When the snow-fall was unusually heavy, and lay for a long time on the ground, the buffalo was forced to fast for days together, and sometimes even weeks.  If a warm day came, and thawed the upper surface of the snow sufficiently for succeeding cold to freeze it into a crust, the outlook for the bison began to be serious.  A man can travel over a crust through which the hoofs of a ponderous bison cut like chisels and leave him floundering belly-deep.  It was at such times that the Indians hunted him on snow-shoes, and drove their spears into his vitals as he wallowed helplessly in the drifts.  Then the wolves grew fat upon the victims which they, also, slaughtered almost without effort.

Although buffaloes did not often actually perish from hunger and cold during the severest winters (save in a few very exceptional cases), they often came out in very poor condition.  The old bulls always suffered more severely than the rest, and at the end of winter were frequently in miserable plight.

Unlike most other terrestrial quadrupeds of America, so long as he could roam at will the buffalo had settled migratory habits.[39] While the elk and black-tail deer change their altitude twice a year, in conformity with the approach and disappearance of winter, the buffalo makes a radical change of latitude.  This was most noticeable in the great western pasture region, where the herds were most numerous and their movements most easily observed.

[Note 39:  On page 248 of his “North American Indians,” vol.  I, Mr. Catlin declares pointedly that “these animals are, truly speaking, gregarious, but not migratory; they graze in immense and almost incredible numbers at times, and roam about and over vast tracts of country from east to west and from west to east as often as from north to south, which has often been supposed they naturally and habitually did to accommodate themselves to the temperature of the climate in the different latitudes.”  Had Mr. Catlin resided continuously in any one locality on the great buffalo range, he would have found that the buffalo had decided migratory habits.  The abundance of proof on this point renders it unnecessary to eater fully into the details of the subject.]

At the approach of winter the whole great system of herds which ranged from the Peace River to the Indian Territory moved south a few hundred miles, and wintered under more favorable circumstances than each band would have experienced at its farthest north.  Thus it happened that nearly the whole of the great range south of the Saskatchewan was occupied by buffaloes even in winter.

The movement north began with the return of mild weather in the early spring.  Undoubtedly this northward migration was to escape the heat of their southern winter range rather than to find better pasture; for as a grazing country for cattle all the year round, Texas is hardly surpassed, except where it is overstocked.  It was with the buffaloes a matter of choice rather than necessity which sent them on their annual pilgrimage northward.