Castor fiber
Eurasian beavers reshape whole valleys by felling trees and building dams that slow and clean water, creating wetlands used by fish, amphibians, birds, and insects. Family groups live in lodges with underwater entrances and slap their broad flat tails on the water to warn of danger. Hunted to near extinction for fur and castoreum by 1900, they have recovered through protection and reintroductions and are now welcomed back as a keystone species across Europe.