In the Medicine Bow Mountains one December day, I came upon a beaver
house that was surrounded by a pack of wolves. These beasts were
trying to break into the house. Apparently an early autumn snow had
blanketed the house and thus prevented its walls from freezing. The
soft condition of the walls, along with the extreme hunger of the
wolves, led to this assault. Two of these animals were near the top of
the house clawing away at a rapid rate. Now and then one of the sticks
or poles in the house-wall was encountered, and at this the wolf would
bite and tear furiously. Occasionally one of the wolves caught a
resisting stick in his teeth, and, leaning back, shook his head,
endeavoring with all his might to tear it out. A number of wolves lay
about expectant; a few sat up eagerly on haunches, while others moved
about snarling, driving the others off a few yards, to be in turn
driven off themselves. Shortly before they discovered me, there was a
fierce fight on top of the house, in which several mixed.
Even though they had broken into the house, it would have availed them
nothing, for in this, as in all old colonies, there were safety
tunnels from the house which extended beneath the pond to points on
shore. In these tunnels the beaver find safety, if by any means the
house is ruined. Although carnivorous animals are fond of beaver
flesh, they rarely take the useless trouble of digging into a house.
Occasionally a wolverine or a bear may dig into a thin-walled house or
one not frozen, then, after breaking in, lie in wait, and endeavor to
make a capture while the beaver are repairing the hole. Beaver are
more secure from enemies during the winter than at any other time. It
is while felling a tree far from the water or while following a
shallow stream that most beaver are captured by their enemies.
Many a time in winter I have made a pleasant visit to a beaver colony.
One day, a few hours after a heavy snowfall, I came out of a dark
forest and stood for a time on the edge of the snow-covered pond.
Around were the firs and spruces of the forest, moveless as statues
and each a pointed cone of snow. Around the small snowy plain of the
pond, the drooping snow-entangled willows held their heads together in
contented and thoughtful silence. Everything was serene.
[Illustration: HOUSE, FOOD-PILE, POND, AND DAM IN WINTER]
A clean fox track led from the woods in a straight line across the
snowy surface of the pond to the house, which stood near the centre of
this smooth white opening. The tracks encircled the house and ascended
to the top of it, where the record imprinted in the snow told that
here he watchfully rested. Descending, he had sniffed at the bushy
tips of the winter food-pile that thrust up through the ice, then
crossed the dam to plunge into the snowy tangle of willows.
Water was still pouring and gurgling down a steep beaver slide. This
was ice-and-snow-covered except at two points where the swift
splashing water dashed intermittently from a deep icy vent. While I
was examining the beauty of the upbuilding icy buttresses by one of
the vents, a water-ouzel came forth and alighted almost within reach.
I stood still. After giving a few of his nodding bows, he reëntered
the vent. Presently he emerged from the lower vent and, alighting
upon an ice-coated boulder, indifferent to the gray sky from which
scattered flakes were slowly falling and despite a temperature of five
below zero, he sang low and sweetly for several seconds.
Beaver do not surrender themselves to the confines of a house and pond
until cold solidly covers the pond with a roof of ice. The time of
this is commonly about the first of December, but the date is of
course, in a measure, dependent upon latitude, altitude, and the
peculiar weather conditions of each year. Most beaver return to the
old colony, or start a new one by the first of September. They have
had a merry rambling summer and energetically take hold to have the
house and dam ready and a harvest stored by the time winter begins.
But they are not always ready. Enemies may harass them, low water
delay them, or an unusually early winter or even a heavy snow may so
hamper them that, despite greatest effort, the ice puts a time lock
upon the pond and closes them in for the winter without sufficient
supplies.
Early one October an early snowfall worked hardship in several
colonies near my home. Fortunately the ponds were not deeply frozen,
and those colonies which had aspen groves close to the water succeeded
in felling and dragging in sufficient food-supplies for the winter. As
snow drifted into the groves, many of the trees harvested were cut
from the tops of snowdrifts, and thus left high stumps. The following
summer a number of these stood four feet above the earth and presented
a striking appearance alongside the sixteen-inch stumps of normal
height.
