UW News

September 19, 2018

DNA testing of illegal ivory seized by law enforcement links multiple ivory shipments to same dealers

UW News

The international trade in elephant ivory has been illegal since 1989, yet African elephant numbers continue to decline. In 2016, the International Union for Conservation of Nature cited ivory poaching as a primary reason for a staggering loss of about 111,000 elephants between 2005 and 2015 — leaving their total numbers at an estimated 415,000.

In a paper published Sept. 19 in the journal Science Advances, an international team led by scientists at the University of Washington reports that DNA test results of large ivory seizures made by law enforcement have linked multiple ivory shipments, over the three-year period when this trafficking reached its peak, to the same network of dealers operating out of a handful of African ports. The researchers linked these ivory shipments together after developing a rigorous sorting and DNA testing regimen for tusks in different ivory shipments. This method allowed the scientists to identify tusk pairs that had been separated and shipped in different consignments to different destinations around the world — yet had been shipped out of the same port, nearly always within 10 months of each other, with high overlap in the geographic origins of tusks in the matching shipments.

African elephants examining a bone from another elephant

African elephants examine a bone from a fellow elephant.Karl Ammann

Our prior work on DNA testing of illegal ivory shipments showed that the major elephant ‘poaching hotspots’ in Africa were relatively few in number,” said lead and corresponding author Samuel Wasser, director of the UW Center for Conservation Biology and a professor of biology. “Now, we’ve shown that the number and location of the major networks smuggling these large shipments of ivory out of Africa are also relatively few.”

Using this protocol, the team identified what appear to be the three largest ivory smuggling cartels in Africa, operating out of Mombasa, Kenya; Entebbe, Uganda; and Lomé, Togo. Out of 38 large ivory shipments analyzed, the team was able to link 11 of these shipments together by identifying tusk pairs that had been separated after poaching, yet shipped out of the same port during the 2011-2014 period when trafficking was at its peak.

Tusks from an ivory seizure in 2015 in Singapore after they have been sorted into pairs.

Tusks from an ivory seizure in 2015 in Singapore after they have been sorted into pairs by the process developed by Wasser and his team.Center for Conservation Biology/University of Washington

Large shipments currently dominate the illegal ivory trade. About 70 percent of ivory seizures between 1996 and 2011 were in large consignments of at least half a metric ton, or about 0.55 U.S. tons, according to a 2013 study in PLOS ONE. Linking multiple large ivory shipments to the same smuggling networks will help build evidence against the cartels that are responsible for the bulk of illegal ivory trade and shipment, Wasser said. These efforts could add multiple counts of trafficking charges against the leaders of smuggling operations, who most often are tried for single, high-profile and occasionally controversial events; the recent acquittal of Feisal Mohamed Ali in Kenya being a case in point.

A person working in a lab.

A staff member isolates DNA from tusk samples. Wasser and his team had to devise methods to extract DNA from ivory without degradation of the genetic material. They freeze the tusk sample in liquid nitrogen, then use tiny magnets to pulverize the frozen sample, which keeps the DNA from deteriorating.Center for Conservation Biology/University of Washington

“We reveal connections between what would otherwise be isolated ivory seizures — linking seizures not just to specific criminal networks operating in these ports, but to poaching and transport networks that funnel the tusks hundreds of miles to these cartels,” said Wasser. “It is an investigative tool to help officials track these networks and collect evidence for criminal cases.”

Wasser and his team had previously developed DNA testing of large ivory shipments to identify what populations of African elephants were most targeted by poachers. For this endeavor, they created a “genetic reference map” of elephant populations across Africa, using DNA samples extracted primarily from elephant dung. Then, the team sampled ivory from elephant tusks seized by law enforcement officials and extracted DNA from them. The researchers matched key regions in the ivory DNA samples to the genetic reference map, which let them identify the region that the elephant had come from, often to within about 300 kilometers, or about 186 miles. In a 2015 paper published in Science, they announced that the bulk of seized tusks came from two “poaching hotspots” on the continent based on these DNA analyses.

While conducting those analyses, Wasser and his team developed a protocol to representatively subsample hundreds of tusks as efficiently as possible.

“We have neither the time nor the money to collect samples and extract DNA from every tusk in a shipment,” said Wasser. “We needed to find a way to sample only a fraction of the tusks in a shipment, but that method also needed to let us get a glimpse at the diversity of poached elephants within that shipment.”

Scientists working to study elephant tusks.

Wasser (left) and his team sort tusks from a seizure in Singapore in 2015 and use saws to cut away ivory samples for subsequent DNA extraction and genetic analysis.Kate Brooks

In each large ivory seizure, they would identify pairs by sorting tusks by the diameter of the base, color, and gum line, which indicates where the lip rested on the tusk. This allowed the researchers to extract DNA from only one tusk in the pair. Using this sorting approach, Wasser and his team noticed that many tusks in large shipments were orphans. The partner tusk was not present. But through comparing DNA samples from tusks among 38 large ivory consignments confiscated from 2011 to 2014, they matched up 26 pairs of tusks among 11 shipments, even though they were only testing, on average, about one-third of the tusks in each seizure.

“There is so much information in an ivory seizure — so much more than what a traditional investigation can uncover,” said Wasser. “Not only can we identify the geographic origins of the poached elephants and the number of populations represented in a seizure, but we can use the same genetic tools to link different seizures to the same underlying criminal network.”

A map of Africa, showing the locations of poached elephants and the African ports where major consignments of illegal tusks are smuggled off the continent.

By using DNA testing to match tusk pairs smuggled in separate consignments, Wasser and his team are able to link multiple ivory shipments to the same smugglers. Each map indicates separate shipments, with the location, date and weight of the seizure shown in the lower left. The blue circles show the geographic origins of the tusks based on genetic analysis; origins of a small number of poached elephant corpses matched to tusks are shown in open red circles. Linked pairs are shown by double-headed arrows, with thickness indicating the number of pairs. Shipments labeled “1” or “2” are linked by other lines of evidence.Wasser et al. 2018, Science Advances

Co-authors on the paper are former UW Center for Conservation Biology research scientists Amy Torkelson and Sean Tucker; Center for Conservation Biology scientists Misa Winters and Yves Horeaux; Moses Otiende with the Forensic and Genetics Laboratory at the Kenya Wildlife Service; Frankie Sitam with the Malaysian Department of Wildlife and National Parks Peninsular Malaysia; forensic scientist John Buckleton, who is a visiting scientist at the UW; and Bruce Weir, a UW professor of biostatistics. The research was funded by the Paul G. Allen Family Foundation, the U.S. Department of State, the U.N. Office of Drugs and Crime, the World Bank, the Woodtiger Fund, the Wildcat Foundation, INTERPOL, the Bosack Kruger Charitable Foundation, Paul and Yaffa Maritz, the U.S. Fish and Wildlife Service and the National Institute of Justice.


For more information, contact Wasser at +1 206-853-4730 or wassers@uw.edu.

DOI: 10.1126/sciadv.aat0625

Grant number: 2011-DN-13X-K541.