Abstract
Water and forage are key non-substitutable resources for herbivores in arid and semi-arid ecosystems. The distribution of surface water determines the distribution and abundance of water dependent animal species yet little is known about the processes involved at the individual level. Thirteen African savanna elephant family groups and ten bulls (Loxodonta Africana) were tracked with GPS collars within and on the outskirts of Hwange National Park, Zimbabwe. Elephants behave as multiple central place foragers: They visit waterholes periodically every 5h, 24h, 48h or 72h and travel further from water during longer trips. During the dry season, temperatures increase and forage becomes depleted closer to water. Elephant family groups visit waterholes more often by increasing the proportion of briefer trips and abandoning 72h trips. However, they forage further during 24h trips by increasing travelling speed. Elephant movement patterns revealed locomotional and navigational abilities are at the core of their coping strategies although they are seldom allowed to vary in most foraging models of animal's use of heterogeneously distributed resources. During these foraging trips, family herds select for areas with low waterhole density at multiple scales. Selection strength for low density areas increases with both distance to water and the advancement of the dry season. Although scaling effects are widely recognized, the effects of the spatial distribution of multiple central places constraining foraging have been ignored yet they determine depletion effects and their feedbacks on habitat selection. I also showed that wildlife strongly avoid livestock and people that herd them at the boundary of a protected area during the rainy season yet avoidance decreases during the dry season when foraging and drinking resources become scares. Elephants are increasingly constrained by surface water availability during the dry season as their drinking requirements increase while they strive to main their forage intake. This study provides quantitative assessment of individual water dependence and of landscape effects of surface water distribution on a large herbivore. These findings can inform surface water management in contexts of aridification resulting from climate change.