Despite a 1989 ban on the slaughter of elephants for their tusks, the illegal ivory trade is as brisk as ever. In an effort to step up efforts to protect elephants, researchers have been using genetic technology to create a map of heavily poached areas in Africa.

The ban on the trade of ivory was adopted almost 15 years ago. But since 1995, the number of slaughtered elephants has been rising each year because poachers have found holes in the prohibition.

To try to clamp down on the increasing slaughter, scientists are using elephant DNA to crack down on heavily poached areas in Africa.

Samuel Wasser heads the Center for Conservation Biology at the University of Washington. Mr. Wasser and colleagues found that the genetic material of elephants is unique in 28 areas throughout Africa, and by deciphering the DNA of tiny pieces of seized ivory, they can trace elephant tusks to particular locations.

"It tells us what's going on with the movement of ivory throughout Africa," Mr. Wasser said. "And it can also lead, when combined with other bits of evidence, it can help crack a case. Just like any forensic case, very rarely does any one single bit of information give you the answer. But it's the combination of everything together that does."

Mr. Wasser says the DNA technique can also help investigators determine a tusk's country of origin, which is important if poachers try to hide it among stocks of legitimate tusks.

"It tells us whether or not did all this ivory really came from the country that it was originally shipped from, which was Zambia? Or did it come from many different countries? And if it came from many countries, then that starts to tell us things like ivory that has been stockpiled in other places as being essentially pulled together and shipped out in single shipments in several key locations. So it tells us what's going on with the movement of ivory throughout Africa," Mr. Wasser said.

Some call it the "white gold" of the animal kingdom because elephant ivory fetches huge sums of money on the black market. Despite the international ban, there was a huge seizure of tusks in Singapore two years ago worth more than six million dollars. The illegal cargo included more than than 500 tusks destined to be carved into intricate figurines costing thousands of dollars each.

In addition to the tusks, Mr. Wasser says the crates contained tens of thousands of small pieces of ivory with family seals carved into them called "hankos" that sell for around $150 a piece.

"To make the 41,000 henkos, who knows how many elephants that was," Mr. Wasser said. "You know, I think conservatively, there were 2,000 elephants in that."

The World Wildlife Fund estimates that 4,000 elephants are currently being killed each year for their ivory. The endangered species groups say many countries cannot afford the cost of monitoring poaching. Other countries are seeking permission to sell existing stockpiles of legitimate ivory collected before the 1989 ban. That has signaled to black marketeers that it is okay to start poaching again.

Wildlife protection groups say the biggest exporters of African ivory are the Democratic Republic of the Congo, Cameroon, Ethiopia and Nigeria. The biggest consumers are countries in Asia and the United States.

The International Fund for Animal Welfare's Peter Pueschel says a stronger international ban on elephant poaching is needed.

"If you see not one, but 10, 20, 40 or even more elephants in a small area being killed and all their tusks are ripped out of their heads, this is a very shocking picture, and it is a horror because you can really see the silence that is coming if all the elephants are gone in that area," Mr. Pueschel said.

The Convention on the International Trade of Endangered Species gets under way this weekend in Bangkok, where it will consider strengthening a ban against elephant poaching and the illegal hunting of other endangered animals.

Research on elephant DNA appears in the Proceedings of the National Academy of Sciences.