UW News

November 8, 2016

Clues in poached ivory yield ages and locations of origin

Elephant tusks

An ivory seizure, 6.5 metric tons, in Singapore in 2002.Benezeth Mutayoba/Sokoine University of Agriculture

More than 90 percent of ivory in large, seized shipments came from elephants that died less than three years before, according to a new study.

A team of scientists at the University of Utah, the University of Washington and partner institutions came to this conclusion by combining a new approach to radiocarbon dating for ivory samples with genetic analysis tools developed by UW biology professor Sam Wasser.

Their approach gave conservationists a picture of when and where poachers are killing elephants. The paper, which includes Wasser as a co-author, was published Nov. 7 in Proceedings of the National Academy of Sciences.

“This work provides for the first time actionable intelligence on how long it’s taking illegal ivory to reach the marketplace,” said Lesley Chesson, a co-author and CEO of Isoforensics. “The answer is not long at all, which suggests there are very well-developed and large networks for moving ivory across Africa and out of the continent.”

“Apart from the actual killing, there’s the trade on the ground before it gets to ports, the actual shipments through shipping containers, and then the problem of the demand side,” said Thure Cerling, the study’s lead author and professor of geology and geophysics at the University of Utah. “This additional information can be helpful to people trying to address those issues.”

In June 2016, the United States banned nearly all commerce in elephant ivory, which came 26 years after a ban on international trade in ivory. Both measures aimed to curtail the widespread poaching of elephants, whose numbers have plummeted since the 1980s.

Poaching still claims an estimated 8 percent of African elephants each year, or around 96 elephants per day. Demand for elephant ivory and other illegal products derived from endangered animals has grown in Asia in recent years, opening a fresh battleground in the struggle against illegal ivory, even as U.S. markets shut down.

Bans usually allow the sale of ivory that was legally acquired prior to 1976, including heirloom or antique pieces. Confirming the age of those pieces, however, relies on proper documentation. Traders in illegal ivory sometimes use this clause as a cover, claiming that their wares are older than they really are.

Cerling and his colleagues applied radiocarbon dating — a technique from forensic science — to estimate the age of samples in seized ivory shipments, with some adjustments for a Cold War legacy.

Mushroom cloud from a hydrogen bomb

Mushroom cloud from “Ivy Mike,” U.S. codename for the first successful test of a hydrogen bomb, on Nov. 1, 1952 on Enewetak Atoll.Comprehensive Nuclear Test Ban Treaty Organization

Above-ground nuclear weapons testing through the 1960s doubled the concentration of radioactive carbon-14 in the atmosphere. This heightened carbon-14 signature was preserved in plants — which take up atmospheric carbon — and transferred to herbivores like elephants. Carbon-14 levels have been declining since the 1960s, and scientists can use the carbon-14 signature in a bone, tusk or tooth to determine, within about a year, when the material was formed. And since elephants grow new material at the base of their tusks, the ivory there contains the carbon-14 signature of the plants the elephant has recently eaten.

Chesson said forensic scientists have used this “bomb carbon” signature to estimate the ages of human remains in cold cases and track the transit time of cocaine shipments. But now their team has applied this method to seized ivory.

Wasser led efforts to gather ivory samples from large stockpiles seized by law enforcement officials between 2002 and 2014. Alerted by contacts in law enforcement, officials in the seizing country or from internet monitoring, Wasser collected some samples himself and directed colleagues in sampling the rest. Officials in countries that had seized these samples were helpful and cooperative, he added.

“They really appreciate the collaborative effort,” Wasser said.

These samples consisted of small sections, only one or two inches on a side, from the inside surface of the base of the tusk — the freshest material with the radiocarbon signature most recent to the death of the elephant. Wasser said the sight of so many tusks in one place was distressing, particularly the tusks of young elephants shot by poachers to attract other larger elephants.

“Sometimes, many of the tusks are so small that you can’t understand why the animal was even killed,” Wasser said. “Tusks can weigh less than one pound, with almost no carvable ivory on them.”

Elephant tusks

An ivory seizure made in Malaysia in 2012, weighing 6 metric tons.Syarifah Khadiejah Syed Mohd Kamil/Malaysia Department of Wildlife and National Parks

Of the 231 samples Wasser collected, only one returned an age of greater than 6 years between the time of the elephant’s death and the seizure of the ivory — known as the lag time. Nearly all of the analyzed ivory had a lag time of around two to three years, suggesting that the shipments did not come from stockpiles or from old sources. Instead, large shipments of ivory are likely composed of recently poached pieces.

“This work demonstrates that little or no ‘old’ ivory, like that held in government stockpiles, is ending up on the black market, which is good news for the security and monitoring of those stockpiles,” Chesson said. “There is no other way to get such intelligence without a technique like ‘bomb-curve’ radiocarbon dating.”

Combining Cerling’s radiocarbon data with Wasser’s genetic analysis to determine the geographic origin of the ivory, the researchers constructed a picture of which regions have established rapid pipelines to get poached ivory to market. In the study, seized ivory is classified as either originating in East Africa, the Tridom region of west-central Africa, West Africa or Zambia. Additionally, samples were classified as having a rapid lag time of less than 12 months, intermediate lag time of 12 to 24 months or a slow lag time of greater than 24 months.

Ivory attributed to East Africa had a higher proportion of rapid-transit samples than the other regions, suggesting a strong distribution pipeline from the region. Ivory from Tridom was more likely to contain slow-transit ivory, and both West African and Zambian ivory exhibited intermediate lag times. The information, Cerling said, can help law enforcement focus on the worst poaching regions and also provide information on the health of elephant populations.

“If all of the seizures are really recent, within the past two to three years, we can use that to determine the overall killing rate of elephants in Africa,” Cerling said.

Time is running out for elephants, but these new analysis tools may help law enforcement officials plug the ivory-smuggling networks.

Co-authors were Janet Barnette with IsoForensics, Iain Douglas-Hamilton with Save the Elephants and Oxford University, Kathleen Gobush with Vulcan, Kevin Uno of Columbia University and Xiaomei Xu at the University of California, Irvine. The work was funded by the Paul G. Allen Family Foundation and Save the Elephants.


For more information, contact Wasser at 206-543-1669 or wassers@uw.edu.

Grant number: 11811.

Adapted from a release from the University of Utah with the permission of the author.