The spatial scaling of habitat selection by African elephants

Abstract

Summary1. Understanding and accurately predicting the spatial patterns of habitat use by organisms is important for ecological research, biodiversity conservation and ecosystem management. However, this understanding is complicated by the effects of spatial scale, because the scale of analysis affects the quantification of species-environment relationships. 2. We therefore assessed the influence of environmental context (i.e. the characteristics of the landscape surrounding a site), varied over a large range of scales (i.e. ambit radii around focal sites), on the analysis and prediction of habitat selection by African elephants in Kruger National Park, South Africa. 3. We focused on the spatial scaling of the elephants' response to their main resources, forage and water, and found that the quantification of habitat selection strongly depended on the scales at which environmental context was considered. Moreover, the inclusion of environmental context at characteristic scales (i.e. those at which habitat selectivity was maximized) increased the predictive capacity of habitat suitability models. 4. The elephants responded to their environment in a scale-dependent and perhaps hierarchical manner, with forage characteristics driving habitat selection at coarse spatial scales, and surface water at fine spatial scales. 5. Furthermore, the elephants exhibited sexual habitat segregation, mainly in relation to vegetation characteristics. Male elephants preferred areas with high tree cover and low herbaceous biomass, whereas this pattern was reversed for female elephants. 6. We show that the spatial distribution of elephants can be better understood and predicted when scale-dependent species-environment relationships are explicitly considered. This demonstrates the importance of considering the influence of spatial scale on the analysis of spatial patterning in ecological phenomena.

Scaling up ideals to freedom: are densities of red knots across western Europe consistent with ideal free distribution?

“…Our approach of predicting animal numbers on the basis of food distributions, known metabolic cost functions and interference-based functional responses should be applicable to other systems. For example, an understanding of the ecological underpinning of the distribution of large herbivores in, for example, the Serengeti or Kruger National Park [64,65] is based on correlative exercises (plotting presence on indirect measures of habitat suitability) rather than the kind of thoroughly understood mechanistic reasoning presented here. There is also a substantial body of work using large-scale surveys of marine mammals to model their habitat selection.…”

Selection for forage and avoidance of risk by woodland caribou (Rangifer tarandus caribou) at coarse and local scales

“…A number of authors (Johnson et al 2002, Fryxell et al 2008 have demonstrated that differences in selection patterns between scales may arise from different movement modes (and different objectives, such as foraging or traveling) at different scales. Other authors aim to find a characteristic scale at which selection is most pronounced (Holland et al 2010, de Knegt et al 2011. Regardless of scale, however, animals select habitats high in forage biomass and low in risk, when possible (Rettie andMessier 2000, Owen-Smith et al 2010).…”

Modeling elephant‐mediated cascading effects of water point closure

“…Initial vegetation biomass density per cell was calculated by combining these imagery-and field-based maps on tree, shrub, and herbaceous cover ( Fig. 1; Kiker 1998, De Knegt et al 2011, vegetation type, mean tree, shrub, and herbaceous root biomass, height data, and on an initial sizeclass distribution for trees. Precipitation and more detailed information about radiation, CO 2 concentration, wind speed, minimum and maximum temperature, and humidity (Coughenour 1993, Boone 2007 were obtained from a series of weather stations.…”

“…To manipulate the impact of elephants on their habitat, the construction or closure of artificial water points (WPs) is considered to be a suitable strategy (Smit et al 2007a, as surface water is a key driver in elephant distribution and population dynamics (Chamaille´-Jammes et al 2007a, De Knegt et al 2011. Due to the construction of WPs, elephants may range into areas that were previously inaccessible to them or spend longer periods in areas where they would only have ranged when natural water was available (Loarie et al 2009, Smit andGrant 2009); elephant home range sizes may decrease in both the dry and the wet season (de Beer andVan Aarde 2008, Van Aarde et al 2008); and elephant densities may increase locally, since young animals are, predominately, susceptible to droughts (Chamaille´-Jammes et al 2007b, Van Aarde andJackson 2007).…”