An online resource based on the award-winning nature guide

Animal Architecture

A Beaver’s Winter Quarters

2-1-17-beaver-lodge-interior-img_4899What exactly is it like inside an active beaver lodge in winter? It’s dark, damp and around 32°F. The living chamber inside usually has a ceiling no more than two feet high with a diameter of 4 to 6 feet, depending on the number of individuals in the family. (A typical beaver family is composed of an adult male and female, 2 to 3 yearlings, and 2- 4 kits that were born in the spring.) Fresh air enters and carbon dioxide leaves through a central vent (where mud is not applied) and through small holes that remain under logs on the side of the lodge. When there isn’t much snow and the outside air falls well below zero, the temperature inside may drop to a degree or two below freezing, but if the sun is out, it warms right back up again during the day.

The dampness is due to the beavers’ repeated need to enter the water both to retrieve sticks from their nearby food supply pile and to defecate. Upon returning to the lodge, the humidity inside increases due to the water draining from the beavers’ fur. No small wonder that if a January thaw permits, beavers will exit their pond for some fresh air, food and a little bit of sunshine.


Bird Nests Visible

11-25-14 black-throated blue nest  043When leaves start falling from deciduous trees, bird nests appear out of nowhere. Most songbirds abandon their nest after raising one brood, never to return to it. An empty nest sits where it was built until the elements break it down, another animal recycles the material from which it was made, or a mouse takes over winter occupancy. The period of time after the leaves fall and before winter and other creatures deconstruct the nests is ideal for discovering who raised their young under your nose this past summer.

Just as each species of bird has its own distinctive song, each species also builds a unique nest. It is often possible to determine what species built a nest without ever setting eyes on the bird. The size, shape, material used and habitat in which a nest is built are remarkably similar for all birds of a given species. Eastern phoebe nests mainly consist of mud covered with moss. Gray catbirds incorporate grape vine into their nests, and line them with rootlets. Ovenbird nests are on the ground, roofed over like old-fashioned ovens. While federal permits are necessary to collect these nests, they can be admired and identified without a permit. (Photo: the combination of this nest’s size (3” outer diameter), location (3’ off the ground) and material used (yellow birch bark strips, grasses, cocoons and black rootlet lining) pinpoint the builder as a Black-throated Blue Warbler.)


A Variety of Beaver Lodge Designs

10-20-14 beaver bank den 080Beavers are hard at work refurbishing their mud and stick lodges in preparation for the coming winter, when their movements will be restricted and they will spend both days and nights inside their lodge. When we think of a beaver lodge, we picture it in the middle of a beaver pond. This was not always the case, however, and still isn’t today. The earliest and most primitive beaver lodges consisted of a burrow in the side of a high bank with the entrance under water (see exposed bank lodge entrance in photo insert). The next advance was the addition of sticks and mud piled over the top of the bank as added protection from predators (see photo). Eventually beavers started building a complete lodge on top of the bank which had an underwater entrance. The most advanced design is the lodge we most commonly associate with beavers — one that is built up from the bottom of the pond and is completely surrounded by water. It requires the greatest amount of work but offers the greatest amount of protection to the beaver.


Signs Of An Active Beaver Pond



A New Book for Budding Naturalists


Winter Mouse House



Beaver Breath

