investigations by us, that the chinese ban on ivory hasn't yet had the effect of stopping the slaughter. the botswanan government says these reports, including our own, are unsubstantiated and sensational, saying "at no point in the last months or eventually were 87 or 90 elephants killed in one incident in any place in botswana." well, there's no indication this was one incident. it appears to be several weeks of killings. and the worry is, is that this could really decimate the herds in a key population center for elephants. the scientists looking at that statement from the government, we asked him what he thought of that. he said, well, i 100% stand by what i saw. the evidence is irrefutable. dave? >> irrefutable and devastating. a very important story. david mckenzie in johannesburg, thank you. just about top of the hour.