Do beavers move rocks?
September 21, 2008 9:36 PM   Subscribe

Do beavers move rocks?

A family member insists that there are fairly large rocks in this beaver dam they saw and that beavers put those rocks there. I am pretty certain that beavers do not move rocks around. I would like somebody that is educated in this area or with master Google skills to help me settle this.
posted by floam to Science & Nature (6 answers total) 2 users marked this as a favorite
- These beavers used mammoth bones instead of rocks.
- HowStuffWorks also says rocks may be part of the mix.
- "Rocks weighing as much as 120 pounds have been found in beaver dams! "
- Beaver Basics says sometimes beavers will also build around rocks that are already there.
- Random message board agrees!
posted by jessamyn at 9:45 PM on September 21, 2008 [1 favorite]

Hmm. I'll read these over and see. If they are building things that are able to have rocks pushed into them by water, or build up from rocks, or something like that, I'm right. The question is specifically if they can pick up and move rocks around.
posted by floam at 10:13 PM on September 21, 2008

Beavers have a reputation for being clever builders, so I see no reason to suspect the rocks found in their dams wouldn't have been placed there intentionally.

The Handbook of the Canadian Rockies, a wonderful book which happens to be at hand, says that "a family of beavers builds up layers of sticks, logs, roots, and stones, plastered together with mud and sod..."
posted by ssg at 11:25 PM on September 21, 2008

My own observations regarding beavers suggests that they aren't that clever at all. It seems that they don't even necessarily chew the side of the tree closest to the stream/creek/river, rather they just randomly chew trees close to the water. About half of the trees that I've seen felled by beavers didn't fall toward the water at all. I'd give much more credit to the flowing water than to the beavers. I don't know, however, if the flowing water could move the rocks. Maybe if the felled trees redirected the flow into a shoreline with some rocks they could be worked loose? I'm not sure.
posted by Dorri732 at 2:37 AM on September 22, 2008

About half of the trees that I've seen felled by beavers didn't fall toward the water at all.

maybe they didn't want them to fall toward the water... beavers like to eat the twigs from the uppermost branches of trees as well as use them for construction - if they felled it for eating then they wouldn't want it to float away


Mass Wildlife says: Their front feet are small and dexterous, which allows the beaver to carry construction material such as stones and sticks.

and Vernon Bailey says: In carrying stones, of which the dams are sometimes largely built, the hands and arms are used. Stones 5 or 6 inches in diameter and weighing 8 or 10 pounds are commonly used, but as they are brought up from the bottom of the pond and carried under water, the water displaced serves to reduce the weight actually lifted.

and Lewis Henry Morgan says: They carry small stones and earth with their paws, holding them under the throat, and walking on their hind feet. Large stones, weighing five or six pounds, of which size they are found on dams, they push along in different ways — with the shoulder, with the hip, and with the tail. They work the tail under a stone, and give it a throw forward. In moving materials of various kinds they are very ingenious and persevering.
posted by jammy at 5:46 AM on September 22, 2008

Yep. My parents used to have a small river & pond in their backyard. Beavers blocked up the river up every other year or so. I never actually saw a beaver, but we sure as heck saw the damage -- the felled trees, the dam, and large missing rocks from the pond. My parents sure as heck didn't move them randomly, so unless the ducks had super powers, the beavers did it.
posted by cgg at 6:06 AM on September 22, 2008

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