Saturday, October 17, 2009

Beaver Lodge Armour

In the last week or so the beavers have plastered a thick coat of fresh mud on their lodge. The frozen mud will provide an impenetrable barrier to protect the beaver family during the winter. It would be pretty hard for a wolf or a late-hibernating bear to break through. More importantly, the mud seals air leaks and provides extra insulation so the body heat of the beavers can keep their lodge warm. OK, warm is a relative term. The recorded temperature inside one lodge in the depth of winter was 0.8-1.0 °C, or just about the same temperature as the water beneath the ice. Compared to outside though, which might be -30 °C or colder, it's a tropical resort. The beavers always leave a small area at the top of the lodge as a breathing hole. On a cold winter day one can see the warm air rising up through the hole, indicating all is well with the beavers below.

Here's the process. A beaver dives to the pond bottom and scoops up a big dollop between it's front legs, chest, and chin. Then it walks up the lodge on it's hind legs using the tail as a brace and balance. At the chosen spot the beaver slaps the load down and smooths it out with it's front paws. Then it's back to the pond, this time on all fours, to get another load. In this photo the wet line on the right side of the lodge is the path recently followed by a wet beaver.

In their book Wild Alberta at the Crossroads Marian and Robin White have a great picture of a beaver carrying mud.

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