A beaver's front teeth - called incisors - never stop growing. They are coated in hard orange enamel and are so strong that a beaver can chew through a tree trunk as wide as a human arm in just a few minutes. The chewed wood is used to build dams across streams.
The dams beavers build slow down the flow of water and create ponds. These ponds become home to fish, frogs, dragonflies, kingfishers and many other animals that would not be there without the beaver. Scientists call beavers 'keystone species' because so many other animals depend on what they build.
In the middle of their pond, beavers build a lodge - a mound of sticks, mud and branches with underwater entrances. Inside, safely above the waterline, is a dry chamber where the beaver family lives and raises its young (called kits). Predators cannot easily reach them.
Beavers were hunted to extinction in Czechia in the 1800s. They were reintroduced carefully from populations in other countries, and today hundreds of beavers live in rivers across Czechia. Where they have returned, the rivers have become richer and more full of wildlife.