The Arctic willow (Salix arctica) is a foundational plant in the harsh polar ecosystems, providing sustenance for numerous animals. This diminutive shrub, typically growing only 2 to 10 centimeters tall, is one of the northernmost woody plants globally. It thrives across the vast circumpolar regions of North America, Europe, and Asia, particularly in the Arctic tundra and alpine environments. Despite its small stature, the Arctic willow plays a critical role in supporting the food web in these extreme conditions, where few other woody plants can survive.
Large Mammalian Grazers
Muskoxen and caribou are prominent large mammalian grazers that depend significantly on the Arctic willow. Muskoxen, adapted to the Arctic, consume Arctic willows, grasses, and other woody plants. During the winter, willows become a particularly important part of their diet. They possess an excellent sense of smell to locate food beneath the snow, often digging through it with their front hooves or breaking through crusted snow by lifting and dropping their heads. This ability allows them to access the woody stems and bark of the Arctic willow when other vegetation is buried.
Caribou also rely on Arctic willow, especially during the summer when its nutritional value peaks. Their diet includes the leaves of willow trees, sedges, and flowering tundra plants. As winter approaches, caribou shift to eating lichens, dried sedges, and small shrubs, but willows remain a component of their diet, with twigs and dry leaves being consumed. Their specialized hooves, which change seasonally, help them dig through snow to reach these buried food sources.
Smaller Terrestrial Consumers
Smaller terrestrial mammals such as arctic hares, lemmings, and voles also feed on Arctic willow. Arctic hares are primarily herbivores, with Arctic willow constituting a significant portion of their diet year-round, sometimes as much as 95%. They consume twigs, roots, and young stems of the willow. During winter, they may dig through packed snow to access these woody parts. In summer, arctic hares show a preference for willow leaves and young stems.
Lemmings, including the northern collared lemming, are herbivorous rodents that incorporate Arctic willow into their diet. In winter, when they live under the snow, lemmings primarily eat twigs and buds of willow. Lemmings prefer the fleshiest parts of the willow, such as flowers in summer and buds in winter, along with roots. Voles, generally, also consume bark from woody vegetation when other food sources are scarce. Tundra voles specifically select willows as part of their diverse diet.
Avian Eaters
Birds in the Arctic also rely on the Arctic willow, with the ptarmigan being a notable example. The willow ptarmigan’s diet consists largely of plant matter, including flower buds, catkins, leaves, and twigs. Arctic willow provides a significant food source for them, particularly during the harsh winter months when other vegetation is limited. During winter, the buds, twigs, and catkins of willows can make up a substantial portion of their food, often four-fifths or more.
Ptarmigan are well-adapted for life in the Arctic, with feathered feet that help retain heat and function like snowshoes, allowing them to move easily over snow. They can also burrow into the snow for insulation and protection while resting. This allows them to conserve energy and survive on a diet primarily composed of willow parts.