Reindeer adaptations
The reindeer is a member of the deer family but, unlike other deer, both sexes grow antlers. Even reindeer calves grow antlers in their first year of life. The bulls keep their antlers no longer than necessary and shed them after the mating season. The females, however, keep their antlers until their calves are born in spring. This gives the females the edge when competing for sparse food resources in winter and spring.  The pregnant females need enough nutrition to ensure that their calves are big enough at birth.
The reindeer’s winter coat is extremely thick and heavy and has three times as many overhairs as the coats of other types of deer, with approx. 700/sq. cm in its winter coat. In addition, reindeer have a woolly undercoat. Its thick coat provides very effective insulation from the wind and rain, and the snow on which it often lies during winter. Reindeer have four deeply cleft hooves, which act as specially designed ‘snow shoes’, enabling them to walk in deep snow in winter and on marshland in summer, and they are also well-suited for digging down through the snow.
Reindeer have a particularly well-developed sense of smell, and make extensive use of their scent glands for communication. Their excellent sense of smell enables reindeer to find lichen during winter, down to a depth of 60 cm under the snow.
What do wild reindeer eat?
The reindeer’s ability to use lichen as winter fodder is its most distinctive feature. Lichen mainly contains easily digestible carbohydrates which make it good maintenance food, but it contains too little protein to stimulate growth. In winter, reindeer prefer cladonia stellaris (reindeer moss) and cetraria nivalis, but if these are not available they eat other types of lichen, leaves and other plants with a lower nutritional value. If they have access to nutrition from other plants, reindeer are by no means dependent on lichen. We see an example of this in the reindeer introduced to the island of South Georgia, which live almost exclusively on grass as there is very little lichen. Since reindeer were introduced there between 1909 and 1925, two viable populations have developed. Another distinctive feature of reindeer in winter is their ability to gnaw on old antlers that have been shed, or on the antlers of other reindeer. Researchers are not sure why they do this, but it is thought that it may be in an attempt to stock up on minerals and nutrients, which are in short supply in their ordinary winter diet.

If reindeer are to acquire enough protein for growth and reproduction, they need access to plants in an early phase of germination. Reindeer find germinating plants when the snow melts in spring and early summer. They follow the green wave up the mountains, which gives them constant access to the ‘freshest’ plants and enables them to eat as much protein as possible to stimulate growth. Reindeer are able to digest 30-40 per cent of the plant material they eat in winter, but they can utilise 70-80 per cent or more of the spring vegetation. This is obvious from the animals’ growth during summer and autumn.

At this time of the year, reindeer eat a number of different herbs and flowering plants that grow in the mountains. They can also eat the leaves of bushes such as dwarf birch (Betula nana) and willow (Salix spp.). Examples of such plants are alpine bistort (Bistorta vivipara), hairgrass (Deschampsia flexuosa) and various sedges. Another special spring phenomenon is nutritional stress, which may cause the reindeer to eat very ‘unusual’ food such as small rodents and birds’ eggs. 

Mushrooms provide important nutrition during autumn, when reindeer may undertake long journeys down into the birch forests to look for them, in places where they would never venture the rest of the year.

Rutting, mating and new life

Adult females normally become pregnant every autumn from the age of one and a half until they are 12-14 years old, but this can vary. In Forollhogna, four-month-old females are known to have been impregnated. Reindeer bulls also become sexually mature at the age of one and a half, but they generally have to wait until they are between three and five before they can take part in mating.

At the end of August, the concentration of sex hormones in bulls makes them more aggressive and they start regarding each other as competitors. Rutting has started! The bulls are now ready to defend their harems against other bulls, and devote all their energy to doing so. The rutting season lasts from the middle of September until the middle of October. The mating act itself does not generally take more than 10 seconds, and the female stands completely still during the act. Immediately afterwards, the bull will turn his attention to other potential ‘female admirers’ in order to mate with as many of them as possible.

Before the females calve in the spring, they find calving spots. Many of the wild reindeer areas in Norway tend to be high up in the mountains in slightly hilly terrain with bare patches. The females generally calve in early May having carried their young for approx. 225 days (7-8 months). Calving times vary from area to area and from year to year, but the time is fairly synchronised between females in the same herd. The calving itself generally only takes about 15-20 minutes, and the calves try to find their feet soon after they are born. After a couple of days, the calf is ready to follow its mother and can accompany her to better grazing ground.