During thousands of years, reindeer have adapted to living under harsh conditions with large seasonal variations in climate and forage availability. This adaptation implies that body functions and nourishment needs are strongly bound to the season. In the summer the reindeer has to maximize food intake to build up fat and protein reserves for the winter. More than 200 different plant species are included in the reindeer diet, but since reindeer have an unique ability to use the nourishment in lichen, different lichen species make up a large portion of their winter diet in many areas. Fundamental for reindeer husbandry is access to natural grazing during most of the year.