Lichens are unique organisms found across the globe, thriving in diverse and often challenging environments. They are a symbiotic association between a fungus and photosynthetic partners, such as algae or cyanobacteria. The fungus provides structure, protection, and absorbs water and minerals, while the photosynthetic partners produce food. This partnership allows lichens to colonize surfaces like rocks, trees, and soil, playing a significant role in many ecosystems.
Animals That Consume Lichen
Many animals, from large mammals to tiny invertebrates, incorporate lichen into their diets. Reindeer and caribou are prominent examples, especially in Arctic and sub-Arctic regions. During winter, when other vegetation is scarce or buried under snow, lichens can constitute a significant portion of their diet, sometimes up to 71% for caribou. These animals possess specialized digestive systems with microorganisms that help them break down lichens.
Beyond these iconic grazers, a variety of other creatures also rely on lichens. Smaller mammals like voles, lemmings, and squirrels consume lichens, often supplementing their winter food sources. Certain deer species, elk, moose, musk oxen, mountain goats, and Dall sheep are also known to graze on them. Invertebrates like snails and slugs are efficient lichen feeders, leaving distinctive scrape marks. Various insects, including bristletails, springtails, termites, barklice, grasshoppers, and moth larvae, also feed on lichens.
Nutritional Aspects of Lichen
Lichens offer a unique nutritional profile to the animals that consume them. They are rich in carbohydrates, which serve as a crucial energy source, particularly for animals in cold environments where metabolic demands are high. For instance, “reindeer lichens” are high in digestible carbohydrates. While generally low in protein, lichens contain some, with reported ranges from 3.1% to 16.2% of dry matter.
Lichens also provide various minerals, including calcium, and some species contain vitamins. However, they can be poor in certain minerals, potentially leading to deficiencies in animals that rely on them exclusively. Unique compounds known as lichen acids are present; some of these can be toxic or deter herbivory, but specialized feeders have adaptations to metabolize them.
Lichen’s Role in Animal Diets and Ecosystems
Lichens play a significant role in supporting animal populations, especially in harsh environments like the Arctic tundra and boreal forests. They serve as a primary winter food source when other vegetation is inaccessible due to snow cover or scarcity. Caribou, for example, rely heavily on lichens for survival and their migration patterns are influenced by lichen availability. They can smell lichens through snow and will dig craters to reach them.
The presence of lichens contributes to the biodiversity and stability of these ecosystems by sustaining primary consumers. The slow growth rate of lichens means that heavy grazing or environmental disturbances like wildfires can have long-lasting impacts on their availability, sometimes requiring decades for recovery. This makes lichen communities particularly susceptible to changes in climate and land use, with potential consequences for the animals that depend on them.