It was that glorious season between spring and summer, when the northern nights were brilliant with moon and stars, that Kazan and Gray Wolf set up the valley between the two ridges on a long hunt.  It was the beginning of that wanderlust which always comes to the furred and padded creatures of the wilderness immediately after the young-born of early spring have left their mothers to find their own way in the big world.  They struck west from their winter home under the windfall in the swamp.  They hunted mostly at night and behind them they left a trail marked by the partly eaten carcasses of rabbits and partridges.  It was the season of slaughter and not of hunger.  Ten miles west of the swamp they killed a fawn.  This, too, they left after a single meal.  Their appetites became satiated with warm flesh and blood.  They grew sleek and fat and each day they basked longer in the warm sunshine.  They had few rivals.  The lynxes were in the heavier timber to the south.  There were no wolves.  Fisher-cat, marten and mink were numerous along the creek, but these were neither swift-hunting nor long-fanged.  One day they came upon an old otter.  He was a giant of his kind, turning a whitish gray with the approach of summer.  Kazan, grown fat and lazy, watched him idly.  Blind Gray Wolf sniffed at the fishy smell of him in the air.  To them he was no more than a floating stick, a creature out of their element, along with the fish, and they continued on their way not knowing that this uncanny creature with the coal-like flappers was soon to become their ally in one of the strange and deadly feuds of the wilderness, which are as sanguinary to animal life as the deadliest feuds of men are to human life.

The day following their meeting with the otter Gray Wolf and Kazan continued three miles farther westward, still following the stream.  Here they encountered the interruption to their progress which turned them over the northward ridge.  The obstacle was a huge beaver dam.  The dam was two hundred yards in width and flooded a mile of swamp and timber above it.  Neither Gray Wolf nor Kazan was deeply interested in beavers.  They also moved out of their element, along with the fish and the otter and swift-winged birds.

So they turned into the north, not knowing that nature had already schemed that they four ­the dog, wolf, otter and beaver ­should soon be engaged in one of those merciless struggles of the wild which keep animal life down to the survival of the fittest, and whose tragic histories are kept secret under the stars and the moon and the winds that tell no tales.

For many years no man had come into this valley between the two ridges to molest the beaver.  If a Sarcee trapper had followed down the nameless creek and had caught the patriarch and chief of the colony, he would at once have judged him to be very old and his Indian tongue would have given him a name.  He would have called him Broken Tooth, because one of the four long teeth with which he felled trees and built dams was broken off.  Six years before Broken Tooth had led a few beavers of his own age down the stream, and they had built their first small dam and their first lodge.  The following April Broken Tooth’s mate had four little baby beavers, and each of the other mothers in the colony increased the population by two or three or four.  At the end of the fourth year this first generation of children, had they followed the usual law of nature, would have mated and left the colony to build a dam and lodges of their own.  They mated, but did not emigrate.

The next year the second generation of children, now four years old, mated but did not leave, so that in this early summer of the sixth year the colony was very much like a great city that had been long besieged by an enemy.  It numbered fifteen lodges and over a hundred beavers, not counting the fourth babies which had been born during March and April.  The dam had been lengthened until it was fully two hundred yards in length.  Water had been made to flood large areas of birch and poplar and tangled swamps of tender willow and elder.  Even with this food was growing scarce and the lodges were overcrowded.  This was because beavers are almost human in their love for home.  Broken Tooth’s lodge was fully nine feet long by seven wide inside, and there were now living in it children and grandchildren to the number of twenty-seven.  For this reason Broken Tooth was preparing to break the precedent of his tribe.  When Kazan and Gray Wolf sniffed carelessly at the strong scents of the beaver city, Broken Tooth was marshaling his family, and two of his sons and their families, for the exodus.

As yet Broken Tooth was the recognized leader in the colony.  No other beaver had grown to his size and strength.  His thick body was fully three feet long.  He weighed at least sixty pounds.  His tail was fourteen inches in length and five in width, and on a still night he could strike the water a blow that could be heard a quarter of a mile away.  His webbed hindfeet were twice as large as his mate’s and he was easily the swiftest swimmer in the colony.

Following the afternoon when Gray Wolf and Kazan struck into the north came the clear still night when Broken Tooth climbed to the top of the dam, shook himself, and looked down to see that his army was behind him.  The starlit water of the big pond rippled and flashed with the movement of many bodies.  A few of the older beavers clambered up after Broken Tooth and the old patriarch plunged down into the narrow stream on the other side of the dam.  Now the shining silken bodies of the emigrants followed him in the starlight.  In ones and twos and threes they climbed over the dam and with them went a dozen children born three months before.  Easily and swiftly they began the journey down-stream, the youngsters swimming furiously to keep up with their parents.  In all they numbered forty.  Broken Tooth swam well in the lead, with his older workers and battlers behind him.  In the rear followed mothers and children.

