered, but a majority of populations are classified as threatened. Those considered endangered are in the Mediterranean Central West Pacific and Central South Pacific. To be more specific, according to the Endangered Species Act (ESA, U.S. Fish and Wildlife) in the 11 distinct population segments (DPSs): green sea turtles are Endangered is the 1) the Central South Pacific. 2) the Central West Pacific; and 3) the Mediterranean. They are Threatened in 4) the Central North Pacific, 5) the East Pacific; 6) the North Atlantic; 7) the South Atlantic; 8) the East Indian Ocean-West Pacific; 9) the North Indian Ocean; 10) the Southwest Indian Ocean; 11) and Southwest Pacific.
Green turtles face a host of threats in the marine environment. Incidental capture in fishing gear is an ongoing threat to green turtles, which also affects many other marine species. Green turtles also suffer from a disease known as fibropapillomatosis in some areas of the world. The main cause of the historical, worldwide decline of the green turtle was the long-term harvest of eggs, juveniles, and adults from their nesting beaches and feeding grounds. These harvests still continue in some areas of the world, compromising efforts to recover this species. [Source: NOAA]
Green turtles are also threatened by the presence of artificial light, especially at their nesting sites. Sea turtles sometimes mistake artificial light for sunlight. It has been suggested that artificial light disorientates green turtles, and affects both their general and nesting behavior. Specific effects of artificial light on these turtles include altered adult return crawl and incomplete nest construction. [Source: Animal Diversity Web (ADW)]
Threats to Green Sea Turtles
The decline of green sea turtle population is mostly due to marine fisheries catching mature and juvenile green turtles in foraging areas and on nesting grounds. In recent years attention has been brought the harmful affects of plastic in the ocean on sea turtle health.
Commercial Fishing Bycatch: A primary threat to sea turtles is their unintended capture in fishing gear which can result in drowning or cause injuries that lead to death or debilitation (for example, swallowing hooks, or flipper entanglement). The term for this unintended capture is bycatch. Sea turtle bycatch is a worldwide problem. The primary types of gear that result in bycatch of green turtles include trawls, gillnets, longlines, hook and line, and pot/traps. [Source: NOAA]
Loss and Degradation of Nesting Habitat: Coastal development and rising seas from climate change are leading to the loss of nesting beach habitat for green turtles. Shoreline hardening or armoring (such as, seawalls) can result in the complete loss of dry sand suitable for successful nesting. Artificial lighting on and near nesting beaches can deter nesting females from coming ashore to nest and can disorient hatchlings trying to find the sea after emerging from their nests.
Vessel Strikes: Various types of watercraft can strike green turtles when they are at or near the surface resulting in injury or death. Vessel strikes are a major threat to green turtles, in particular large juveniles and adults near ports, waterways, and developed coastlines throughout their range. High boat traffic areas such as marinas and inlets present a higher risk to green turtles. Adult green turtles, in particular nesting females, are more susceptible to vessel strikes when making reproductive migrations and while they are nearshore during the nesting season.
Climate Change: For all sea turtles, a warming climate is likely to result in changes in beach morphology and higher sand temperatures, which can be lethal to eggs or alter the ratio of male and female hatchlings produced. Rising seas and storm events cause beach erosion, which may flood nests or wash them away. Changes in the temperature of the marine environment are likely to alter the abundance and distribution of food resources, leading to a shift in the migratory and foraging range and nesting season of green turtles. A warmer climate may also create too many females since turtle gender is determined by ambient temperatures in the sand where eggs are incubating. Cooler temperatures favor males, while warmer temperatures result in females.
Disease: Fibropapillomatosis is a disease that causes external and internal tumors in green turtles. These tumors can significantly affect their ability to swim and feed and can lead to death. The disease is most prevalent in green turtles and some evidence has linked the disease prevalence to degraded marine habitats.
