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  National Geographic 17 Aug 06
Record Ivory Cache Traced to Zambia Elephants, DNA Shows
Susan Brown for National Geographic News

A trail of DNA has helped investigators trace the largest shipment of contraband ivory ever seized to African forest elephants from Zambia.

The size of the shipment--more than 500 whole tusks and thousands of individual pieces--means that elephants from a single region have been hit hard.

Forest elephants are a distinct species, as different from their savanna cousins as lions are from tigers. They are smaller with rounded ears, sloping brows, and straighter tusks, which carvers prize for their hardness and pinkish color. Poaching of forest elephants is easily hidden, as their carcasses are difficult to spot beneath the dense canopy of central African rain forests.

In the 1980s African elephant numbers plummeted from 1.3 million to fewer than 600,000. Conservationists estimate that about a third of those left are forest elephants. The decline was partly due to loss of habitat, but ivory poaching played a major role.

Despite treaties prohibiting international shipments, poaching continues today. "The ivory trade right now is as bad as it's ever been," Sam Wasser, a wildlife biologist at the University of Washington in Seattle, said at a meeting of the Society for Conservation Biology in San Jose this June.

Tracing the Trade

In June 2002 customs agents in Singapore intercepted a 20-foot (6-meter) container holding 13,000 pounds (5.9 metric tons) of elephant ivory.

The confiscated shipment is the largest seizure since the United Nations Convention on the International Trade of Endangered Species banned the ivory trade in 1989.

By tracking movements of the container, investigators learned that smugglers had packed it in Malawi and shipped it through South Africa to Singapore. The ivory was destined for Japan. Some tusks bore the imprint "Yokohama," a seaport south of Tokyo. The shipment included 42,000 small cylinders--blanks for hanko, the stamps Japanese artists use to sign their work.

But investigators wanted to identify which populations of African elephants the ivory had come from, and for that they needed a "fingerprint" that would lead them to the animals that were killed.

Elephant Map

Two years ago Wasser and his colleagues at the University of Washington published a continent-wide map of genetic fingerprints for African elephants in the Proceedings of the National Academy of Sciences.

To make this map, Wasser's team had sequenced DNA recovered from nearly 500 samples of dung collected from elephants in 23 African countries. Ample roughage in the elephants' diets helps slough off plenty of cells from the intestines, making DNA easy to extract from dung.

Wasser's team found that they were able to identify which forest--even which game preserve--new dung samples came from.

Bill Clark, secretary for the Interpol Working Group on Wildlife Crime, asked Wasser to match DNA from the seized ivory to his genetic map.

But getting DNA out of the tusks proved to be a challenge. Drilling or grinding ivory heats it, destroying any DNA present, so Wasser's research group borrowed a technique from forensic dentistry.

The team sealed slices of ivory sawed from tusks in a tube along with a stainless steel plug, then froze the tube to -240°F (-150°C). Using a rapidly reversing electromagnet to shake the metal plug, they smashed the ivory into a fine powder from which DNA could be extracted.

When Wasser's team compared 75 samples from the illegal shipment to their genetic map, they found that all of the ivory came from Zambia.

"This blew Interpol's mind," Wasser said.

Just months before the shipment was seized, Zambia had requested permission for a one-time sale of stockpiled ivory. That request was subsequently denied.

"Wasser's work is potentially extremely useful," Intepol secretary Clark said. "Regrettably it is still quite new and being applied for the first time, so we have not yet any experience with prosecutions or the technique's admissibility as evidence in court."

But just knowing where the ivory is coming from could help, Clark said, by identifying poaching hot spots where efforts to prevent hunting could be focused.

Meanwhile the illegal trade continues. On May 10 customs officials in Hong Kong announced they had confiscated a shipment of 600 African elephant tusks.
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