Mountain Beaver, binomial Aplodontia rufa, is very familiar to country residents of the coastal Pacific Northwest, but less so in the towns and cities, or on University campuses, where it may have an aura of mystery (or misinformation). Though many rural citizens rarely see the animal itself, they are well aware of it from the abundant holes and dirt-piles it excavates (and its landscape-depredations). The general country can seem saturated with the tunnel-warrens of mountain beaver.
Those who spend much of their days performing work or pursuing their interests in the brush & woods, typically encounter a live mountain beaver going about its business, several times a year. Often, it is not aware of the person, and continues its activity, allowing substantial observation. They do not act especially wary, nor particularly sharp of eye or ear. They are mostly, but not entirely, nocturnal.
Sometimes when we are able to watch a mountain beaver, it is just poking around, investigating, exploring. These may often be the young, displaced from their birth-burrows and seeking new homes of their own. Other times, we see established animals going about their beaver-like business – cutting vegetation and hauling it back to their cache (in burrows, though, not in water).
Mountain beavers do 2 kinds of gathering, so far as the spectator is concerned. In one kind, they push up against plant-stems at ground-level and chew them off a few inches up. Commonly, they will gather several stems, carrying the growing bundle from stem-to-stem as they continue cutting. They may place small bundles along their cutting-trail (oriented), then turn around and head home, picking up the intervening parked bundles on the way back to the hole. They may also cold-deck oriented bundles at the mouth of the hole, and some of this material may be left for later, or ‘forgotten’ – a portion of a cold-deck often remains in its spot permanently.
The second kind of gathering they do is to climb the stems of brush, or the trunks of sapling trees, go out on a limb and cut it off behind them. They and their cutting then fall to the ground with a plop (if it’s a short drop), or quite adeptly & amazingly parachute down, swinging below their bough by the cut-end. This is a startling thing to see.
Routinely, chosen harvest-sites are severe thickets. That a little animal only inches tall can fall into a tangled thicket-mat several feet thick, and then drag a small tree-branch (up to several yards long) through this ‘virtually impenatrable’ tangle, is a marvel. The larger branches may be bucked into shorter pieces.
Mountain beavers are famous for their seriously indiscriminate cutting. A major component of the harvest may be mature sword fern. Essentially, nothing eats this plant. That is partly why sword fern is so successful – it is unnutritious, unpalatable, and at least moderately toxic. Red elderberry comes up in clearcuts profusely, and the beavers dutifully gather it. When one brushes against or crushes the foliage (or buds or bark) of the red elderberry, the plant releases a harsh, repellant, volatile chemical. It is loaded with something nasty and unhealthful. Again, this is part of the elderberry’s success-formula, and it is effective. Stinging nettle is a common harvest-item. Rhododendron and conifers … one is tempted to intone, ‘anything’ … but I have never noticed the abundant Pacific Trailing Blackberry vines in cut-piles.
Some types of cuttings could be nesting-material (not food, or otherwise eaten), but old nesting-material is not seen at the entry of burrows. Certainly not in quantity.
Mountain beaver scat is never seen. They do not leave droppings above-ground. Evidently it is kept underground. Some type of indirect food-path is probably at work; either eating the properly-aged and externally-‘digested’ scat (from carefully-manages ‘compost-piles’?), or maybe something more-complex, like the rabbit-behavior.
Mountain beaver are heavily preyed upon by coyotes. In some areas, every coyote scat one sees contains their bones & fur. Coyotes make formal scat-posts on bare, smooth gravel at sites along little-used logging roads. A site will have several obvious scats of varying age, and by looking closely, there will also be several additional specimens in an advanced stage of decay. A small green flush of algae or moss often marks the spot. Old scats may contain only bits of bone & fur.
The animal may have annual activity-cycles; above-ground movement may halt for long periods. The mouths of burrows can accumulate light debris or spider-webs, showing non-use, yet later in the season ‘the area comes alive with them’. Yet at other times & places, activity and animal-sightings might continue through any weather or season.