Many animals eat lichen , including snails, voles, squirrels and snub-nosed monkeys. In winter, they are an important source of food for reindeer, which avoid the ones containing poisonous cyanobacteria. A large number of related lichen species that the reindeer and caribou eat are known, depending on which continent they inhabit, as reindeer lichens or caribou lichens . Cladina stellaris is the most heavily eaten species. Caribou prefers eating lichen because it is very healthy. Musk-oxen live in the frozen Arctic and roam the tundra in search of the roots, mosses , and lichens that sustain them. Humans sometimes eat lichens too, and some species are used in Asian traditional medicines. Only a few lichens are truly poisonous , with species of Letharia and Vulpicida being the primary examples. These lichens are yellow be...