Factbox: What could be causing Botswana’s mysterious elephant deaths?

GABORONE (Reuters) – Botswana is investigating hundreds of unexplained elephant deaths in one of Africa’s top tourist destinations.

Botswana is home to a third of Africa’s elephants, and there is concern that whatever is causing the deaths, first recorded in May, could affect animals in neighboring countries.

Below are some theories about what might be behind the unexplained deaths.

POACHING

The government and conservationists ruled out poaching at an early stage because the bodies have been found intact, with their fangs on.

Africa’s overall elephant population is declining due to poaching, but Botswana has been an exception, with the number of elephants growing to 130,000 from 80,000 in the late 1990s.

POISON

Poachers sometimes use poisons like cyanide to kill elephants before removing tusks for ivory. But scavengers do not appear to be dying near carcasses, which would be a sign that the culprit was the poison.

ANTHRAX

Anthrax, an infectious disease caused by spore-forming bacteria, sometimes affects wildlife in Botswana. But government veterinary experts say the samples taken from the dead animals in the Okavango Panhandle contained no traces of anthrax.

ALGAE BLOOMS

Another possible cause could be algal blooms, which can make the water toxic to large animals.

Up to 70% of dead elephants have been found clustered near water wells. But other animals don’t seem to be dying in large numbers.

DROUGHT

Drought is a common cause of death in arid areas of southern Africa, but it has rained in the Okavango Panhandle in recent months, and researchers who have visited the area say there is plenty of water.

A NEW PATHOGEN?

Conservationists have speculated that another pathogen, a known or new virus or bacteria, could be to blame.

Researchers reported seeing live elephants physically weakened or wandering in circles, indicating neurological decline. Some were found face down, which could indicate sudden death.

The government says it has sent samples of dead animals to laboratories in Zimbabwe, South Africa and Canada for further testing.