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The industrialization of agriculture in western societies has often led to either intensified use or abandonment of farmland and open pastures, but experimental evidence on how the dynamics of farmed ecosystems affect space use by large herbivores is limited. We experimentally manipulated farmland patches with cutting and (early summer) low- and high-intensity domestic sheep Ovis aries grazing according to traditional use in north Norway. After treatments, grazing reindeer Rangifer tarandus were exposed to the pastures the subsequent fall (2 months after treatments) and spring (11 months after treatments) as they typically do on their migratory route between summer and winter ranges. The experiment was conducted over 2 subsequent years. We predicted that sheep grazing on farmland during early summer may affect the critical fall and spring range conditions for reindeer either through negative (delayed competition) or positive (grazing facilitation) interactions. We found that the most marked effect of land use on the grazing pattern of reindeer was between no use (the control treatment) and all the other management options involving active land use. The grazing reindeer avoided the pastures no longer in use likely due to senescent plant material. There was a tendency that the lower intensity sheep grazing patches attracted more reindeer than the highest intensity use. These results highlight not only the general principle that large-scale agricultural changes may affect large herbivores in natural ecosystems, but they also increase our understanding of grazing facilitation as a mechanism in large herbivore assemblages.
