Anatomy of an urban beaver pond

*** This will be the first in a series of three or four postings on the beavers that are inhabitant the detention pond under the powerlines in Centennial Woods. I’ve got some videos from a game cam as well as other information on how they prepare for and deal with the transition into winter. Subscribe with link to the right to keep up to date on Wild Burlington happenings!

What: The above photo I took on November 28. The pond started to freeze over on the 23rd with a thin sheet. Over the first few days the beavers were actively maintaining openwater. They’ve since stuck to maintain some exists along the edge of the water as well as a few openings in the middle of the water. The darker “C” shape in the middle is where the water is deeper and therefore warmer. The little snow fall we’ve gotten has melted into the ice. There’s more snow on the right side of the pond (it’s the south side and is shaded by a thick wall of white pines). The lodge is constructed on the bank. It’s unclear if they’ve also dug into the bank while constructing it.

Walking the perimeter, they’ve done substantial work since they moved in about a month and a half ago. Looking at the northern border of the detention pond, there’s no doubt that beavers are skilled at what they do. Each of the few dozen trees they’ve felled are all in perfect alignment. The one thing they didn’t account for was the chainlink fence. Hopefully when the big red maple still standing in the background comes down it will crush the fence and make some of those trees a bit more accessible for the beavers.

The “dam” is really just an outlet flow structure for the detention pond. You can see the open water channel running on the upper left corner where the beavers move back and forth from their lodge to the dam to do maintenance work. They maintain holes throughout the winter, or at least try to. I’m not sure the exact reason, but I would assume it has something to do with keeping an escape route in a dire emergence and also having access to land if their food cache runs low mid-winter. It might also allow them to access early spring vegetation even if their pond hasn’t frozen over.

The beavers have a number of runs that extend from the pond up to the surrounding woods. They’ve harvested mostly staghorn sumac, and actually have climbed a rather steep slope maybe 60′ or so from the water to drag them back down. They did quite a bit of work flattening out a good deal of the phragmites, making channels to bring back the haul back to their larder.

And our beavers appear to have a flair for the artistic. I’ve been continually impressed at their ability to chew plants that are three plus feet off the ground. This one stood about 2.5 feet at the top.