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:—
“The period of hibernation in any mammal not only varies in a given species, but is largely influ enced by the available supply of food to which it is accustomed or that is necessary for its requirements.
“Examples of this character may be cited among several species of mammals. It is the custom of the chipmunks, or ‘ground squirrels,’ to hoard up at least a partial supply of food in the autumn for consumption during the winter months; but this is rarely, if ever, sufficient to keep these interesting little animals active for the entire period. In most localities, there is no available food with which to augment their scant store and they are never in evidence from late October to April. In other locations where the fruit of the Cratægus, or ‘thorn apple,’ is to be had, they may be seen almost daily, although the ground may be covered with several feet of snow and low temperatures prevail.
“Another example is the opossum. Ordinarily these animals are active throughout the entire year, but towards the northern edge of their range they frequently hibernate for considerable periods (thirty-one days from personal observations).
“Certain of the small rodents can, and probably do, hoard sufficient food for actual need during the winter months; but the problem is in direct ratio to the size of the animal. Hence we find the marmot, a much larger animal, making no provision, although his habitat is confined to the higher altitudes and his period of hibernation is extended over a greater length of time than many other species. His food consists wholly of grass and other green plants, and it is doubtful if he could subsist on dry food. Granting that he could, the amount required would be prohibitive, otherwise he would make some effort in that direction, as do the conies, a much smaller animal.
“Being omnivorous and of great size, a bear could not secure or preserve the necessary amount of food to carry him through five months. Such food could not consist of any variety other than vegetation, and he is not a ‘hay’ eater, and so, nature has provided him a means of surviving the long period of fasting and probably, without discomfort.
“It is well known that bears show a distinct preference for fruit during the late summer and autumn months. Not because that is the season for the various fruits, but through a need of their sugar content and its fattening qualities. Composed largely of juices which are quickly absorbed, the digestive process is very brief and the discarded residue is discharged at once. This may give rise to the belief that a purgative has been employed as a means of cleansing the bowels and explains the presence of unbroken berries in the excrement and the absence of offensive odors. As a means of exploding the purgative theory we need only refer to bears in captivity. Although the latter may be confined to cement floors and have no access to any matter whatever, other than the food regularly supplied, they frequently hibernate in a quite orderly manner.
“It must be conceded that bears are irregular in the period of ‘holing up’ and that they do so only when food has become too scarce to sustain activities without a drain upon the store of fat they have acquired; or during very severe weather. In the mean time there has been a gradual reduction in food as the period of hibernation approaches and a consequent lessened activity of the bowels. Nor is there reason for surprise because of the absence of excrement in the burrow and the presence of matter in the rectum when the bear emerges in the spring.
“In captivity bears may, or may not, hibernate. As a rule they ‘sleep’ for more or less varying periods during severe weather. One authority states the grizzly has been known to sleep from sixty to seventy-five days and during that time it was not difficult to awaken him. Black bears frequently pass the winter without evidence of even drowsiness. Others awake at irregular intervals, and after feeding lightly, return to their slumber.”