The long-eared owl (Asio otus), also known as the northern long-eared owl or, more informally, as the lesser horned owl or cat owl, is a medium-sized species of owl with an extensive breeding range. The scientific name is from Latin. The genus name Asio is a type of eared owl, and otus also refers to a small, eared owl. The species breeds in many areas through Europe and the Palearctic, as well as in North America. This species is a part of the larger grouping of owls known as typical owls, of the family Strigidae, which contains most extant species of owl (while the other taxonomic family of owls are the barn owls, or Tytonidae).
This owl shows a partiality for semi-open habitats, particularly woodland edge, as they prefer to roost and nest within dense stands of wood but prefer to hunt over open ground. The long-eared owl is a somewhat specialized predator, focusing its diet almost entirely on small rodents, especially voles, which quite often compose most of their diet. Under some circumstances, such as population cycles of their regular prey, arid or insular regional habitats or urbanization, this species can adapt fairly well to a diversity of prey, including birds and insects. All owls do not build their own nests. In the case of the long-eared owl, it generally utilizes nests that are built by other animals, with a partiality in many regions for those built by corvids. Breeding success in this species is largely correlated with prey populations and predation risks. Unlike many owls, long-eared owls are not strongly territorial or sedentary. They are partially migratory and, although owls appear to generally use the same migratory routes and wintering sites annually, can tend to appear so erratically that they are sometimes characterized as “nomadic”. Another fairly unique characteristic of this species is its partiality for regular roosts that are often shared by a number of long-eared owls at once. The long-eared owl is one of the most widely distributed and most numerous owl species in the world, and due to its very broad range and numbers it is considered a least concern species by the IUCN.