Unlike Norwegian Lemmings, Brown Lemmings do not migrate en masse when they overpopulate their homes in the treeless regions of the north, but they do tend to wander. These are stout-bodied, herbivorous rodents with extremely short tails. Learn more about the Lemmus trimucronatus (Lemmus sibiricus), more commonly known as a Brown Lemming, in this easy-to-read species overview by the Smithsonian's National Museum of Natural History.