In Beaver World

There was more wasted labor, too, in the Island Colony. This was noticeable in the attempts that had been made to fell limb-entangled trees that could not fall. One five-inch aspen had three times been cut off at the bottom. The third cut was more than three feet from the ground, and was made by a beaver working from the top of a fallen log. Still this high-cut aspen refused to come down and there it hung like a collapsed balloon entangled in tree-tops.

Prowling hunters have compelled most beaver to work at night, but the Spruce Tree Colony was an isolated one, and occasionally its members worked and even played in the sunshine. Each day I secluded myself, kept still, and waited; and on a few occasions watched them as they worked in the light.

One windy day, just as I was unroping myself from the shaking limb of a spruce, I saw four beaver plodding along in single file beneath. They had come out of a hole between the roots of the spruce. At an aspen growth about fifty feet distant they separated. Though they had been closely assembled, each appeared utterly oblivious of the presence of the others. One squatted on the ground by an aspen, took a bite of bark out of it, and ate leisurely. By and by he rose, clasped the aspen with fore paws, and began to bite chips from it systematically. He was deliberately cutting it down. The most aged beaver waddled near an aspen, gazed into its top for a few seconds, then moved away about ten feet and started to fell a five-inch aspen. The one rejected was entangled at the top. Presently the third beaver selected a tree, and after some trouble in getting comfortably seated, or squatted, also began cutting. The fourth beaver disappeared and I did not see him again. While I was looking for this one the huge, aged beaver whose venerable appearance had impressed me the first evening appeared on the scene. He came out of a hole beneath some spruces about a hundred feet distant. He looked neither to right nor to left, nor up nor down, as he ambled toward the aspen growth. When about halfway there he wheeled suddenly and took an uneasy survey of the open he had traversed, as though he had heard an enemy behind. Then with apparently stolid indifference he went on leisurely, and for a time paused among the cutters, which did nothing to indicate that they realized his presence. He ate some bark from a green limb on the ground, moved on, and went into the hole beneath me. He appeared so large that I afterward measured the distance between the two aspens where he paused. He was not less than three and a half feet long and probably weighed fifty pounds. He had all his toes; there was no white spot on his body; in fact, there was neither mark nor blemish by which I could positively identify him. Yet I feel that in my month around the colony I beheld the patriarch of the first evening in several scenes of action.

Sixty-seven minutes after the second beaver began cutting he made a brief pause; then he suddenly thudded the ground with his tail, hurriedly took out a few more chips, and ran away, with the other two beaver a little in advance, just as his four-inch aspen settled over and fell. All paused for a time close to the hole beneath me, and then the old beaver returned to his work. The one that had felled his tree followed closely and at once began on another aspen. The other beaver, with his aspen half cut off, went into the hole and did not again come out. By and by an old and a young beaver came out of the hole. The young one at once began cutting limbs off the recently felled aspen, while the other began work on the half-cut tree; but he ignored the work already done, and finally severed the trunk about four inches above the cut made by the other. Suddenly the old beaver whacked the ground and ran, but at thirty feet distant he paused and nervously thumped the ground with his tail, as his aspen slowly settled and fell. Then he went into the hole beneath me.

This year’s harvest was so much larger than usual that it may be the population of this colony had been increased by the arrival of emigrants from a persecuted colony down in the valley. The total harvest numbered four hundred and forty-three trees. These made a harvest pile four feet high and ninety feet in circumference. A thick covering of willows was placed on top of the harvest pile,—I cannot tell for what reason unless it was to sink all the aspens below reach of the ice. This bulk of stores together with numerous roots of willow and water plants, which are eaten in the water from the bottom of the pond, would support a numerous beaver population through the days of ice and snow.

When I took my last tour through the colony everything was ready for the long and cold winter. Dams were in repair and ponds were brimming over with water, the fresh coats of mud on the houses were freezing to defy enemies, and a bountiful harvest was home. Harvest-gathering is full of hope and romance. What a joy it must be to every man or animal who has a hand in it! What a satisfaction, too, for all dependent upon a harvest, to know that there is abundance stored for all the frosty days!

The people of this wild, strange, picturesque colony had planned and prepared well. I wished them a winter unvisited by cruel fate or foe, and trusted that when June came again the fat and furry young beavers would play with the aged one amid the tiger lilies in the shadows of the big spruce trees.

