I have till next spring to decide if I will fight them or adapt to them. Given some of the posts, I am leaning toward adapting. Their current location will require me to make some new tractor trails, but that will probably be just a weekend rental of a 6' dozer. The kids have lost their swimming hole, but that should only be building a digger dam further upstream. The area has always been on the swampy side, and the current trails provided access to cut dead trees down, clear brush, and provide a nice circular property walking path. I don't believe they will move further upstream. Their source of food and building supplies disappear as it turns to open fields bordering the stream. If they did move up, I would be forced to take action. At this point, not sure I am willing to get into a long term conflict/w3tcompact/icons/wink.gif or an all out war!
On the plus side, I have already seen additional wildlife due to or inpart to the dam construction. A heron and a couple of species of ducks, have been spoted numerous times. Deer and fox have been seen more regular in the nearby field, ie pushed upstream for easier stream crossing. Also thought I saw a river otter, or at least a similar type animal, dart infront of the tractor, and quickly disappear in the brush. It will also make it harder for tresspassers to cross onto my property, without being noticed. That is, unless they brought some waders with them/w3tcompact/icons/wink.gif.