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The impact of an introduced population of elk upon the biota of Banff National Park Mair, William Winston

Abstract

In 1949, a study was carried out in Banff National Park to determine the relationship existing between introduced elk (Cervus canadensis nelsoni) and the other biota of the region; particular emphsis was placed upon possible competition with the indigenous moose (Alces americana americana). Subsequently, the historic relationships of the major floral and faunal species were further studied. Elk were introduced into the Park in 1917 and 1919-20. They flourished and became so numerous that in 1943 their control by non-selective mechanical removal became necessary. This control has been continued to date but the condition of the main ranges is still unsatisfactory. Most elk winter ranges are heavily over-browsed and over-grazed and summer ranges are now beginning to suffer. Unorganized predator control has possibly worsened the situation. Moose first entered the area (in recent times, at least) in 1916 and probably increased steadily to the late 1930's. They then apparently declined somewhat to reach a stable maximum by about 1943. Their reproductive rate appears to be excellent. They show no present apparent detrimental effect arising from the elk population, although the latter exerts a steady pressure by encroachment upon the drier portions of the moose range, and by almost complete removal of aspen, willow and dwarf birch reproduction in the Bow Valley and some adjacent areas. They will probably eventually affect the beaver-moose complex to the final detriment of these species. Mule deer (Odocolleua hemnionus heminonus) are indigenous to the Park, summering throughout the area but wintering, in the main, outside its confines. Destructive use, by elk, of much of the main Park winter range, below the 7 mile Beaver Dam in the Bow Valley, has depressed the resident deer population to a near static low. Herd Increment appears to be low compared to other mountain regions such as in Utah. Bighorn sheep (Ovis canadensis canadensis) have been in the Park area since earliest record, but have been dependent, for much of their range upon openings created by fires. Thus, Park policy of fire control has brought about containment of suitable bighorn sheep areas; these areas have, more recently, been invaded by elk. Bighorn have been numerous, and reached a possible maximum in the early 1930's. They then rapidly declined, possibly due to some epizootic. Recovery, if any, has been slow, probably due to the encroachment of the elk in recent years. Thus the sheep, suffering from debilitating parasitism and range impoverishment, are failing in the competition against the more aggressive and versatile elk, that apparently suffers less from parasitism and other biological limiting factors. It is suggested that few of the components of the Park biota will eventually escape the influence of the elk. Man, as a member of the biotic community, by his actions and his very presence, influences that community often beyond the confines of his present perception.

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