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Document Type

Thesis - University Access Only

Award Date

2011

Degree Name

Master of Science (MS)

Department

Wildlife and Fisheries Science

First Advisor

Susan Rupp

Abstract

Bighorn sheep (Ovis canadensis) are an ecologically fragile species (Valdez and Krausman 1999). Bighorn sheep are not federally listed as threatened or endangered, but they should be considered a species of concern due to human-induced disturbance and encroachment on their habitat (Krausman 1993). Historical accounts report that sheep were once widely distributed and more numerous than their present day numbers (Buechner 1960). Historically, there have been estimates of four million mountain sheep, which includes bighorn (Ovis canadensis) and thinhorn (Ovis dalli and Ovis stonei), in North America (Seton 1929). A survey in 1991 estimated 50,000 bighorn sheep in the United States, about 15,000 in Canada, and about 3,500 in Mexico; according to a regional report conducted in 1997 there were no significant changes since the 1991 survey (Krausman 1997). They have battled against extinction, and many factors are believed to contribute to their decline. These factors include overharvesting, habitat loss, competition with domestic livestock, and disease (Buechner 1960). Conservation of the bighorn sheep is a major concern of wildlife managers throughout North America. The three species of bighorn sheep in North America are Rocky Mountain (Ovis canadensis canadensis), California (Ovis canadensis californiana), and Desert (Ovis canadensis nelsoni). Rocky Mountain bighorn sheep’s distribution closely follows the Rocky Mountains, which extends from Alberta, British Columbia, Montana, Idaho, Utah, Wyoming, Colorado, and northern New Mexico (Stelfox 1971, Clark 1978). California bighorn sheep’s distribution occurs in California, Oregon, Washington, Idaho, Nevada, and North Dakota (Demarchi and Mitchell 1973). Desert bighorn sheep’s distribution includes Mexico, Nevada, western Texas, southern New Mexico, Arizona, western Colorado, Utah, and California (Monson 1980). Bighorn sheep inhabit mountainous regions with rugged terrain. Bighorn habitats range from open grasslands to rock outcrops and cliffs, but an important feature is close proximity to escape terrain to provide protection from predators. The habitat varies daily and seasonally depending on their needs and requirements at that time. They migrate to different ranges during different seasons throughout the year, such as winter and summer (Shackleton et al. 1999). According to the 2008 Proceedings of the Biennial Symposium of the Northern Wild Sheep and Goat Council, the current status of bighorn sheep was given for several states and provinces (Table1). The current status of bighorn sheep may not reflect historical numbers, but there are herds still existing that are worth protection.

Library of Congress Subject Headings

Mountain sheep
Bighorn sheep--North America

Description

Includes bibliographical references (page 29-33)

Format

application/pdf

Number of Pages

33

Publisher

South Dakota State University

Rights

Copyright © 2011 Jacquelyn Murray. All rights reserved.

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