Introduction
Koh Tao, or 'Turtle Island' has historically been a popular feeding and nesting area for sea turtles, as evidenced by the island's name and the local reverence for these ancient sea creatures. But years of habitat destruction and commercial fishing in the Gulf of Thailand is leading to an ecological collapse of the island's visiting turtle populations. With many scientists predicting that the turtles we see today will be the last generation of turtles in the Gulf, the end of an animal that as been around since the age of the dinosaurs. 
There are currently 9 species of sea turtles on the planet, all of them endangered or threatened. Today turtles are a rare site in the Gulf of Thailand, especially turtle laying eggs. For about the last 15 years the local community and the Thai Navy have been releasing baby turtles from the island in hopes they come back. Additionally, for the last 2 years the Save Koh Tao Group has been releasing more turtles, and also has started a sea turtle nursery/head-starting program. In March of this year, on record for the first time in 20 years, a turtle came and laid about 120 eggs in Tanote Bay. This has been followed by 2 turtles laying eggs on the beach near Laem Tien in late June. These events are bringing hope to our community and increasing the demand for adequate protection of our remaining turtles species. Click to jump to another section of this page: Also, Click here to See Kwan's article about the turtle eggs in Tanote Background on Sea TurtlesSea Turtles are long-lived marine organisms that have very complex life cycles. Some of their life traits include; high mortality rate for eggs and juveniles, a delayed sexual maturity, repeated reproduction (iteroparity), and high adult survivorship rates (Frazer 1992, Congdon 1993). Turtle species specific to Thailand include the Leather Back (Dermochelys coriacea), Green (Chelonia mydas), Hawksbill (Eretmochelys imbricate), and Olive Ridley (Lepidochelys olivacea) turtle species (Eckert 1999, Settle 1995). The Loggerhead previously been found in Thailand, but is thought to be extirpated. Like all reptiles, turtles lay eggs. Generally this is done on sandy beaches, but it is important to realize that not all species desire the same beach and approach types. Species such as the Leatherback will prefer to nest on beaches that have steep slopes and unobstructed approaches, while species such as the Hawksbill prefer narrow island beaches with coral reefs obstructing the approach (Eckert 1999). This fact is important when selecting the release site for hatchlings as they will generally return to this site as adults to nest.
Different turtle species will have varying amounts of eggs per nest, or clutch. The Hawksbill may only have about 70-90 eggs per clutch, while the Green Turtle may have as many as 130 eggs per clutch. Eggs incubate on beach areas until conditions are right and they hatch. Hatchling sex is dependent upon incubation temperature, at temperatures cooler than 29.2°C the clutch will be 100% male, and above 30.4°C the clutch will contain  100% females. Generally, in natural conditions the periphery of the clutch will be male and the eggs in the center will be female, this is due to higher temperatures in the center from metabolic heating (Chan 1995). These hatchlings (age <1year) move into the sea where they swim a short distance and then are taken away by ocean currents, for this reason, hatchlings are considered to be planktonic organisms (Carr 1987). Survival rates for the hatchlings are very low for all turtles, for the Green Turtle species only about 2.5 per every thousand will reach adulthood (Frazer 1992). After entering the sea, the hatchlings float into the open ocean, or pelagic zone, where they continue to drift until occurring an ocean front. Ocean fronts are areas of convergence or divergence between water masses and are generally areas of high nutrient concentration due to upwelling forces. Also contained in these ocean fronts are beds of sea grass, algae, and floating debris, which provide refuge and feeding sites for the young turtles throughout this life stage. Here the hatchlings will feed mainly on pelagic tunicates, snails, and barnacles attached to floating debris, but will eat almost anything that is small and within reach (Carr 1987).
The turtles then move into the juvenile stage (age 1-20 years) where they will continue to live both in pelagic and coastal areas, feeding both in coral reefs on sponges and invertebrates and also in pelagic zones. Turtles then reach the adult stage (age > about 20 years) in which they reach sexual maturity and begin to reproduce. Some turtles are able to lay eggs every year, while others may lay eggs only once every other year (Heppell 1998). Due to the delayed sexually maturity of turtles, they have a high risk of death before reproduction large time spans between generations (Congdon 1993). Because of this fact, turtles are slow to adapt to changing environmental conditions, and are very susceptible to chronic disturbances.
