This hardworking beaver didn’t notice us quietly fishing as he worked furiously on his dam. According to wikipedia:

The North American beaver population was once more than 60 million, but as of 1988 was 6–12 million. This population decline is due to extensive hunting for fur, for glands used as medicine and perfume, and because their harvesting of trees and flooding of waterways may interfere with other land uses.

A pretty sad situation indeed. Beavers are really clever in the methods they use to build their homes which are the dams. I have heard that they are the animal after humankind that is said to alter their environment the most drastically.