Bighorn Sheep Populations of the Desert Game Range

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Abstract
The population of desert bighorn sheep (Ovis canadensis nelsoni) on the Desert Game Range in Nevada has varied from about 1000 to 3000 anim animals since the early 1930''s and now is estimated at 1200. Studies indicate that about 1000 of these live on the Sheep Range Management Unit. Lamb to ewe ratios are approximately 70:100 from birth to 1 mo. of age and 35:100 from 1-6 mo. of age. The yearling to ewe ratio is about 15:100. Mortality of the bighorn sheep is relatively low after 2 years of age but reaches a peak at about 10-11 years. The oldest animals found were 16 or 17 years of age. Regulated hunters killed 139 rams between 1954 and 1963. Each year the killed rams were progressively younger, averaging 8.9 years to a low of 6.6 years in 1963. During this same period the population sex ratio changed. The ratio of adult rams to ewes varied from 100:100 in the pristine population before hunting to approximately 23:100 in 1962, 1963, and 1964. The loss of the younger animals to hungers and the nature of the population structure suggest that the total population can be reduced by the continued removal of young rams by hunters. Total numbers have actually decreased from about 3000 in the early 1950''s to about 1200 in the early 1960''s. On the Sheep Range Management Unit this reduction appears to consist of a loss of rams without a reciprocal gain in ewes. Also, the removal of young rams by hunters reduces the number of rams that will reach an age when their horns are sought as trophies.

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