Toxins in water produced by cyanobacteria killed more than 300 elephants in Botswana this year, officials said Monday, announcing the outcome of an investigation into the deaths that had confused and alerted conservationists.
Cyanobacteria are microscopic organisms that are common in water and are sometimes found in soil. Not everyone produces toxins, but scientists say that toxins occur more often as climate change drives global temperatures.
Cyril Taolo, deputy director of the Department of Wildlife and National Parks, told a news conference that the number of bodies of elephants found since deaths were first reported around early May had risen to 330, from 281 in July.
“What we just know at this point is that it is a toxin caused by cyanobacteria,” Taolo said, adding that the specific type of neurotoxin had not yet been established.
Authorities will monitor the situation during the next rainy season, and Taolo said so far there is no indication that Botswana’s wildlife was still threatened as officials no longer saw deaths.
The department’s chief veterinary officer Mmadi Reuben told the same press conference that there were still questions about why only elephants had been affected.
Other animals in the Okavango Panhandle region appeared unharmed.
Some cyanobacterial flowers can harm humans and animals, and scientists are concerned about their potential impact, as climate change leads to warmer water temperatures, which many cyanobacteria prefer.
Southern Africa’s temperatures are doubling the global average, according to the Intergovernmental Panel on Climate Change.
“It’s like having the right conditions at the right time in the right place, and these species will spread,” Patricia Glibert, a professor at the University of Maryland Center for Environmental Science who has studied cyanobacteria, told Reuters.
“These conditions come together more often in several places, so we see more of these poisonous flowers around the world.”
In neighboring Zimbabwe, about 25 carcasses were found near the country’s largest game park, and authorities suspect they succumbed to a bacterial infection.
The animals were found with tusks intact and ruled out poaching and deliberate poisoning. Park officials believe the elephants may have ingested the bacteria while searching for food. The carcasses were found near water sources.
“We were considering the possibility of cyanobacteria, but we have no evidence that this is the case here (in Zimbabwe),” said Chris Foggin, a veterinarian at the Victoria Falls Wildlife Trust who tested samples from dead elephants from Zimbabwe and Botswana.
Zimbabwe has sent samples to Britain and is awaiting permission to send samples to two other countries, Foggin said.
Africa’s total elephant population is declining due to poaching, but Botswana, home to nearly a third of the continent’s elephants, has seen the number grow to around 130,000.