18 May 2009
World's Largest Leatherback Turtle Population Found
An international team of scientists has identified a nesting population of leatherback sea turtles in Gabon, West Africa as the world's largest.The research, published in the May issue of Biological Conservation, involved country-wide land and aerial surveys that estimated a population of between 15,730 and 41,373 female turtles using the nesting beaches.
The study highlights the importance of conservation work to manage key sites and protected areas in Gabon.
Leatherbacks are of profound conservation concern around the world after populations in the Indo-Pacific crashed by more than 90 percent in the 1980s and 1990s. The International Union for Conservation of Nature (IUCN) lists leatherback turtles as critically endangered globally, but detailed population assessments in much of the Atlantic, especially Africa, are lacking.
During three nesting seasons between 2002 and 2007, the team’s members carried out the most comprehensive survey of marine turtles ever conducted in Gabon. This involved aerial surveys along Gabon’s 600 km (372 mile) coast, using video to capture footage for evaluation, and detailed ground-based monitoring. By covering the entire coastline, they were not only able to estimate the number of nests and nesting females, but also to identify the key sites for leatherback nesting, data which are crucial to developing conservation management plans for the species. Leatherbacks were first described nesting in Gabon in 1984.
The study also revealed that around 79 percent of the nesting occurs within National Parks and other protected areas. This gives added hope that Gabon can continue to be one of the world’s most important countries for these magnificent creatures.
Dr Angela Formia of the Wildlife Conservation Society, a co-author of the paper, said: “These findings show the critical importance of protected areas to maintain populations of sea turtles. Gabon should be commended for creating a network of National Parks in 2002 that have provided a sanctuary for this endangered species as well as other rare wildlife.”
The leatherback is the largest sea turtle, reaching up to nearly two metres (6.5 feet) in length and 540kg (1190 pounds) in weight. Unlike other sea turtles, the leatherback does not have a hard shell. Its shell is made-up of a mosaic of small bones covered by firm, rubbery skin with seven longitudinal ridges. Leatherbacks are the most widely spread marine turtles, and are found in the Pacific, Indian and Atlantic oceans, particularly in tropical regions. They are also the deepest diving of all sea turtles. The deepest recorded dive is 1.2 kilometres (3/4 mile), which is slightly more than the deepest known dive of a sperm whale.
As with other reptiles, the sex of leatherbacks is determined by the temperature of eggs during incubation. With leatherbacks, temperatures above 29 degrees centigrade (84 degrees Fahrenheit) will result in female hatchlings.
Leatherbacks are strong swimmers and tagged individuals have been known to cross ocean basins and are known to travel many thousands of kilometres in search of their jellyfish prey.
To see turtles currently being tracked from Gabon see: http://www.seaturtle.org/tracking/?project_id=340
The research was led by the University of Exeter working in collaboration with the Wildlife Conservation Society (WCS) which spearheads the Gabon Sea Turtle Partnership, a network of organisations concerned with the protection of marine turtles in Gabon.
Related News:
California waters for leatherback turtles?
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Labels: Africa, research, SCUBA News, sealife, turtles
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4 March 2008
Turtles at risk from non-stick pans
The same chemicals that keep food from sticking to our frying pans and stains from setting in our carpets are damaging the livers and impairing the immune systems of loggerhead turtles - an environmental health impact that also may signal a danger for humans.A scientific team monitoring the blood plasma of loggerhead turtles along the U.S. East Coast consistently found significant levels of perfluorinated compounds (PFCs). PFCs are used as nonstick coatings and additives in a wide variety of goods including cookware, furniture fabrics, carpets, food packaging, fire-fighting foams and cosmetics. They are very stable, persist for a long time in the environment and are known to be toxic to the liver, reproductive organs and immune systems of laboratory mammals.
PFC concentrations measured in the plasma of turtles found along the coast from Florida to North Carolina indicated that PFCs have become a major contaminant for the species. The levels of the most common PFC, perfluorooctane sulfonate (PFOS), were higher in turtles captured in the north than in the south. Data recently evaluated by NIST and College of Charleston graduate student Steven O’Connell shows that this northern trend of higher PFOS concentrations continues up into the Chesapeake Bay.
Blood chemistry analyses of PFC-contaminated loggerheads suggested damage to liver cells and the suppression of at least one immune function which could lead to a higher risk of disease. To support the “cause-effect relationship” between PFCs and illness, the researchers exposed Western fence lizards to the same PFOS levels found in loggerheads in the wild. The lizards showed significant increases in an enzyme that indicates liver toxicity. They also had signs of suppressed immune function.
These findings, Keller said, indicate that current environmental PFC exposures—at concentrations comparable to those seen in human blood samples—are putting marine species at enhanced risk of health problems from reduced immunity and may suggest a similar threat to us.
Keller reported that a recently completed study led by colleague Margie Peden-Adams of the Medical University of South Carolina that showed PFOS is toxic to the immune systems of mice at concentrations found both in loggerhead sea turtles and humans. The ability of the mouse immune system to respond to a challenge was reduced in half by PFOS—and this occurred at the lowest level of the compound ever reported for a toxic effect.
Further Reading: NIST Tech Beat
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Labels: marine biology, research, turtles
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10 April 2007
Turtle hatchery established in North Sulawesi
With the advice and support of the WWF in Indonesia, the NSWA has established a turtle hatchery in Bunaken Marine Park on a section of beach where the turtles come ashore to lay their eggs. To ensure minimum interference in the natural process only those eggs at risk from being swept away by high tides will be moved to the hatchery to give them a better chance of survival. Any eggs laid by turtles that are safe will be left in place but will be monitored to make sure that they are well protected and untouched during the 45-60 day period of incubation.
The chances of survival for young turtles are quite slim and the NSWA hopes that the establishment of the hatchery will boost the odds for them. It takes 35 years before a turtle is sexually mature and once fertilized the female returns to the beach on which she was born to lay her eggs. They have been known to swim right across the Pacific in order to return to the beach of their birth. When the baby turtles hatch they have to scramble across the sand to reach the sea, a time when they are very vulnerable from swooping sea birds looking for an easy meal. Once in the sea they are still open to attacks from predators.
The first turtle laid 120 eggs on 13th February close to the hatchery and the NSWA reports that all is going well and they are expected to hatch in early April. Many more turtles are expected soon as the peak nesting season is between now and the end of June. The NSWA are using the opportunity to involve local schoolchildren in the monitoring process to educate them about the turtles and their importance in the balance of all marine life.
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Labels: environment, sealife, turtles
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