Yellowstone Reports

New Beaver Colony

Examining The Life Of A Beaver Colony
by Dan Hartman

Oct. 27, 2012

     Cindy and I were driving to Cody Monday when I spotted something suspicious along the river. Orange spots dotted an island. That could only mean one thing. Beavers!

     We parked and walked out across the sage flat to the stream edge. Sure enough, just below us spanned a brand new dam. Its mud, rock and stick structure had already raised the water level 1 ½ feet. Down stream I found another, smaller dam. This one I was able to walk across to the island of stumps.

     Obviously everything had been cut in the last two weeks. As I searched for more evidence, I located two more dams. One where this little inlet forked off from the river, and one just as it was about to join up again. As ¾ of the building and feeding material had already been removed from the island I wondered if the beaver could find enough forage to survive the winter. Walking along the deepest part of the pond I came across their food cache. Here they had scooped out the stream bottom 2-3 additional feet and filled the hollow with aspen branches. A little farther down stream was another smaller cache. Then I noticed a mud slick runway that led to a pile of fresh branches and mud. That would be the beginning of their lodge. Since it was twelve feet off shore there had to be an underground tunnel that led to the structure.

     I looked around a bit more, but knew I had found the essentials of a beaver colony. Dam system, food storage and lodge. What I didn’t understand were the two dams at each end of the inlet. They really didn’t seem to serve any purpose. Also why was the lodge so far up on the slope?

     I knew whom to ask. My good friend, Jeff Hogan had filmed and produced a great film called “American Beaver”. He also supplied beaver footage for many other films including David Attenborough's “Life of Mammals”.

     As for the little dam at the head of the channel, Jeff explained it was for the spring or any sudden run off that might unexpectedly threaten the pond. He wasn’t sure about the one down stream except, “Beavers think things through pretty thoroughly, so there must be a good reason”.

     As for the lodge being up on the bank, “Every colony is different so it’s hard to assume what a beavers thought process is”. The pile of brush and mud is basically just the roof of the lodge while the living quarters is underground with an under water escape tunnel.

     He also thought these were probably dispersing beaver looking for new territory.

     I returned yesterday after a fresh snow. The dam was higher with rocks lying across the top. I called Jeff again and he explained it meant more building was forthcoming because these rocks will soon be lodged inside the dam to provide stability. Because of the snow I could see where they had left the water to feed. Also what other animals were about. Bear and coyote tracks trailed along the waters edge, ermine tacks were at the lodge. A bald eagle fished nearby.

     The pass will close soon so I won’t be able to check on this new family. I’ll be waiting expectantly for spring to see how they wintered.

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