Cotton grass (Eriophorum spp.) is a resilient plant found in the cold, wet, and often nutrient-poor environments characteristic of tundra, bogs, and moorlands across the Northern Hemisphere. Despite its common name, it is a sedge, not a true grass, recognized by its tufted, grass-like leaves and distinctive cottony seed heads that sway in the wind. These fluffy fibers play a role in seed dispersal and help insulate the plant’s reproductive organs in cold conditions. This plant serves as a foundational species in its native habitats, providing sustenance for various wildlife.
Key Mammalian Consumers
Large mammalian herbivores extensively graze on cotton grass, especially in habitats where other vegetation is scarce. Reindeer and caribou consume cotton grass stems and flower heads, particularly during the spring and early summer when new growth is abundant. It is a significant component of their diet, especially in the winter when other food sources are limited, with some studies indicating it as an important wintergreen plant. Musk oxen also graze on cotton grass, utilizing its leaves and stems during the growing season, as it is a preferred food source.
Smaller rodents like lemmings and voles also feed on the nutritious shoots and leaves of cotton grass. Brown lemmings, for example, consistently include cotton grass in their diet, alongside other sedges and grasses. Collared lemmings also consume it, especially in summer. Cotton grass is a primary food source for lemmings.
Avian and Smaller Herbivores
Various bird species, including geese and ptarmigan, incorporate cotton grass into their diets. Snow geese, for instance, feed on the underground parts of tall cotton grass. Barnacle geese and Greylag geese have also been observed uprooting and consuming the protein and carbohydrate-rich stem-bases of common cotton grass. The seeds of cotton grass are also an important food source for many birds, including migrating geese.
Ptarmigan, like the willow ptarmigan, eat the shoots of cotton grass, especially in spring when new growth emerges, which provides digestible and nutrient-rich forage. Additionally, the larvae of certain insects, such as the large heath butterfly, feed on cottongrass.
Cotton Grass in the Ecosystem
Cotton grass plays a foundational role in the arctic and subarctic ecosystems. Its presence contributes to the structural diversity of peatlands, creating microclimates that support other plant species like Sphagnum moss. The plant’s root systems help stabilize soil, preventing erosion in wet and challenging environments.
The abundance and widespread distribution of cotton grass across the Northern Hemisphere underscore its contribution to maintaining ecological balance. It supports a wide range of wildlife, from insects to large mammals, by providing essential foraging resources and habitat. Its role in the food web demonstrates its significance in sustaining the biodiversity of these unique and often harsh environments.