Green Turtles, Plastic, Ocean Pollution and Marine Debris
Increasing pollution of nearshore and offshore marine habitats threatens all sea turtles and degrades their habitats. The Deepwater Horizon oil spill was the largest offshore oil spill in U.S. history and affected nesting (including nesting females, eggs, and hatchlings), small juvenile, large juvenile, and adult sea turtles throughout the Gulf of Mexico. Ingestion of marine debris is another threat to all species of sea turtles. Green turtles may ingest marine debris such as fishing line, balloons, plastic bags, floating tar or oil, and other materials discarded by humans which they can mistake for food. They may also become entangled in marine debris, including lost or discarded fishing gear, and can be killed or seriously injured. [Source: NOAA]
In 2021, Reuters reported: “A young green turtle defecated almost a dozen of bits of plastic and trash from its tiny stomach after being rescued in a fishing net off the coast of Argentina. The turtle, about 35 centimeters long, expelled a total of 18 grams of plastic fragments such as nets, plastic caps, styrofoam, nylon, and cellophane, according to vets. "When the animal was isolated in these pools, we saw that it quickly began to eliminate a large amount of plastic waste in its feces. We were impressed by the amount of plastic it excreted in such a short time due to the small size of the animal," said Karina Alvarez, a biologist at the Mundo Marino Foundation. Despite the turtle releasing a large amount of waste, x-rays revealed a blockage of debris in the animal's intestines. It continues under treatment at the rescue center of Mundo Marino foundation. [Source: Reuters Videos, December 19, 2021]
Green Sea Turtle Conservation
To protect green sea turtles laws have been passed and regulation was have been introduced to address the threats against them, particularly by commercial fishing. Both the U.S. Fish and Wildlife Service and National Marine Fisheries Service enforce the laws prohibiting the capture of sea turtles. Internationall, there are the Memorandum of Understanding on ASEAN Sea Turtle Conservation and Protection, the Memorandum of Understanding Concerning Conservation Measures for Marine Turtles of the Atlantic Coast of Africa, and the Inter-American Convention for the Protection and Conservation of Sea Turtles. The population in the Ogasawara Islands of Japan is increasing at the world’s highest annual rate,[Source: Animal Diversity Web (ADW)]
Since 1977, NOAA Fisheries and the U.S. Fish and Wildlife (U.S. FWS) Service have shared jurisdiction of sea turtles listed under the U.S. Endangered Species Act. (ESA). NOAA Fisheries leads the recovery and conservation efforts for sea turtles in the marine environment, and the U.S. FWS does the same for sea turtles on nesting beaches. [Source: NOAA]
To protect green sea turtles NOAA is: 1) Working with partners to ensure compliance with national, state, and U.S. territory laws to protect sea turtles; 2) cooperating with international partners to implement conservation measures and establish agreements, such as international treaties that protect sea turtles; 3) Researching, developing, and implementing changes to fishing gear practices and/or fishing gear modifications (such as, turtle excluder devices), using large circle hooks in longline fisheries, and implementing spatial or temporal closures to avoid or minimize bycatch; 4) Designating critical habitat areas essential for the conservation of green turtles
5) Protecting and monitoring green turtles in the marine environment and on nesting beaches Conducting research on threats and developing conservation measures that reduce threats and promote recovery; 6) Collecting information on the species biology and ecology to better inform conservation management strategies and to assess progress toward recovery; 7) Conducting and supporting education and outreach efforts to the general public by raising awareness on threats to sea turtles, highlighting the importance of sea turtle conservation, and sharing ways people can help sea turtles; and 8) Working with partners to study and raise awareness about illegal sea turtle trade. [Source: NOAA]
Maybe all these measures are paying. Divers and snorkelers see a lot of green turtles. In 2020, Reuters reported: The world's largest population of nesting green turtles is nearly twice as big as previously thought, scientists said after drones enabled better surveys of the animals. Australian scientists determined that there were about 64,000 green turtles waiting to lay eggs on Raine Island"When we compared drone counts to observer counts we found that we had under-estimated the numbers in the past by a factor 1.73," Richard Fitzpatrick, research partner at Biopixel Oceans Foundation said in an emailed statement. The research is good news for scientists concerned about declining numbers of green turtles. Getting an accurate picture of how the species is responding to protection efforts has been difficult. Previously, researchers would paint a non-toxic white stripe down the turtles' shells and would count them, those with and without white stripes, from a small boat. But this way of counting proved inaccurate due to poor visibility, the researchers said. [Source: Reuters, June 10, 2020]
Image Sources: Wikimedia Commons, NOAA, World Wildlife Fund
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated May 2023