The Lily Lake beaver house, in which the old beaver spent the drouthy
winter, was a large roughly rounded affair that measured twenty-two
feet in diameter. It rose only four feet above the normal water-line.
This house had been three times altered and enlarged, and once raised
in height. Its mud walls were heavily reinforced with polelike sticks,
which were placed at the junctures of the enlargements. The one large
room was more than twelve feet in diameter. Near the centre stood a
support for the upper part of the house. This support was about one
and a half by two and a half feet, and was composed for the most part
of sticks. But few houses have this support; commonly the room is
vaulted. The room itself averaged two and a half feet high. It had
four entrances.
A house commonly has two entrances, but it may have only one or as
many as five. Thus the way to the outer world from the inside of the
house is through one or more inclined passageways or tunnels. The
upper opening of these entrances is in the floor a few inches above
the water-level, and the lower opening in the bottom of the pond under
about three feet of water. These extend at an angle through the solid
foundation of the house, are about one foot in diameter and four to
fifteen feet long, and are full of water almost to floor-level. This
dark, windowless hut has no other entrance.
Most beaver houses stand in a pond, though a number are built on the
shore and partly in the water, and still others on the bank a few feet
away from the water. The external appearance and internal construction
of the houses are in a general way the same, regardless of the
situation or size. Most beaver houses appear conical. Measured on the
water-line, they are commonly found to be slightly elliptical. The
diameter on the water-line is from five to thirty-five feet, and the
height above water is from three to seven feet.
A house may be built almost entirely of sticks, or of a few sticks
with a larger proportion of mud and turf. In building, a small opening
is left,--or built around and over,--which is afterwards enlarged
into a room.
Houses that are built in a pond usually stand in three or four feet of
water. The foundation is laid on the bottom of the pond, of the size
intended for the house, and built up a solid mass to a few inches
above water-level. This island-like foundation is covered with a crude
hemisphere or dome-shaped house, the central portion of the foundation
forming the floor of the low-vaulted room which is enclosed by the
thick house-walls. In building the house the beaver provide a
temporary support for the combined roof and walls by piling in the
centre of the floor a two-foot mound of mud. Over this is placed a
somewhat flattened tepee- or cone-shaped frame of sticks and small
poles. These stand on the outer part of the foundation and lean inward
with upper ends meeting against and above the temporary support. The
beaver then cover this framework with two or three feet of mud, brush,
and turf, and thus make the walls and the roof of the house. When the
outer part of the house is completed, they dig an inclined
passageway, from the bottom of the pond up through the foundation,
into the irregular space left between the supporting pile of mud and
the walls. And of this space they shape a room, by clawing out the
temporary support and gnawing off the intruding sticks. This
represents the most highly developed type of beaver house.
In most houses the temporary support is not used, but a part of the
wall is carried up to completion, and against it are leaned sticks,
which rest upon the edge of the remaining foundation. A finished house
of this kind has a slightly elliptical outline. However, many a house
is a crude haphazard pile of material in which a room has been
burrowed.
The room is from one to three feet high, and from three to twenty feet
across. The room is a kind of a burrow and is without either door or
window. Half-buried sticks make a comparatively dry floor, despite the
fact that it is only a few inches above water-level. Beaver sleep on
the floor, usually with tail bent along the side after the fashion of
a dozing cat, in a nest of shredded wood, which they patiently make by
thinly splitting and paring pieces of wood. Just why this kind of
bedding is used cannot be said, but probably because this material
dries more quickly, is more comfortable and more sanitary, and harbors
fewer parasites. However, a few beds are made of grass, leaves, or
moss.
But little earthy matter is used in the tip-top of the house, where
the minute disjointed air-holes between the interlaced poles give the
room scanty ventilation.
Except in a few cases where house-walls are overgrown with willows or
grass, the erosive action of wind and water rapidly thins and weakens
them. Hence the house must receive frequent repairs. Each autumn it is
plastered or piled all over with sticks or mud. The mud covering
varies in thickness from two to six inches. The mud for this purpose
is usually dredged from the bottom of the pond close to the foundation
of the house. It is carried up, a double handful at a time, the beaver
waddling on his hind legs as he holds it with his fore paws against
his breast. A half-dozen or more beaver may be carrying mud up at
once. The covering not only thickens the walls and increases the
warmth of the house, but also freezes and becomes an armor of stone
that is impregnable to most beaver enemies. The "mudding" of the house
is a part of the natural and necessary preparation for winter. It may
also be a special means of protection deliberately carried out by the
beaver. The fact that an occasional thick-walled or grass-covered
beaver house was not thus plastered in autumn--perhaps because it did
not need it--has led a few people to affirm that beaver houses are not
mud-covered in the autumn. Many years of observation show that most
beaver houses do receive an autumnal plastering, and the few that do
not have this attention usually have thick, well-preserved walls and
do not need it.
