The response of elephants to the spatial heterogeneity of vegetation in a Southern African agricultural landscape

Scale-dependent selection of greenness by African elephants in the Kruger-private reserve transboundary region, South Africa

“…Based on behavioural observations for elephants in Sengwa, Zimbabwe, patch selection occurs on the order of 0.25 km 2 , or over a linear distance of 500 m (2 pixels) and a time period of approximately 1 day (Guy 1976). Murwira and Skidmore (2005) further demonstrated that presence of elephants was optimally related to vegetation heterogeneity over a linear distance of 457-734 m (2-3 pixels). Time in a patch and movements between patches likely vary considerably across African elephant range and are influenced by local conditions, climate and soils (Young et al 2009, Loarie et al 2009b), but the results of Guy (1976) and Murwira and Skidmore (2005) suggest that the use of 16 days as a representation of large-patch selection likely resulted in a mismatch between the scale of elephant biology and that of the MODIS NDVI imagery.…”

“…Simple productivity should be related to abundance and quality of forage, but heterogeneity is relevant because elephants are more likely to find required resources within a home range if there is wide variation in structure and composition of the plant community to provide those resources (Murwira and Skidmore 2005). Overall, smaller home ranges are associated with higher vegetation productivity and more heterogeneous vegetation because elephants range over shorter distances to meet their requirements (Grainger et al 2008, Young et al 2009).…”

“…The former situation might be a consequence of the high energetic cost for very large animals to traverse hilly landscapes (Wall et al, 2006). The latter situation could arise if environmental heterogeneity were associated with elevation and if elephants were selecting habitat based on vegetation heterogeneity (Grainger et al 2008;Murwira and Skidmore 2005;Young et al 2009) or aspect diversity at higher altitudes (Hebblewhite et al 2008). Furthermore, particular vegetation communities are associated with higher or lower elevations, for example, along a catena sequence (Venter et al 2003) or with respect to a riparian zone (Rogers and O'Keefe 2003).…”

“…The NDVI imagery gives a representation of the spatial and temporal variability in the biomass and nutritional quality of vegetation (i.e., greenness; Huete et al 2002;Parker 2003;Pettorelli et al 2005a), and a growing number of studies have demonstrated that movements, habitat use and distribution of elephants are associated with the greenness characteristics of the landscape (Murwira and Skidmore 2005;Chamaillé-Jammes et al 2007;Young et al 2009;Loarie et al 2009a, b). It might appear obvious that greener vegetation is more beneficial to a foraging elephant, but the mechanisms underlying that association remain vague.…”

Identifying transit corridors for elephant using a long time-series

“…In many Eastern and Southern African countries elephant has been monitored since the 1970s through total counts and Systematic Reconnaissance flights (SRF, see NortonGriffiths, 1978) to determine population abundance and trends over extensive areas (Blanc et al, 2005;de Leeuw et al, 1998;Stoner et al, 2007). The studies investigating the determinants of elephant distribution from long-term aerial surveys (Chamaillé-Jammes et al, 2008;Murwira and Skidmore, 2005;Murwira et al, 2010;Prins and Douglas-Hamilton, 1990;Shrader et al, 2010;Young et al, 2009b) do not include the analysis of transit corridors. The elephant movement Galanti et al, 2000;Graham et al, 2009) and its interaction with the environment (Galanti et al, 2006;Harris et al, 2008;Loarie et al, 2009;Ngene et al, 2009b) were investigated by radio-and satellitetelemetry studies.…”