Transportation Facilities

Two successive dry years had greatly reduced the water-level of Lily Lake, and the consequent shallowness of the water made a serious situation for its beaver inhabitants. This lake covered about ten acres, and was four feet deep in the deepest part, while over nine tenths of the area the water was two feet or less in depth. It was supplied by springs. Early in the autumn of 1911 the water completely disappeared from about one half of the area, and most of the remainder became so shallow that beaver could no longer swim beneath the surface. This condition exposed them to the attack of enemies and made the transportation of supplies to the house slow and difficult.

In the lake the beaver had dug an extensive system of deep canals,—the work of years. By means of these deep canals the beaver were able to use the place until the last, for these were full of water even after the lake-bed was completely exposed. One day in October while passing the lake, I noticed a coyote on the farther shore stop suddenly, prick up his ears, and give alert attention to an agitated forward movement in the shallow water of a canal. Then he plunged into the water and endeavored to seize a beaver that was struggling forward through water that was too shallow for his heavy body. Although this beaver made his escape, other members of the colony may not have been so fortunate.

The drouth continued and by mid-October the lake went entirely dry except in the canals. Off in one corner stood the beaver house, a tiny rounded and solitary hill in the miniature black plain of lake-bed. With one exception the beaver abandoned the site and moved on to other scenes, I know not where. One old beaver remained. Whether he did this through the fear of not being equal to the overland journey across the dry rocky ridge and down into Wind River, or whether from deep love of the old home associations, no one can say. But he remained and endeavored to make provision for the oncoming winter. Close to the house he dug or enlarged a well that was about six feet in diameter and four feet in depth. Seepage filled this hole, and into it he piled a number of green aspen chunks and cuttings, a meagre food-supply for the long, cold winter that followed. Extreme cold began in early November, and not until April was there a thaw.

Before the lake-bed was snow-covered, all the numerous canals and basins which the beaver had excavated could be plainly seen and examined. The magnitude of the work which the beaver had performed in making these is beyond comprehension. I took a series of photographs of these excavations and made numerous measurements. To the north of the house a pool had been dug that was three feet deep, thirty feet long, and about twenty wide. There extended from this a canal that was one hundred and fifty feet long. The food basin was thirty feet wide and four feet deep. This had a canal connection with the house. In the bottom of the basin was one of the feeble springs which supply the lake. Another canal, which extended three hundred and fifty feet in a northerly direction from the house, was from three to four feet wide and three feet deep. The largest ditch or canal was seven hundred and fifty feet long and three feet deep throughout. This extended eastward, then northeasterly, and for one hundred feet was five feet wide. In the remaining six hundred and fifty feet it was three to four feet wide. There were a number of minor ditches and canals connecting the larger ones, and altogether the extent of all made an impressive show in the empty lake-basin.

Meantime the old beaver had a hard winter. The cold weather persisted, and finally the well in which he had deposited winter food froze to the bottom. Even the entrance-holes into the house were frozen shut. This sealed him in. The old fellow, whose teeth were worn and whose claws were bad, apparently tried in vain to break out. On returning from three months’ absence, two friends and I investigated the old beaver’s condition. We broke through the frozen walls of the house and crawled in. The old fellow was still alive, though greatly emaciated. For some time—I know not how long—he had subsisted on the wood and the bark of some green sticks which had been built into an addition of the house during the autumn. We cut several green aspens into short lengths and threw them into the house. The broken hole was then closed. The old fellow accepted these cheerfully. For six weeks aspens were occasionally thrown to him, and at the end of this time the spring warmth had melted the deep snow. The water rose and filled the pond and unsealed the entrance to the house, and again the old fellow emerged into the water. The following summer he was joined, or rejoined, by a number of other beaver.

In many localities the canals or ditches dug and used by the beaver form their most necessary and extensive works. These canals require enormous labor and much skill. In point of interest they even excel the house and the dam. It is remarkable that of the thousands of stories concerning the beaver only a few have mentioned the beaver canals. These are labor-saving improvements, and not only enable the beaver to live easily and safely in places where he otherwise could not live at all, but apparently they allow him to live happily. The excavations made in taking material for house or dam commonly are turned to useful purpose. The beaver not only builds his mound-like house, but uses the basin thus formed in excavating earthy material for the house for a winter food depository. Ofttimes, too, in building the dam he does it by piling up the material dug from a ditch which runs parallel and close to the dam, and which is useful to him as a deep waterway after the dam is completed.

In transporting trees for food-supply, water transportation is so much easier and safer than land, that wherever the immediate surroundings of the pond are comparatively level the beaver endeavors to lead water out to tree groves by digging a canal from the edge of the pond to these groves. The felled trees are by this means easily floated into the pond. One of the simplest forms of beaver canal is a narrow, outward extension of the pond. This varies in length from a few yards to one hundred feet or more.

