AUDIE CORNISH, HOST:
Our next story comes from African and new research on migratory elephants. Their migratory behavior is in part what makes them harder to protect from poachers. It also makes elephants extremely difficult to count. Today, a study was released that offers the first scientific, peer-reviewed estimate of how many African elephants have been killed by poachers. It looks at the period from 2010 through 2012. As NPR's East Africa correspondent Gregory Warner reports, researchers arrived at the death toll using old-fashioned detective work.
GREGORY WARNER, BYLINE: George Wittemyer is a conservation biologist at Colorado State University, and he's been working in Kenya since 1997 studying the sophisticated behavior of elephants - their famous memory, how orphaned animals go about reconstructing their lives. But more recently, he's been walking through the forest counting carcasses.
GEORGE WITTEMYER: So the idea is we go out and whenever we can locate a dead elephant, we try to assess how it died.
WARNER: Sometimes it's obvious.
WITTEMYER: You know, very fresh cases, you can follow the footprints, you can find the cartridges from the bullets. And we can track them. And we'll find where a motorcycle came in and the nearest route to take the ivory away.
WARNER: But sometimes poachers are bad shots, and the wounded animal gets away.
WITTEMYER: And what happens when an elephant gets shot is it starts internally bleeding, externally bleeding - both. And it gets very thirsty if it hasn't died immediately. And so the animal will run into the park where it knows it's safe, and it will come down to the river to get water. And we find quite a few of our carcasses that way, where they've come in and died.
WARNER: This took painstaking forensic work - body by body, over more than a decade. But Wittemyer's team is now able to say not just how many elephants died in this part of Kenya, but how many died as a result of poaching. He's extrapolated that finding to all of Africa using data from the United Nations on the numbers of elephant carcasses spotted in 45 different sites. That carcass data is a little fuzzier. It's self-reported by countries. Still, Wittemyer says he's confident in saying that more than 100,000 elephants were killed by poachers in three years. That's the first peer-reviewed scientific estimate of its kind. And he says it's a rate of killing high enough to destroy the species. He hopes it's a number large enough to make not just his fellow conservationists, but also world leaders, take notice.
WITTEMYER: It's much easier to dismiss this issue if you don't have the numbers to present.
WARNER: He hopes that his research out today in the proceedings of the National Academy of Sciences will motivate countries to do more to rein in demand for ivory. Even as he knows that his own motivation to do this detective work comes not from that huge, round number - 100,000 deaths - but from watching the elephants that he's lived with and studied dying one by one. Gregory Warner, NPR News, Nairobi. Transcript provided by NPR, Copyright NPR.