In my wildlife blog entry I mentioned that I was hoping to see a beaver dam on my trip to the middle fork of the OT. But in the subsequent blog entry, where I document that trip, you'll notice I didn't mention seeing any beaver dams. I was really bewildered. I had seen the following pictures by Danny M (whose motrails site is the definitive guide to hiking in Missouri) which looked pretty impressive. These were taken near Barton Fen, about half-way through the middle fork section.
When I got to Barton Fen and didn't see any dams I actually took off my pack and went exploring to see if I had missed them somehow. I did photograph the following tiny thing which hardly looks like Danny's pictures of beaver dams.
I was really disappointed and worried I had somehow missed what I had come to see. Then it occurred to me that the severe flooding we had had in Missouri during 2008 may have wiped out the dams (and maybe the beavers!). When I got home I made inquiries on Danny's yahoo group. John Roth, president of the Ozark Trail association, told me that the beaver dams get obliterated every few years due to flooding. In fact the pictures on the Barton Fen gallery at ozarktrail.com are of a previous set of dams which existed in early 2002 but were destroyed that year by floods.
So it appears that flooding is an occupational hazard for beavers. It may be that the little dam I saw is the beavers attempt at rebuilding.
I learned something else as well. Beavers are kind of like suburbanites. They are always remodeling their homes. So if their dam is not knocked down by a flood in a given year then they raise the dam and make it higher. Actually this can be bad for the surrounding ecosystem because the dam pond grows and grows. So an effort was made to keep the most recent set of dams from growing. A PVC pipe with holes drilled through was laid across the top of the dam so that even if it the dam were built above it water would continue flowing through so the pond wouldn't get any higher. Thinking back I did see the end of a PVC pipe sticking out from the bank at one point. That must have been the location of the dam. Perhaps in a few years there will be another 6 foot dam on the creek.