锯齿国家森林里的海狸坝，爱达荷州 Beaver dam in the Sawtooth National Forest, Idaho (© Charles Knowles/Alamy)

锯齿国家森林里的海狸坝，爱达荷州 Beaver dam in the Sawtooth National Forest, Idaho (© Charles Knowles/Alamy)

Beaver achievers

Don't get distracted by the awesome top half of today's photo. The postcard appeal of Idaho's Sawtooth Range is undeniable, but our focus today is on the humble structure at the bottom.

Beaver dams like this can be found coast to coast in the United States and Canada, and now is the time of year when these industrious rodents put in extra time to reinforce their dams. Listening closely for trickles of running water, they patch compromised sections with logs and mud, securing their habitat for the chilly winter. And their efforts have important downstream effects: Beaver dams help prevent floods by slowing water flows, and also filter out sediment to create cleaner streams and rivers.