Elephants in Botswana. Credit: Bernard Gagnon
Over the course of four months, from March to June 2020, 350 elephant carcasses were discovered in a small area of northern Botswana. The cause of the deaths was not immediately obvious, and speculation led to many theories of what happened. After considering possible causes, a new study looks into the likelihood of disease as a factor, and how barriers to dispersal affect its spread.
Several possible causes into the elephants’ deaths were initially suggested. The region where most of the die-offs occurred – the NG11 management area of the Kavango–Zambezi Transfrontier Conservation Area – is non-protected and high in human-wildlife conflict, and considered a hotspot for elephant poaching. However, no other animals were affected, and all elephant tusks were intact, suggesting that poisoning or poaching were unlikely causes. The presence of a toxic bacteria in watering pans was another suggested cause, but the species-specific mortality made this also unlikely, since many other wildlife and livestock use the same watering pans as elephants and were unaffected.
One thing to note is that elephants in NG11 are highly restricted in their movements: the deep water of the Okavango River forms the southwestern border, and the rest of the area is bordered by fencing. This has created an isolated population of elephants, with no options for movement or dispersal to other, non-confined regions. This population has a particularly high growth rate, and elephants must travel through human settlements in order to reach the main water source, elevating stress levels.
Given this setting, it’s likely that a disease outbreak could move quickly through the population. The combined effects of a large, isolated population, stress due to poaching and other human interactions, and frequent elephant interactions with each other, create a perfect setting for disease to spread. Many individuals would find that disease inescapable.
The event highlights the broader impacts of wildlife fencing, and whether it has conservation value that outweighs other negative consequences. By isolating populations and limiting dispersal, fencing makes it more difficult for elephants to escape a disease outbreak, leading to higher mortality. However, the isolation of a diseased population makes it more difficult for the disease to spread to other populations. Regardless of its role in the elephant deaths, wildlife fencing remains a complicated conservation strategy for limiting animal movement.
Resources
van Aarde, R.J., Pimm, S.L., Guldemond, R., Huang, R. and Maré, C. 2021. The 2020 elephant die-off in Botswana. PeerJ 9: e10686.
Wildlife fencing: how effective is it for conservation? (June 2020)
Maron, DF. “What’s killing Botswana’s elephants? Here are the top theories.” National Geographic, 14 July 2020.