Threats to sea turtles
Almost all of the earth’s turtle species are currently experiencing increased stresses and decreased adult populations due to the anthropogenic factors. Scientific research of turtles is still far from comprehensive, but  information gained in the last few decades has greatly increased knowledge about environmental problems and how they effect sea turtle populations. In Asia, the main threat to turtles is the exploitation for markets. Here, turtles are sold for meat, shells, oil, skins, eggs, and medicines. The overexploitation of Turtles for Asian food markets is the largest factor contributing to decreased number throughout the Asian continent (Engstrom 2002, Eckert 1999). Another large problem faced by turtles is the accidental capture and drowning of turtles from fishing operations. Tens of thousands of turtles die every year in active and abandoned nets, and fixed lines (Eckert 1999, Congdon 1993, Kemf 2000). In the U.S. Atlantic and Gulf of Mexico, over 10,000 to 12,000 turtles die every year from shrimp trawl nets (Frazer 1992). Even if the numbers of accidental capture could be decreased, many scientists such as Congdon believe that the “sustainable harvest of long-lived organisms is an oxymoron” (1993).
Coastal development is occurring at very high rates around the world, especially on Koh Tao, and decreases the habitat available for the nesting turtles. Increases in tourism and recreational activities generally fuel development in coastal areas, and create disturbances that negatively affect the turtles (Congdon 1993, Eckert 1999, Kemf 2000). In addition to the loss of habi
tat and safety, both adult turtles and hatchlings can be disoriented by artificial light and be unable to locate the sea (Frazer 1992). Pollution concentration levels tend to be high around developed coastal areas or in areas where petroleum operations take place.
Turtles are faced with a wide range of environmental hazards and pollutants. Among the highest dangers to the turtles are oil spills, high heavy metal concentrations, chemical wastes, plastic, and other debris (Eckert 1999, Kemf 2000). These pollutants can leak into coastal areas and be concentrated around bays or in ocean fronts. The concentration of pollution in fronts greatly inhibits hatchlings ability to reach the juvenile stage as the young carnivores tend to eat anything small and available (Carr 1987). In a study around San Miguel, Mexico, turtle autopsies revealed that the dead turtles had ingested “polyethylene sheet plastic, bits of solid plastic, pieces of paper, and nylon line; all were also found to have semi-solid clots of petroleum oil” inside their digestive system (Carr 1987). Save Koh Tao Sea Turtle Release Efforts
For the last two years the Save Koh Tao Group has been working together with the Thai Navy to release sea turtles from the island that have been breed in captivity. The idea behind this project is that by increasing the numbers of turtles in the sea we can attempt to help them adapt to changing conditions and sustain populations until policy involving fishing and habitat destruction can be changed. The turtles we receive from the Thai Navy range in age from a few months to a few years, and at last year's Save Koh Tao Festival we were able to release 49 turtles into the sea.
Save Koh Tao Sea Turtle Head-starting Program“Head-start” programs are those that protect and care for the turtles for about 9 months to a year after hatching. After the turtles have reached a size when they are no longer vulnerable to predation by birds and aquatic organisms they are released. This program is based on the fact that very few, on the order of 1 in a 1,000, baby sea turtles make it to reproductive age in the Gulf of Thailand. Most of these turtles are eaten by predators in the first few months, then snarled up by nets or choked by liter and pollution while still juveniles.
Many projects around the world are in place to keep baby sea turtles in captivity until they become large enough to escape prey, and often this is done in an artificial enclosure such as a plastic tub or concrete pool, where the turtles are fed dead fish and vegetables at regular intervals. Initially we began our project in the same way, but what we found was that the turtles appeared unhealthy and overly aggressive. We believe that in the pools there is a scarcity of resources, and the turtles natural instinct is to compete for those limited resources and attack the smaller individuals. After studying their behavior and looking at their damaged fins we decided that this was not a proper way to be stewards of these animals. We also expected that in close proximity a virus or disease could attack and kill our entire stock.