One of these storm-caught colonies fared badly. The inhabitants were
obliged to go a long distance from the water for trees, and their all
too scanty harvest was gathered with some loss of life. Apparently
both wolves and lions discovered the unfortunate predicament of the
harvesters, and lay in wait to catch them as they floundered slowly
through the snow. The following winter these colonists tunneled
through the bottom--perhaps the least frozen part of the dam--and came
forth for food long before the break-up of the ice. The water drained
from the pond, and after the ice had melted, the bottom of the pond
revealed a torn-up condition as though the starving winter inmates had
dug out for food every root and rootstock to be found in the bottom.
While visiting ponds at the beginning of winter, I have many times
noticed that, shortly after the pond was solidly frozen over, a hole
was made through the dam just below the water-surface of the pond.
This lowered the water-level two inches or more. Did this slight
lowering of the water have to do with the ventilation of the
ice-covered pond, or was it to put a check on deep freezing, or for
both purposes?
In the majority of cases these holes were made from ponds which,
during the winter, received but a meagre inflow of fresh water.
Naturally, ponds receiving a strong inflow of water would be better
ventilated, and would freeze less swiftly and deeply than those whose
waters became stagnant. This drawing-off of water after a few inches
of ice had formed, would, in some places, despite the settling of the
ice, form an air blanket that would delay freezing, and thus possibly
prevent the ice from forming so thickly. The air admitted by drawing
off the water would be inclosed beneath the ice, and might thus be
helpful to the beaver inclosed in house and pond. In only a few cases
were these holes made from ponds which had subway tunnels,--tunnels
which run from alongside the house through the bottom of the pond to a
point above water-level on the shore. In a few instances the beaver, I
do not know how many, came out of this hole, cut and ate a few twigs,
and then returned and closed it. Twice this was used as a way out by
beaver who emerged and went to other colonies. In one case the beaver
entered the other pond by making a hole through the dam. In the other
they entered the pond through a subway tunnel. While these holes which
lower the pond-level may have chiefly to do with ventilation, or may
be for the purpose of putting a check on freezing, my evidence is not
ample enough for final conclusions.
A sentence of close confinement for about a third of the year for an
animal that breathes air and uses pure water, is simply one of the
strange ways that work out with nature. While winter lasts, a beaver
must spend his time either in the dark, ill-ventilated house or in the
water of the pond. Apparently he does much sleeping and possibly has
a dull time of it. No news, no visitors, and apparently nothing to do!
Still a beaver has food, and when dangers surround the wild folk
outside the pond's roof of glass, he would be considered a good risk
for life insurance.
Although the pond is commonly covered with snow, or the ice curtained
with air bubbles, there have been numerous times during which I have
had clear views into the water, and could see and enjoy all that was
going on within, as completely as though looking at fish or turtles
through the glass walls of an aquarium. Often I have peered through
the ice which covered the most used place of a winter beaver
pond,--the area between the house-entrance and the food-pile. The
thinness of the ice over this place was maintained by spring-water
which came up through the bottom, and the beaver had so arranged their
affairs that they made the best use of this shallow-freezing water. Of
course most ponds are without springs.
Many a time I have seen a beaver come out of the doorway of his house
and go swimming toward the food-pile with his hands against his
breast. At the pile, if there was nothing small or short enough, he
set to work and gnawed it off. The piece secured was taken into the
doorway either in his hands or in his teeth. Afterward a beaver--the
same one, I suppose--came out of the doorway, and cast the clean bone
of the stick, from which the bark had been eaten, into the bottom of
the pond.
When there is nothing else to do, the beaver apparently comes into the
pond a few times each day for a swim. In the midst of swimming he
rises at times to the under surface of the ice and, with his nose
against it, exhales a quantity of air. After remaining with nose at
this point a few seconds, the action of the air bubbles indicates that
he is inhaling the purified air.