All of that night the journey continued.  The otter, their deadliest enemy ­deadlier even than man ­hid himself in a thick clump of willows as they passed.  Nature, which sometimes sees beyond the vision of man, had made him the enemy of these creatures that were passing his hiding-place in the night.  A fish-feeder, he was born to be a conserver as well as a destroyer of the creatures on which he fed.  Perhaps nature told him that too many beaver dams stopped the run of spawning fish and that where there were many beavers there were always few fish.  Maybe he reasoned as to why fish-hunting was poor and he went hungry.  So, unable to cope singly with whole tribes of his enemies, he worked to destroy their dams.  How this, in turn, destroyed the beavers will be seen in the feud in which nature had already schemed that he should play a part with Kazan and Gray Wolf.

A dozen times during this night Broken Tooth halted to investigate the food supplies along the banks.  But in the two or three places where he found plenty of the bark on which they lived it would have been difficult to have constructed a dam.  His wonderful engineering instincts rose even above food instincts.  And when each time he moved onward, no beaver questioned his judgment by remaining behind.  In the early dawn they crossed the burn and came to the edge of the swamp domain of Kazan and Gray Wolf.  By right of discovery and possession that swamp belonged to the dog and the wolf.  In every part of it they had left their mark of ownership.  But Broken Tooth was a creature of the water and the scent of his tribe was not keen.  He led on, traveling more slowly when they entered the timber.  Just below the windfall home of Kazan and Gray Wolf he halted, and clambering ashore balanced himself upright on his webbed hindfeet and broad four-pound tail.  Here he had found ideal conditions.  A dam could be constructed easily across the narrow stream, and the water could be made to flood a big supply of poplar, birch, willow and alder.  Also the place was sheltered by heavy timber, so that the winters would be warm.  Broken Tooth quickly gave his followers to understand that this was to be their new home.  On both sides of the stream they swarmed into the near-by timber.  The babies began at once to nibble hungrily at the tender bark of willow and alder.  The older ones, every one of them now a working engineer, investigated excitedly, breakfasting by nibbling off a mouthful of bark now and then.

That day the work of home-building began.  Broken Tooth himself selected a big birch that leaned over the stream, and began the work of cutting through the ten-inch butt with his three long teeth.  Though the old patriarch had lost one tooth, the three that remained had not deteriorated with age.  The outer edge of them was formed of the hardest enamel; the inner side was of soft ivory.  They were like the finest steel chisels, the enamel never wearing away and the softer ivory replacing itself year by year as it was consumed.  Sitting on his hindlegs, with his forepaws resting against the tree and with his heavy tail giving him a firm balance, Broken Tooth began gnawing a narrow ring entirely around the tree.  He worked tirelessly for several hours, and when at last he stopped to rest another workman took up the task.  Meanwhile a dozen beavers were hard at work cutting timber.  Long before Broken Tooth’s tree was ready to fall across the stream, a smaller poplar crashed into the water.  The cutting on the big birch was in the shape of an hour-glass.  In twenty hours it fell straight across the creek.  While the beaver prefers to do most of his work at night he is a day-laborer as well, and Broken Tooth gave his tribe but little rest during the days that followed.  With almost human intelligence the little engineers kept at their task.  Smaller trees were felled, and these were cut into four or five foot lengths.  One by one these lengths were rolled to the stream, the beavers pushing them with their heads and forepaws, and by means of brush and small limbs they were fastened securely against the birch.  When the framework was completed the wonderful cement construction was begun.  In this the beavers were the masters of men.  Dynamite was the only force that could hereafter break up what they were building now.  Under their cup-like chins the beavers brought from the banks a mixture of mud and fine twigs, carrying from half a pound to a pound at a load and began filling up the framework with it.  Their task seemed tremendous, and yet Broken Tooth’s engineers could carry a ton of this mud and twig mixture during a day and night.  In three days the water was beginning to back, until it rose about the butts of a dozen or more trees and was flooding a small area of brush.  This made work easier.  From now on materials could be cut in the water and easily floated.  While a part of the beaver colony was taking advantage of the water, others were felling trees end to end with the birch, laying the working frame of a dam a hundred feet in width.

They had nearly accomplished this work when one morning Kazan and Gray Wolf returned to the swamp.