Part 8

In climbing along the bottom of a deep, narrow ravine one November day, I saw on the slope above me what appeared to be a carload or more of freshly dumped earth. My first thought was that a prospector was at work driving a tunnel; but upon examination it proved to be a recently finished but not yet occupied hibernating-den. The entrance was about three feet in diameter. Just inside the den was a trifle larger. It extended, nearly level, about twelve feet into the mountain-side. At the back it was six feet across and four feet high.

The size of the den varies and is apparently determined by the character of the soil in which it is made and also by the inclination of the bear making it. Most other dens measured were smaller than this one.

The grizzly may use the same den for several winters or have a new one each year. He may dig the den himself or take an old one that some other bear has used, or he may make use of one shaped by Nature--a cave or a rock-slide. I knew of one grizzly hibernating in a prospector's abandoned tunnel. Sometimes, like the black bear, he will dig a den on a steep mountain-side beneath the widely spreading roots of trees; sometimes beneath a large fallen log, close to the upturned roots which support it. In crossing the mountains one February I noticed a steamy vapor rising from a hole in the snow by the protruding roots of an overturned tree. I walked to the hole to investigate. The vapor was rank with the odor of a bear. Near my home on the slope of Long's Peak I have known grizzlies to den up beneath the snow-crushed, matted tree-growths at the timber-line, at an altitude of about eleven thousand feet.

Twice I have known bears to hibernate in enormous nests that were made of the long fibres of cedar bark. It must have taken days to construct one of these nests, as more than forty cedar trees had been more or less disrobed to supply material for it. It resembled the nests of trash that razor-back hogs in the South construct, though much larger. The bear, after piling it up, worked his way in near the bottom, somewhat after the fashion of a boy crawling into a haycock. Over this hibernating-nest the snow spread its blanket and probably afforded all the protection needed.

Sometimes the entrance to a den is partly closed by the occupant. Once in, he reaches out and claws the lower part full of earth, or rakes in trash and leaves. In most instances nothing is done to close the entrance. The snows drift back into the den, pile upward, and at last close the entrance most effectually.

All the dens that I recall were upon northerly or easterly--the cooler--slopes. The snow as it fell would be likely to remain and close or blanket the entrance all winter long. Snow evidently enters into the grizzly's winter plans.

Late one cold, snowless December I came upon a grizzly carrying spruce boughs into his den. Evidently he had used the den and found it cold. The den had a large opening; this he may have been intending to close. The rocky floor was already piled a foot deep with boughs. I have seen two other dens with floor-coverings; one of these was of pine twigs, and the other of coarse grass and kinnikinnick. But in most cases the bear sleeps upon the uncovered rocks or the naked earth.

Snow is a factor in determining when a bear begins his winter sleep. If he is fat and food is scarce, an early, heavy snow is pretty certain to cause him to turn in early. If no snow comes and food is still to be had, the bear is likely to delay his hibernation.

The individual inclination of the bear and his condition--whether fat or thin--are also factors which influence his time of retiring. I knew of two bears, apparently of similar condition, one of whom turned in three weeks earlier than the other. Two bears whom I noticed one winter ran about more than a month after all the other bears had disappeared. Both were thin--just why I should like to know. They also turned in shortly after they became rounded out. Generally bears of a locality turn in for winter at about the same time. Hibernating may begin early in November, but in most localities, and in most years, the time is likely to be a month later.

In Alaska and the Northwest many bears hibernate in the heights above the timber-line. I have found a number in the mountains of Colorado with winter quarters at an altitude of twelve thousand feet. In southern Colorado and in the Yellowstone Park region many have denned up at about the altitude of six thousand feet. But a grizzly may hibernate anywhere in his territory where he can find or make a den to his liking.

Except when there are cubs, a grizzly dens alone. Accounts which tell of a number of full-grown grizzlies spending the winter in one den lack verification. The cubs are born in the hibernating-den, and they den up with the mother the first, and sometimes the second, winter after their birth. The cubs generally den up together the first winter after they are weaned.

Once in for the winter, the bear is likely to stay in the den for weeks. Most of the time probably is spent sleeping, and, so far as known, without either food or water. A bear may be routed out of his winter quarters without difficulty. Generally his sleep is not heavy enough greatly to deaden his senses. Hunters, trappers, floods, and snow-slides have driven grizzlies from their dens during every stage of hibernation, and in each case a moment after the bear came forth his senses were as alert as ever; he was able either to run away or to fight in his normal manner.

Prospectors in Jefferson Valley, Montana, told me of staking claims and starting to drive a tunnel early one December. A day or two after they began blasting they saw a bear break out of a snowy den and scamper away on the mountain-side. They tracked him to the place where he had holed up again. It was their belief that the noise or the jar of their shots had awakened and re-awakened the bear, until, disgusted, he left the region for a quieter sleeping-place.

A sniffling and grunting attracted my attention one midwinter day as I was snowshoeing along the side of a ravine. Presently, a short distance ahead of me, I saw a grizzly's nose thrust out of a hole in the snowy slope. Then his head followed. Sleepily the grizzly half-opened his eyes, then closed them again. His shaking and drooping head fell lower and lower, until with a jerk he raised it only to let it droop again. He repeated this performance a number of times. Evidently it was the head of a very sleepy grizzly. Occasionally he opened his eyes for a moment, but he did not seem interested in the outside world and he finally withdrew his head and disappeared in the den.