The rootstocks of the water-lily are sometimes dug from the bottom of
the pond. At other times the beaver eats the stalks of plants that
grow in the water, or digs out willow or other roots around the edge
of the pond. Numbers of trout frequently lie in the water close to the
doorway of a beaver house or around the food-pile. Possibly the
beaver dispense tidbits of food that are liked by the trout.
Occasionally grubs fall from the holes in wood from which beaver have
eaten the bark. While beaver are digging in the bottom of the pond
they doubtless unearth food-scraps that are welcome to trout, for
these often hover in numbers on the outskirts of the muddy water which
beaver roil while digging.
Although it appears that beaver have dull winters with but little to
do but eat, sleep, and swim, it is probable that some of their time is
spent at work. A part of their tunneling and pond-bottom canal-digging
is done in winter. I have known of their extending canals in the
bottom of the pond and making submarine tunnels while the pond was
ice-covered.
There are times when the dam has sprung a leak and must be repaired on
the inside beneath the ice. Early thaws and spring freshets sometimes
wreck a dam beyond repair, or do extensive damage to the house or dam
at the time when beaver enemies are likely to be at their leanest. The
house and dam are sometimes ruined when the streams are so low and icy
that it is not safe for beaver to go about. I know of two colonies
that were crushed out of existence by snow-slides.
The dam is on rare occasions broken by late spring ice-jams. Sometimes
the ice-cakes pile up on the dam and raise the water in the pond to
such a height that it rises in the house and drives the beaver forth.
A few beaver houses that are situated in places where the ice or
spring floods may raise the water much above normal level are shaped
to meet this trouble. The house is built higher and the room
internally is twice the usual height. Thus there is space for the
beaver to build a "platform bed" on the floor and thus raise
themselves a foot or more above the common level. Despite all pains,
floods sometimes drive beaver to the housetops.
By laying up supplies, and by the help of artificial pond, canal, and
house, the beaver is able to spend his winter without hunger and with
comfort and far greater safety than his neighbors. The winds may blow
and blinding snow or flying limbs may endanger those outside; snow may
bury the forage of bird and deer, and make the movement of beasts of
prey slow and difficult; the cold may freeze and freeze and strew the
wilds with lean and frozen forms; but the beaver beneath ice and snow
shelter serenely spends the days with comfort and safety.
The winter, with its days long or short, never comes to an end,
however, quite early enough to suit the beaver. They emerge from the
pond at the earliest moment that frozen conditions will allow. If
their subway is choked with ice, and food becomes exhausted, they will
sometimes bore holes through the base of the dam.
Apparently, too, holes of this kind are bored through, or a section
cut through the dam to the bottom, for the purpose of completely
draining the pond. As this appears to be most often done with ponds
that are full of stagnant water, or water almost stagnant, this
draining may be a part of the beaver's sanitary work,--done for the
purpose of getting filth and stale water out and also that the sour
bottom may be sterilized by sun and wind.
Conditions determine the length of time before the dam is repaired and
the pond refilled. In some cases this is done after the lapse of a few
weeks and in others not until autumn. Ponds that have large pure
streams running through them do not need this emptying, but
occasionally they accidentally have it. Most beaver colonies are
deserted in summer, and fall thus into temporary decline.
By late summer or early autumn the beaver have assembled at the place
where the winter is to be spent. There are patriarchs, youngsters, and
those in the prime of life. Around the old home are many who set forth
from it when the violets were blooming, when the grass was at its
greenest, and when mated birds were building. During the summer a few
perished, while others cast their lot with other established colonies.
A few of the younger make a start for themselves in new scenes,--found
a new colony. Again the dam is repaired and the house recovered; again
the harvest home, and again a primitive home-building family are
housed in a hut that willing hands have fashioned. Again the pond
freezes, and again the snow falls upon a home that stands in a valley
where countless generations of beaver have lived through ice-bound
winters and the ever-changing happy seasons.