Ancient reptiles of the deep, sea turtles have long been surrounded by mystery and ignorance. Now as a result of much research by dedicated scientists and conservationists, our knowledge of these puzzling wild creatures is expanding. Experts believe that obtaining a complete picture of a turtle’s life cycle may be the key to saving them from extinction.

Green turtles were heavily exploited in the 1920’s for turtle soup by canneries on Heron and North-West Islands off central Queensland. Around a thousand nesting female turtles were harvested each year from North-West alone, almost resulting in the total decimation of that island’s breeding population. In other parts of the world such as the Cayman Islands, Bermuda and the Dry Tortugas, entire populations have become extinct through commercial exploitation by man.

Of the seven existing species of sea turtle, six are today listed as threatened or endangered. In 1950, Green turtles became protected in Queensland and in 1968 this legislation extended to include all turtle species. Despite this, most of the remaining populations are still in danger of disappearing.

Will Sea Turtles still be here for our children and grandchildren to enjoy? Research is necessary to determine the migratory habits of the sea turtle.

QUEENSLAND SEA TURTLE PROJECT:
Colin Limpus, zoologist in charge of the Queensland Sea turtle project, has been studying turtles for twenty years, but having grown up near a turtle rookery his involvement with them goes back even further. “We still don’t know how to manage a sea-turtle population to ensure that they will survive,” he says. “We don’t know if what we are doing now will guarantee that there will be turtles still here for our children and our grandchildren.”

Limpus is assisted in his research by Emma Gyuris, a microbiologist and zoologist who has been working with turtles for six years. “I first became interested in 1980, when I went to Heron Island for a holiday and saw Colin Unloading turtles from a boat. I hung around and made a nuisance of myself for the rest of my stay. I wanted to get more involved in turtle work and found that I could do so through an education program Colin had going at Mon Repos Beach near Bundaberg. It was like a childhood dream materializing in front of me. I am now working toward a PhD on turtles.”

The problems involved with conserving turtles are numerous and perhaps one of the greatest difficulties lies in determining the size and structure of the populations we are trying to preserve. Much of the work being done by Colin Limpus and Emma Gyuris concentrates on piecing together this complex jigsaw puzzle.

Every day during the summer they can be seen perusing Heron Reef in their aluminium boat, searching for Green, Loggerhead and Hawksbill turtles. Because of the skill and speed involved in capturing these strong and agile animals, this catching has come to be called “turtle rodeo” and indeed as Gyuris dives from the speeding boat onto a turtles’ back and swims it to the surface, one can see why. Once aboard, the turtles are tagged by their front flippers with numbered titanium labels and some are taken back to shore for laparoscopic examination, by which their sex and maturity level are ascertained.

Loggerhead sea turtles Caretta caretta swimming freely in the waters of the Great Barrier Reef

“We are still looking at turtles that were born before we were,” says Limpus. “We’ve got to, as fast as we can, learn the basic parameters of a turtles life cycle so that we can see just where the weak points are in that life cycle and start addressing them.”

Turtles spend almost all of their lives at sea migrating thousands of miles across international boundaries, making them extremely difficult to track and more importantly to protect. "The problem is that even if we do achieve total protection of turtles within the Barrier Reef, many of the turtles that nest here migrate through developing countries such as Indonesia, the Philippines, New Caledonia and Papua New Guinea," says Gyuris. "In these countries protection laws may be inefficiently enforced or there simply may be no laws to enforce."

TURTLE EXPLOITATION versus SURVIVAL:
The people of these countries are under great economic pressure and turtles can bring in a great deal of money. Unfortunately, there is a high world demand for turtles and turtle products and it is these developing countries which supply the ever-expanding market.
Almost every part of a sea-turtle can be used for commercial purposes: The carapace or shell is much sought after for jewellery and ornaments; the skin of the neck and flippers is used for leather; the meat and eggs can be eaten; the calipash and calipp (flesh of the breast and flippers) along with the neck and tail bones are used in making turtle soup; the offal is manufactured into fertilizer; and the oil is used as a base for beauty creams. Some unlucky specimens are stuffed or freeze-dried and sold as souvenirs to tourists in countries like Indonesia and Thailand.
The three species mainly being exploited today are the Hawksbill, Olive Ridley and Green turtles. Unlike other varieties the Hawksbill does not regularly shed its scales, making its carapace the thickest and most beautifully patterned of turtle shells. From the Hawksbill comes "tortoiseshell" and international trade in this product is alarmingly extensive. "In 1978 world raw tortoiseshell imports totalled 319,290 kg." (Mack, Duplaix and Wells, 1981.) Indonesia appears to be the chief exporter and Japan, Taiwan and Hong Kong the main importers. It is believed that at least 111,000 Hawksbills must have been slaughtered that year for their pretty shells. As statistics point to an increasing volume of tortoiseshell on the world market, scientists report ever declining Hawksbill numbers. It seems that Hawksbill turtles have never been very numerous and if the tortoiseshell trade continues as it is, the species will certainly be unable to survive.

