Some PEI wildlife travel our fields and forests all winter, leaving conspicuous tracks in their wake. Others prepare a cozy, well-stocked home and don’t wander far once cold weather hits. I appreciate that latter approach, and Beavers are masters of it.
I’ve never been lucky enough to see Beaver tracks in snow, which may be just as well. I know of one otherwise level-headed Islander who was very much unnerved at the sight of strange tracks in winter. Only the imprints of the Beaver’s hind feet were visible, which this person was convinced was a man walking through the snow on his hands – clearly an unnatural occurrence!
Beaver tracks are more commonly found in mud around our rivers and ponds (Photo 1). The small front feet have five toes, but their imprints are often obscured under the tracks of the hind feet or drag of the tail. Hind feet are larger, with five webbed toes, but it’s rare to find perfect tracks that show them all. I most commonly see imprints from only three toes, as shown here (along with a mark from the nail of a fourth toe).
While Beaver tracks can be subtle and easy to miss, their homes are much more obvious (Photo 2). Beavers build houses (also called lodges) of sticks and mud, often along the edge of a stream. The entrances – usually at least two – are always under water, and tunnels connect the entrances to one or more cozy chambers inside.
Each house typically holds two to as many as eight Beavers, and their combined body heat keeps it well above freezing all winter. The top of the house has an opening to allow fresh air in. You can tell an active house by the lack of snow around this air vent, melted away by the body heat inside. On the coldest days you can see heat rising from the opening like a chimney.
A warm winter house isn’t much good without a well-stocked pantry, and that’s where the feed patch comes in. In fall, Beavers start piling branches in the stream near the house. Those branches in Photo 2 are the top of the patch, which extends deep enough under water that it won’t freeze. The dam keeps the water deep enough for this, and those branches above the surface trap snow, further insulating the patch. All winter, the Beavers will swim under the ice from the house to the feed patch, grab a stick and take it back to the house to eat.
They don’t eat the entire stick, just the bark and soft outer layer (called the cambium) and it’s common to find stripped sticks floating along a PEI stream or pond where a Beaver has been feeding. Poplar is the preferred winter food (Photo 3), but Alder, Willow, Cherry and even Maple or Ash will do in a pinch. (I found one site where Beavers were feeding on ornamental Lilac trees, and another where they repeatedly returned to an apple tree to eat the fallen fruit before cutting down the entire tree). In summer, Beavers feast on leaves and roots of aquatic vegetation.
Tree bark and cambium are high in tannins and cellulose, neither of which is easy to digest. Beavers overcome this in three ways. First, they have proteins in their saliva that bind to the tannins and make them more digestible. Second, they have specialized bacteria in their guts that break down the cellulose, allowing about 30% of it to be digested. Finally, just before the material is excreted, it gets coated in different types of bacteria that continue breaking down the cellulose. Beavers re-ingest these pellets and send them through the digestive system again. After a second passage, close to 90% of the cellulose will be digested. (Snowshoe Hare use this same double-digestion approach).
Beavers are not only extremely well-adapted animals, they also have a very interesting history here on the Island. I’ll cover that in a future edition of PEI untamed!