Aerial views of elephants that have been found dead in Botswana National Park Rescue
  • Almost 400 elephants have dropped dead in Botswana since early May. Nobody knows why.
  • Tests ordered by Botswana's government in laboratories in South Africa and Zimbabwe have proved inconclusive.
  • Pesticides, agrochemicals, and pathogens as possible reasons for the unexplained deaths of the world's biggest land animals have been ruled out, a government statement said.
  • Botswana is home to Africa's largest elephant population of 130,000.
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The question of what killed hundreds of elephants in Botswana remains answered after long-awaited test results proved inconclusive.

Between May and July of this year, the remains of hundreds of elephants were discovered near the Okavango panhandle, in northwest Botswana.

They were often found close to waterholes and distressing photographs showed they had crashed headfirst into the earth, indicating a sudden death. Other sickly elephants were emaciated, weak, and barely able to walk.

Deliberate poisoning was initially suspected due to the ongoing conflict between farmers and elephants. However, this was later discounted as carrion feeders such as vultures were unaffected.

Results from test samples sent to laboratories in South Africa and Zimbabwe ruled out pesticides, agrochemicals, and pathogens commonly implicated in deliberate wildlife poisoning as possible reasons for the unexplained deaths, Bloomberg reported.

Botswana's environment ministry in a statement said it was investigating natural poisoning as a potential cause of death.

"The results received so far do not eliminate poisoning, therefore environmental factors, including naturally occurring toxins, are still being investigated," it said.

"This is a mass die-off on a level that hasn't been seen in a very, very long time. Outside of drought, I don't know of a die-off that has been this significant," National Park Rescue's Dr Niall McCann told The Guardian newspaper.

Botswana is home to around 130,000 elephants, Africa's highest population of the animals, according to the BBC. Around 10,000 of those live in the grassy Okavango Delta, which floods seasonally.

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