River TurtlesNesting habitsThe arrau turtle’s shell is approximately【L31】 ____

Today on Nature Focus we’re looking at the river turtle and the threats it’s facing in today’s world. Two main places we see the giant river turtles are South America and South-east Asia. The best way to see the big rivers of South America, such as the Amazon and the Orinoco is probably by plane. But then you might miss the strange shallow craters that cover the sandbanks along these rivers. These are the nests of the arrau turtles, and at night thousands of turtles rise up out of the river water and scuttle into these holes. The holes are around ninety centimetres in diameter, so the turtles, whose shells are about seventy-five centimetres in length, fit neatly. Enormous numbers of eggs are laid on the beaches. Since hundreds of females, each laying between seventy and eighty eggs, crowd together it means that literally thousands of eggs fill the sandy nests, waiting to hatch.
A similar story is played out in Asia, where the river terrapins also lay their eggs communally and in the open. The difference is that the terrapins, once they have used the nests, cover them over and then beat the sand down with their limbs, making an amazing sound, like drums. The noise at night of many terrapins doing this is incredible, and drowns out the sound of the river water. And the male terrapins are fascinating too. Throughout the breeding season, they are famous for the colour changes to their oddly-shaped heads that take place.
However, these wonderful creatures are under threat, and this has been the case for quite some time. As long ago as 1811, the scientist and explorer Alexander von Humboldt was a witness to the mass destruction of turtle eggs at the Orinoco river. The eggs made oil and the oil made money. He recorded that, ’A jar contains twenty-five bottles of oil, each bottle being the production of two hundred eggs, and allowing for the wastage of eggs damaged in the nest, thirty-three million eggs had been harvested to fill the five thousand jars’ — and that was a sight and a calculation that appalled him.
And it appalled many others too, so there have been, over the years, various initiatives designed to protect turtles and terrapins from such slaughter. For example, the Sultans of Perak in Asia ensured the safety, at least to some extent, of the beaches for terrapins when they issued licences to official egg collectors. These collectors would only collect eggs in numbers that were sustainable. However, the scheme, of course, vanished with the Sultans. And despite efforts at protecting turtles, there axe ever-growing demands for them, for pets in some countries, and as food in others and also heavily in traditional medicine in various parts of Asia. These levels of exploitation unfortunately far exceed their ability to reproduce and so replace their lost stock. It takes a turtle a long time — many years — to grow from a baby, or hatchling, to an adult that can reproduce, and so the survival of eggs and hatchlings is crucial to the survival of the species. But the threat never stops being acute. Once adult, a female turtle can continue reproducing for a number of decades, provided they are not killed or injured, so the loss of even a single adult can mean many years of reproduction are lost forever.
Is it all gloom? Well, there are some grounds for cautious optimism. There are some well thought out management systems in place which can help the stocks of threatened turtles and terrapins to rebuild. In Brazil, for example, the government has been encouraging and supporting the farming of river turtles, with the idea that this happens alongside the banning of the hunting of wild turtles. The idea Of the scheme is to provide farmers with a one-off batch of hatchlings, which they are urged to keep until they become mature. This should mean that good quantities of turtles capable of reproducing come to the rescue of the species. Will it work? Let’s hope so. The scheme has its doubters, who point out that, while the biology arguments for the scheme certainly do make sense, the farmers on the scheme, of course, have no experience of this kind of farming. That means it’s impossible at this stage to know if the turtles they develop will be sufficiently marketable, and thus if the scheme will work well from an economic point of view. It may be that it has to rely on subsidies, and that would mean, in the long term, that it would probably fail. But it’s certainly worth a try, and I hope to be back on this programme in a few years’ time, reporting on its great success.