We apparently have beavers. We haven't seen any beavers; nor have we seen any fallen trees or chewed logs. But what other creature would build a dam this substantial?
Last year we battled some kind of dam critter, but it never really approached this level of engineering, so we had hoped it was just a muskrat. Now I'm thinking maybe it was an inexperienced beaver, and he spent the winter really perfecting his dam building techniques.
This spring's dam is situated in a more critical spot on the stream, and is much higher than anything he attempted last season. We're seeing a real change in the water table around our place, as the spring rains are caught in the swamp and backed up behind this dam.
This is the second time this week that we've dismantled it. As you can see from the below pictures (taken just downstream from the dam site at the bridge), the water level really comes up in the stream once the dam is removed.
That's the same tree in the center of these two shots, the second one was taken about an hour after the dam was removed on Saturday. The water came up about a foot, and looked like it would continue to flow at that level for at least 24 hours before the water level would come down in the wider area.
Notice that I said "looked like it would continue" above. After the dam was removed Saturday afternoon, the critters completely rebuilt it Saturday night. Sunday morning it was as if nothing had ever changed. Not knowing what else to do, we removed it again... although I suspect that tomorrow morning it will have reappeared. I'm not sure what we can do, realistically, to prevent beavers from building dams. I guess the hope is that we can hassle them enough that they will move the dam back into the swamp where it will (hopefully) not back the water right up into our backyard.