Reindeer is a master in adapting to winter

In the winter, the growth and activity of a reindeer lessens. The metabolism, heart beat and breathing slows down. The biggest change happens in the digestion; however, it adjusts well to the winter food. With all that and the soft snow layer, the willingness of a reindeer to move around diminishes.

Lichen has only little protein, minerals, trace elements and vitamins. The proteins of the lichen do not digest very well either, which means that reindeer are often in negative nitrogen balance and lose weight. Whilst eating a kilo of lichen, reindeer uses the proteins from its body all the time. However, lichen has plenty of easy carbohydrates so reindeer get a good amount of energy from it during the winter.

The fat layer collected over the summer is vital for reindeer in the spring. It is where most of the weight loss occurs. If it ends, reindeer have to use proteins from other parts of the body.

The beard mosses have more protein than the lichens in the ground.  They also digest more easily. This explains also why reindeer like to eat beard moss if it is available.