A wide variety of animals live in and around New River Gorge National River. The New River has long served as a migration corridor for both plants and animals. For this reason, animals more commonly found much farther south may reach the northern extent of their range in the New River Gorge area. Likewise, animals more commonly associated with the northern forests may reach the southern extent of their range in this area. Other animals are found only in the New River area. These species, called endemics, were isolated from similar populations by the steep, rugged terrain of New River Gorge and/or the tumultuous rapids and waterfalls of New River. Thus isolated, these animals evolved to be adapted to the unique circumstances of New River Gorge.