One autumn in Montana, of twenty-seven beaver houses which I examined,
twenty-one received mud covering; three of the others were thickly
overgrown with willows and two were grass-grown. Only one thin-walled
house that needed reinforcement did not receive it; and this one, by
the way, was broken into by a bear before the winter had got fairly
under way.
[Illustration: AN UNPLASTERED AND A PLASTERED HOUSE]
In the autumn of 1910 I made notes concerning eighteen houses. These I
watched during October and November. Thirteen were plastered; a
willow-grown one and a weed-grown one, both of which had thick walls,
were not plastered. The remaining three were not greatly in need of
additional thickness, so received only a scanty covering of sticks.
Two of these were broken into by some animal during the winter, while
none of the others were disturbed.
Beaver frequently show good judgment in that important matter of
selecting a site for the house. Ice and sediment are two factors with
which the beaver must constantly contend. In the pond the house is
commonly placed in deep water, and apparently where the depth around
it will not be rapidly reduced by the depositing of sediment. Keeping
the house-entrance, the harvest-pile basin, and the canals from
filling with sediment is one of the difficult problems of beaver life.
To guard against the rapid encroachments of the deposits of sediment,
one group of beaver, apparently with forethought, built a dam that
formed a pond from the waters of a small spring which carried but
little or no sediment. I have noticed a number of instances in which a
pond was made on a small streamlet with greater labor than it would
have required to form a pond in a near-by brook. As there were a
number of other conditions favorable to the brook situation of the
house, the only conclusion I could reach was that these selections for
colony-sites were made with the intention of avoiding the
ever-encroaching sediment,--for in some beaver ponds this sediment is
deposited annually to the depth of several inches.
Ice is one of the troubles of beaver existence. It is of the utmost
importance to the beaver that he should have his house so situated
that the ice of winter does not close the entrance to it, and also
that the deep water in which his pile of green provisions is deposited
does not freeze solid and thus exclude him from the food-supply. The
ice fills the pond from the top and compels him to be constantly
vigilant to save himself from its encroachments. Many a beaver home
has been built alongside a spring, around which the beaver dredged a
deep hole and in this deposited the winter food-supply. The constant
flow of the spring water prevented thick ice from forming, both around
the food-pile and between it and the house-entrance.
Large numbers of beaver do not possess a house. Beaver who live
without a dam or pond commonly do not build a house, but are content
with a burrow or a number of burrows in the banks of the waters which
they inhabit. In the severe struggle to live, there is a tendency on
the part of the beaver to avoid the building of dams and houses, as
these reveal their presence and put the aggressive trapper on their
trail.
Many colonies have both houses and burrows. Apparently the houses were
used in the winter-time, the burrows in summer. One beaver burrow
which I examined was about one foot above the level of the pond and
twelve feet distant from it. The entrance tunnels were sixteen feet in
length, and began a trifle more than three feet under water near the
edge of the pond. This burrow measured five and a half feet long,
about half as wide, and seventeen inches high. It was immediately
beneath the outspreading roots of an Engelmann spruce. The majority
of beaver burrows are about two thirds the size of this one.
One November I examined more than a score of beaver colonies. There
was no snow, but recent cold had covered the pond with ice and
solidified the miry surroundings. Over the frozen surface I moved
easily about and made many measurements. One of these colonies was a
fairly typical one. The colony was on a swift-running stream that came
down from the snowy heights, three miles distant. The top of Long's
Peak and Mt. Meeker looked down upon the scene. The altitude of this
colony was about nine thousand feet. The ponds were in part surrounded
by semi-boggy willow flats, with here and there a high point or a
stretch of bank that was covered with aspens. The tops of a few huge
boulders thrust up through the water. All around stood guard a tall,
dark forest of lodge-pole pines. These swept up the mountainside,
where they were displaced by a growth of Engelmann spruce which
reached up to timber-line on the heights above.
This colony had a number of ponds, with a few short canals extending
outward from them. A conical house of mud and slender poles stood in
the larger pond. Above this pond there were half a dozen pondlets, the
uppermost of which was formed across the brook by a semi-circular dam.
Over the outward ends of this dam the water flowed and was caught in
other ponds; these in turn overflowed, the water traversing two other
ponds, one below the other, just above the main one. Below the large
pond were three smaller ones in close succession. The dam of each pond
backed the water against the dam above it.
The dam of the main pond was two hundred and thirty feet long. Each
end bent upward at a sharp angle and extended a number of yards
upstream. This dam measured five feet at its highest point, but along
the greater portion was only a trifle more than three feet high. The
central part was overgrown with sedge and willows and appeared old;
but the extreme ends appeared new, and probably had been in part
constructed within a few weeks. The whole dam was formed of earth and
slender poles. The pond formed by it was one hundred and eighty feet
wide, and had an average length up and down stream of one hundred and
ten feet. The average depth was only two feet.
