The reason behind the mysterious death of around 350 elephants in Botswana’s Okavango Delta four years before was found using satellite imagery and geographic examination which was caused by the animals drinking from contaminated water holes where toxic algal populations had grown due to climate change. This incident was the largest documented elephant die-off where the cause was unknown.
The deaths in Botswana’s Okavango delta were described as a “conservation disaster” by scientists. Elephants of all ages were seen walking in circles before collapsing and dying. Dead bodies were first discovered in north eastern Botswana in May and June 2020 with many theories circulating at the time about the cause of death including cyanide poisoning or an unknown disease.
The cause of the incident was potentially a “toxic brew” of open water contaminated by a cyanobacteria species that emitted cyanotoxins thereby poisoning the elephant’s watering holes, a new study revealed. Researchers found that about 20 watering holes spread across about 6,000 square kilometers (2,316 square miles) in Botswana’s Okavango Delta were poisoned by this blue-green algae or cyanobacteria due to climate change.
Cyanobacteria and how it affects Elephants:
A specific cyanobacteria often known as blue-green algae can create a kind of harmful algal blooms (HABs) in standing water even though not all of them are hazardous. This harm full of algal bloom was found in this research done by the King’s College London researchers for the mass elephant’s death. The study stated that the drinking water from holes contaminated with these harmful algal blooms caused the deaths of African elephants (Loxodonta africana) in May and June of 2020.
The lead researcher of the study stated, “Scientists believe that the production of cyanotoxins is related to certain environmental triggers, for example, sudden rise in water temperature, nutrient loading, and salinity.” In southern Africa, 2019 was the driest year in decades which was followed by a heavy rainy year in 2020. These conditions led to more sediment and nutrients being suspended in the water which led to this unusual algal growth.
According to the study, the elephants typically walked 62 miles (just over 100 km) from the waterholes and died within 88 hours of consuming water. Researchers looked at nearly 3,000 waterholes in total and discovered that there were higher amounts of dead bodies in areas that had more cyanobacteria blooms.
Other animals might have also died from drinking from the water holes but small dead animals might have already been eaten by predators or bodies might not have been visible during aerial surveys.
Elephants Death:
Several elephant dead bodies were discovered scattered around the Ngamiland province of northern Botswana in early to mid 2020 during a series of routine helicopter aerial surveys carried out by the conservation group Elephants Without Borders. In addition to finding 2,682 live elephants over the eastern Okavango Panhandle, the helicopter survey revealed 161 elephant dead bodies and 222 sets of bones. Furthermore, the distance between the dead elephants suggested that the dead had occurred suddenly rather than a gradual natural death.
