Okay, my radical thought that beavers do not notch their dams created some argument on the beaver management forum. Including this comment from Emily Fairfax which I repost here:
I’ve seen beavers pull sticks out of their dams and “notch” them. They’re pretty good about moving water through their wetland complexes, and hydrologic extremes like drought and flood are good motivators for the beavers to try to move water around. There was a pretty big dam in Colorado that I studied during grad school that the beavers removed sticks from the same notch each year before snowmelt, presumably to give the water a spillway and take pressure off the rest of the dam face. Definitely could use some more research on how common this is, but I wouldn’t say it’s impossible or something that never happens.
Hmm. Its an interesting idea of course. And I have great respect for her observations and research. But it requires that beavers know when the snow is going to melt, Also since the effect of removing a stick would be exactly the same as the effect of a stick getting washed away so I’m choosing to remain censorious.
It makes as much sense to me as suggesting they notch them so the salmon can get over easier. Or that spiders destroy their webs so that moths can pass thru at night. Or that animals remove their footprints after a fresh snow so that hunters can’t find them. Its a cause and effect problem.
I know that all beavers are not the same. And that our beavers didn’t know everything or show us everything. I remember the difference between the “Useless bookends” and “Reed” for example. I even have seen beavers get smarter over time.
I had the odd fortune of watching beavers construct dams directly under me for a decade including little dams and failed dams and trial dams by kits that were made with reeds.I’ve seen dams wash out in storms and get ripped out by kayaks and even watched otters poke holes in them with their heads. I’ve seen Dad beaver move sticks his kids placed to better locations and bring larger trunks for kids that refused to work with wood. One morning I even saw Dad actually lift one end onto the dam to strongly suggest wood was used. and watched that stubborn little iconoclast push it off because that kit [referred reeds.
I have never seen beavers notch a dam before a storm and until I do I’m not going to believe it happens. I love beavers enormously and am their greatest admirer but I do not think they watch the weather channel.
