The mystery of the unexplained deaths of hundreds of elephants in Botswana
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Around 400 have mysteriously perished in the north of the Okavango Delta since the first reported deaths in March this year.
“The bottom line being that until the results are released from accredited laboratories, the cause of death is unknown and remains speculative,” said Dr Michelle Henley, principal researcher at the NPO Elephants Alive.
“It would appear that it could be due to a localised virus or bacteria outbreak. A potential natural poisoning event can also not be ruled out.”
Quick answers, said Henley, may not be available “if elephants are new hosts”.
Reuters reported yesterday that Botswana had received test results from samples sent to Zimbabwe to determine the cause of death but is awaiting more results from South Africa next week before sharing findings with the public.
The die-off was first highlighted by Elephants Without Borders in a confidential report to the Botswana government after its researchers counted 356 dead elephants in the Okavango Panhandle in May and June.
There was “good evidence to show elephants of all ages and sex appear to be dying”, its report said.
Live elephants its researchers spotted looked weak, lethargic and emaciated. Some appeared disoriented and had difficulty walking.
Henley said the probability of starvation, poaching, elephant endoheliotrophic herpes viruses, floppy trunk syndrome and anthrax was very low. There was a “medium” probability both of fatal enteritis from Clostridium bacteria or of encephalomyocarditis, a natural virus.
Dr Kate Evans of Elephants for Africa in Botswana said “until the authorities have the results from their samples it is speculation”.
“The cause of these deaths is not known and appears to only be affecting elephants,” said Elephants for Africa in a statement. “Most deaths have been reported near the village of Seronga in the north of the Okavango Delta. Most carcasses have been found near water.
“The elephants have not been shot and carcasses have been found with their tusks intact, therefore poaching has been ruled out. The elephants appear to be dying quickly with some found in an upright position, which is often the case with anthrax.”
But while Botswana has suffered a drought recently, it has since had good rains so this is unlikely to be the cause.
“Poisoning by blue-green algae or cyanobacteria blooms in water or by humans could cause sudden deaths to otherwise healthy elephants, but we would expect to see other species, particularly scavengers, which feed on their carcasses, dying. So far, this has not been observed.”
A study during the 1990s of unexplained elephant deaths in Kruger National Park concluded encephalomyocarditis virus was the culprit, “which affects the heart and brain and brings on sudden death. In Kruger, most elephants that died were male”.
Elephant endotheliotropic herpes viruses causes fatal haemorrhagic disease in mostly young Asian elephants.
"Related viruses are found in African elephants but are generally benign. Thus it would seem likely the deaths by either a bacterial or viral infection but until conclusive laboratory results confirm the cause of death, this is still speculation."
Chris Thouless, head of research at Save the Elephants, said: “The patterns of mortality and symptoms do not appear to match any poison that has previously been used to kill elephants or any natural pathogen that has resulted in mass elephant mortality in the past.
“This suggests it may be an unrecorded pathogen, or less probably, a new poison or method of poisoning. If it is a natural pathogen then the relatively high density of elephants in this area could be a contributory factor.”
Botswana is home to 130000 savannah elephants, about one-third of the world’s remaining population.
The government, which did not respond to the Saturday Star this week, has been criticised for its lack of urgency in dealing with the deaths.
It said last week that investigations are ongoing with samples sent to labs identified in South Africa, Canada and Zimbabwe. It has verified 281 carcasses.
“The Botswana government has had a team on the ground,” said Thouless. “The investigation has gone slowly, but these are difficult conditions in the midst of the Covid-19 crisis and government agencies cannot move as fast as the private sector can.
“The initial results proved negative for anthrax, which is the usual cause of large-scale elephant mortality, and taking samples to test for an unknown suspected disease from a partly decayed elephant carcass is a big job.”
Professor Graham Kerley of the Centre for African Conservation Ecology at Nelson Mandela University, said in December he was in the Makgadikgadi Pan National Park and “we encountered a number of elephant carcasses, as described in the Delta, but this is south east of the Delta” (so the problem is more widespread).
There was no evidence of poaching or poisoning “so it does seem more likely to be disease”.
Botswana’s is one of the larger remaining populations of elephant “so important for conservation and also that these are now occurring in relatively high densities due to human pressure and population growth”.
These are good conditions for disease transmission.
“It’s also important as the Botswana population of elephants is linked to those in Namibia, Angola, Zambia, Zimbabwe and SA, so this problem may spread. It’s important to identify the cause of these deaths and to monitor its distribution and spread across these six nations.”
Thouless said there have not been any reports of deaths outside the Panhandle. “But elephants live in remote parts of Botswana and usually only a small proportion of elephant deaths are reported. We would be concerned if it spread to other populations and if elephants continued to die, especially if the cause was not fully understood.”
The death of any elephant is distressing.
“However, if it is correct that the number of deaths is less than 500, then this situation does not currently threaten the elephant population of Botswana. Much larger numbers have been killed by poachers in many places across Africa in recent years.
“We can expect an annual natural mortality of at least 3000 per year in Botswana, so this will make a tiny dent in the population if the number of deaths does not greatly increase.
“It may become a concern if elephants continue dying and if the problem spreads to a wider area. This is why monitoring the situation is so important,” Thouless said.