State of California Natural Resources Agency Department of Fish and Wildlife REPORT TO THE FISH AND GAME COMMISSION FIVE-YEAR STATUS REVIEW OF RIPARIAN BRUSH RABBIT (Sylvilagus bachmani riparius) February 21, 2020 Riparian Brush Rabbit, Lee Eastman/USFWS Charlton H. Bonham, Director Department of Fish and Wildlife TABLE OF CONTENTS I. EXECUTIVE SUMMARY .................................................................................................... 3 II. INTRODUCTION ................................................................................................................ 4 A. Five-Year Status Review ............................................................................................... 4 B. Listing and Status Review History ................................................................................. 5 III. BIOLOGY ........................................................................................................................... 5 A. Taxonomic and Physical Description ............................................................................. 5 i. Physical Description ............................................................................................. 5 ii. Taxonomy ............................................................................................................ 6 B. Life History and Ecology ............................................................................................... 6 i. Food Habits and Foraging Behavior ..................................................................... 6 ii. Home Range and Population Densities ................................................................ 6 iii. Reproduction and Survival ................................................................................... 7 iv. Activity Patterns and Dispersal ............................................................................. 7 v. Predators, Competitors, and Disease ................................................................... 8 C. Habitat Necessary for Species Survival ........................................................................ 8 IV. DISTRIBUTION AND ABUNDANCE .................................................................................. 9 A. Range and Distribution .................................................................................................. 9 i. Historic Range and Distribution ............................................................................ 9 ii. Current Range and Distribution ............................................................................ 9 B. Population Trend and Abundance ................................................................................10 i. Historic Abundance .............................................................................................10 ii. Current Populations .............................................................................................12 V. THREATS AND SURVIVAL FACTORS ............................................................................13 A. Factors Affecting Ability to Survive and Reproduce ......................................................13 i. Present or Threatened Modification or Destruction of Habitat ..............................13 ii. Overexploitation ..................................................................................................13 iii. Predation .............................................................................................................14 iv. Competition .........................................................................................................14 v. Disease ...............................................................................................................14 vi. Small Populations ................................................................................................14 vii. Flooding ..............................................................................................................14 viii.Wildfire ...............................................................................................................15 ix. Invasive Species .................................................................................................15 x. Rodenticides .......................................................................................................15 xi. Recreation ...........................................................................................................15 i xii. Climate Change...................................................................................................15 B. Degree and Immediacy of Threats ...............................................................................16 i. Present or Threatened Modification or Destruction of Habitat ..............................16 ii. Overexploitation ..................................................................................................19 iii. Predation .............................................................................................................20 iv. Competition .........................................................................................................21 v. Disease ...............................................................................................................21 vi. Small Populations ................................................................................................22 vii. Flooding ..............................................................................................................24 viii.Wildfire ...............................................................................................................28 ix. Invasive Species .................................................................................................31 x. Rodenticides .......................................................................................................31 xi. Recreation ...........................................................................................................32 xii. Climate Change...................................................................................................32 VI. MANAGEMENT AND RECOVERY ...................................................................................33 A. Impact of Existing Management Efforts ........................................................................33 i. Captive Propagation ............................................................................................33 ii. San Joaquin River National Wildlife Refuge ........................................................34 iii. Regional Habitat Conservation Plans ..................................................................35 iv. Caswell Memorial State Park ...............................................................................36 B. Recommendations for Management Activities and Other Recommendations for Recovery of the Species ..............................................................................................36 i. Establishment of Additional Flood-secure Populations ........................................36 ii. Secure South Delta Populations ..........................................................................37 iii. Complete a Recovery Plan ..................................................................................37 iv. Basic Research on Biology and Ecology .............................................................37 v. Fuel Management on Caswell Memorial State Park ............................................38 vi. Update Closed Hunting Zone ..............................................................................38 VII. RECOMMENDATION TO THE COMMISSION ..................................................................38 VIII. SOURCES .........................................................................................................................39 A. Literature Cited ............................................................................................................39 B. Personal Communication .............................................................................................45 C. Other ............................................................................................................................46 IX. LIST OF FIGURES ............................................................................................................46 ii I. EXECUTIVE SUMMARY The riparian brush rabbit (Sylvilagus bachmani riparius) is currently listed as endangered in California. Pursuant to Fish and Game Code § 2077, subdivision (a), the California Department of Fish and Wildlife (Department) has prepared this Five-Year Status Review to evaluate whether conditions that led to the original listing of riparian brush rabbit are still present. This review is based on the best scientific information currently available to the Department regarding each of the components listed under § 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: The riparian brush rabbit