Modern turtles are thought to have evolved from an ancestor over 200 million years ago. This ancient animal, which has survived many millions of years, is being threatened by climate change & pollution, initiated and fueled by man.
Climate change is a serious threat to sea turtle biodiversity during the reproductive phase. In San Diego, Camryn Allen from the US National Oceanic and Atmospheric Administration in Hawaii, (NOAA), had previously seen average female sea turtle populations from 65 to 78 per cent in hatchlings, now it is thought that female hatchlings number, as much as 99 per cent, in newborn turtle populations.
In Costa Rica’s Playa Grande beaches, scientists have found that when females lay their eggs on beaches, where temperatures are higher than in previous decades, a much higher proportion of female turtles are born. The percentage of females is as much as 90 per cent. Male turtles have been shown to be hatched from eggs incubated in sands on beaches having lower sand temperatures; and with climate change, beach temperatures are on the rise.
Female turtles often return to the beach where they were hatched, once they reach maturity at about 16 years of age. The tiny hatchlings are born 60 to 80 days later. Eggs can be eaten by animals like raccoons, foxes, dogs and ants. And once born, babies must sprint to the sea, or else be eaten by seabirds. And in water, they are prey for many fish like sharks, octopus and other cephalopods. Only one of a thousand babies are thought to make it to adulthood.
Man is also impacting the survival rate of sea turtles due to rising waters from melting polar icecaps washing away beaches and egg clutches. More intense storms, and the development of beach properties are also to blame. Turtles are also widely affected by rising ocean temperatures bleaching and killing coral reefs.
Sea turtles are also caught in fishing nets and drown because they do not have gills. Turtles and turtle eggs are subject to poaching. Their shells are used for jewelry; and in many areas of the world–like Indonesia, Latin America, India and China–their eggs, meat and shells, are sold on the black market.
Instead of earning a living selling turtle meat and shells, residents of Tortuguero, Costa Rica now are leaders in turtle-based eco-tourism. The founders of turtle conservation, The Caribbean Conservation Corporation, (now called Sea Turtle Conservancy), was able to convince villagers that conserving the sea turtle, rather than reducing numbers to dangerously low levels, was in their best interest. Also, to minimize disturbance to nesting sea turtles, certified eco guides now help tourists watch the hatching of baby turtles in the area.
Punta Pargos, in the coastal Guanacaste region of Costa Rica, is also making a difference. By instituting patrols to guard from poachers, Sea Turtles Forever, an organization which is also based in Oregon, USA, is giving jobs to Costa Rican local people. The community also helps collect eggs to be incubated by scientists, ensuring that as many as 11,000 baby turtles hatch, and are returned to the wild per year.
Raine Island in Australia is near the Great Barrier Reef. As one of the largest sea turtle nesting sites in the world, it sees up to 60,000 female turtles nesting there each season. Unfortunately, erosion has meant their nests have been washed out to sea. Baby turtles can only hatch on land. As many as 2,000 adult turtles can also die from heat exhaustion, or being turned over by the tide, or getting trapped in rocky cliffs.
The Raine Island Recovery Project, tags more than 2,000 turtles per annum, and has installed 1,100 meters of fencing to prevent turtles from reaching cliffs. It has also been responsible for training indigenous rangers, and the rebuilding of some beaches, so turtle eggs are no longer washed away by the sea.
Florida sees as many as 90 percent of sea turtle eggs in the US, laid on its beaches. The Sea Turtle Preservation Society, in Indialantic, FL, helps rescue sick and injured turtles in Brevard County and in the Indian River Lagoon system; particularly during the May to October nesting season. They also have a turtle information and education centre in Indialantic.
Near the African equator in the Atlantic Ocean, the Programa Tatô in São Tomé and Príncipe Archipelago, locals, biologists, and law enforcement have become educated concerning the Green Sea, Olive Ridley, Hawksbill, Loggerhead and Leatherback Turtle, native to the area. Thirty-three beaches are monitored in the program. Using in-water monitoring, the health of the foraging grounds of several turtle species are examined.
To take advantage of the Odisha region fish, mollusk, prawn and crab spawning grounds in India; the Olive Ridley sea turtle congregates there from October to May. In the delta sea turtles mate, and then lay their eggs on the area’s unpolluted beaches. Ninety percent of all of India’s turtles’ nest in the intertidal area, and up to 50% of the world’s Olive ridley sea turtles. There are also mangrove swamp forests, estuaries, creeks, and rivers in Odisha that are home to sea turtles.
The Odisha Wildlife Organization reports that regular patrolling of nesting areas is done in the turtle nesting areas near the mouths of the Dhamara, Devi, and Rushikulya Rivers. These areas have also been declared ‘No Fishing Zones’, when turtles are mating and nesting.
It is no longer a sure thing that Green sea turtles will continue to return to their traditional nesting grounds in Sham Wan, Hong Kong. Coastal development, pleasure crafts and light and plastic pollution have taken their toll. Baby turtles nesting on Lamma Island are confused by lighting on buildings and boats, and sometimes head inland instead of out to sea.
At the crossroads between Asia and Africa, the Seychelles Islands near Somalia, is the home of an award-winning Turtle Foundation. It is also here invasive species are being removed, and replaced by traditional flora and fauna. Volunteers patrol beaches, and incubate baby turtles, when nests have been disturbed by man, and other predators.
In the US Virgin Islands, at St. Croix, scientists are deploying acoustic satellite tags to monitor migration patterns, home ranges of the Hawksbill, Leatherback, and Green sea turtles. The Buck Island Reef National Monument (BIRNM) area is protected.
