The tundra biome is characterized by its extremely cold climate, low precipitation, and a short growing season. Temperatures often remain below 0°C for much of the year, with permafrost beneath the surface. This harsh environment limits plant life, resulting in a landscape dominated by dwarf shrubs, sedges, grasses, mosses, and lichens. Lichens, a symbiotic association of fungi and algae, are well-adapted to these conditions and form a significant component of the tundra’s vegetation. They serve as an important food source for various animals, especially during the long, cold winters when other vegetation is scarce.
Key Tundra Animals That Consume Lichen
Several animals in the tundra rely on lichen as a food source, particularly during winter. Reindeer, also known as caribou in North America, are prominent consumers of lichen, which can constitute a large portion of their winter diet. These animals possess specialized hooves and a keen sense of smell, enabling them to locate and dig through snow to access buried lichen. While lichens are a main component in winter, caribou consume more graminoids and vascular plants during warmer seasons.
Musk oxen graze on lichens, alongside grasses, willows, and mosses. Although they prefer more succulent vegetation when available, lichens, roots, and mosses become important during winter, especially on hillsides with thinner snow cover. Musk oxen, like reindeer, are ruminants with a four-compartment stomach that allows them to digest plant-based foods efficiently.
Smaller mammals like lemmings and voles include lichens in their diets. Lemmings, in particular, feed on mosses and lichens, often foraging under the snow in winter. Voles, while having a varied diet that includes grasses, seeds, and fungi, also consume lichens, especially when other food sources are limited. These smaller herbivores play a role in the tundra food web, serving as prey for larger carnivores.
Lichen’s Role in the Tundra Ecosystem
Lichens provide a consistent and accessible food source in the tundra, particularly during winter when most other plants are dormant or covered by deep snow. Their nutritional value lies primarily in their high carbohydrate content, ranging from 53% to 79%. Lichens also contain some protein and minerals, though generally low in nitrogen compared to other plant types.
Animals like reindeer digest lichens due to specialized microorganisms within their digestive systems, such as the rumen, which break down complex carbohydrates and allow animals to extract energy. Despite their importance, lichens grow very slowly, typically only a few millimeters per year. This slow growth means lichen pastures are vulnerable to overgrazing and can take decades to recover after heavy consumption. Therefore, the availability and regeneration of lichens significantly influence the populations and movements of dependent animals. Lichens also contribute to nutrient cycling, with some species fixing nitrogen, a limited nutrient in tundra soils.