State of California Natural Resources Agency Department of Fish and Wildlife REPORT TO THE FISH AND GAME COMMISSION FIVE-YEAR SPECIES REVIEW OF SIERRA NEVADA BIGHORN SHEEP (Ovis canadensis sierrae) March 2021 Sierra Nevada Bighorn Sheep Ram, photo by Josh Schulgen Charlton H. Bonham, Director California Department of Fish and Wildlife TABLE OF CONTENTS I. EXECUTIVE SUMMARY .................................................................................................... 4 II. INTRODUCTION ................................................................................................................ 5 A. Five-Year Species Review ............................................................................................ 5 B. Listing and Review History ............................................................................................ 6 C. Notifications and Information Received ......................................................................... 6 III. BIOLOGY ........................................................................................................................... 6 A. Taxonomic and Physical Description ............................................................................. 6 B. Life History and Ecology ............................................................................................... 7 C. Habitat Necessary for Species Survival ........................................................................ 8 i. Vegetation Communities and Foraging Habitat .................................................... 8 ii. Geology and Soils ................................................................................................ 9 iii. Climate and Hydrology ......................................................................................... 9 iv. Reproductive Habitat ...........................................................................................10 v. Wintering Habitat/Hibernacula/Other Seasonal Habitats ......................................10 IV. DISTRIBUTION AND ABUNDANCE .................................................................................11 A. Range and Distribution .................................................................................................11 V. THREATS AND SURVIVAL FACTORS ............................................................................17 A. Factors Affecting Ability to Survive and Reproduce ......................................................17 i. Limited Distribution and Small Populations ..........................................................17 ii. Predation .............................................................................................................18 iii. Disease ...............................................................................................................20 iv. Habitat Modification or Destruction ......................................................................22 v. Climate Change...................................................................................................22 vi. Human Recreation ..............................................................................................22 vii. Overexploitation ..................................................................................................23 viii. Competition ..................................................................................................23 B. Degree and Immediacy of Threats ...............................................................................23 i. Limited Distribution and Small Populations ..........................................................23 ii. Predation .............................................................................................................24 iii. Disease ...............................................................................................................27 iv. Habitat Modification or Destruction ......................................................................28 v. Climate Change...................................................................................................28 vi. Human Recreation ..............................................................................................29 vii. Overexploitation ..................................................................................................29 viii. Competition ..................................................................................................29 2 VI. MANAGEMENT AND RECOVERY ...................................................................................29 A. Impact of Existing Management Efforts ........................................................................29 i. Translocations .....................................................................................................30 ii. Predation Management .......................................................................................31 iii. Disease Monitoring and Management .................................................................36 iv. Habitat Protection and Enhancement ..................................................................39 v. Human Recreation Research and Outreach ........................................................40 vi. Competition Mitigation .........................................................................................40 B. Recommendations for Management Activities and Other Recommendations for Recovery of the Species ..............................................................................................40 i. Monitoring and Translocations .............................................................................40 ii. Captive Breeding .................................................................................................41 iii. Predation Management .......................................................................................41 iv. Disease Monitoring and Prevention .....................................................................43 v. Habitat Protection and Enhancement ..................................................................44 vi. Human Recreation ..............................................................................................44 vii. Competition Mitigation .........................................................................................44 VII. RECOMMENDATION TO THE COMMISSION ..................................................................45 VIII. Sources ............................................................................................................................45 A. Literature Cited ............................................................................................................45 IX. LIST OF FIGURES ............................................................................................................54 X. LIST OF TABLES ..............................................................................................................54 XI. List of Appendices ...........................................................................................................54 3 I. EXECUTIVE SUMMARY Sierra Nevada bighorn sheep (Ovis canadensis sierrae; hereafter Sierra bighorn) were listed as threatened under the California Endangered Species Act in 1971 and uplisted to endangered in 1999. The subspecies has been listed as endangered under the federal Endangered Species Act since 2000. Pursuant to Fish and Game Code section 2077, subdivision (a), the California Department of Fish and Wildlife (Department) has prepared this Five-Year Species Review to evaluate whether conditions that led to the original listing of Sierra bighorn are still present. This species review is based on the best scientific information currently available to the Department regarding each of the components listed under section 2072.3 of the Fish and Game Code, and Section 670.1, subdivisions (d) and (i)(1)(A), of Title 14 of the California Code of Regulations. In addition, this document contains a review of the identification of habitat that may be essential to the continued existence of the species, and the Department’s recommendations for management activities and other recommendations for recovery of the species (Fish & G. Code, § 2077, subd. (a)). After reviewing the best available scientific information, the Department determined the following: Sierra bighorn, a distinct subspecies of bighorn sheep, occur in 14 relatively isolated subpopulations throughout the Sierra Nevada. Sierra bighorn select for visually open, snow-free habitat in proximity to steep, rugged terrain that may facilitate escape from predators. Historically, subpopulations of Sierra bighorn likely interacted as a functional metapopulation, but the distribution and connectivity of inhabited areas are much reduced from their historical extent. Population trajectories are largely driven by adult female survival, which is variable. The Sierra bighorn population has increased since its listing as a federally endangered species from 122 to 525 individuals, including 266 adult and yearling females. While the subspecies currently meets the distribution requirements for downlisting specified in the Recovery Plan for the Sierra Nevada Bighorn Sheep (U.S. Fish and Wildlife Service 2007), abundance goals have not yet been met. The primary threats impeding recovery of Sierra bighorn are small population sizes that create a fragile distribution, predation by mountain lions, and disease transmission from