Summit Outside: Beaver dams taking shape in Summit County
November 10, 2012
Beavers are active this time of the year!
My friend Terese Keil, property manager for Trappers Villas, called me the other day to tell me a bunch of landscaping aspen had been chewed down literally overnight by beavers.
A call to Fish and Wildlife confirmed several reports of beaver activity in Summit County and loss of trees on properties. Apparently, they are busy building dams and lodges in preparation for winter. The advice was to protect the trees with wire mesh along the bottom of the trunks.
Beavers are prolific engineers and builders, and prefer to work mostly at night; their specially adapted incisor teeth and powerful lower jaw muscles allow them to chew down trees. Their teeth never stop growing, and their four front teeth are self-sharpening. They have been seen to work as a team to carry a large piece of timber.
When a beaver cuts down a tree, it makes two cuts in the trunk, one above the other and then tears off the piece of wood between the cuts working their way around the trunk until the tree breaks. The beaver removes the branches then rolls the trunk into the river.
Along the Blue River in the Warriors Mark area there is a new dam and the start of a second dam. They build the dams so that the lodges will have an underwater entrance which will protect them from predators.
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Beavers can build a 35-foot long dam in just one week.
They also build canals to float building materials that are difficult to haul over land. The dams are built by first putting in place vertical poles, then filling between the poles with a crisscross of horizontally placed branches. They fill in the gaps between the branches with a combination of weeds and mud until the dam traps sufficient water to surround the lodge. The dam is built like a layer cake held together by mud, which is smeared on with their paws and noses. Beavers can rebuild such primary dams overnight.
The lodges, which appear to be a bunch of branches, are actually very well designed. There are typically two dens or rooms within the lodge, one for drying off after exiting the water, and the second, a drier, inner chamber is where the beaver family actually lives.
The inner chamber has one or two vent holes in the roof. The inner chamber is lined with grasses or shredded bark which absorbs moisture. Beddings of grasses, reeds and wood chips are changed regularly.
Even if the outside temperature is -40° F, the inside of the lodge remains above freezing.
The beavers cover their lodges in the fall with fresh mud, which freezes and hardens when the frost sets in. Some of the pile is generally above water and accumulates insulating snow in the winter.
Even though a beaver dam is well constructed, it is not something to be relied on as was evidenced recently in an area near Seattle. A beaver dam was holding back a 28-acre pond near the town of Carnation, northeast of Seattle in King County, when it burst just before noon. Water and mud reportedly surrounded and flooded several buildings and homes and filled up fields in the area of State Route 203 and NE 124th Street.
Joanne Stolen is retired from teaching microbiology at Rutgers University.