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.