The European beaver (Castor fiber) is widely distributed mainly in Eastern and Northern Europe, with small populations also present in China and Mongolia. It builds dams and lodges around ponds and rivers and is an important keystone species that supports surrounding wetlands and biological communities. Body length is about 70–100 cm; the tail is somewhat narrow and the fur is dense. Its ecology is primarily nocturnal and it lives in family-based colonies. Its diet is herbivorous, eating bark in winter, and breeding occurs from winter through spring. The species declined drastically in the 20th century, but conservation efforts have led to a recovering population; its current status is Least Concern.