Date of Award:
Master of Science (MS)
Jessop B. Low
In May 1965, the first investigation and research in the native desert bighorn sheep in Utah was undertaken. The study was centered in the White Canyon area, San Juan County, in southeastern Utah. Seven other areas along the Colorado River were found to have smaller reminant populations of desert bighorns.
The White Canyon population was determined to be between 124 and 144 desert bighorns (Ovis canadensis nelsoni), excluding lambs.
The desert bighorns in southeastern Utah return from surrounding range lands each year to the same areas, known as lambing grounds, to give birth to their lambs. Ewes under one year of age were not known to breed. Rams over one year of age, although believed physiologically capable of breeding, were not observed doing so.
The longevity of the bighorns was estimated at approximately 13 years. A relatively static population probably exists with a 50-5- ram-ewe ratio in the White Canyon area.
Pneumonia, predators and lack of free water were believed to be responsible for the high lamb mortality found in the desert bighorn population. The lack of some nutrient in the diet is thought to be the reason for the high lamb susceptibility to pneumonia. Predators and the lack of the free water were believed to be major factors in lamb survival.
The lack of available free water was found to be the greatest limiting factor to the bighorn population. Competition for forage and water by cattle and deer was found to be a major factor limiting bighorn populations. Internal parasites were found in numbers great enough to be detrimental to the sheep.
All plant communities occupied by the sheep were found to be climax communities. On the south side of White Canyon the vegetation was in excellent condition and was in poor condition on the north side. Bighorns graze slightly more than they browse.
Recommendations for the management of the desert bighorn sheep in southeastern Utah include continued studies, water developments, hunting rams over seven years of age, predator control and livestock reductions.
Wilson, Lanny O., "Distribution and Ecology of the Desert Bighorn Sheep in Southeastern Utah" (1968). All Graduate Theses and Dissertations. 3472.
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