The distinguishing feature of a beaver pond is that it is shallow. The beavers want it to be shallow because they will do a great deal of foraging for food along the bottom of the pond and it does them no good to have to dive a great depth. Humans like depth in ponds. Our dams are prized for the volume of water they hold back and thus control. Even after seven years of watching beavers and seeing time and again how little importance they put on the depth of their ponds, I still fret about shallow ponds. I'm searching for an analogy that will make apparent the beavers' view of the matter. The pond is the beavers' pantry; their refrigerator; their highways; their garden, and so on. They are after convenience, not the Guinness Book of Records.
Yes, I have photos of a large lodge in the middle of a big pond; but look at this: two lodges (can you find them?) in a shady shallow pond.
In a sense, with a pond the beavers invert the human sense of reality. When I began watching beavers what I most liked to see was a beaver taking branches from a felled tree. I thought that is what a beaver is all about, its essence, and the pond was essentially a medium that made it easier to collect tree branches. At first I thought the frequent diving the beaver did in the pond was unimportant. Indeed at first I thought each dive was a beaver's attempt to avoid me. Now I see that the diving is the ultimate expression of the beavers' sense of the world. When it dives, it is reaching for the fruit from the good earth. We see the Tree of Life reaching to the heavens. The beaver sees it secure in the bottom of its pond.
Highlighting this shallowness might seem to impugn our conceit that the beaver is a great engineer. We do not like to think of engineers as doing shallow things. Yet, it is the premium beavers put on shallowness that makes them great engineers. To hold back water is one thing. To hold back water that is neither too deep nor too shallow, and that extends as far back as the next dam, that is something. Indeed the beavers have a more sophisticated conception of their environment than we do. In seven years I have spent much time numbering dams and naming ponds. I viewed each pond in the valley as a discreet achievement, much like a new sovereign state added to the union. The beaver however, in time, demonstrated to me its own piercing sense of overriding shallowness as they turned two or sometimes three ponds that I cherished, ascribing to each different virtues, into one pond. They accomplish this in two opposing ways: by flooding over the back dams and by breaching the back dams and letting the water take the level of the leading dam. This latter feat can create a series of pitifully shallow ponds that simply infuriate me. The beavers however come up to those shallow ponds and eat off the bottom.
So what I am saying is that while to me the pond is the most sacred thing the beavers create, for beavers it is surely a temporary arrangement. I should probably pay less attention to individual ponds and more to what might be called a beaver valley.
To be sure, the water level in a pond has to suit the lodge the beavers are using, but examine this lodge closely. The fresh mud on it demonstrates the beavers committment to it as winter approaches, but look how shallow the water is around it:
Here is another view of the lodge, looking down toward the underwater entrance of the lodge -- just deep enough to survive a dry spell.
However, when there is a drought and the water level goes down, the beavers I watch simply build a new lodge. One colony of beavers, in three successive home ponds, have built their first lodge toward the shore so that they can build it more quickly in the shallow water which will get deeper as the dam grows. Then they built a lodge right off the deepest part of the ponds, where the old creek runs channels through the pond. In the time, in the next pond down, they built a lodge right on the dam where the creek channel runs. What better place to be assured of some depth!
I have never seen a beaver attacked by any predator other than man so I don't know how the shallowness of a pond can affect that. There are coyotes on the island and I've seen them on the pond in winter and heard them around the ponds in the summer. Once when I knew some beavers were in a very small pond, I heard the coyotoes causing a commotion in the night. I investigated the next morning expecting to find a dead beaver. I didn't even find any blood stains.
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