This dataset is a count of Lemming nests in Tuktut Nogait National Park. The counts are done annually in mid-July at 12 predetermined sample locations 1 ha in size. Lemmings are an important herbivore and source of food for predators. Lemming populations often fluctuate dramatically, typically growing and declining every three to four years. Monitoring lemming abundance is important to understand the state and consistency of this population cycle and its relationship to biodiversity and the state of the Arctic ecosystem over the long term.