In most places the grizzly hibernates, or, as old hunters say, “holes up,” during the cold season, precisely as does the black bear; but, as with the latter species, those animals which live farthest south spend the whole year abroad in mild seasons. The grizzly rarely chooses that favorite den of his little black brother, a hollow tree or log, for his winter sleep, seeking or making some cavernous hole in the ground instead. The hole is sometimes in a slight hillock in a river bottom, but more often on a hill-side, and may be either shallow or deep. In the mountains it is generally a natural cave in the rock, but among the foot-hills and on the plains the bear usually has to take some hollow or opening, and then fashion it into a burrow to his liking with his big digging claws. Before the cold weather sets in, the bear begins to grow restless, and to roam about seeking for a good place in which to hole up. One will often try and abandon several caves or partially dug-out burrows in succession before finding a place to its taste. It always endeavors to choose a spot where there is little chance of discovery or molestation, taking great care to avoid leaving too evident trace of its work. Hence it is not often that the dens are found. Once in its den the bear passes the cold months in lethargic sleep; yet, in all but the coldest weather, and sometimes even then, its slumber is but light, and if disturbed it will promptly leave its den, prepared for fight or flight as the occasion may require. Many times when a hunter has stumbled on the winter resting-place of a bear and has left it, as he thought, without his presence being discovered, he has returned only to find that the crafty old fellow was aware of the danger all the time, and sneaked off as soon as the coast was clear. But in very cold weather hibernating bears can hardly be wakened from their torpid lethargy. The length of time a bear stays in its den depends of course upon the severity of the season and the latitude and altitude of the country.