Another and fairly common form of canal is one that is built across low narrow necks of land which thrust out into large beaver ponds, or on narrow stretches of land around which crooked streams wander.

The majority of beaver ponds are comparatively shallow over the greater portion of their area. In many cases it is not easy, or even possible, to deepen them. They may be so shallow that the pond freezes to the bottom in winter except in its small deeper portion. The shallow ponds are made more usable by a number of canals in the bottom. These canals assure deep-water stretches under all conditions. Most beaver ponds have a canal that closely parallels the dam. In some instances this is extended around the pond a few yards inside the shore-line. Two canals usually extend from the house. One of these connects with the canal by the dam, the other runs to the place on the shore (commonly at the end of a trail or slide) most visited by the beaver.

In Jefferson Valley, Montana, not far from Three Forks, I enjoyed the examination of numerous beaver workings, and made measurements of the most interesting system of beaver canals that I have ever seen. The beaver house for which these canals did service was situated on the south bank of the river, about three feet above the summer level of the water and about two hundred feet north of the hilly edge of the valley. From the river a crescent-shaped canal, about thirty-five feet in length, had been dug halfway around the base of the house. Connected with this was a basin for winter food; this was five feet deep and thirty-five feet in diameter. From this a canal extended southward two hundred and seven feet. One hundred and ten feet distant from the house was a boulder that was about ten feet in diameter. This was imbedded in about two feet of soil. Around this boulder the canal made a detour, and then resumed its comparatively straight line southward.

Over the greater portion of its length this canal was four feet wide, and at no point was it narrower than three feet. Its average depth was twenty-eight inches. For one hundred and forty-seven feet it ran through an approximately level stretch of the valley, and seepage filled it with water. A low, semi-circular dam, about fifty feet in length, crossed it at the one hundred and forty-seven-foot mark, and served to catch and run seepage water into it, and also to act as a wall across the canal to hold the water. The most southerly sixty feet of this canal on the edge of the foothills ran uphill, and was about four feet deep at the upper end, four feet higher than the end by the house. The dam across it was supplemented by a wall forty-eight feet further on. This wall was simply a short dam across the canal, in a part that was inclined, and plainly for the purpose of retaining water in the canal. The upper part of the canal was filled with water by a streamlet from off the slope. Apparently this canal was old, for there was growing on its banks near the house, a spruce tree, four inches in diameter, that had grown since the canal was made.

The wall or small dam which beaver build across canals that are inclined represents an interesting phase of beaver development. That these walls are built for the purpose of retaining water in the canal appears certain. They are most numerous in canals of steepest incline, though rarely less than twenty feet apart. I have not seen a wall in an almost dead-level canal, except it was there for the purpose of raising the height of the water. This wall or buttress is after all but a dam, and like most dams it is built for the purpose of raising and maintaining the level of water.

Extending at right angles westward from the end of the old canal was a newer one of two hundred and twenty-one feet. A wall separated and united the two. One hundred and sixty feet of this new canal ran along the contour of a hill, approximately at a dead level. Then came a wall, and from this the last sixty-one feet extended southward up a shallow ravine. In this part there were two walls. The upper end of the sixty-one-foot extension was nine feet higher than the house, and four hundred and twenty-eight feet distant from it. The two-hundred-and-twenty-one-foot extension was from twenty-six to thirty-four inches wide, and averaged twenty-two inches deep. The entire new part was supplied with spring water, which the beaver had diverted from a ravine to the west and led by a seventy-foot ditch into the upper end of their canal. Thirty feet from the end of the canal were two burrows, evidently safe places into which the beaver could retreat in case of sudden attack from wolves or other foe. There were two other of these burrows, one at the outer end of the old canal and the other alongside the boulder one hundred and ten feet from the house.

At the time I saw these canals, the only trees near were those of an aspen grove which surrounded the extreme end. It was autumn, and on both tributary slopes by the end of the canal, aspens were being cut, dragged, and rolled down these slopes into the upper end of the canal, then floated through its waters, dragged over and across the walls, and at last piled up for winter food in the basin by the house. In all probability this long, large canal had been built a few yards at a time, being extended as the trees near-by were cut down and used.

