Eighty-seven elephants have been found slaughtered near a famous Botswana wildlife sanctuary.
The carcasses were discovered by conservation non-profit Elephants Without Borders as they conducted an aerial survey of the land.
Poachers had cut off the elephants' tusks and tried to hide the corpses under bushes.
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Many had been killed within the past three weeks.
Mike Chase from Elephants Without Borders says the animals were victims of a "poaching frenzy" which has been ongoing since the disarmament of Botswana's anti-poaching unit.
"I'm shocked, I'm completely astounded," he told the BBC.
"The scale of elephant poaching is by far the largest I've seen or read about anywhere in Africa to date."
Botswana is home to the world's largest elephant population, with 130,000 of the animals within its borders.
The country had been a safe haven for elephants from neighbouring Angola, Namibia and Zambia thanks to its armed anti-poaching units patrolling the border regions and protecting the animals from being killed for ivory.
However the Botswana government disarmed those units in May after President Mokgweetsi Masis was sworn into office. Government officials did not explain the decision.
Mr Chase says the government must take action to prevent more elephants being killed.
"The poachers are now turning their guns to Botswana," he told the BBC. "We have the world's largest elephant population and it's open season for poachers."