In Canada, many Leatherback and Loggerhead sea turtles often become ensnared in commercial fishing gear once they migrate from Central and South America. The Canadian Sea Turtle Network assists fishermen save the turtles that have come North to feed on jellyfish.
While sea turtles spend little time on land except when laying eggs; other types of turtles and tortoises are semi-aquatic, or live almost solely on land. Tortoises, which are terrestrial land animals only swim in shallow water; while other turtles like freshwater turtles are found in ponds, and swamps.
Endangered Sea Turtles species
Leatherback Sea Turtles
Leatherbacks, the long-distance commuters of the sea turtle world, prey mostly on jellyfish. Their size, nine feet long and sometimes more than 900 kg., allows them to travel across oceans. They use their beaks to destroy jellyfish. Some Leatherbacks have been known to feed near the Arctic Circle, and travel down to warm Caribbean to nest.
Jellyfish have been seen to replace declining food fish stocks in the food chain; and are known to eat fish eggs and larvae. They pose a threat to fish number recoveries, and affect attempts to stock fish in the ocean by man. The Leatherback turtle is a dark grey, and black turtle with a tear-dropped shaped shell, and is known to eat 440 lbs. of jellyfish per day. Leatherbacks are different from other turtles, as their shells are not made of keratin like human fingernails. They have seven ridges on their upper shells made of osteoderm, or bony deposits, that form scales or plates. Their lower shells or bellies are light colored, making them less visible to predators, swimming below them.
While most sea turtles return to their original spawning beaches, Leatherbacks may choose other nearby beaches instead. Turtles are particularly suspectable to being fooled by clear, plastic bags floating in the ocean, as they can resemble jellyfish. Blockage of the intestines by plastic, results in starvation and a long, slow death for many turtles and other animals. Leatherbacks are categorized as critically endangered by the ICUN (International Union of Conservation of Nature).
Green Sea Turtles
Greens also consume jellyfish, as well as mowing down seagrass beds. Unlike other sea turtles, green sea turtles are different because they have one pair of scales near the front of their eyes, not two prefrontal scales.
Green sea turtles prevent seagrass from obstructing currents, and shading the bottom of the ocean. If seagrass becomes overgrown it can begin to decay; causing slime, algae and fungi to stifle nutrient growth in the oceans. Instead of a decrease in nitrogen, seagrass maintenance results in growth of animal colonies, reef fish, and healthy predator habitats. It is thought that the decrease of Green sea turtles in Florida Bay, the Gulf of Mexico and the Caribbean, has meant a decrease in the number of fish being brought to market.
Green sea turtles are usually olive green and black, but are named because the fat beneath their shells is green. Mature turtles have a marbled or variegated shell, but are prominently brown. Green sea turtles also have short snouts, and on average are 5 ft. long, and weigh up to 700 lbs. The Green sea turtle is listed as an endangered species.
Hawksbill Sea Turtles
Hawksbill sea turtles foster reef diversity because they are adept at controlling sponges by ripping them up. This allows other species to feed on these sponges as well. It is particularly important for reefs, as corals are not good at competing with sponges for nutrients and territory.
The Hawksbills’ shells have beautiful serrated edges, made by overlapping scales. They have long made them a favorite for the making of tortoiseshell combs and ornaments. The sale of turtle shells was outlawed in 1973, by the Convention on International Trade in Endangered Species (CITES). The smaller Hawksbill sea turtle lives in lagoons and coral reefs; weighs up to 150 lbs., is about 35 inches long, and is critically endangered.
Loggerhead and Olive Ridley Sea Turtles
Loggerhead and Olive ridley sea turtles are listed as vulnerable on the ICUN Endangered Species List. Vulnerable means that unless their circumstances change, they are likely to become endangered.
Both species are smaller, with some Loggerhead weighing in at 400 lbs., and the Olive ridley turtle, (or Kemp’s ridley turtle), weighing about 110 lbs. Ridleys and Loggerheads are only two feet long. Ridleys have a round, heart-shaped shell; while Loggerheads are known to have large heads, that contain powerful jaws.
Olive ridleys eat a wide range of seafood from jellyfish, sea urchins, snails, algae, fish eggs, worms, crabs and other crustaceans. The loggerheads’ powerful jaws allow them to feed on clams, as well as large sea urchins.
Devices to save turtles from drowning in nets
The World Wildlife Fund is always looking for ways to prevent turtles from getting caught, and drowning in fishing nets. Every year a contest is held searching for new ways to prevent turtles from becoming caught in nets meant for fish.
Trash and Turtle Excluder Devices, or TTEDs are designed as conduits in shrimp nets that allow turtles, as well as sharks and manta rays, to escape from the inside of fine, shrimp fishing nets. TTEDs were developed by local fisherman and the government in French Guiana, as well as the French Guiana Regional Fishery and Ocean Farming Committee, the European Federation for Fisheries, the French Research Institute for Exploitation of the Sea, the French Ministry of Agriculture and Fisheries, and the World Wildlife Fund.
In 2003, it was decided at a conference in Lanzarotte, Spain, that using large circular hooks on long lines pose a much lesser risk to sea turtles. Replacing J-shaped fishing hooks, with circle hooks, may result in as much as 90 per cent fewer turtles being hooked as bycatch, according to the World Wildlife Fund (WWF). There were over 100 tuna and mahi-mahi fishing boats involved in the study, presented at an annual meeting of the Inter-American Tropical Tuna Commission.
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International Smart Gear Competition. (2020). World Wildlife Fund. https://www.worldwildlife.org/initiatives/international-smart-gear-competition
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Year-long Study Shows Circle Hooks Help Save Sea Turtles. (2005, June 23). World Wildlife Fund.