SPECIES REPORT FOR STEPHENS’ KANGAROO RAT (Dipodomys stephensi) Stephens’ kangaroo rat habitat, Naval Weapons Station Seal Beach Detachment Fallbrook, San Diego County Photo credit: Stephens’ kangaroo rat (Photo credit: Joanna Gilkeson, USFWS). U.S. Fish and Wildlife Service Carlsbad Fish and Wildlife Office, Carlsbad California Version 1.1 July 30, 2020 Stephens’ Kangaroo Rat Species Report 2020 [This page intentionally left blank] ii Stephens’ Kangaroo Rat Species Report 2020 Suggested citation: U.S. Fish and Wildlife Service. 2020. Species Report for the Stephens’ kangaroo rat (Dipodomys stephensi). Version 1.1, July 30, 2020. U.S. Fish and Wildlife Service, Pacific Southwest Region, Sacramento, California. xi + 125 pp. iii Stephens’ Kangaroo Rat Species Report 2020 TABLE OF CONTENTS Table of Contents ....................................................................................................................... iv EXECUTIVE SUMMARY .................................................................................................................. viii ABBREVIATIONS AND ACRONYMS USED .......................................................................................... x 1.0 INTRODUCTION........................................................................................................................... 1 2.0 SPECIES DESCRIPTION ................................................................................................................ 2 2.1 Taxonomy ............................................................................................................................. 2 2.2 Physical Appearance ............................................................................................................. 2 3.0 RANGE AND HABITAT USE ......................................................................................................... 3 3.1 Historical Biogeography ....................................................................................................... 3 3.2 Geographical Distribution ..................................................................................................... 4 3.2.1 Range Maps ................................................................................................................... 4 3.3.1 Physical Setting .............................................................................................................. 8 3.3.2 Ecological Setting ........................................................................................................ 10 3.3.3 Suitable Habitat ............................................................................................................ 13 4.0 LIFE HISTORY AND ECOLOGY .................................................................................................. 19 4.1 General Habits .................................................................................................................... 19 4.2 Reproduction, Growth, Longevity ...................................................................................... 21 4.3 Diet and Foraging Behavior ................................................................................................ 24 4.4 Movement and Home Range .............................................................................................. 26 4.5 Genetics............................................................................................................................... 28 4.6 Mortality/Predation ............................................................................................................. 31 4.7 Summary ............................................................................................................................. 32 5.0 SPECIES BIOLOGICAL STATUS .................................................................................................. 33 5.1 Introduction ......................................................................................................................... 33 5.2 Riverside County ................................................................................................................ 34 5.3 San Diego County ............................................................................................................... 39 5.3.1 Lake Henshaw/Warner Springs ................................................................................... 39 5.3.2 Marine Corps Base Camp Pendleton Stephens’ Kangaroo Rat Monitoring Program . 41 5.3.3 Fallbrook ...................................................................................................................... 42 5.3.4 Ramona Grasslands County Preserve .......................................................................... 44 5.3.5 Rancho Guejito Ranch ................................................................................................. 45 5.4 Summary ............................................................................................................................. 46 iv Stephens’ Kangaroo Rat Species Report 2020 6.0 STRESSORS ............................................................................................................................... 46 6.1 Habitat Loss Due To Urban and Agricultural Development .............................................. 48 6.1.1 Conserved Lands—Riverside County.......................................................................... 50 6.1.2 Conserved Lands—San Diego County ........................................................................ 51 6.1.3 Summary ...................................................................................................................... 51 6.2 Habitat Fragmentation ........................................................................................................ 51 6.2.1 Introduction .................................................................................................................. 51 6.2.2 Habitat Fragmentation Analysis .................................................................................. 53 6.2.3 Current Impact to Stephens’ kangaroo rat from Habitat Fragmentation ..................... 56 6.2.4 Summary ...................................................................................................................... 56 6.3 Habitat Modification—Conversion of Native Vegetation .................................................. 57 6.3.1 Wildfire ........................................................................................................................ 57 6.3.2 Nonnative Grasses ......................................................................................................... 57 6.3.3 Invasive Species ............................................................................................................ 57 6.4 Habitat Destruction or Modification—Other ...................................................................... 59 6.4.1 Nonnative Ungulates .................................................................................................... 59 6.4.2 Unauthorized Off-Highway Vehicles (OHVs) ............................................................ 59 6.4.3 Wildfire Suppression and Prevention Activities .......................................................... 61 6.4.4 Summary ...................................................................................................................... 62 6.5 Overutilization for Commercial, Recreational, Scientific, or Educational Purposes ......... 63 6.5.1 Summary ...................................................................................................................... 63 6.6 Disease ................................................................................................................................ 63 6.6.1 Summary ...................................................................................................................... 64 6.7 Predation ............................................................................................................................. 64 6.7.1 Summary ...................................................................................................................... 65 6.8 Use of Rodenticides ............................................................................................................ 65 6.8.1 Summary ...................................................................................................................... 67 6.9 Wildfire ............................................................................................................................... 67 6.9.1 Evaluation of Wildfire—Direct, Short-term Effects .................................................... 68 6.9.2 Evaluation of Wildfire—Indirect, Long-term Effects ................................................. 68 6.9.3 Conclusion ................................................................................................................... 69 6.10 Climate Change ................................................................................................................. 69 6.10.1 Current Trends–Temperature and Precipitation ......................................................... 71 6.10.2 Future Projections ...................................................................................................... 73 v Stephens’ Kangaroo Rat Species Report 2020 6.10.3 Summary ...................................................................................................................