. The bison of Yellowstone National Park. American bison; Mammals. Habitat Relationships 103. Fig. 46. Bison in one of the scattered small thermal areas west of Astringent Creek in the Pelican country. they could not be located in the usual places. Winters (except 1964-65) were not severe during the study period, and mixed herd groups were not observed at Mud Volcano nor in Pocket Basin. The areas were not preferred by the herd groups, since use apparently was restricted to periods of severe conditions or late winter. Forage appeared very limited in these areas and the period of use was usuall
. The bison of Yellowstone National Park. American bison; Mammals. Habitat Relationships 103. Fig. 46. Bison in one of the scattered small thermal areas west of Astringent Creek in the Pelican country. they could not be located in the usual places. Winters (except 1964-65) were not severe during the study period, and mixed herd groups were not observed at Mud Volcano nor in Pocket Basin. The areas were not preferred by the herd groups, since use apparently was restricted to periods of severe conditions or late winter. Forage appeared very limited in these areas and the period of use was usually very brief—a few days or perhaps a week. In spite of very limited use, these areas probably represent the margin for sur- vival of the herd groups in Fire- hole, Hayden, and Pelican valleys during the most extreme winter conditions. Effects on Habitat Effects on habitat as observed throughout the study period were considered from two points of view: those which seemed to occur even under low population densi- ties of bison, and those which might have resulted from an eco- logical imbalance and overpopula- tion by bison. Bison caused or con- tributed to five kinds of impact on their habitat: debarking of trees, formation and maintenance of trails and wallows, trampling of sinter rock deposits in areas of thermal activity, and alteration of plant cover. Trees which were debarked and even girdled by the rubbing and horning of bison in summer were not scattered throughout the bison use areas, but occurred in certain localities, apparently favored by both the mixed herds and the scat- tered bulls. In extensive areas of lodgepole pine forest on the south side of Hayden Valley (Fig. 47), in groves on the lower end of the Cache-Calfee ridge, and at a few sites on the Mirror Plateau, nearly every tree had been rubbed to some degree. Elsewhere, very small groves of trees located far from the normal summer range of the mixed herds also showed hard use, apparently by one or more of the
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Keywords: ., bookauthorunitedstatesnatio, bookcentury1900, booksubjectmammals
