In May this year, elephants started dying in the Okavango Delta region of Botswana, a country known for its large and burgeoning elephant numbers. With a population estimated at some 135,000 individuals, Botswana has the largest concentration of these pachyderms in Africa. But there are no fences between neighbouring countries, so Botswana’s elephants are able to move between that country, Angola, Namibia, Zambia and Zimbabwe. To date, an estimated 400 elephants have apparently died, without any cause having been pinpointed to date. A mystery indeed.

The Botswana government has come under fire for not finding out what is killing their elephants, but reports say that samples are now being examined by several different laboratories. It should be remembered that the movement of humans and goods in southern Africa have been negatively affected by the COVID-19 ‘lockdowns’. The following reasons for the elephant mortality have been considered:

Poaching? No – dead animals have not had their tusks removed, so poaching seems unlikely.

Persecution? Many rural folks in Botswana are very disgruntled with elephants which destroy their crops, houses and often people at times. Some may be tempted to take revenge on elephants for this reason, but no evidence of gunshots is visible on any of the carcasses examined.

Poison? A number of elephants were killed in neighbouring Zimbabwe when a waterhole was poisoned with cyanide. But such poisoning incidents usually affect other species drinking water from the same waterhole, or scavengers like vultures that feed on poisoned carcasses. No such evidence is forthcoming from Botswana.

Toxic algae? Some blue-green algae are known to be toxic to mammals, but again, if this was the cause we would expect other species drinking from the same waterholes to be affected. They are not – this thing is apparently elephant-specific.

Anthrax? This disease is known to kill elephants, but during an outbreak, many different species are usually affected. There is no evidence that anthrax is the culprit.

Starvation? No – Botswana has had reasonable rains, and the elephant carcasses do not appear to be emaciated. Starvation normally affects the very young and the very old, but the carcasses examined so far seem to be subadults and adults in good condition.

A new, previously unknown virus affecting the nervous system? In the outbreak area, elephants have been seen to be walking in circles. A number of the elephants have apparently collapsed face-down and died like that, indicating a very sudden onset of a fatal neurological event.

This last one got me thinking about events many years ago when my friend and colleague Dr Peter Mundy was studying vultures in then Rhodesia (Zimbabwe) for his Doctoral degree. He kept a number of different species in captivity for his research, and had the sad experience of quite a few of these birds dying of what he described as ‘epileptic fits’. Affected birds would stagger about in circles, falling on their backs with convulsions and quickly die. The mysterious agent responsible was spread from affected birds to healthy individuals.

Brain tissue from the dead birds was sent to Dr Bob Swanepoel, a very good veterinary researcher in the country. However, due to various circumstances beyond his control, Dr Swanepoel could only get around to examining these specimens several years later, when he was working at the Onderstepoort Veterinary Research Institute in South Africa.

He found evidence of a virus in brain tissue that probably caused this deadly neurological syndrome in the affected vultures. Unfortunately, nothing further has ever been done to conduct more research on this particular avian disease.

Living in the age of COVID-19, it seems clear that a virus from bats managed to transfer to humans in Wuhan, China, possibly via pangolins. Given this potential for interspecies transmission of viruses, is it possible that Peter Mundy’s vultures picked up their deadly virus from eating dead elephants that had succumbed to the same agent? And that the same or a similar virus has now resurfaced in the elephants in the Okavango Delta? What happens to disease transmission when animal (or human?) populations grow too large? Again, I am reminded of an epidemic of rabies that decimated the very large population of Kudu in Namibia many years ago.…

Hopefully the mystery of Botswana’s elephant mortality will be solved, sooner or later. But these things do take time, as critics of the Botswana government should be reminded. It took many years, and the near-extinction of the vultures in India and Pakistan, before it was finally discovered that the birds were being killed in their thousands by Diclofenac (‘Voltaren’), a drug commonly used to treat sick cattle in both countries. When some of these medicated livestock died, they were consumed by vultures, with devastating results. What a terrible outcome for these magnificent birds, which “Even when bloody, have done no creature harm”.

Dr John Ledger is a past Director of the Endangered Wildlife Trust, a consultant and academic on energy and the environment, and a columnist for the African Hunting Gazette. He lives in Johannesburg, South Africa.