Where beaver long inhabit a locality it is not uncommon for them to have two or three distinct and well-used trails from points on the water’s edge which lead into neighboring groves or tree-clumps. These are the beaten tracks traveled by the beaver as they go forth from the water for food, and over which they drag their trees and saplings into the water. On steep slopes by the water these are called slides. This name is also given to places in the dam over which beaver frequently pass in their outgoings and incomings. Commonly these trails avoid ridges and ground swells by keeping in the bottom of a ravine; logs are cut through and rolled out of the way, or a tunnel driven beneath; obstructions are removed, or a good way made round them. Their log roads compare favorably with the log roads of woodsmen who cut with steel instead of enamel.

In most old beaver colonies, where the character of the bottom of the pond permits it, there are two or more tunnels or subways beneath the floor of the principal pond. The main tunnel begins close to the foundation of the house, and penetrates the earth a foot or more beneath the water to a point on land a few feet beyond the shore-line. If there are a number of small ponds in a colony that are separated by fingers of land, it is not uncommon for these bits of land to be penetrated by a thoroughfare tunnel. These tunnels through the separating bits of land enable the beaver to go from one pond to another without exposing themselves to dangers on land, and also offer an easy means of intercommunication between ponds when these are ice-covered. Pond subways also afford a place of refuge or a means of escape in case the house is destroyed, the dam broken, or the pond drained, or in case the pond should freeze to the bottom. Commonly these are full of water, but some are empty. On the Missouri and other rivers, where there are several feet of cut banks above the water, beaver commonly dug a steeply inclined tunnel from the river’s edge to the top of a bank a few feet back.

Most of this tunnel work is hidden and remains unknown. A striking example was in the Spruce Tree Colony, elsewhere described. These colonists, apparently disgusted by having their ponds completely filled with sediment which came down as the result of a cloudburst, abandoned the old colony-site. A new site was selected on a moraine, only a short distance from the old one. Here in the sod a basin was scooped out, and a dam made with the excavated material. The waters from a spring which burst forth in the moraine, about two hundred yards up the slope and perhaps one hundred feet above, trickled down and in due time formed a pond. The following year this pond was enlarged, and another one built upon a terrace about one hundred feet up the slope. From year to year there were enlargements of the old pond and the building of new pondlets, until there were seven on the terraces of this moraine. These, together with the connecting slides and canals, required more water than the spring supplied, especially in the autumn when the beaver were floating their winter supplies from pond to pond. Within the colony area, too, were many water-filled underground passages or subway tunnels. One of these penetrated the turf beneath the willows for more than two hundred feet.

While watching the autumnal activities of this colony, as described in another chapter, I broke through the surface and plunged my leg into an underground channel or subway that was half filled with water. Taking pains to trace this stream downward, I found that it emptied into the uppermost of the ponds along with the waters from a small spring. Then, tracing the channel upwards, I found that, about one hundred and forty feet distant from the uppermost pond, it connected with the waters of the brook on which the old colony formerly had a place. This tunnel over most of its course was about two feet beneath the surface, was fourteen inches in diameter, and ran beneath the roots of spruce trees. The water which the tunnel led from the brook plainly was being used to increase the supply needed in the canals, ponds, and pools of the Spruce Tree Colony. The intake of this was in a tiny pond which the beaver had formed by a damlet across the brook. That this increased supply of water was of great advantage to the busy and populous Spruce Tree Colony, there can be no doubt. Was this tunnel planned and made for this especial purpose, or was the increased water-supply of the colony the result of accident by the brook’s breaking into this subway tunnel?

The canals which beaver dig, the slides which they use, the trails which they clear and establish, conclusively show that these animals appreciate the importance of good waterways and good roads,—in other words, good transportation facilities.

The Primitive House

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.

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.

The Beaver’s Engineering

Realizing that the supply of aspens near the waters of the Moraine Colony close to my home was almost exhausted, I wondered whether it would be possible for the beavers to procure a sufficient supply downstream, or whether they would deem it best to abandon this old colony and migrate.

Out on the plains, where cottonwoods were scarce, the beavers first cut those close to the colony, then harvested those upstream, sometimes going a mile for them, then those downstream; but rarely were the latter brought more than a quarter of a mile. If enemies did not keep down the population of a colony so situated, it was only a question of time until the scarcity of the food-supply compelled the colonists to move either up or down stream and start anew in a place where food trees could be obtained. But not a move until necessity drove them!

Not far from my home in the mountains the inhabitants of two old beaver colonies endured hardships in order to remain in the old place. One colony, in order to reach a grove of aspens, dug a canal three hundred and thirty-four feet long, which had an average depth of fifteen inches and a width of twenty-six inches. It ended in a grove of aspens, which were in due time cut down and floated through this canal into the pond, alongside the beaver house. The other colony endured dangers and greater hardships.

