Not until one year of drought did I realize how dependent the beaver
is upon a constant water-supply that is both fresh and ample. A number
of beaver colonies close to my cabin were badly afflicted by this dry
period. I was already making special studies of beaver ways among the
forty-odd beaver colonies that were within a few miles of my mountain
home, and toward the close of this droughty summer I made frequent
rounds among the beaver. By the middle of September I confined these
attentions to five of the colonies that were most affected by low
water. Two were close to each other, but upon separate brooks. The
other three were upon one tumbling streamlet.
Autumn is the busiest time of the year in beaver world. Harvest is
then gathered, the dam is repaired, sometimes the pond is partly
dredged, and the house is made ready for winter,--all before the pond
freezes over. But drought had so afflicted these colonies that in
only one had any of the harvest been gathered. This one I called the
Cascade Colony. It was the uppermost of the three that were dependent
upon this one stream. Among the five colonies that I observed that
autumn, this one had the most desperate and tragic experience.
Toward the close of September the colonists in each of the five
colonies gave most of their attention to the condition of their dam.
Every leak was stopped, and its water face was given a thick covering
of mud, most of which was dredged from the bottom of the pond.
The beaver is intimately associated with water. He is not a landsman,
and only necessity will cause him to go far from the water. The water
in a main beaver pond is usually three or more feet deep, a depth
needed all the year around. Where nature has provided a place of this
kind that is close to his food-supply, the beaver uses it; he will not
trouble to build a dam and form a pond of deep water unless this is
necessary. But deep water he must have; to him it is a daily necessity
in getting a living, moving about the easiest way, and protecting his
life.
Early in October the first colony below the Cascade had to leave the
old home because of the scarcity of water. There were seven or eight
of them, and all went down-stream and joined another colony. From what
I know of the two colonies I judge that this was probably a case of
the old folks being forced to take refuge with their fortunate
children. Apparently they were welcome.
A few days later the lowest of the three colonies on the Cascade
streamlet was also abandoned. Two days before leaving home the beaver
had commenced to harvest aspen for winter food. A few aspens were
standing partly cut; a number untrimmed were lying where they fell;
several had been dragged into the pond. But suddenly the beaver
deserted the place.
The fifteen or sixteen in this colony went down-stream and took
possession of an old and abandoned house and pond. They hastily
repaired the dam and the house, and they had only just begun to gather
supplies for the winter when the pond froze over. In the bottom of
the pond, below the ice, there may have been an abundance of the
tuberous growths of the pond-lily or a supply of intruding willow
roots; both of these the beaver often dig out even while the pond is
frozen over. These beaver in this old pond may have pieced out their
scanty food-supply with these roots and endured until springtime; but
I fear that at best they had a close squeak.
One brook went dry and the beaver folk on it moved up-stream. They
left the dam well repaired, a new house, and a pile of green aspen
cuttings in the pond. They were ready for winter when the
water-failure forced them to find a new home. They scooped out a small
basin by a spring in the top of a moraine, used the material for a
dam, and into the pond thus formed dragged a few aspens and willows. A
winter den was dug in the bank.
The colonists at the other low-water place abandoned their home and
moved three miles down-stream. The tracks in the mud, a few bits of
fur, told too well a story of a tragedy during this enforced journey.
While traveling along the almost dry bed of the stream and at a point
where the water was too shallow to allow them to dive and escape, two,
and probably three, of their number were captured by coyotes. The
survivors found a deep hole in a large channel, and here they
hurriedly accumulated a scanty supply of green aspen. As winter came
on, they dug a burrow in the bank. This had a passageway which opened
into the water about two feet below the surface and close to their
food-supply.
The Cascade colonists held on for the winter. Their pond was deep, and
their careful repair of the dam had enabled them to retain water to
the very top of it. However, beaver cannot long endure water that is
stagnant. This is especially true in winter-time. A beaver house is
almost without ventilation, but its entrance ways are full of water;
the fresh water of the pond appears to absorb impurities from the air
of the house. Apparently stagnant water will not do this. Then, too, a
stagnant pond freezes much more rapidly than the waters of a pond
that are constantly stirred and aerated by the inflow of fresh water.
The Cascade colonists entered the winter with an abundant food-supply
that was stored close to the house. The pond was full of water, but it
was becoming stagnant. The drought continued and no snow fell. This
was another disadvantage to the colony. If a pond is thickly blanketed
with snow, it does not freeze so deeply nor so rapidly as when its
surface is bare. By the middle of October the pond was solidly frozen.
Drought and continued cold weather came and stayed. Christmas week not
a drop of water was flowing from the pond and apparently none was
flowing into it. The ice was clear, and, the day I called, there
appeared to be digging going on in the pond beneath the ice; close to
the dam the water was so roily that I could not see into it.
On the first of February I sounded the ice in a number of places. It
seemed to be frozen solidly to the bottom. This pond was circular in
outline, and the house stood near the centre in about three feet of
water. I climbed up on the house and stood there for some time.
Commonly in the winter an inhabited beaver house gives a scent to the
small amount of air that escapes from the top, and this tells of the
presence of the living beaver inside. But I was unable to detect the
slightest beaver scent in the air. Apparently the water in the pond
was frozen from top to bottom; probably all the beaver had perished,
unless they had managed to dig out, as they sometimes do, by tunneling
beneath the dam into the brook-channel below. Many old beaver ponds
have a subway in the mud of the bottom. One opening is close to the
entrance of the house; the other at a point on shore a few feet or
several yards beyond the edge of the pond. This offers a means of
escape from the pond in case it is frozen to the bottom or if it be
drained. A careful search failed to reveal any tunnel, new or old,
through which these beaver might have escaped.
I determined to know their fate and went to my cabin for an axe and a
shovel. A hole was cut in the ice midway between the beaver house and
the food-pile,--a pile of green aspen cuttings about twelve feet away
from the house. The pond was solidly frozen to the bottom, and the
beaver had all been caught. The entrances to their house were full of
ice. One beaver was found at the food-pile, where he apparently had
been gnawing off a bark-covered stick. One was dead between the
food-pile and the house. The others were dead by the entrance of an
incomplete tunnel beneath the dam, which they apparently had been
digging as a means of escape when death overtook them. One had died
while gnawing at the ice-filled entrance of the house. Inside of the
house were the bodies of two very old beaver and four young ones,
frozen solid.
The death of these little people, one and all, in their home under the
ice, may have come from suffocation, from cold, from starvation, or
from a combination of all these; I do not know. But my observations
made it clear that the drought was at the bottom of it all.