The illegal hunting of African elephants could soon be slowed down based on the results of a new sleuthing technique scientists have devised for pinpointing the geographic origin of illicitly traded ivory.
The numbers of African elephants fell from 1.3 million to 600 million between 1979 and 1987. Despite an international ban on ivory trade that was set in 1989 and designed to save African elephants, demand for their cream-colored tusks often used to carve cane and knife handles and other small objects remains high.
Three of the largest seizures of ivory after the ban happened in 2002, and some nations have received suspensions of the ban.
Authorities could benefit from a way to figure out where poachers are most active by tracing seized ivory back to the forests and savannas where the elephants that were killed for their tusks once roamed.
Samuel Wasser of the University of Washington and his colleagues isolated DNA from 315 tissue and 84 scat samples from African elephants from countries including Botswana, Cameroon, Central African Republic, Congo, Democratic Republic of Congo, Kenya, Namibia, South Africa, Ethiopia, Gabon, Ghana, Ivory Coast, Tanzania, and Zimbabwe. They studied the DNA to make a map of genetic variation among elephant populations.
University of Washington statistician Matthew Stephens enhanced the map by extrapolating genetic signatures to fill in gaps between sampled populations. The result is a tool that can analyze any tusk DNA and accurately tell the region of Africa whence it came.
African elephants live in open savanna and deep forest habitats, where their populations are hardest to monitor. Often, steep declines in their numbers are observed after it is too late, Wasser said. Poaching is particularly severe now in Central Africa, the authors note in their paper. African ivory is usually smuggled out of West Africa to markets in such places as Cairo, Bangkok, Tokyo, Singapore, Hong Kong and Shanghai.
The new technique, described in a paper published in the Proceedings of the National Academy of Sciences, can predict where different genetic variations will be found over the entire range where African elephants live. This genetic and statistical technique is relatively inexpensive compared to conventional field techniques to monitor African elephants and could complement them.
The approach was good enough to correctly pinpoint the geographic origin of half of the samples Wasser, Stephens and their colleagues studied within 500 kilometers (300 miles) and 80 percent of the samples within 932 kilometers (540 miles).
Now, authorities can use DNA data from seized ivory to monitor poaching and focus enforcement efforts in regions with the most active trade. The information will also help with decisions about whether to add elephants and other animals to endangered species lists and about whether trade bans should be lifted.
The noose also could be tightened around the illicit trade in other wildlife and marine life, such as whales and sharks, using the same techniques, Wasser said.
And authorities could slow the trade in elephant "bushmeat" as small tusks probably come from elephants killed for their meat, not their ivory.
"We may be able to get a quick handle on bushmeat simply by tracking the origin of small tusks in recent seizures," he said.