Thursday, June 24, 2021

New theories about cause of mysterious elephant deaths

Joint research by the University of Pretoria in South Africa and Duke University in the United States has offered a new set of theories about what may be causing the mysterious deaths of elephants in the North West District. However, the researchers admit that the cause “may never be known.” Most of the deaths occurred in an area that the Department of Wildlife and National Parks has administratively designated as NG11.

In rejecting the theory that single factors alone may be a sufficient explanation, the researchers posit their own: that “several forces likely operated in concert.” One is that fencing restricted elephant movement, which confined the death-causing agent to the area where the die-off occurred.

“Impaired dispersal likely caused the high population growth and enhanced local densities of elephants, which could facilitate the spread of a contagious disease,” the researchers write in an academic paper titled “The 2020 elephant die-off in Botswana.”

In elaboration of the latter, they point out that past incidences of poaching and limitations on access to the Okavango River due to the relatively high number of people and harassment, may have forced the elephants to rely on stagnant water sources and cause stress which increased their susceptibility.

“Those sources may have hosted the agents of their illness, which would have additionally stressed the elephants,” the researchers suggest.

As part of a long-running research programme which considers regional elephant populations and their management, the researchers have tracked 10 elephants within NG11 and several hundred elephants in other areas across southern and eastern savanna Africa. They found that NG11’s elephants are isolated by the Okavango River to the south-west and by fences on the other sides and surmised that this state of affairs could be problematic.

“NG11 imprisons the elephants preventing their dispersal when numbers are high or when conditions may become harmful.”

The researchers found that the population growth rate within NG11 differs from those outside and argue that restricted elephant movements made the sudden die-off much more likely.

“If a contagious agent were responsible, it would have implications for elephants beyond NG11 and neighbouring NG12 and the consequences of this are important for managing elephant populations across Africa.”

They also posit the theory that poaching may be indirectly responsible.

“Elephants respond to poaching by changing their movement patterns. Poaching induces stress in elephants which may challenge their immune system and susceptibility to disease. Such susceptibility, the relatively high densities, and the resulting increased contact between individuals could explain the relatively fast spread of a contagious disease that may have been responsible for this die-off in the Seronga area. It would not have had the same impact in the surrounding areas where elephants could move away when harassed.”

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