Snow and Digging – the Winter of the Reindeer

The long dark period in the northern winter is called “kaamos”. In the midst of the winter, the sun does not rise at all. The longest kaamos period is in Utjoki, where the sun sets in the end of November and rises again in mid-January. This period of darkness, thick snow cover and cold temperatures is challenging for reindeer. During the winter, reindeer loose around 10 to 20 percent of the weight gained in the autumn, in harsh winters even 40 percent. The quality and availability of the winter food and the fat layer are crucial for the survival of a reindeer.

The food under the snow becomes difficult to reach particularly if the weather changes from fairly warm to cold. When it gets warmer, the content of the snow becomes wetter and when it gets colder again, it freezes. For reindeer it is difficult to dig through frozen snow. However, nowadays, herders feed reindeer during midwinter when it is most difficult to find food. By doing this, herders make sure their reindeer survive through the winter and are able to calve in the spring.

Reindeer eat in the hole that they have dug

Reindeer and deer are the only bigger herbivores that can use lichen as the main source of their food. Reindeer digs lichen from under the thick layer of snow. In the winter, reindeer also eat twigs, hay and beard moss. Herders give them mostly hay and branches with dried leaves. These foods are also used to feed game in Finland.

Reindeer locates lichen under the snow with its good sense of smell. Round traces from reindeer muzzle can be seen in soft snow during the winter. If there is no smell, the reindeer does not start digging.

The pit that a reindeer digs into the snow is called “kiekerö”. First it throws the snow away and if there is a thick layer of snow, it expands the hole. Expanding makes it easier to dig as there is no need to throw away the snow. In the end, there are corridors around the area. When the layer of snow is really thick, the calves dig themselves through and continue digging within the snow. Then, all you can see of them is the hole they started digging.

Towards the spring, it gets more difficult to dig. Then reindeer start eating beard moss or move further up to fells.

Antlers are useful for female reindeer

The antlers are important for pregnant females when they are seeking for food in the winter. In fact, they are the only ones with antlers in the food critical period from April and May. The females can defend or take over holes from other reindeer. They can also chase away bigger reindeer from their diggings, because of their antlers. The female can wait for other reindeer to dig and when they are finished, they chase them away from the hole.  From the evolutionary perspective this is well justified as the female has to take care of both the unborn calf and the calf following it from the previous spring and itself.

Lichen is the most popular, but not the only winter food

The easiest places to find food are the sides of fells where there is less snow. In the spring, lichen and beard moss are the bases of the nutrition of a reindeer in Fennoscandia, but it can also use other plant species. For example, the Svalbard reindeer (Rangifer tarandus platyrhynchus) living in the Svalbard, has only very little lichen to eat. The Norwegian reindeer that were taken to South Georgia Island in the beginning of the 20th century had no lichen to eat at all. There the reindeer lived through winter with using different hays (Poa). Also, caribous in Alaska live without lichen.

Reindeer can survive winter without lichen if needed. If there is lichen, it is the most popular option, but as said, not the only winter food.