unite to build a single large house,
but always in such cases each family has its separate apartment. When
a house is dug open it is evident from the different impressions that
each member of the family has his own bed, which he always occupies.
Beavers are exemplary in their neatness; the house after five months'
use is as neat as when first made.

All their building is primarily a matter of instinct, for a tame
beaver builds miniature dams and houses on the floor of his cage.
Still it is not an uncontrollable instinct like that of most birds;
nor blind, like that of rats and squirrels at times. I have found
beaver houses on lake shores where no dam was built, simply because
the water was deep enough, and none was needed. In vacation time the
young beavers build for fun, just as boys build a dam wherever they
can find running water. I am persuaded also (and this may explain some
of the dams that seem stupidly placed) that at times the old beavers
set the young to work in summer, in order that they may know how to
build when it becomes necessary. This is a hard theory to prove, for
the beavers work by night, preferably on dark, rainy nights, when they
are safest on land to gather materials. But while building is
instinctive, skilful building is the result of practice and
experience. And some of the beaver dams show wonderful skill.

[Illustration]

There is one beaver that never builds, that never troubles himself
about house, or dam, or winter's store. I am not sure whether we ought
to call him the genius or the lazy man of the family. The bank beaver
is a solitary old bachelor living in a den, like a mink, in the bank
of a stream. He does not build a house, because a den under a cedar's
roots is as safe and warm. He never builds a dam, because there are
deep places in the river where the current is too swift to freeze. He
finds tender twigs much juicier, even in winter, than stale bark
stored under water. As for his telltale tracks in the snow, his wits
must guard him against enemies; and there is the open stretch of river
to flee to.

There are two theories among Indians and trappers to account for the
bank beaver's eccentricities. The first is that he has failed to find
a mate and leaves the colony, or is driven out, to lead a lonely
bachelor life. His conduct during the mating season certainly favors
this theory, for never was anybody more diligent in his search for a
wife than he. Up and down the streams and