Went running with some friends down by a canal this morning (good god was it cold) and we were lucky enough to see a beaver swimming in it. We’ve seen beavers three or four times, although I don’t know if it’s the same animal or different ones. (Why yes, they are indeed wet. And natural.)
There’s a dam at that end of the canal which I believe still produces some power for the city. If Mr. and Mrs. Beaver are looking at beaver apartments and they find a body of water like that one, do they build their own dam somewhere anyway (there might be a dammed stream on the other side of the canal - it’s very overgrown on that side) or are they all “Oh, look, Mabel, it’s already furnished! We’ll take it!”
(At any rate, Mr. and Mrs. Beaver should have checked the lease a little more thoroughly, as I doubt they really wanted to live next door to Snappy the Alligator. He was not out this morning, though. It was 34 and before dawn. Poor Snappy.)
Okay, some minimal information. Beavers will build their lodges in existing bodies of water. Even in an existing pond created by a beaver dam, they will tend to move upstream and build new dams, creating a series of ponds.
Would they normally mind that the body of water they’re hanging out in (I don’t know where this guy’s lodge is, although there was a suspicious number of sticks where he was heading, which is where I’d be if I were an animal in a busy park - across the canal from the footpath and under a sheer drop from the housing development above where nobody’s going to bother him) has a really fast undercurrent? Very dangerous to people who don’t realize it and a serious drowning hazard? Or does it not bother beavers?
There’s no way these beavers are going to dam the canal itself unless they’re some sort of Earth’s Mightiest Beaver Heroes team. There are streams that feed into the river (which is just down the slope - it’s the kind of canal that was built because a section of river is unnavigable, not the kind that connects two bodies of water) but I’m not sure that there are any going into the canal itself that could be dammed. Will beavers stay in a place they can’t build a dam?
We were so excited when we started seeing them - I’ve seen beaver dams before but never the animals themselves. And last week we saw otters. Otters! In real life!
Before I was born, my mother used to work in a zoo which kept beavers- despite them only having access to a concrete lined pool which was emptied and scrubbed out completely every few months, they still built a dam across it every time it was refilled. Dam building appears to be instinctive, even if there is no use at all for it, so I don’t think they’d be happy to hang around long if they couldn’t build one.
They also need to have a deep pool with a slow or no current to store branches in, so a canal with a strong undercurrent- though it would probably not be dangerous to the animals as they’re much better swimmers than humans- would not be suitable for them to live in.
They need to have a lodge to sleep in as well, so if there’s no lodge in the canal, then they’re not going to be living there. They’ll happily use natural (or man-made) streams to swim down, and they will travel quite a long distance to look for food or whatever, so I guess you’re seeing commuter beavers. Maybe they could be damming one of the side streams going into the river? Can you go look?
It’s a big river - actually it’s two big rivers forming a third big river! So finding a dammed stream would be a pretty big order. We’ve seen them in the same place each time - going under a footbridge. I found a picture at the Library of Congresshere: they’ve since demolished the prison and all, but twice we’ve seen beavers swimming under the small bridge between the upper two highway bridges, and once just a bit downstream of that bridge before the middle highway bridge. (Interesting picture - the Broad is crazy muddy in it and I wonder if that’s something that’s changed or if it was weird spring weather or something when it was taken?)
As you can see, even when this was taken it’s the confluence of two pretty big rivers in an urban environment. I’d love to know where these beavers are hanging out if it isn’t in the relatively protected parkland!
One problem is, beavers don’t like leaks in a dam, the sound of water running out of their pond/lake is a pretty powerful stimulus for their dam-building. If you have a flowing spillway or outlet at a man-made dam, they will often try to plug it up to stop the “leak”.
It’s fascinating to fly over the northern Canadian shield; hundreds of miles of flat, scraggy muskeg and rock outcroppings. The beavers basically will build a dam across any shallow stream, then extend it as the pond fills up. Once it is filled with silt, and becomes mushy meadow, they move on up or down stream.
From the air it looks like a series of terraces like the hillside chinese rice paddies (only much flatter). If Mother Nature intended for some animal to turn marsh into meadow, they could not have designed a better system.
But the are a nuisance when they want to block ditches by the roadside (flooding the road) or flooding streamside cottages.
As for the OP - if they can find a small inlet or water “cul de sac”, they will likely build their home there. Faster-moving water, and deep water are not particularly useful. If their cul-de-sac permits, they may dam it off. Otherwise they will gnaw down trees and cause problems at the dam as these get away from them.
I live in a fairly suburban area that has many small streams and a few ponds. One or two of these ponds have an artificial dam and small spillway to prevent flooding. At the far end of a couple of these ponds is a beaver lodge. The resident beavers do try to block the spillway, probably to raise the level of the pond, but people frequently remove their little “dams” to allow water to escape to a level below the spillway.
As I recall, the beaver lodge is a place of refuge, and can only be accessed from an underwater entrance. If the lodge is under attack by a predator, they will escape via another underwater entrance. In open water they can easily outswim most enemies.
They will excavate steep banks in a pinch, but a flooded area with a lodge surrounded by water seems to be preferred. I do not think they care if the pond or lake is manmade or not, so long as the lodge is surrounded by water all the time, and there is plenty of food nearby.
Beavers will also build lodges in stream- and riverbanks. I was really surprised to see a beaver hanging out in the shallows of the Colorado River at Lees Ferry (where rafters put in for Grand Canyon trips)
Obviously, swift-moving water can be a problem to build in - but any slow-moving eddy or lee will provide a nice refuge to build. The only other issue is if it’s not too deep so that they don’t have to build like crazy to get the ground floor. Being wood, it’s easier if you can stick the foundations into the bottom mud.
Yea, in a concrete dam and spillway they might, if left alone, block the sillway then start build up across the dam. As the water rises they will build higher, I’ve seen them 8 to 10 feet high in the right (wrong?) places. Eventually it should silt, turn to marsh and then meadow. Presto! Topsoil!