Researchers have quantified the contribution of poaching to elephant decline for the first time, and they found that illegal killing is enough to endanger the survival of the species. Across the African continent, poachers have driven an average reduction of 2 to 3 percent a year between 2010 and 2012 -- that’s 100,000 elephants in just three years. The work was published in Proceedings of the National Academy of Sciences this week.
Because of its covert nature, poaching has been difficult to quantify, and the scale of the ivory crisis has been left to speculation. "Witnessing the killing of known elephants, some that we have followed since they were born, has been terrible," says George Wittemyer from Colorado State University in a news release. "Our data has become the most sensitive barometer of change during this poaching epidemic. We needed to quantify the scale of killing and figure out how to derive rigorous interpretation of poaching rates."
So, to develop a repeatable and verifiable, data-based way to estimate poaching rates, Wittemyer and an international team examined species demographic data and analyzed the cause of death for elephant populations using the UN-mandated Monitoring of Illegal Killing of Elephants (MIKE) program.
First, the team investigated poaching rates at the local scale by surveying carcasses in Kenya’s Samburu National Reserve -- where illegal killing began to surge after 2008. Locally, poaching rates rose with increases in the price for ivory, as well as with the volume and number of seizures of illegally harvested ivory: The surge was directly correlated with the quadrupling of black market prices and the tripling of trafficked ivory seizures at Kenyan ports, with the destination increasingly shifting to China.
This work also helped distinguish between illegal and natural causes of mortality. Clustered kills -- such as these two adults killed in close proximity in northern Kenya -- are usually a sign of professional poaching.
Then, to estimate poaching at a continental scale, the team extended their Samburu analysis and combined demographic data with MIKE’s carcass survey covering African elephant populations at 45 sites. According to this extrapolation, elephant populations at this larger scale suffered illegal killing rates of 7 to 8 percent of the entire population each year from 2010 to 2012 -- that’s an average of 33,630 elephants killed a year. The killing peak in 2011 equated to more than 40,000 deaths. Preliminary 2013 data suggest an “unsustainable” killing rate higher than 5 percent.
The timing and magnitude of declines varied by region, with central Africa experiencing the worst levels. These populations "are on the front end of the spear,” Wittemyer tells Science. “It’s been a disaster." Poaching has reached a level that new elephant births can’t overcome.
Images: David Daballen (top), Chris Leadisimo (middle)