The trade in elephant tusks and ivory is prohibited - at least if the material was later than 1989 won. (Hogle Zoo)
Reading Even 25 years after the ivory trade was banned, with a few exceptions, the killing of elephants continues. Around 30, 000 of the gray pachyderms in Africa are shot illegally every year and robbed of their tusks. The problem: Because the trade in old ivory is often still allowed, authorities must first find out how old a confiscated piece is. But that was just difficult. A method now presented by an international team of researchers could remedy this situation: they use the fallout from past nuclear tests to determine the age of ivory or coat samples. The big advantage: not only is this dating accurate to the year, it is also affordable for customs and other authorities. Trafficking in illegal ivory reached a new record in 2011: 39, 000 kilograms of hot goods were confiscated - equivalent to the tusks of nearly 6, 000 elephants. And the demand for the matt white natural material continues to increase. China is the largest importer with a share of 70 percent, where ivory is mainly processed into works of art and carved seals. In the US, the second largest market, it becomes knife and pistol grips. In order to protect the elephants and put an end to the brutal slaughter, the trade in tusks of Asian elephants was banned in 1975, that of ivory of African origin in 1989. But that does not stop the poaching: 30, 000 African elephants annually fall victim to ivory hunters, estimated Representatives of the CITES Convention.

Customs and authorities are often powerless against the flood of illegal ivory. The biggest problem is that in the US and some other countries, African ivory objects made before 1989 are still allowed to be imported and traded. An exact age determination of such pieces was hardly possible - until now. "We have developed a method that allows us to determine the age of a piece of ivory or a tusk at an affordable price, " says lead author Kevin Uno of the University of Utah. In tests with 29 samples of animal hair, tusks and other animal and plant materials of different ages, the researchers managed to date them precisely down to the year.

C-14 from nuclear weapon explosions as a dating aid

The new method is based on the so-called bomb curve - the atmospheric changes caused by the nuclear tests of the 1950s and 60s. The explosions of the nuclear weapons caused much of the heavy carbon isotope C-14 in the atmosphere. As a result, the C-14 levels increased sharply from 1952 and dropped slowly after the end of the nuclear weapons tests in the early 1970s again. The C-14 also enters the plant and animal tissues via carbon dioxide and the food chain. If one compares the content of this carbon isotope with the known curve of the atmospheric C-14 values, one can conclude from this, when an animal last built carbon into its body - and thus, when it probably died. display

In the case of the elephants, this balance is particularly well possible because the tusks grow a little bit further year after year, with the youngest section lying directly at their base. If you measure the C-14 content there, you can determine when the elephant died. For their study, the researchers used the so-called accelerometer mass spectrometry (AMS). In this method, the sample is bombarded with cesium atoms. Upon impact, these precipitate carbon atoms from the material, the iosotopic ratio of which can then be determined. The big advantage: The analysis requires a thousand times less material than previous C-14 tests and it goes fast, as the researchers report. "It could therefore be used well to date seized ivory and determine whether it is legal or illegal, " said co-author Thure Cerling of the University of Utah.

The process could also help combat on-site poaching more effectively: In 2004, a University of Washington researcher created a distribution map of African elephant populations using waste DNA samples. Based on traces of genetic material in ivory its origin can be traced so. Combining this with the C-14 dating, one can not only tell more accurately when the elephant was killed, but also where - and take appropriate protective measures for the rest of the population. How necessary that is, the latest figures from the International Union for Conservation of Nature (IUCN) show that only around 423, 000 African elephants now roam the savannahs and forests of Africa - and there are fewer and fewer.

Kevin Uno (University of Utah, Salt Lake City) et al., Proceedings of the National Academy of Sciences (PNAS), doi: 10.1073 / pnas.1302226110 © science.de - === Nadja Podbregar

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