Box 1.

The Reindeer—Adaptations to Pasture Conditions

The seasonal cycle in the reindeer’s circumpolar distribution area is characterized by a short summer with good forage supply and limited forage quantity and quality during the rest of the year. The reindeer adapts to these conditions by seasonal cycles in its metabolism. Productivity and growth is limited to the summer season with access to high quality pastures at slopes and depressions (Danell et al. 1999a). During late spring and summer, the animals—in general opportunistic feeders with more than 200 species registered as forage plants (Gaare and Danell 1999)—feed on protein-rich herbs, grasses and leaves to support growth and lactation. Their energy demand sums up to 45 MJ day−1, corresponding to the intake of 2.5–2.9 kg dry matter (Danell et al. 1999a). With withering of green pastures during autumn, metabolism switches towards maintenance (Gaare and Danell 1999). During winter, the energy demand drops to about 20 MJ day−1. As reindeer have due to a specialized microbial flora in their rumen the unique ability to digest carbohydrate-rich lichens (Storeheier et al. 2002), this corresponds to the intake of 1.6–1.7 kg dry matter of lichens per day. Lichens dominate in areas with limited snow cover and are thus comparably easy accessible. Even if lichens constitute up to 80% of forage during winter, the reindeer does not depend solely on lichens—it might feed on accessible other phytomass as well (Gaare and Danell 1999). Due to the limited spatial extent (10–30% of the total grazing area) and their low productivity per unit area (10–30% compared to summer pastures), winter pastures are often described as the bottle-neck for reindeer husbandry as they determine the number of animals to be kept inside a grazing area (Gaare and Danell 1999; Jernsletten and Klokov 2002). To summarize, pasture usage by reindeer is naturally characterized by a seasonal migration between summer and winter pastures to meet the different seasonal needs—evidence for these natural migrations is provided by ancient trapping systems (e.g. Jordhøy 2008). Seasonal migrations in combination with marked differences between summer and winter diet secure an optimal utilization of the low primary production patterns in space and time. Due to migrations and feeding strategies, reindeer naturally affect their pastures to a much lesser extent than smaller herbivores (e.g. Olofsson et al. 2004a), like for instance the lemming (Lemmus lemmus).