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 influenced by the available supply of food to which it is accustomed or that is necessary for its requirements.