Pinpointing poachers: gene sleuths map illicit elephant kills.

An elephant tusk never forgets its homeland. Every piece of ivory contains DNA unique to its place of origin. Now, researchers say a genetics-based technique they've developed is geographically precise enough to aid forensic pursuit of African-elephant poachers.

The new method, which is described in the Oct. 12 Proceedings of the National Academy of Sciences, appears on the eve of an international meeting in Bangkok that could relax some rides governing the sale of ivory from southern Africa.

Elephant hunting and the scale of new ivory have been largely outlawed since 1989, when 115 nations adopted antipoaching regulations under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). But ivory trade persists.

According to a September report by, the antipoaching network called TRAFFIC, U.S. customs officials annually confiscate or block from importation about l,000 ivory objects. Yet online marketplaces such as eBay.com advertise a comparable number of ivory items each week, many of which investigators suspect are illegal.

To discover where poachers operate and how they move ivory out of Africa, CITES monitors elephant populations and retraces the routes of interdicted ivory shipments. However, existing detective practices include only crude DNA analysis that can't directly link a poached tusk or piece of ivory to the scene of an elephant's death.

Thus it's unclear which elephant ranges are in greatest need of rigorous law enforcement and which borders require more thorough customs inspections, says conservation biologist Samuel Wasser of the University of Washington in Seattle.

So, Wasser and his colleagues developed a map of Africa that identifies individual elephant populations by" their genetic characteristics. The scientists used 399 samples of DNA from tissue or scat that had been collected in 28 elephant ranges across 16 countries. They filled in other parts of the map by using statistics to infer the genetic makeup of elephants living between the sampled locales.

The researchers now can assign a geographic origin to any sample of African ivory by comparing its DNA with the sequences on the map. Wasser says the map already has more than an 80 percent chance of being accurate to within 1,000 kilometers, and it will improve as the scientists collect and map more geographically identified samples.

The new technique could complement CITES' efforts, says Simon Habel, who directs TRAFFIC's North American research from Washington, D.C. To prod African countries to crack down on illicit ivory trade, he says, "knowing which national park that ivory came from would be beneficial."

Next week, CITES member nations are scheduled to consider relaxing ivory-trade restrictions in countries where elephants are relatively abundant. However, permitting even such limited ivory sales may encourage poachers elsewhere.

Researchers using the new DNA map could determine whether ivory on sale in a legal market originated in an illegal hunting ground outside that country's borders, Wasser says.