After midwinter, and especially towards spring, a bear sometimes comes out for fresh air and exercise, or to sun himself. One gray February day, snowshoeing along the Big South Poudre, I chanced to look across an opening from the edge of the woods and saw a grizzly walking round and round in a well-beaten pathway in the snow. Occasionally he reared up, faced about, and walked round in the opposite direction. His den was near by. Half a mile farther on I came upon a bear trail near the entrance to another den. Here the bear had walked back and forth in a pathway that was about sixty feet long. It was beaten down in the snow to a depth of fifteen inches. Two places showed that the bear had rolled and wallowed about in the snow.

Elsewhere, another year, about the middle of March, I examined much-worn pathways near a grizzly's den. These had been made at least three weeks before and had been used a number of times. One pathway led to the base of a cliff that faced the east, where the bear had probably lain in the morning sun. Another led to a much-used spot that caught the afternoon sun.

Perhaps a bear sometimes becomes tired or restless during his long winter sleep. Now and then he comes forth in spring with the fur worn off his hips, back, or shoulders. He may kill time, when through sleeping, with a short excursion outside the den. If the den is large, he sometimes tramples about like a caged animal.

Climatic conditions, the altitude at which the bear hibernated, and other factors determine the time when grizzlies leave their dens. Most of them come forth during March, but stragglers may not appear until late in April. Mothers with cubs remain in the den a few weeks longer than bears without cubs.

At the limits of tree growth, one cold March day, I came upon the tracks of a grizzly bear descending the mountain. I back-tracked them and found the den in which the grizzly had spent the winter. The inside of the den was gravelly and comparatively clean. Only this single line of tracks led from the den, though the weather had been clear for a week; so I judged this was the first time the grizzly had sauntered forth. It was just sundown when I reached the den. The heights were icy, and I hesitated about continuing across the Divide that night, so concluded to occupy the den. I knew that bears often take a short ramble in the spring and then return to the den, but I took the chances of sharing it with him. I do not know what the grizzly did that night--whether or not he came back. But my fire in the mouth of the den may have kept him at bay.

The hard, cracked skin on the soles of the grizzly's feet is shed during hibernation, and the feet in spring are soft and tender. For several days he avoids traveling over rough places. His claws grow out during the winter rest, also. When he goes to sleep they are worn, broken, and blunt; but he comes out of winter quarters with claws long and moderately pointed.

What is the grizzly's condition in the spring after months of fasting? He has hibernated from three to five months, and in this time probably has taken neither water nor food. First of all he comes forth fat and not in the least hungry. The walls of his stomach have greatly contracted, almost completely closing the interior. Two stomachs which I saw taken from grizzlies killed early in the spring were as hard as chunks of rubber, and had capacity for not more than two or three spoonfuls. But when the grizzly reappears after his long winter sleep he is as strong as ever and can run for hours or fight with normal effectiveness.

He may not eat anything for a few days after leaving the den. For many days he eats lightly, and it may be two weeks before he has a normal appetite. His first food is likely to be the early, tender shoots of plants or trees, tuberous roots, swelling buds, and green grass.

I once watched a grizzly for seven days after he emerged from his hibernating-cave. His winter quarters were near timber-line on Battle Mountain, at an altitude of nearly twelve thousand feet. The winter had been of average temperature, but with scanty snow-fall. I saw him, by chance, just as he left the den, on the first day of March. He walked about aimlessly for an hour or more, then returned to his sleeping-place without eating or drinking anything.

The following day he wandered about until afternoon before he broke his fast. He ate a mouthful of willow twigs and took a taste of water. He walked leisurely down the mountain and towards sundown made himself a nest at the foot of a cliff in the woods. Here he remained, apparently sleeping, until late the next afternoon. Then, just before sundown, he walked out a short distance, smelled of a number of things, licked the snow a few times, and returned to his nest.

The fourth day he went early for water and ate more willow twigs. In the afternoon he came upon a dead bird,--apparently a junco,--which he ate. After another drink he lay down at the foot of a tree for the night. The following morning he drank freely of water, surprised and devoured a rabbit, and then lay down. He slept until noon the next day, then set out foraging; he found a dead mouse and toward evening caught another rabbit. The seventh day was much like the preceding one. During the first week out the grizzly did not eat food enough to make him one ordinary meal.

Hibernation is not well understood. The habit probably originated from the scarcity of food. However, in Mexico grizzlies sometimes hibernate even though the climate be mild and food plentiful. As these grizzlies probably came from the cold north, the habit may have been fixed in the species when it arrived. Hibernation appears to be helpful and not harmful, and it may therefore continue for ages even though not required. The rest which hibernation gives to mind and stomach, with the entire organism relaxed, may both increase efficiency and lengthen life.

The polar bear has its own peculiar hibernating-habits. The food of this bear is sea food. This is available even in the winter-time, on or beneath the ice. The male polar bears do not hibernate; the females do not except when about to give birth to young. The cubs at birth are small and helpless, and require the mother's constant care and the shelter of the den for some weeks after birth.

Mr. J. D. Figgins has written one of the best comments on hibernation that I have read. I quote as follows:--