The BBC has released stunning footage from its Yellowstone series showing a beaver felling a cottonwood tree as it readies its dam for winter. According to the narrator, beavers will fell hundreds of such trees in a year and the incredible footage captures exactly how they do it. “The beaver doesn’t chew through the whole trunk, just enough to make the tree unstable. It then retreats and lets the wind do the rest,” says the narrator. Once the tree is down, the beaver continues its carpentry by chopping the branches down into more manageable pieces and carries them down canals to its dam. The footage is from the ‘Autumn’ episode released back in 2009. It explains that fall is the busiest time of year for beavers as they race against the coming winter when it won’t be as easy to repair their dam because the pond will freeze — making transporting materials virtually impossible. The video contains a mix of underwater shots and above-ground shots as the busy beaver plugs the gaps in its dam.…