The beavers have sharp and powerful teeth. They cut down trees to make their dams in rivers and streams. They are the world’s second largest rodent. The beavers are from the genus Castor and the North American beavers are from Castor canadensis (Wikipedia).
There is a stream behind the condo in Incline Village, Lake Tahoe where some beavers live. They converted part of the stream into a pond by building a dam downstream.
One night, about a year ago, I startled one beaver swimming in the stream. It dived very quickly into the water and disappeared.