Winter habitat–space use in a large arctic herbivore facing contrasting forage abundance

Abstract

We analysed how changes in resource levels influence foraging trade-offs in late winter by wild Svalbard reindeer. Forage plants, and particularly lichens, were less abundant at the overgrazed Broggerhalvoya compared with the neighbouring Sarsoyra. Strong interactions occurred between habitat selection, home range size, and feeding crater selection. At Broggerhalvoya, radiocollared females generally selected productive habitat (high summer NDVI; Normalised Difference Vegetation Index). “Immigrants” at Sarsoyra (dispersed from Broggerhalvoya in early winter) had similar habitat preferences, probably due to past experience. In contrast, “residents” at Sarsoyra were more influenced by abiotic conditions, using habitat with low NDVI, but selecting for high-quality forage (lichens) when cratering. This suggests more quality-based selection at the expense of quantity when forage abundance increases. Habitat–space use relationships also differed between the animal categories, as home range size decreased with availability of preferred habitat. Thus, changes in forage abundance can strongly influence winter habitat–space use interactions in predator-free systems.