Caribou, also known as reindeer in some regions, are migratory ungulates inhabiting the vast northern expanses across North America, Europe, and Asia. Understanding their dietary habits offers insight into how these remarkable animals thrive in challenging environments.
Primary Food Sources
Caribou primarily consume a variety of plant matter, with their diet heavily influenced by seasonal availability. During the long winter months, lichens become their most significant food source, often constituting a large portion of their diet. Specifically, species like Cladonia rangiferina, commonly known as “reindeer moss” or “caribou moss,” are crucial due to their abundance in northern ecosystems and high digestible energy content from carbohydrates.
Beyond lichens, caribou also consume other vegetation when available, particularly outside of winter. Their diet includes various sedges, grasses, and mosses, which provide additional nutrients. They also browse on small shrubs, such as the twigs and leaves of willow and birch, which contribute to their nutritional intake. Fungi, like mushrooms, are also a part of their diet when they emerge, offering a concentrated source of nutrients.
Seasonal Diet Shifts
The diet of caribou changes considerably throughout the year, adapting to the varying availability of vegetation and their changing nutritional demands. In winter, when snow covers the ground, caribou largely depend on lichens, which they are able to locate and access beneath the snow. They also consume dried grasses and sedges that remain from the previous growing season, which they dig out from under the snow cover.
As spring arrives and the snow melts, the caribou’s diet transitions to newly emerging green vegetation. They seek out fresh grasses, sedges, and the tender leaves of deciduous shrubs, which are rich in protein and help them replenish energy reserves depleted during winter. This protein-rich forage is particularly important for pregnant females and for the development of calves. By autumn, caribou further diversify their diet, incorporating berries and other richer, more abundant vegetation to build up fat stores in preparation for the upcoming winter.
Adaptations for Foraging
Caribou possess several physical and physiological adaptations that enable them to effectively forage in their harsh northern habitats. Their large, broad hooves are a notable adaptation, acting like shovels to dig through snow and ice, a behavior known as “cratering,” to reach buried lichens and other vegetation. These hooves also provide excellent traction on slippery surfaces, helping them navigate snowy and icy terrains. The pads of their hooves change seasonally, becoming softer and spongier in summer for grip and shrinking and hardening in winter for better ice traction.
Their strong jaws and specialized teeth allow them to efficiently grind fibrous plant material. While they lack upper incisors, caribou use their lower incisors against a tough dental pad on their upper jaw to clip off vegetation. Internally, caribou have a four-chambered ruminant digestive system, similar to cows, which is highly efficient at breaking down tough plant matter. This complex stomach system allows them to extract maximum nutrients from their often low-quality diet, including the unique ability to digest the complex carbohydrates in lichens through microbial fermentation in their rumen.