Baseline Biodiversity Survey For The Santa Ysabel Ranch Open Space Preserve U.S. Geological Survey Prepared for: The Nature Conservancy San Diego County Department of Parks and Recreation U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY WESTERN ECOLOGICAL RESEARCH CENTER Baseline Biodiversity Survey For The Santa Ysabel Ranch Open Space Preserve By Stacie Hathaway, Robert Fisher, Carlton Rochester, Chris Haas, Mark Mendelsohn, Greta Turschak, Drew Stokes, Melanie Madden-Smith, Ed Ervin, Krista Pease, and Chris Brown U.S. GEOLOGICAL SURVEY WESTERN ECOLOGICAL RESEARCH CENTER Prepared for: The Nature Conservancy San Diego County Department of Parks and Recreation U.S. Geological Survey Western Ecological Research Center 5745 Kearny Villa Road, Suite M San Diego, CA 92123 This report should be cited as: Hathaway, S., R. Fisher, C. Rochester, C. Haas, M. Mendelsohn, G. Turschak, D. Stokes, M. Madden-Smith, E. Ervin, K. Pease, and C. Brown. 2004. Baseline biodiversity survey for the Santa Ysabel Ranch Open Space Preserve. USGS Technical Report. Prepared for The Nature Conservancy and San Diego County Department of Parks and Recreation. Sacramento, California 2004 ii U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, SECRETARY U.S. GEOLOGICAL SURVEY Charles G. Groat, Director The use of firm, trade, or brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. For additional information, contact: Center Director Western Ecological Research Center U.S. Geological Survey 3020 State University Dr., East Modoc Hall, Room 3006 Sacramento, CA 95819 iii Table of Contents Abstract................................................................................................................................1 1. Introduction.....................................................................................................................1 2. Study Area ......................................................................................................................2 3. Methods...........................................................................................................................2 3.1 Aquatics ............................................................................................................3 3.1.1 Visual Encounter Survey ...................................................................4 3.1.2 Hand Capture .....................................................................................4 3.1.3 Dip Netting.........................................................................................4 3.1.4 Aural Detection..................................................................................4 3.1.5 Focused Surveys for Arroyo Toads ....................................................5 3.2 Herpetofauna.....................................................................................................6 3.2.1 Vegetation and Site Characterization.................................................7 3.3 Ants...................................................................................................................7 3.4 Avifauna............................................................................................................7 3.4.1 Diurnal Point Count Surveys and Nocturnal Driving Surveys ..........8 3.4.2 Focused Surveys for California Spotted Owls...................................9 3.5 Bats .................................................................................................................10 3.5.1 Foraging Bat Surveys.......................................................................10 3.5.2 Roost Surveys ..................................................................................11 3.6 Small Mammals ..............................................................................................11 3.7 Medium and Large Mammals.........................................................................12 3.7.1 Scent Station Surveys ......................................................................12 3.7.2 Camera Surveys ...............................................................................13 4. Results and Discussion .................................................................................................13 4.1 Aquatics ..........................................................................................................13 4.1.1 Visual Encounter Survey .................................................................13 4.1.2 Hand Capture ...................................................................................14 4.1.3 Dip Netting.......................................................................................14 4.1.4 Aural Detection................................................................................14 4.1.5 Focused Surveys for Arroyo Toads ..................................................14 4.1.6 Survey Discussion............................................................................15 4.2 Herpetofauna...................................................................................................19 4.2.1 Vegetation and Site Characterization...............................................21 4.3 Ants.................................................................................................................22 4.4 Avifauna..........................................................................................................23 4.4.1 Diurnal Point Count Surveys and Nocturnal Driving Surveys ........23 4.4.2 Focused Surveys for California Spotted Owls.................................26 4.5 Bats .................................................................................................................26 4.5.1 Foraging Bat Surveys.......................................................................26 4.5.2 Roost Surveys ..................................................................................27 4.5.3 Survey Discussion............................................................................28 4.6 Small Mammals ..............................................................................................29 4.7 Medium and Large Mammals.........................................................................30 4.7.1 Scent Station Surveys ......................................................................31 iv 4.7.2 Camera Surveys ...............................................................................31 4.7.3 Survey Discussion............................................................................31 5. Conclusions and Management Recommendations .......................................................34 5.1 Aquatics ..........................................................................................................34 5.2 Herpetofauna...................................................................................................36 5.3 Ants.................................................................................................................37 5.4 Avifauna..........................................................................................................37 5.5 Bats .................................................................................................................38 5.6 Small Mammals ..............................................................................................41 5.7 Medium and Large Mammals.........................................................................41 5.8 Additional Management Recommendations...................................................42 5.8.1 Restoration .......................................................................................42 5.8.2 Illegal Off-Road Activity.................................................................42 5.8.3 Unauthorized Grazing......................................................................43 5.8.4 Unauthorized Trail Access and Development .................................43 5.8.5 Collection.........................................................................................43 5.8.6 Patrol by County Staff .....................................................................44 5.8.7 Education .........................................................................................44 5.8.8 Additional Surveys...........................................................................45 5.8.9 Site Access.......................................................................................45 5.8.10 Baseline Survey Materials Removal..............................................45 6. Acknowledgements.......................................................................................................45 7. References.....................................................................................................................46 Tables ................................................................................................................................55 Table 1. Occurrence of aquatic and aquatic-associated species as determined by surveys and incidental observations......................................................55 Table 2. Number of herpetofauna individuals and species captured at pitfall arrays by array............................................................................................56 Table 3. Number of herpetofauna individuals and species captured at pitfall arrays by month..........................................................................................57