Foraging behavior and spatial use of a rock specialist: the southern vizcacha (Lagidium viscacia), and the exotic European hare (Lepus europaeus) in rocky outcrops of northwestern Patagonia, Argentina

The southern vizcacha (Lagidium viscacia) and the exotic European hare (Lepus europaeus) are two medium-sized herbivores that inhabit rocky outcrops in Patagonian steppe. These species overlap in diet and spatial use at medium distances from rocky outcrops in summer. We evaluated the spatial use through feces distribution in winter and determined seasonal foraging intensity in relation to the distances from rocky outcrops in order to elucidate how these herbivores use food and spatial resources in food scarcity periods. The vizcacha utilized the habitat close to rocky outcrops (<40 m) independent of season, while the hare exploited the space more widely, especially distances >40 m. However, in winter, at medium distances from rocky outcrops, there was partial spatial overlap because hares' activities were closer to rocky outcrops. Foraging intensity increased significantly in areas used by the vizcacha closer to rocky outcrops when food availability decreased, and the grasses Stipa speciosa, Poa sp., and Festuca pallescens were strongly foraged. In contrast, foraging intensity showed no changes in further distances to rocky outcrops and more use by the hare. The spatial and feeding behavior of the vizcacha, restricted to vicinity of rocky outcrops, showed high vulnerability to food availability changes. In resource scarcity situations, the spatial opportunistic behavior of the hare and the overlap in diet with the vizcacha constitutes a threat to this native herbivore. It is necessary to monitor populations of hare, since high densities could lead to food competition, impacting the small colonies of the southern vizcacha.