During the summer of 1900 an extensive forest fire on the northerly slope of Long’s Peak wrought great hardship among beaver colonies along the streams in the fire district. This fire destroyed all the aspens and some of the willows. In order to have food while a new growth of aspens was developing, the beavers at a colony on the Bierstadt Moraine were compelled to bring their winter supply of aspens the distance of a quarter of a mile from an isolated grove that had escaped the fire. This stood on a bench of the moraine at an altitude about fifty feet greater than that of the beaver pond. Aspens from the grove were dragged about two hundred feet, then floated across a small water-hole, and from this taken up the steep slope of a ridge, then down to a point about one hundred feet from the pond. Between this place and the pond was a deep wreckage of fire-killed and fallen spruces. To cut an avenue through these was too great a task for the beavers; so with much labor they dug a canal beneath the wide heap of wreckage, and through this, beneath the gigantic fallen trees, the harvested aspens were dragged and piled in the pond for winter food. The gathering of these harvests, even by beavers, must have been almost a hopeless task. In going thus far from water many of the harvesters were exposed to their enemies, and it is probable that many beavers lost their lives.

Beavers become strongly attached to localities and especially to their homes. It is difficult to drive them away from these, but the exhaustion of the food-supply sometimes compels an entire colony to abandon the old home-site, migrate, and found a new colony. Some of the beavers’ most audacious engineering works are undertaken for the purpose of maintaining the food-supply of the colony. It occasionally happens that the food trees near the water by an old colony become scarce through excessive cutting, fires, or tree diseases. In cases of this kind the colonists must go a long distance for their supplies, or move. They prefer to stay at the old place, and will work for weeks and brave dangers to be able to do this. They will build a dam, dig a new canal, clear a difficult right-of-way to a grove of food saplings, and then drag the harvest a long distance to the water; and now and then do all these for just one more harvest, one more year in the old home.

The Moraine Colony had lost its former greatness. Instead of the several ponds and the eight houses of which it had consisted twenty years before, only one house and a single pond remained. The house was in the deep water of the pond, about twenty feet above the dam. A vigorous brook from Chasm Lake, three thousand feet above, ran through the pond and poured over the dam near the house. The colony was on a delta tongue of a moraine. Here it had been established for generations. It was embowered in a young pine forest and had ragged areas of willows around it. A fire and excessive cutting by beavers had left but few aspens near the water. These could furnish food for no more than two autumn harvests, and perhaps for only one. Other colonies had met similar conditions. How would the Moraine Colony handle theirs?

The Moraine colonists mastered the situation in their place with the most audacious piece of work I have ever known beavers to plan and accomplish. About one hundred and thirty feet south of the old pond was a grove of aspens. Between these and the pond was a small bouldery flat that had a scattering of dead and standing spruces and young lodge-pole pines. A number of fallen spruces lay broken among the partly exposed boulders of the flat. One day I was astonished to find that a dam was being built across this flat, and still more astonished to discover that this dam was being made of heavy sections of fire-killed trees. Under necessity only will beavers gnaw dead wood, and then only to a limited extent. Such had been my observations for years; but here they were cutting dead, fire-hardened logs in a wholesale manner. Why were they cutting this dead wood, and why a dam across a rocky flat,—a place across which water never flowed? A dam of dead timber across a dry flat appeared to be a marked combination of animal stupidity,—but the beavers knew what they were doing. After watching their activities and the progress of the dam daily for a month, I realized that they were doing development work, with the intention of procuring a food-supply. They completed a dam of dead timber.

At least two accidents happened to the builders of this dead-wood dam. One of these occurred when a tree which the beavers had gnawed off pinned the beaver that had cut it between its end and another tree immediately behind the animal. The other accident was caused by a tree falling in an unexpected direction. This tree was leaning against a fallen one that was held several feet above the earth by a boulder. When cut off, instead of falling directly to the earth it slid alongside the log against which it had been leaning and was shunted off to one side, falling upon and instantly killing two of the logging beavers.

The dam, when completed, was eighty-five feet long. It was about fifty feet below the main pond and sixty feet distant from the south side of it. Fifty feet of the new dam ran north and south, parallel to the old one; then, forming a right angle, it extended thirty-five feet toward the east. It averaged three feet in height, being made almost entirely of large chunks, dead-tree cuttings from six to fifteen inches in diameter and from two to twelve feet long. It appeared a crude windrow of dead-timber wreckage.