Green sea turtles Chelonis mydas are feeding on jellyfish in these photos. It is easy to see why many turtles die every year while choking on plastic bags. Sea turtles easily mistake plastic bags floating in the water as jellyfish and feed on these with fatal consequences.

A MILLION TURTLES TAKEN:
Another species giving considerable cause for concern is the Olive Ridley turtle, which nests in large numbers on the Pacific coast of Central America. Because the gravid females concentrate their nesting activity to only a few major rookeries, they are extremely vulnerable and are heavily harvested in Ecuador and Mexico. Reptile skins - tanned and fashioned into shoes, bags and belts have always been like furs, expensive luxury items for conceited display. They traditionally came from crocodiles, caymans and snakes, but now those sources have been severely exhausted and the market has turned around and begun using turtles for leather. The unfortunate Olive Ridley turtle has been the main species to come under this latest assault. "From 1970 to 1977, an estimated one million Olive Ridleys were taken on the Eastern Pacific coast by Mexico and Ecuador to supply the skin and leather trade. Skins from an estimated 85,000 Ridleys were exported in 1978 to Ecuador and during the same year, Mexico captured 50,000 Ridley turtles (mainly gravid females) in the state of Oaxaca alone." (Mack, Duplaix and Wells, 1981) Olive Ridleys continue to be killed at this rate, the Central American rookeries will cease to exist within the next few years.
The vegetarian Green turtle is thus named because of its green body fat and is known for its tasty flesh. Consequently the threat to this species arises from local consumption and trade in canned turtle steaks and soup. The main importers of turtle meat are West Germany and the United Kingdom, although most of this comes from the Cayman Turtle Farm on Grand Cayman Island where Green turtles are raised and farmed commercially. Although turtle farming would seem to many people an ideal solution to the problem of wild turtle harvesting, there is much criticism that it in fact perpetuates and encourages a market for turtle commodities. Apart from all that, turtle farming is a very expensive enterprise and one it seems, that has proven to be economically impractical. When the Australian Government sponsored several experimental farms on the Torres Strait Islands back in the 1970s, they were found to be hopelessly uneconomical and were closed.
Under Australian law, indigenous peoples North of Cooktown are permitted to catch turtles for their own use as their ancestors have done for thousands of years. However their ancestors did not have speed boats, nor were the numbers of turtles so severely depleted in those days.
"Surveys indicate that an annual harvest rate of the order of 10,000 Green turtles occurs in the Torres Strait area." (Limpus, 1981.) Is this more than the population can replace? We don't know.

Loggerhead sea turtle Caretta caretta nesting on her natal beach (top left). Green sea turtle Chelonis mydas depositing ping pong sized eggs in a specially dug sand chamber. She then covers the eggs which are incubated in the sand, and then makes her way (top right) back to the ocean. An unusually large aggregation of Green sea turtles Chelonia mydas on the edge of Raine Isand reef. At nightfall emerge on Raine Island, Great Barrier Reef, in their thousands to lay eggs (bottom left). Each female laying up to three times in one season.