So in 2008 we decided to make a natural enclosure and move the baby turtles out of the tubs. The enclosure was constructed between rocks in a secluded bay, we built a bamboo wall to contain the turtles, but still allow water to flow in and out of the enclosure naturally. We removed all predators such as groupers and crabs from the enclosed area, and then put the turtles inside. Immediately they appeared happier and healthier. In the tubs they spent there time floating around and would bite any other turtles they bumped into, but in the natural cage they would rest on the rocks, and even huddle together without attacking one another. They could also eat at will by consuming the algae and barnacles growing on the ro cks, after observing the turtles in the natural enclosure we feel that this is the only responsible way to keep baby sea turtles when conducting headstarting programs, but other groups should be aware of a few complications.
The first problem we encountered was mortality due to octopus predation. This is very difficult if not impossible to prevent while in the natural enclosure. The groupers, crabs, birds, and other larger predators can be kept out easily, but an octopus can fit through any hole or crevice as big as their beak. One way to reduce mortality from octopuses is to take the turtles out of the enclosure and put them into pools at night, but this can be stressful and introduce problems or the possibility of disease transmission during handling. Still we feel this is a good alternative to keeping them in the artificial pools all the time.
Our project in 2008 ended prematurely after only 2 months when a storm broke down the bamboo wall, releasing the 18 baby turtles. This release was of course earlier than planned, but the turtles were released into the sea, and hopefully have an increased chance of survival than if they had been released immediately after hatching. No shells were found by divers in the area, and we found no evidence that any turtles died during the storm that broke down the wall.
For 2009 we decided to build an artificial enclosure that would mimic natural conditions to prevent the problem we had in 2009. We built a pool using stones and concrete and  put a bamboo roof over the top to reduce the heat build up in the pool. The pool was built a few meters from the sea, so that fresh sea water could be circulated constantly, flushing out the pool and allowing a natural exchange of algae and plankton. We also had plans to add sand and coral rubble as substrate, and introduce sea cucumbers and reef fish to clean waste organic matter and algae from the enclosure and the turtles shells. Unfortunately, before we could move the turtles into the new enclosure they were stolen. We still do not know the fate of the turtles, whether they were stolen by locals wishing to eat them, or a tourist who spotted the turtles and released them thinking that somebody was holding them to be eaten. We hope is was the later, but due to the problems of the last few years we will be reevaluating the program and the importance of head-starting programs over the next few months while focusing primarily on education and raising awareness.
References Carr, A. 1987. New Perspectives on the Pelagic Stage of Sea Turtle Development Conservation
Biology 1:103-121. Chan, E.H. and H.C. Liew. 1995. Incubation Temperatures and Sex-ratios in the Malaysian
Leatherback Turtle (Dermochelys Coriacea). Biological Conservation 74:169-174. Congdon, J.D., A.E. Dunham and R. C. Van Loben Sels. 1993. Delayed Sexual Maturity and
Demographics of Blanding's Turtles (Emydoidea blandingii): Implications for
Conservation and Management of Long-Lived Organisms. Conservation Biology
7:826-833
Eckert, K. L., K. A. Bjorndal, F. A. Abreu-Grobois and M. Donnelly (Editors). 1999. Research
and Management Techniques for the Conservation of Sea Turtles. IUCN/SSC Marine
Turtle Specialist Group Publication.
Engstrom T. N., H.B. Shaffera and W.P. McCord. 2002. Phylogenetic Diversity of Endangered and
Critically Endangered Southeast Asian Softshell Turtles (Trionychidae: Chitra).
Biological Conservation 104:173-179.
Frazer, N. B. 1992. Sea Turtle Conservation and Halfway Technology. Conservation Biology
6:179-184.
Heppell, S. S. 1998. Application of Life-History Theory and Population Model Analysis to Turtle
Conservation. Copeia 2:367-375.
James, M.C., A.C. Ottensmeyer and R.A. Myers. 2005. Identification of High-use Habitat and
Threats to Leatherback Sea Turtles in Northern Waters: New Directions for
Conservation. Ecology Letters 8:195–201.
Kemf E., B. Groombridge, A. Abreu and A. Wilson. 2000. Marine Turtles in the
Wild. World Wide Fund for Nature.
Settle, S. 1995. Status of Nesting Populations of Sea Turtles in Thailand and Their Conservation. Marine Turtle Newsletter 68:8-13.
Yasuda T. and N. Arai. 2005. Fine Scale Tracking of Marine Turtles Using GPS-Argos PTTs.
Zoological Science 22:547-553.
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