Carcasses of nearly 90 elephants have been found near a famous wildlife sanctuary in Botswana, conservationists say.
Elephants Without Borders, which is conducting an aerial survey, said the scale of poaching deaths is the largest seen in Africa.
The spike coincides with Botswana's anti-poaching unit being disarmed.
Botswana has the world's largest elephant population, but poachers have been breaching its border.
The scientist carrying out the extensive wildlife survey, Dr Mike Chase, said many of the 87 dead elephants were killed for their tusks just weeks ago. Five white rhinos have also been poached in the last three months.
"I'm shocked, I'm completely astounded. The scale of elephant poaching is by far the largest I've seen or read about anywhere in Africa to date," Dr Chase said.
"When I compare this to figures and data from the Great Elephant Census, which I conducted in 2015, we are recording double the number of fresh poached elephants than anywhere else in Africa."
That census estimated a third of Africa's elephants had been killed in the last decade and 60 percent of Tanzania's elephants had been lost in five years.
Botswana's reputation for an unforgiving approach to poachers means it has largely escaped the elephant losses seen elsewhere.
Despite a lack of fences on the international border, data from tracking collars showed elephants retreating from Angola, Namibia and Zambia and deciding to stay within the boundaries of Botswana where it was thought to be safe.
Incidents of poaching in the country were rare because of armed and well-managed anti-poaching units.
With 130,000 elephants, Botswana has been described as their last sanctuary in Africa as poaching for ivory continues to wipe out herds across the rest of the continent.
The first sign that was changing came two years ago when the BBC flew with Mr Chase close to the Namibian border and he discovered a string of elephant carcasses with their tusks removed for the first time.
But these latest killings have been found deep in Botswana - close to the protected Okavango Delta wildlife sanctuary, which attracts tourists from around the world.
"People did warn us of an impending poaching problem and we thought we were prepared for it," said Mr Chase, who pointed to the disarmament of the country's anti-poaching unit as a cause.
"The poachers are now turning their guns to Botswana. We have the world's largest elephant population and it's open season for poachers."
The government disarmed its anti-poaching units in May - a month after President Mokgweetsi Masisi was sworn into office.
The units have focussed much of their effort on the border regions, which have historically been more vulnerable.
A senior official in the president's office, Carter Morupisi, told journalists in Botswana at the time that the "government has decided to withdraw military weapons and equipment from the Department of Wildlife and National Parks", but he did not explain why.