This fascinating picture is from the photoblog Along the Airline Trail by Stan Malcom of CT and captures the surprising and watery moment when a cozy beaver lodge stopped being a cozy beaver lodge. It makes me think of those images from Katrina of folks retreating to roof, waiting for help. This can’t be an uncommon occurrence for beavers given that they live in water and water changes with the season. As good as they are at controlling and directing water, there must be moments like these, when even beavers have to wait out the floods in relative discomfort.
This makes me think of that big storm back in March of 2011 which washed out their dams and their beautiful lodge. The next morning we saw footprints in the mud where there home had been and I imagined our kits coming back and saying, where is our house? Kind of like how the inside of a tent, which could be a child’s cozy fort, disappears when the tent is collapsed and folded away.
Since our beavers lost their lodge, and the hardworking mother who always made them for them, they have become ‘bank dwellers’. Which, I’m learning, brings mysteries if its own.
This illustration is from the chapter on beavers by Joseph Grinnell, published in 1937. He gets a lot of things woefully wrong in this chapter, saying California beavers don’t live above 300 meters elevation or leave footprints, but I have always thought this is an excellent drawing. Recently I got to wondering how beavers breathe in bank lodges. Island lodges have vent holes on the top so that fresh oxygen can get through. Sometimes I read descriptions of lodges in winter with steam rising from the vent, as if the beavers were inside smoking! Do bank lodges have vents? With all those hot bodies breathing into the same space, they must need fresh air from time to time!
Of course I did what I always do with these questions, and passed them around. I thought this morning I would share what wiser folks had to say about the answers. Enjoy!
Skip Lisle: Beaver Deceivers International
They make the tops of the chambers close to the surface of the ground so they “breath.” Because the ceilings are thin they are relatively easy to break through and therefore chambers often “open up” and can be viewed from above.
Owen Brown: Beavers: Wetlands and Wildlife
Yes, but they are hard to find. Many lodges start out as bank burrows on a stream and then the sticks are placed on top of the vent holes on the bank. Then once the lodge is well under way they dam the stream and voila a lodge seems to have been built in the middle of a beaver pond.
When we raised 4 babies in our farm pond they built a bank burrow without me knowing since the entrance was under water. I noticed a pile of sticks on the shore and I moved them to a nicer location. The next day they had moved them back to the original location and that is how I found the vent hole. It is not very big at the surface and hard to find.
Mike Callahan: Beaver Solutions
Often the lodges are dug out under the root canopy of a bush or small tree which prevents the roof of the den from collapsing as well as allowing ventilation to occur. On rare occasions I’ll see sticks laid on the ground above the burrow as a “roof”. However, sometimes the ground seems thick where there does not seem to be a root system or roof of sticks for ventilation. On those occasions I am baffled as to how fresh air gets in.
Sherri Tippie: Wildlife 2000
Well, I’m sure they do because they’ve been doing it like that for a long time. I have seen however, I don’t know exactly how to explain it . . . . places behind the opening to a den where there are openings with sticks laced together – like an air hole. And, I’ve seen bank dens with nothing of the sort. The thing I’ve realized about beaver is, they really are all different. Some beaver do things one way,others do it differently. It really gets interesting when it comes to scent mounds. I have a slide of a scent mound that is so interesting!! I didn’t know what it was until I climbed down the bank and smelled it! It was a purple area in the sand, and it looked like a human had taken their four fingers and made a ran it criss crossed them. There were NO sticks! Just this purple place in the sand. But I would know that smell anywhere! It was really neat.
Joe Cannon: The Lands Council
Hmm. .. good question. I’ve been assuming that they don’t raise the kits in the type of bank lodge without the branch cover/ reinforcement on top (and venting). So you’re only seeing the bank holes with the Martinez beavers? I’m curious about this also.
Whenever I’ve explored abandoned bank lodges the extensive burrows in the bank have exhausted me — or I should say my kid, I used to push him into them with a flashlight. I’ve never pried in the winter looking for vent holes but the coyotes seem to have no trouble finding a place to dig in and I assume got a scent. In some cases the beavers seemed to be paying attention because they covered any holes that were dug. Of course in high water the entrance to burrows might be below the water but my impression is that the burrows are generally dug with part of the burrow entrance being open to the air which is why the beavers then pile on logs to hide the entrance. That said, I have seen beavers torpedo out of burrows entrances completely below the water, but that was in pretty porous bank of loose soil with several burrows with some completely open to the air. I think beavers are probably more comfortable in burrows than in lodges, at least my kid seemed to be.
Leonard Houston: Beaver Advocacy Committee
If the beavers are living in there then there is ventilation this is how the lodge or den is dried and vent holes often double as plunge holes allowing beavers to escape predators without making it back to the water
I have attached two photos one is a vent hole into a bank den as you can see it is to small for the animals to enter, the second is inside the bank den photoed by sticking the camera down the vent…….. there was two underwater entrances and a plunge hole and tunnel some 15 ft from the waters edge…..no kits were present at this site but we did have a breeding pair living here
It appears that the consensus of the experts is that bank lodges DO have vents to let in fresh air. So think of that the next time you’re watching the creek for movements!
