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Distribution of Cane Toads (Rhinella Marina) in Florida and Their Status in Natural Areas

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Distribution of Cane Toads (Rhinella Marina) in Florida and Their Status in Natural Areas DISTRIBUTION OF CANE TOADS (RHINELLA MARINA) IN FLORIDA AND THEIR STATUS IN NATURAL AREAS By AUDREY C. WILSON A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2016 © 2016 Audrey C. Wilson To my family ACKNOWLEDGMENTS I would like to thank my advisor, Steve A. Johnson, for his guidance throughout this project and for providing financial support. I am grateful to my committee members, Christina Romagosa and Betsie Rothermel, for their constant support. Jamie Barichivich provided invaluable advice during the planning and analysis of my thesis. The USGS loaned me the equipment necessary for the fieldwork, without which this project would not have been possible. Camila Rodriguez frequently assisted me in the field. James Colee from IFAS statistical consulting helped with analysis. I am also grateful to the faculty, students, and staff of the Department of Wildlife Ecology and Conservation for their patience and support. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 7 LIST OF FIGURES .......................................................................................................... 8 LIST OF ABBREVIATIONS ............................................................................................. 9 ABSTRACT ................................................................................................................... 10 CHAPTER 1 BACKGROUND ON CANE TOADS IN FLORIDA .................................................. 12 Invasive Species ..................................................................................................... 12 Florida’s Nonnative Herpetofauna .......................................................................... 13 Cane Toad Natural History ..................................................................................... 13 Global Invasions ..................................................................................................... 15 Ecology in Florida ................................................................................................... 17 Research Design and Thesis Structure .................................................................. 18 2 PRESENCE OF CANE TOADS ALONG A DISTURBANCE GRADIENT IN FLORIDA ................................................................................................................ 19 Introduction ............................................................................................................. 19 Materials and Methods............................................................................................ 24 Study Sites ....................................................................................................... 24 Autonomous Recording Units ........................................................................... 24 Disturbance Levels ........................................................................................... 25 Song Scope ...................................................................................................... 26 Occupancy Modeling ........................................................................................ 27 Results .................................................................................................................... 28 Occupancy Modeling ........................................................................................ 29 Recognizer Performance .................................................................................. 29 Discussion .............................................................................................................. 30 3 CURRENT DISTRIBUTION OF CANE TOADS IN FLORIDA ................................. 46 Introduction ............................................................................................................. 46 Methods .................................................................................................................. 48 Results .................................................................................................................... 49 Discussion .............................................................................................................. 50 4 FUTURE DIRECTIONS .......................................................................................... 60 5 APPENDIX A SUPPLEMENTAL GRAPH ..................................................................................... 64 B RECORDS .............................................................................................................. 65 LIST OF REFERENCES ............................................................................................... 69 BIOGRAPHICAL SKETCH ............................................................................................ 76 6 LIST OF TABLES Table page 2-1 Descriptions of each of the study areas. ............................................................. 40 2-2 Dates ARUs were deployed at each of the study areas. .................................... 41 2-3 Descriptions of each of the disturbance levels.................................................... 41 2-4 Number of ARUs deployed at each disturbance level within each site. .............. 41 2-5 Summary of ARU results. ................................................................................... 42 2-6 Model rankings for 2015, all five disturbance categories .................................... 43 2-7 Model rankings for 2016, all five disturbance categories .................................... 44 2-8 Model rankings for 2015, binary ......................................................................... 44 2-9 Model rankings for 2016, binary ......................................................................... 44 2-10 Results for top ranked models for each season with binary habitat type ............ 45 3-1 Citizen science reports by county ....................................................................... 59 B-1 Summary of all cane toad records by county and decade. ................................. 65 B-2 All citizen science reports of cane toads from Jul. 2014 through Sept. 2016 ...... 66 7 LIST OF FIGURES Figure page 2-1 Map of study areas. ............................................................................................ 38 2-2 Cane toad distribution. ........................................................................................ 39 3-1 Accurate cane toad records from all sources, regardless of establishment status. ................................................................................................................. 55 3-2 Established cane toad records only.. .................................................................. 56 3-3 Cane toad records from southwest Florida reported prior to 2010...................... 57 A-1 Weekly rainfall and deployment dates of ARUs at Archbold Biological Station during 2015......................................................................................................... 64 8 LIST OF ABBREVIATIONS ABS Archbold Biological Station AIC Akaike information criterion ARU Autonomous recording unit BCNP Big Cypress National Preserve BNP Biscayne National Park ENP Everglades National Park FFT Fast Fourier transform FLMN Florida Master Naturalists FWC Florida Fish and Wildlife Conservation Commission SE Standard error SNR Signal-to-noise ratio SPI Standardized precipitation index UF University of Florida 9 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science DISTRIBUTION OF CANE TOADS (RHINELLA MARINA) IN FLORIDA AND THEIR STATUS IN NATURAL AREAS By Audrey C. Wilson December 2016 Chair: Steve A. Johnson Major: Wildlife Ecology and Conservation Nonnative cane toads (Rhinella marina) have been established in Florida since the 1950s. Although they are prevalent in human-modified habitat in much of south and central Florida, there are few reports of cane toads in natural areas. I sampled intensively at five levels of habitat disturbance to determine cane toad presence along a disturbance gradient. I deployed autonomous recording units (ARUs) in five natural areas and surrounding disturbed habitat in 2015 and 2016. Each ARU was deployed near a potential breeding site and programmed to record for five minutes each hour from sunset to sunrise. I then scanned all files with an automated recognizer using Song Scope® software (Wildlife Acoustics). Although I regularly detected cane toads in urban areas, I detected very few at sites with the lowest disturbance levels. I conducted single- season, single-species occupancy models for the 2015 and 2016 seasons. For each season, I ran a model with all five disturbance levels and one with the disturbance levels collapsed into binary disturbed and undisturbed habitat. Occupancy for disturbed habitat was 0.2004 (SE=0.1035) and 7.05e-5 (SE=0.0024) in natural in 2015; occupancy was 0.2238 (SE=0.09862) and 0.000234 (SE=0.003952) in disturbed and natural categories, respectively, for 2016. I found no evidence that cane toads are established in natural 10 areas in Florida. I also compiled records from online databases, citizen scientists,
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