Near the centre of this large pond stood the house, a trifle nearer to
the dam than to the upper edge of the pond. I measured it on the
water- or rather the ice-level. It took twenty-six feet of rope to go
around it. The top of the house rose exactly five feet above the ice.
The house was built of a mixture of sods and willow sticks. The ends
of the sticks here and there thrust out through the three-or-four-inch
covering of mud which the house had recently received. Wondering how
much of the house was in the water below the level of the ice, I
thought to measure the depth by thrusting a pole through the ice to
the bottom. Holding it in an upright position, I raised it and brought
it down with all my strength. The pole went through the ice and so did
I. The water was three feet deep. This depth covered only a small area
around the house and was maintained by frequent digging. The house is
often plastered with this dredged material. Altogether, then, the
house from its lowest foundation on the bottom of the pond to the
conical top was eight feet high. The foundation of this house was made
of turf, masses of grass roots, and a small percentage of mud thickly
reinforced with numerous willow sticks. The floor was mostly sticks.
As the entrance tunnels were filled with water to a point about three
inches below the floor-level, and as these were the only entrances or
openings into the house, friend or foe could enter only by coming up
through one or the other of these water-filled tunnels from the bottom
of the pond.
The single, circular, dome-like room of this house was four and a half
feet in diameter and about two feet in height. Its ceiling was roughly
formed by a confused interlacing of sticks, which stood at an angle.
The spaces between were filled with root-matted mud. The walls were a
trifle more than two feet thick, except around the conical top. Here
was a small space, mostly of interlacing sticks, the thickness of
which was but one foot. As very little mud had been used in this part,
there were thus left a few tiny air-holes. As I approached, there
could be seen arising from these holes the steamy and scented breath
of the beaver inhabitants within. Since the ventilation of beaver
houses is exceedingly poor, and as this animal probably does not
suffer from tuberculosis, it is possible that ventilation is assisted,
and some of the impure air absorbed by the water, which rises almost
to the floor in the large entrance-holes.
The early trappers from time to time noted extended general movements
or emigrations among beaver, which embraced an enormous area. They, as
with human emigrants, probably were seeking a safer, better home. Some
of these movements were upstream, others down; commonly away from
civilization, but occasionally toward it. For this the Missouri River
was the great highway. Limited emigrations of this kind still
occasionally occur.
The annual migration is a different affair. This has been noted for
some hundred and fifty years or more, and probably has gone on for
centuries. This peculiar migration might be called a migratory outing.
In it all members of the colony appear to have taken part, leaving
home in June, scattering as the season advanced. Rambles were made up
and down stream, other beaver settlements visited, brief stays made at
lakes, adventures had up shallow brooks, and daring journeys made on
portages. The country was explored. The dangers and restrictions
imposed during the last twenty-five years appear in some localities to
have checked this movement, and in others to have stopped it
completely. But in most colonies it still goes on, though probably not
usually enjoyed by mothers and children except to a limited extent.
By the first of September all have returned to the home, or joined
another colony or assembled at the place where a new colony is to be
founded. This annual vacation probably sustained the health of the
colonists; they got away from the parasites and the bad air of their
houses. The outing was taken for the sheer joy of it. Incidentally, it
brought beaver into new territory and acquainted them with desirable
colony-sites and the route thereto,--useful information in case the
colonists were compelled suddenly to abandon the old home.
It is natural for the beaver to be silent. In silence he becomes
intimate with the elements, and, while listening, hears and
understands all moods and movements that concern him. He is a master
in translating sound. It wakens or warns, threatens or gladdens, and
woos him back to slumberland.
On the wild frontier in his fortress island home in safety he sits and
sleeps in darkness. He cannot see outside, but the ever-changing
conditions of the surrounding outer world are revealed to him by
continuous and varying sounds that penetrate the thick windowless
walls of his house. He hears the cries of the coyote and the cougar,
the call of moose, the wild and fleeting laugh of the kingfisher, the
elemental melody of the ouzel, and many an echo faintly from afar. He
hears the soft vibrations from the muffled feet of enemies; and, above
his head, the raking threat of claws upon the top of his house.
Endlessly the water slides and gently pours over the dam, and softly
ebbs around the pond's primeval shores. The earthquake thunder warns
of storm, the floods roar; then through day and night the cleared and
calmed stream goes by. The wind booms among the baffling pines, and
the broken and leafless tree falls with a crash! There is silence!
Along the stream's open way through the woods numberless breezes
whisper and pause by the primitive house in the water.