All the long summer he belongs to the tribe of Ishmael, wandering through lakes and streams wherever fancy leads him.  It is as if he were bound to see the world after being cooped up in his narrow quarters all winter.  Even the strong family ties, one of the most characteristic and interesting things in beaver life, are for the time loosened.  Every family group when it breaks up housekeeping in the spring represents five generations.  First, there are the two old beavers, heads of the family and absolute rulers, who first engineered the big dam and houses, and have directed repairs for nobody knows how long.  Next in importance are the baby beavers, no bigger than musquashes, with fur like silk velvet, and eyes always wide open at the wonders of the first season out; then the one-and two-year-olds, frisky as boys let loose from school, always in mischief and having to be looked after, and occasionally nipped; then the three-year-olds, who presently leave the group and go their separate happy ways in search of mates.  So the long days go by in a kind of careless summer excursion; and when one sometimes finds their camping ground in his own summer roving through the wilderness, he looks upon it with curious sympathy.  Fellow campers are they, pitching their tents by sunny lakes and alder-fringed, trout-haunted brooks, always close to Nature’s heart, and loving the wild, free life much as he does himself.

But when the days grow short and chill, and the twitter of warblers gives place to the honk of passing geese, and wild ducks gather in the lakes, then the heart of the beaver goes back to his home; and presently he follows his heart.  September finds them gathered about the old dam again, the older heads filled with plans of repair and new houses and winter food and many other things.  The grown-up males have brought their mates back to the old home; the females have found their places in other family groups.  It is then that the beaver begins to be busy.

His first concern is for a stout dam across the stream that will give him a good-sized pond and plenty of deep water.  To understand this, one must remember that the beaver intends to shut himself in a kind of prison all winter.  He knows well that he is not safe on land a moment after the snow falls; that some prowling lucivee or wolverine would find his tracks and follow him, and that his escape to water would be cut off by thick ice.  So he plans a big claw-proof house with no entrance save a tunnel in the middle, which leads through the bank to the bottom of his artificial pond.  Once this is frozen over, he cannot get out till the spring sun sets him free.  But he likes a big pond, that he may exercise a bit under water when he comes down for his dinner; and a deep pond, that he may feel sure the hardest winter will never freeze down to his doorway and shut him in.  Still more important, the beaver’s food is stored on the bottom; and it would never do to trust it to shallow water, else some severe winter it would get frozen into the ice, and the beavers starve in their prison.  Ten to fifteen feet usually satisfies their instinct for safety; but to get that depth of water, especially on shallow streams, requires a huge dam and an enormous amount of work, to say nothing of planning.