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DNA pinpoints poached ivory tusks

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12:42pm, March 5, 2007
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Poaching of elephants in Africa has surged in recent years, driven by ivory prices that have more than quadrupled since 2004. Bans on killing elephants are difficult to enforce, partly because authorities don't often know where on the vast continent the poaching is happening.

Scientists had previously attempted using DNA analysis to trace the origins of confiscated tusks, but the information was too imprecise to aid law enforcement. Now, scientists have demonstrated that they can trace the ivory to a single country.

In 2002, police seized more than 6.5 tons of illegal ivory in Singapore. Interpol, an organization that coordinates international police forces, asked Samuel K. Wasser of the University of Washington in Seattle to investigate the source of the ivory.

Wasser and his colleagues adapted the existing technique to work for batches of ivory rather than for single tusks. They compared DNA from each of 37 seized tusks with that from the other samples.

The genetic similarities among the tusks suggested how far apart the elephants lived. When the researchers referred to a reference map of DNA taken from elephant tissue or dung at locations throughout central Africa, the new technique revealed that nearly all the poaching occurred in Zambia. The team confirmed the approach by testing fecal samples of known origin.

The researchers report their findings in the March 6 Proceedings of the National Academy of Sciences.

"We're pretty struck by how much better [the new technique] does," Wasser says. "When we showed that it all came from Zambia, it changed the entire scope of [Interpol's] investigation."

So far, though, the organized-crime network behind the poaching and illegal trade remains intact, Wasser says.


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