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Resources driving landscape-scale distribution patterns of grazers in an African savanna


  • Izak P. J. Smit

I. P. J. Smit (, South African National Parks, Scientific Services, Private Bag X402, Skukuza, 1350, South Africa, and Geography Dept, Univ. of Cambridge, Downing Place, Cambridge, CB2 3EN, UK.


In order to effectively manage and conserve indigenous herbivores, a good understanding is needed of how resources drive their distribution patterns. This study employed a unique dataset to test a range of ecological theories and hypotheses on free-ranging grazers. Using aerial census data collected over 14 yr across the 2 million ha Kruger National Park (South Africa), this study employs spatial autologistic regression models to explore the spatial relationships that exist between the distribution of eight indigenous grazer species and a set of resource variables. It was found that ecological theories relating to feeding guild, water-dependence, allometric scaling, gut-morphology and vulnerability to predation could explain most of the grazer distribution patterns observed in relation to surface-water, forage quality, forage quantity and habitat openness. All the grazers studied were water-dependent and occurred close to a permanent source of water in the dry season. This was ascribed to the lack of moisture in the diet of grazers during the dry season. Most ruminants’ distribution patterns were significantly associated with areas of high forage quality whereas hind-gut fermentors were neutral towards forage quality. Average forage quantity was not a significant predictor of long-term, landscape-scale distribution patterns for any of the grazer species studied. Most small- and medium-bodied grazers preferred open habitats above closed habitats, probably due to higher visibility and a lower predation risk. Large-bodied grazers did not bias their distribution patterns towards open habitats. The way in which grazers distribute themselves with respect to different resources can potentially inform management actions on appropriate scales.