Herbivores that eat grass, moss, and lichen, such as musk oxen, lemmings, caribou, and arctic hares, are the principal tundra consumers. These creatures supply food for predators such as arctic foxes and polar bears, who are secondary consumers.
Arctic and alpine tundra are the two main forms of tundra. The Arctic tundra is a cold, arid region above the Arctic Circle with a surprising amount of plant and animal life. The chilly, dry part of a mountainous environment above the tree line is known as Alpine tundra. While still grass- and lichen-eating herbivores, the principal consumers in these habitats differ by region.
Not all tundras have primary consumers; for example, the land is hostile to mammals in the limited-area Antarctic tundra. The predominant inhabitants of the island are penguins, who eat largely seafood.