Tule elk selection of surface water and forage is mediated by season and drought

Abstract

Climate change is expected to affect arid-system ungulate populations by altering the distribution and availability of critical resources such as water and forage, particularly through more frequent and extreme droughts. Tule elk (Cervus canadensis nannodes), a subspecies of North American elk endemic to the Mediterranean climate regions of California, USA, can provide insight into the habitat selection behaviors arid-system ungulate populations use in response to changing resource availability. We used location data collected between 2005⁠–⁠2017 from GPS-collared tule elk to model elk response to surface water sources, forage dynamics (i.e., spatio-temporal changes in forage quality and abundance), and drought in the wet and dry seasons. These data spanned the extreme drought that occurred from 2012–⁠2017, a time when survival was apparently stable in the population. We found that, in the dry season, tule elk localized around water sources but selected areas farther from water with greater forage abundance. In the wet season, high quality forage and road avoidance were the primary factors influencing selection. These patterns were intensified by the extreme drought, with elk selecting areas closer to water in the dry season and farther from water sources in the wet season. Tule elk appeared to modify their behavior to minimize the impacts of drought on their survival. These findings suggest that water source availability and the relationship between water sources and other landscape features, including forage and roads, are a critical component of ungulate management in drought-prone regions.