Date of Award:
Master of Science (MS)
J. Juan Spillett
The ecology of bighorn sheep in Canyonlands National Park, Utah was investigated between July 1974 and December 1975. Primary objectives of this study were: (1) to determine the distribution and abundance of bighorn sheep in the Park; (2) to examine the effects of human encroachment, and (3) to determine key habitat factors in relation to bighorn sheep movements. Data were collected by ground and aerial surveys.
There were between 60 and 100 bighorn sheep in the Island in the Sky District and between 20 and 30 in the Needles District. Bighorn sheep distribution was closely related to the history of livestock grazing and landform characteristics of the canyons. Human activities have restricted bighorn ewe distribution more than ram distribution. Bighorn ewes were observed in canyons which were not used by domestic livestock or where much of the canyon was isolated from domestic livestock.
Deer and bighorn sheep demonstrated different landform preferences. Deer occupied large level areas, washes, and river bottoms. Bighorn sheep remained on the more rugged terrain, moving to level areas to feed. In canyons which were completely isolated from deer and livestock, bighorn sheep preferred t he broad level areas and washes.
Bighorn ewes did not demonstrate seasonal movements, whereas rams had definite movement patterns. In the southern portion of the Island in the Sky District , rams formed small bands and remained in a series of four canyons throughout the late winter and spring . In June, these rams dispersed individually or in pairs to higher elevations. During October they returned to the canyons below the White Rim to search for ewes. In the eastern portion of the Island in the Sky District, mature rams remained below the White Rim only during the rut, dispersing to higher elevations for the rest of the year.
Physical barriers may minimize the impact of tourism upon bighorn sheep. If bighorn sheep were above or unable to see the source of disturbance , the impact was not as great as when bighorn were able to see the source. This may explain the tendency for bighorn ewes to quickly retreat when vehicles approached them on the White Rim Road where few physical barriers are present. Human encroachment also decreases the energy intake and increases the energy output of bighorn sheep.
Bighorn sheep appear to be at equilibrium with the current range they inhabit. The National Park Service should monitor the use of the White Rim Road to evaluate effects on the bighorn sheep and restrict hiking below the White Rim to minimize stress on the bighorn sheep within this range. Studies should be initiated to investigate the bighorn sheep expansion of its range within the Park as a result of the cessation of lives tock grazing, and the role tourism plays in limiting it.
Dean, H. Clay, "Desert Bighorn Sheep in Canyonlands National Park" (1977). All Graduate Theses and Dissertations. 3279.
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