The test could help block the illegal ivory trade

Previous difficulty in determining the geographic area where illegal ivory came from presents an obstacle to combating illegal trafficking.

Researchers devised a genetic map of African elephant populations capable of pinpointing the source of ivory.

The study appears in Proceedings of the National Academy of Sciences.

The illicit trade in African elephant ivory has seen a resurgence in recent years, placing the elephant at renewed risk.

In the forest you don't notice the change in population until it's so dramatic that it's almost too late to do anything about it Samuel Wasser, Center for Conservation Biology

Despite a 1989 ban on the trading of ivory, some of the largest ivory seizures have occurred since 2002.

US researchers carried out calculations to estimate how common 16 genetic markers were over different geographic regions across the elephants' entire range.

The team, led by Samuel Wasser of the Center for Conservation Biology in Seattle, Washington, US, collected 315 skin biopsy samples and 84 samples of elephant dung from forest and savannah elephants at 28 different locations.

Dung sample

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"Some of the most pressing needs in elephant conservation include timely identification of current poaching 'hot spots' where greater law enforcement is needed," the researchers write in the PNAS journal.

Other requirements include monitoring how international trade decisions affect elephant poaching throughout Africa, determining whether government ivory stockpiles are being illegally traded and replenished, whether sanctioned one-time sales are using illegal tusks from other locations and whether illegal stockpiles are being consolidated and exported.

The accuracy with which genetic methods can determine the origin of DNA can "greatly contribute" to all of these needs.

The African elephant population fell by 60% from 1979 to 1987

The study found 50% of the samples tested were accurately located within 480km (300 miles) and 80% were accurate to within less than 965km (600 miles).

Accuracy was much greater among forest populations, which are more clearly defined because of terrain.

"In the central African or west African forests, we have incredibly high precision," Dr Wasser told the BBC. "We can almost do it down to the individual forest and right now, poaching is probably at levels higher than it's ever been in central African forests.

"My colleagues working in the forests are saying, 'there are no elephants left here'."

"That's the problem - in the forest you don't notice the change in population until it's so dramatic that it's almost too late to do anything about it."

The African elephant population plummeted by 60%, from 1.3 million to just 500,000 between 1979 and 1987, largely because of ivory poachers.