(Bloomberg) --

The mystery of unexplained elephant deaths in northwest Botswana deepened, with a study of the carcasses of hundreds of the animals indicating a rapid demise.

Since early May, 356 elephants have been found dead in the Okavango Panhandle, Elephants Without Borders said in a report submitted to the Botswana government. The state is waiting for results of tests, but poaching has been ruled out as their ivory tusks have been left intact.

“Many carcasses were near natural waterholes,” according to the non-profit group, which conducted an aerial survey by helicopter. “Elephant carcasses also occurred along trails and died in a sternal position on their chests, suggesting a fast and sudden death.”

With about 135,000 elephants, Botswana has the world’s biggest population of the animals. Still, they have become a political issue, with President Mokgweetsi Masisi last year lifting a hunting ban and saying more needed to be done to stop the animals from damaging crops and occasionally trampling villagers.

That caused a global backlash from conservation organizations, including threats of travel boycotts. Tourism accounts for a fifth of Botswana’s gross domestic product.

Elephants Without Borders said its attempts to work with the government have been rebuffed. The organization confirmed the report but officials weren’t immediately available to comment.

“We reiterate our numerous efforts to support the Department of Wildlife and National Parks to address this escalating and concerning mass elephant mortality,” it said in the document. “Swift action and disclosure are needed to avert a potential public relations fiasco.”

Not Poison

The acting director of the Department of Wildlife and National Parks, Cyril Taolo, and the regional wildlife director in the area, Dimakatso Ntshebe, didn’t answer calls made to their mobile phones.

The carcasses didn’t show signs of poisoning as no dead vultures and other scavengers were seen nearby, the group said. The 97-page report contained photos of 187 elephant carcasses.

Elephants Without Borders also recorded a number of live elephants that “appeared to be weak, lethargic and emaciated,” it said. “Some elephants appeared disorientated, had difficulty walking, showed signs of partial paralysis or a limp in their legs. One elephant was observed walking in circles, unable to change direction although being encouraged by other herd members.”

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