After the death of their popular elephant Misha, Utah's Hogle Zoo agreed to donate one of her tusks to science. (Hogle Zoo.)
Nearly 25 years after an international ban was placed on ivory, African elephants are being slaughtered at a rate that could bring about their extinction this century. By allowing the trade of ivory acquired before 1989 to continue, the ban put the burden on law enforcement to distinguish between legal ivory and poached. Now, a new method for dating elephant tusks, described in the latest issue of the Proceedings of the National Academy of Sciences (PNAS), could make it easier to enforce the ivory ban and save the African elephant from extermination say researchers. The method might also be applied to endangered rhinoceroses and other wildlife.
"We've developed a tool that allows us to determine the age of a tusk or piece of ivory, and this tells us whether it was acquired legally," said the study's lead author, Kevin Uno, a postdoctoral researcher at Columbia University's Lamont-Doherty Earth Observatory. "Our dating method is affordable for government and law enforcement agencies and can help tackle the poaching and illegal trade crises."
In the highly-regulated market for legal ivory, finding tusks for scientific research is not easy. With the help of a Salt Lake City zoo and several agencies in Kenya, the researchers gained access to the tusks of two elephants: Misha, euthanized at Utah's Hogle Zoo in 2008, and Amina, who died naturally at Kenya's Samburu National Preserve in 2006. Study co-author Thure Cerling, a geochemist at the University of Utah, read about Misha's death in the local newspaper and immediately called the zoo. "They told us, we can work with you because we haven't buried her yet," he said. The researchers traveled to Kenya for Amina's tusk, which they sawed into domino-sized samples under the watch of Kenya Wildlife Service.
In the lab, the researchers measured radiocarbon levels at the base of each tusk to independently calculate when the elephants died. Similar tests were done on monkey hair, hippo canines, oryx horn and elephant tail hairs to verify that the method worked across tissues of different ages. Two steps were key to getting precise ages. The researchers sampled each tusk lengthwise, along the growth ring, and used the most advanced technology--an accelerator mass spectrometer--to measure the radiocarbon. In addition, the study calculated growth rates for the teeth, which can be applied to elephant teeth in the fossil record to understand how climate and vegetation varied in Africa when humans were evolving. In other applications in wildlife forensics, the technique can be applied to rhino horns, which are intensely sought after for their perceived medicinal benefits.
|Global demand for elephant ivory is fueling the slaughter of African elephants. (Lucy King, Save the Elephants).||