LIFE CYCLE:
One aspect of sea turtles which makes them such fascinating animals is their obscure and perplexing life cycle. For instance, when a newly hatched turtle leaves its natal beach it is unlikely to be seen again until it reaches around 30 centimetres in length and an estimated age of ten to fifteen years. Where these young turtles spend the early part of their lives is a complete mystery, though it is speculated that they drift with ocean currents for great distances and remain in the open ocean until they reach a certain level of maturity. Says Limpus: "it used to be thought that turtle hatchlings were lost at sea for a year. Since 1979 we have thought that they are lost for at least a decade. Some people still don't believe us. Between 1973 and 1982 we tagged about a quarter of a million hatchlings. None of them have returned yet." It is believed that turtles return to where they were born many years later to nest. Says Limpus: "Since in the South Pacific, Loggerhead turtles nest only in the Capricorn - Bunker group of islands, the assumption is that they must have been born there." He adds ironically: "We have only got to wait another forty years to find out whether it's true."
Turtles take many years to grow to maturity. It is thought that a female turtle is around fifty years old when she begins to mate and breed. When her first breeding season finally comes around, she drags herself up onto the beach, digs first a body pit and then an egg chamber of around 50 cm. depth and lays an average of 50 to 130 ping-pong ball sized eggs depending on the species. Over the course of that one season she may repeat the procedure up to eight times, laying a total of 500 to 1000 eggs. Of these maybe one or two will reach adulthood. Her nesting season complete, the female will probably not mate again for another three to six years.

TEMPERATURE DETERMINES SEX:
The turtle eggs incubate in the sand for around seven weeks during which time the embryos develop into miniature turtles of 4 to 6 cm. in length. Recent studies have uncovered some astonishing facts about embryonic turtles. The nest is in fact a complete micro-environment where factors such as temperature, sand type, moisture and position on the beach will affect the outcome of the eggs. The sex of a turtle embryo is not genetically determined at conception. When the eggs are laid the embryos within are sexless and whether they turn out to be male or female depends entirely upon the temperature of the sand around the nest. If the sand is 27 degrees Celcius or cooler there will be more males and if it is over 30 degrees, females will predominate. Thus, some beaches produce greater numbers of one sex than others. Though most of the eggs will develop into healthy baby turtles, some will fall victim to crabs and infestation by fungus.

When the baby turtles hatch they spend a few days in the sand, gradually making their way to the surface and when the time is right (usually at night) they emerge together and make an energetic dash down to the water. It is by some innate sense that these tiny creatures, which look something like wind-up bath toys, know exactly in which direction the sea lies, even when it is obscured by ridges or walls. They instinctively more toward the brightest light source which is normally the light area on the horizon. They can be disorientated by artificial light, however, so every effort is made at rookeries to educate the public about the distraction unnecessary lights may cause. At least 90% of the hatchlings will escape birds and crabs to successfully reach the water, but it is here in the sea that their journey becomes perilous. The helpless little turtles are very easy prey to many reef fish and sharks and most will not make it across the reef flat.

Green sea turtle hatchlings Chelonis mydas emerging from sand (top left) making way to the sea (bottom right). Loggerhead turtle hatchlings Caretta caretta emerging from sand (top right).

Wesley Jones is a young scientist whose zoology thesis involves the study of growth and energy in hatchling Green sea-turtles. "At the moment it is almost impossible to study hatchlings in the wild, so we try to gather as much data about them as we can in captivity," says Jones. "When they first emerge, they are using up the yolk sac as an energy reserve and they swim continuously for about four or five days, just to escape the area where there is a high concentration of predators."
For scientists such as Limpus, Gyuris and Jones, turtle research must sometimes seem unrewarding. "The work is longterm when you're looking at an animal that you think lives 150 years. Scientists are probably not going to see the fruits of their labour and the work they do will be of more value in centuries to come," says Jones. Yet it is only through their tireless research that we hopefully may be able to learn enough about sea turtles to procure a safe future for them.
As for the many remaining mysteries and unknowns about sea-turtles, Wesley Jones sums it up by saying: "There are definitely not going to be any shortage of questions that you can ask about turtles for quite a while to come."

REFERENCES
1 . D. MACK, N. DUPLAIX and S. WELLS, Sea Turtles, Animals of Divisible Parts: International Trade in Sea Turtle Products - Biology and Conservation of Sea Turtles, Smithsonian Institution Press (1981).
2. C.J. LIMPUS, The Status of Australian Sea Turtle Populations - Biology and Conservation. of Sea Turtles, Srnithsonian Institution Press (1981).

Text: Sandra Eugarde
Photography: Gary Bell
Published: Underwater Geographic - Australia