1. Concerns over the ecological impacts of high African elephant Loxodonta africana densities suggest that it may be necessary to control their numbers locally, although the best management approach is still widely debated. Artificial water supply is believed to be a major cause of local overabundance, and could be used as a potential tool to regulate elephant distribution and impact across landscapes, but its effect on elephants at the population scale has never been studied. 2. We assessed how dry-season surface-water availability constrained the distribution of an entire elephant population, using aerial and waterhole census data from Hwange National Park, Zimbabwe. The study was initiated in 1986, when the population was released from culling. We studied how artificial waterholes, holding water throughout the dry season, and vegetation production, estimated from a normalized difference vegetation index (NDVI), influenced the long-term distribution of elephant densities. We also investigated how the elephant distribution responded to changes in population density and annual rainfall, a driver of surface-water availability. 3. Long-term dry-season elephant densities across the park tended to increase with vegetation production, and increased asymptotically with the density of artificial waterholes. 4. Since the culling stopped, dry-season elephant densities have increased in most areas of the park, except in areas of low vegetation production and low water availability. Interannual fluctuations in elephant distribution are linked to rainfall variability through its effect on surface-water availability. During dry years elephants concentrated in areas where artificial pumping maintained surface-water availability during the dry season. 5. During dry years elephant numbers at waterholes increased because of reduced surface-water availability, and elephants were distributed more evenly across waterholes, although active waterholes were unevenly distributed across the park. 6. Synthesis and applications . Surface-water availability drives the distribution and abundance of elephants within Hwange National Park, and therefore appears to be at the heart of the trade-off between elephant conservation and the extent of their impact on ecosystems. Artificial manipulation of surface water is one of the tools available for the management of elephant populations and should not be overlooked when considering options for controlling elephant numbers in places where they are considered to be overabundant.

https://besjournals.onlinelibrary.wiley.com/doi/epdf/10.1111/j.1365-2664.2007.01300.x

Managing heterogeneity in elephant distribution: interactions between elephant population density and surface‐water availability

https://repository.up.ac.za/bitstream/handle/2263/2622/VanAarde_Megaparks(2007).pdf?sequence=1

Megaparks for metapopulations: Addressing the causes of locally high elephant numbers in southern Africa

How to respond to growing elephant numbers in the Kruger National Park and elsewhere in southern Africa continues to be a contentious issue. In contrast to the public perception, scientists have attained a high degree of consensus on the ecological basis for such decisions. In this article we summarize these ecological principles and the management responses that are indicated, in order to counter some of the misunderstanding that has been evident in the popular media.

A scientific perspective on the management of elephants in the Kruger National Park and elsewhere : elephant conservation

Managers in southern Africa are concerned that continually increasing elephant populations will degrade ecosystems. Culling, translocation and birth control are flawed solutions. An alternative is providing elephants more space but this hinges on identifying landscape preferences. We examined two diverse eco- systems and uncovered similarities in elephant habitat use, expressing these as 'rules'. We considered arid Etosha National Park, (Namibia) and the tropical wood- lands of Tembe Elephant Park (South Africa) and Maputo Elephant Reserve (Mozambique). Landscape data con- sisted of vegetation types, distances from water and settlements. To surmount issues of scale and availability we incorporated elephant movements as a function that declined as distance from an elephant's location in- creased. This presumes that elephants optimize trade- offs between benefiting from high-quality resources and costs to find them. Under a likelihood-based approach we determined the important variables and shapes of their relationships to evaluate and compare models separated by gender, season and location. After consid- ering elephants' preferences for areas nearby, habitat use usually increased with proximity to water in all loca- tions. Elephants sought places with high proportions of vegetation, especially when neighbouring areas had low vegetative cover. Lastly, elephants avoided human set- tlements (when present), and cows more so than bulls. In caricature, elephants preferred to move little, drink easily, eat well, and avoid people. If one makes more areas available, elephants will probably favour areas near water with high vegetative cover (of many different types) and away from people. Managers can oblige elephants' preferences by supplying them. If so, they should anticipate higher impacts to neighbouring vegetation.

/pdf/rules-of-habitat-use-by-elephants-loxodonta-africana-in-41col72n8x.pdf

Rules of habitat use by elephants Loxodonta africana in southern Africa: insights for regional management

Elephant seasonal vegetation preferences across dry and wet savannas

http://www7.nau.edu/mpcer/direnet/publications/publications_d/files/deBeer-2006.pdf

W. Kilian

Papers

Elephants and low rainfall alter woody vegetation in Etosha National Park, Namibia