Despite a long-standing international ban on ivory trade, African elephants continue to be killed in large numbers for their prized tusks. But a team headed by a University of Washington biologist has devised a new means of determining the geographic origin of ivory that could prove a potent tool in slowing elephant poaching and the illegal ivory trade by identifying hot spots where enforcement should be increased.
It is relatively easy to monitor elephant populations with flights over the open savannas of eastern, central and southern Africa, but it is much harder to do the same in the dense forests of central and western Africa. Those forests are where elephants are currently being slaughtered wholesale, said Samuel Wasser, who holds the UW's endowed chair of conservation biology and is director of the Center for Conservation Biology.
"My colleagues working in the forests are saying, 'There are no elephants left here,'" he said. "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."
Wasser is lead author of a paper describing the new means of determining ivory origins, being published the week of Sept. 27 in the Proceedings of the National Academy of Sciences.
The African elephant population plummeted by 60 percent – from 1.3 million to just 500,000 – between 1979 and 1987, largely because of ivory poachers. An international agreement banning ivory trade was enacted in 1989, but still three of the largest ivory seizures have occurred since 2002.
In June 2002, authorities in Singapore seized a shipment of about 6.5 metric tons of ivory bound for the Far East. The shipment included 532 whole tusks, many more than 6 feet long, and 41,000 small carved ivory cylinders about the size of hanko stamps, used for document signatures. The cylinders alone were worth more than $6 million.
The new methods developed by Wasser's team can show generally where such ivory came from, alerting authorities to specific areas where added enforcement is needed to curb poaching.
Wasser and his colleagues extracted DNA from elephant droppings and skin biopsy samples collected from numerous locations in 16 African nations. They used that information to build a DNA-based reference map to assign tusk origin. They noted genetic differences in populations from one location to another, and used a statistical method to extrapolate genetic signatures to fill in gaps between sampled populations.
Matthew Stephens, a UW associate professor of statistics, developed a model allowing the researchers to build genetic profiles for elephant populations from which they do not have genetic samples. The model is weighted toward genetic information obtained from populations nearest those for which information is unavailable.
The method allows a DNA sample to be assigned to a fairly specific location, with a relatively high confidence that the assignment is correct. The study indicated that 50 percent of the samples tested were accurately located within 300 miles and 80 percent were accurate to within less than 600 miles. Accuracy was much greater among forest populations, which are more clearly defined because of terrain.
The new method allows for speedy determination of where a particular ivory sample came from, Wasser said. That is important because there is mounting pressure to lift the 1989 ivory trade ban enacted under the Convention on International Trade in Endangered Species. But many experts believe any legalization of ivory trade will only increase poaching. The new sampling method can help determine quickly whether that is true in time for exemptions to be altered before elephant populations suffer catastrophic damage, he said.
Two years ago, five African nations sought, and three received, an exemption from the ban so that they could conduct one-time ivory sales. Now numerous other countries are considering seeking exemptions, and some hope to obtain permanent exemptions.
"Once the door is cracked open, they try to force it open all the way," Wasser said.
He noted that a number of countries have kept ivory stockpiles since the 1989 ban, and the small central-African nation of Burundi has a stockpile of 80 tons – despite the fact that it had only one elephant at the time of the ban. Some observers believe ivory has been sold from that stockpile and replenished from poached ivory.
"This method could detect such restocking in the future," Wasser said.
Tracking elephant ivory is just one example of the value of the sampling and statistical method, he said. The same methods can be used to establish the locations from which any endangered species' products originated, to help conservationists find ways to keep those species from extinction.
Wasser and his colleagues have trained narcotics-detection dogs to find the droppings from endangered species over large remote areas. The dogs can track up to 18 species at once at distances greater than a quarter-mile. Such non-invasive techniques can be used to quickly assemble genetic reference maps to apply this technology to other at-risk species.
Besides Wasser and Stephens, authors of the PNAS paper are Andrew Shedlock, formerly of the UW and now at Harvard University; Kenine Comstock and Elaine Ostrander of the Fred Hutchinson Cancer Research Center in Seattle; and Benezeth Mutayoba of Sokoine University of Agriculture in Tanzania.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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