Wetenschap - 4 oktober 2016

Drought is killing the African elephant

tekst:
Rik Nijland

Drought plays an increasingly large role in the decline of the African elephant. When precipitation on the savanna fails to occur for longer periods of time, many animals end up perishing. Not due to a water shortage, but rather due to a shortage of food.

This was shown by the research of Yussuf Wato in the Tsavo Conservation Area. The area is a cluster of national parks in Kenya. During long periods of drought, herds gather along rivers, because the water sources elsewhere have dried up. This puts elephants in a horrible dilemma. They need to drink every two days; if they wander off too far, they will perish of thirst. But they also need to gather food that becomes increasingly scarce in a limited territory crowded with many members of the species. When this lasts for more than four months, the food situation becomes acute. A disaster follows.

Wato, who works at the Kenya Wildlife Service and is a PhD candidate in the chair group Resource Ecology, studied the influence of droughts over a period of ten years. He used the location data of carcasses, which are narrowly kept up to date by the rangers in Tsavo. In his study, he only included elephants that did not perish due to poaching or illness.

Death among elephants during droughts mostly occurs in the neighbourhood of rivers. There is also a clear correlation with the decrease in vegetation (measured by a satellite), he concludes in an article that will be published in the November issue of Biological Conservation. In this article, Wato explains that drought is a natural regulating mechanism of the number of elephants. In the national parks where the animals have access to artificial water sources, such as lodges, the populations often soar.

The new data shows that the factor of drought is at least as important for the decline of the elephant.
Ignas Heitkönig

The managers of these parks sometimes shoulder their rifles to prevent the elephants from consuming all the grass and other greens, which would cause antelopes and zebras to pine away as well. However, Wato finds culling to be less natural than drought. But there is a different side to the story. In the past forty years, the number of elephants in Tsavo decreased by two thirds. Drought was a ‘large contributor’ to this process, the researcher thinks. In addition, climate models predict a further decrease of precipitation on the savannas.

The decline of elephants in Africa is usually attributed to poaching and the reduction of their habitat. In late September, conservationists raised the alarm over the increase of illegal trade of ivory. ‘The new data shows that the factor of drought is at least as important for the decline of the elephant’, says copromotor Ignas Heitkönig of Resource Ecology. He expects that if the occurrence of droughts will increase in the future, then elephant populations will have less and less time to recover. ‘And on top of that, we have the poaching, which gets worse by the year.’


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