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

Abstract

Foraging behaviour and habitat selection occur as hierarchical processes. Understanding the factors that govern foraging and habitat selection thus requires investigation of those processes over the scales at which they occur. We investigated patterns of habitat use by African elephants (Loxodonta africana) in relation to vegetation greenness to investigate the scale at which that landscape attribute was most closely related to distribution of elephant locations. We analysed Global Positioning System radiocollar locations for 15 individuals, using the Normalized Difference Vegetation Index as a representation of vegetation greenness in a Geographic Information Systems framework. We compared the importance of vegetation greenness at three spatial scales: the total home range, the seasonal home range and the 16-day home range. During the wet season, seasonal home ranges for both sexes were associated with intermediate greenness within the total home range; there was no evidence of selection based on greenness at finer scales. During the dry season, the strongest associations were within the 16-day home range: individual locations for males tended to be in areas of intermediate greenness, and those for females were in areas of intermediate and high greenness. Our findings suggest that the role of vegetation greenness varies with the scale of analysis, likely reflecting the hierarchical processes involved in habitat selection by elephants.

Exploring the relationship betweenNDVIand African elephant population density in protected areas

“…Marshal et al . () have shown that elephants will occupy areas with different levels of primary productivity based on whether the season was wet or dry. Yet without more details on the surveys performed, factors such as these cannot be incorporated into continent‐wide ungulate studies.…”

Resource selection in reintroduced lions and the influence of intergroup interactions

“…Used resources were defined as GPS locations of the lions within their respective seasonal Time Local Convex Hull (T-LoCoH) home ranges calculated in Yiu et al (2017) following Lyons, Turner, and Getz (2013), as T-LoCoH excludes locations where the animals explore only occasionally thus did not represent the daily use of resources. Within-home range available resources were defined as random points created within seasonal minimum convex polygon (MCP) home ranges (Marshal et al, 2010;Davidson et al, 2012;DeCesare et al, 2012), as MCP are includes all areas available to that animal in that time period (Northrup et al, 2013). We sampled random points at a ratio of 1:1 to the number of used locations to ensure that the random points representing the available resources were accessible to the animals at the specific spatial and temporal scale (Recio et al, 2014).…”

Overwhelming presence of non-food vegetation undermines the reliability of NDVI as a surrogate of forage abundance for a large herbivore in a tropical forest habitat

“…Such variability in food abundance is expected to affect the spatio-temporal patterns of movement, foraging, and habitat use, as seen in African elephants (e.g. Blake 2002, Marshal et al 2010). Total abundance or NDVI that do not reflect food species abundance patterns would, therefore, yield misleading results.…”

“…Murwira and Skidmore 2005, Young et al . 2009, Marshal et al 2010, Rood et al 2010, Bohrer et al 2014). However, while NDVI has been found to be a good surrogate of total vegetation biomass/primary productivity in various habitats (savannahs: e.g.…”