The tundra is a cold biome that supports a unique array of herbivorous animals. These plant-eaters have developed strategies to survive in an extreme environment. Their existence shapes the landscape and sustains the broader food web. The challenges these animals face are intensifying as the global climate continues to change.
The Arctic Tundra Environment for Herbivores
The Arctic tundra’s harsh conditions dictate life for its herbivores. The climate is characterized by extremely low temperatures, long winters, and a brief, cool summer. This short growing season restricts plant growth, limiting the annual food supply. The ground itself presents an obstacle in the form of permafrost, a layer of permanently frozen soil.
This permafrost prevents deep root growth for plants and impedes water drainage. When the shallow top layer of soil thaws in the summer, it becomes saturated, creating bogs and ponds. Vegetation is consequently dominated by low-growing forms that can withstand the cold, such as mosses, lichens, grasses, sedges, and dwarf shrubs.
Meet the Tundra’s Plant-Eaters
A diversity of herbivores has adapted to the tundra, ranging from large mammals to tiny invertebrates. Among the most recognizable are large ungulates like caribou (known as reindeer in Eurasia) and muskoxen. While caribou travel for forage, muskoxen are more sedentary and endure the winters in place.
The tundra is also home to smaller mammals whose populations experience dramatic cycles. Arctic hares, lemmings, and voles are prevalent, feeding on grasses, roots, and other low-growing vegetation. During the brief summer, migratory birds like snow geese arrive to breed and feed on fresh plant growth. Invertebrates, like the caterpillars of arctic moths, also emerge to consume plant matter.
Adaptations to a Frozen Land
To combat the cold, animals have developed specialized physical traits. The muskox possesses a dense undercoat called qiviut, one of the warmest natural fibers in the world. Animals like the Arctic hare and ptarmigan undergo seasonal changes in coloration, turning white in winter for camouflage. A compact body shape with shorter limbs and ears reduces surface area, minimizing heat loss.
Behavioral adaptations are also important for survival. Small mammals like lemmings and voles survive the winter by burrowing in tunnels beneath the insulating snowpack to access roots and sedges. Muskoxen exhibit a social defense, huddling in tight groups to conserve body heat and protect their young. For many species, migration is the primary strategy; caribou and snow geese travel vast distances to escape the harshest parts of winter and find food.
Physiological adaptations allow herbivores to make the most of a sparse, low-nutrient diet. Caribou have specialized hooves that are large and sharp-edged, enabling them to dig through snow to reach buried lichens. Ruminant animals like muskoxen and caribou have complex digestive systems that efficiently extract nutrients from tough, fibrous plant materials.
How Herbivores Shape the Tundra Landscape
Tundra herbivores are active agents of change in their ecosystem. Through their foraging activities, they influence the composition and structure of plant communities. Grazing by animals like caribou and geese creates “grazing lawns,” patches of vegetation kept short by grazing-tolerant grasses, which can increase local plant diversity.
These animals also play a role in the tundra’s nutrient cycle. Tundra soils are nutrient-poor due to cold temperatures that slow decomposition. The waste products of herbivores provide concentrated patches of nutrients like nitrogen and phosphorus. This localized fertilization can stimulate plant growth, creating nutrient hotspots.
The physical impact of these animals also modifies the land. Trampling from herds can affect soil compaction, while the burrowing of lemmings aerates the soil. These actions influence drainage patterns and the depth of the summer thaw. As a food source for predators like Arctic wolves and snowy owls, herbivores transfer energy from plants to the rest of the food web.
Tundra Herbivores in a Warming World
The Arctic is warming faster than the global average, and this change is affecting its herbivores. Altered weather patterns are creating new survival challenges. An increase in “rain-on-snow” events during winter is dangerous, as the rain freezes into a hard layer of ice that locks away vegetation, making it impossible for animals like muskoxen and caribou to access food.
Climate change is also altering the tundra vegetation itself. Warmer temperatures are allowing taller, woody shrubs to expand northward, a process known as “shrubification.” While this might seem to provide more food, it can be detrimental to grazers that rely on low-growing lichens and grasses, which are being shaded out by the new shrubs. These shifts in plant communities can lead to mismatches in the timing of food availability and the needs of migratory animals that have evolved to arrive at specific times.
Furthermore, a warming climate allows for the northward expansion of new species, including parasites and diseases to which native tundra herbivores have little resistance. The changing environment disrupts traditional migration routes and alters the delicate balance of population cycles that have defined the tundra for millennia. These pressures combine to create an uncertain future for many of the tundra’s iconic plant-eaters, with cascading consequences for the entire ecosystem.