SPATIAL ECOLOGY OF THE EASTERN COACHWHIP (Masticophis flagellum flagellum) IN AN EASTERN TEXAS UPLAND COMMUNITY By Richard W. Johnson, Bachelor of Science in Biology Presented to the Faculty of the Graduate School of Stephen F. Austin State University In Partial Fulfillment Of the Requirements For the Degree of Master of Science STEPHEN F. AUSTIN STATE UNIVERSITY May 2001 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SPATIAL ECOLOGY OF THE EASTERN COACHWHIP (Masticophis flagellum flagellum) IN EASTERN TEXAS By Richard W. Johnson, Bachelor of Science in Biology , Thesis Director Dr. Michael B. Keck, Committee Member &, ______________ Dr. Dennis A. Gravatt, Committee Member Dr. David L. Jeffrey Associate Vice President for Graduate Studies and Research Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Ten Masticophis flagellum were caught, radiotransmitters were implanted and radio-tracked between 11 April and 19 October 2000 for the purpose of determining spatial activity and habitat use. Snakes moved between successive locations 78% of the time and averaged moves of 93 m per day. Coachwhips utilized macrohabitats disproportionately to their availability. Of three available macrohabitats, coachwhips utilized open oak savannas and avoided pine monocultures and forested seeps. These snakes utilized microhabitats that offered the greatest concealment and protection from possible predators, which supports empirical evidence about the wariness of this species. Familiarity with their environment was demonstrated wherein individuals returned to previously used burrows in their large home ranges. Home range size was the largest reported for a snake species and was not correlated with mass or snout vent length. After an average of 25 locations and 68 days, home range size was 93% of maximum. i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENTS I would like to thank my thesis director, Dr. Robert R. Fleet, and Dr. Michael B. Keck for initially sparking the interest of wondering what a snake does. I thank Dr. Fleet for his guidance, patience and help in the field. I thank Dr. Keck for help in surgery, statistical support and revisions of the manuscript. Without Philip Blackburn, this project would not have been possible, for he designed and built the radio transmitters. I would also like to thank Dr. D. Craig Rudolph of the U. S. Forest Service Southern Experimental Station for providing the traps used to capture snakes in this study. I also greatly appreciate Jason C. Helvey, who unknowingly committed so much time to this project as well as helping me keep my sanity during 112° F days. Lastly, but most importantly, I owe special thanks to my parents, sister and other family who supported and encouraged me to return to school and further my education. ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS Page ABSTRACT......................................................................................................................i ACKNOWLEDGMENTS.......................................................... ii TABLE OF CONTENTS............................................................................................... iii LIST OF TABLES........................................................................................................... v LIST OF FIGURES......................................................................................................vii INTRODUCTION............................................................................................................ 1 OBJECTIVES................................................................................................................. 4 LITERATURE REVIEW.................................................................................................5 Studies of the genus Masticophis................................................................... 5 Spatial Ecology of Other Snake Species.......................................................10 JUSTIFICATION...........................................................................................................16 METHODS....................................................................................................................17 Study Area........................................................................................................ 17 Radiotelemetry................................................................................................. 18 Transmitters.......................................................................................... 18 Snakes.................................................................................................. 19 Relocation Methods ............................................................................ 20 Data Collection.................................................................................................22 iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Snake Locations 22 Random Locations................................................................................24 Analytical Methods............................................................................................25 Habitat Use............................................................................................. 25 Movement ...............................................................................................26 Home Range.......................................................................................... 27 RESULTS.......................................................................................................................29 Habitat Use.........................................................................................................30 Movement ...........................................................................................................35 Home Range...................................................................................................... 36 DISCUSSION.................................................................................................................42 LITERATURE CITED....................................................................................................48 VITA.................................................................................................................................54 IV Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES Page Table 1: Sex, size, weight, transmitter weight, and % of body mass represented by transmitters of coachwhips in our study .........................................19 Table 2: Information regarding date of capture, surgery, release and fate of individual snakes. Date in parenthesis indicates last data point................. 20 Table 3: Data recorded in a 1 m radius at both snake and random locations. Random locations excluded Date, GPS file name, location, return to a previous location and time of day. Asterisk (*) denotes those variables not recorded at random points .......................................... 23 Table 4: Sex, snout-vent length (SVL) and mass data for radio tracked individuals. Two individuals were depredated before mass could be re-measured (151 and 582) and one individual (502) was not recaptured.............................................................................................30 Table 5: Mean values for microhabitat variables and their significance level. A significant difference was defined as P<0.05 and designated by an asterisk (*)........................................................................................................... 34 Table 6: Activity percentages for individual snakes and population Means.............................................................................................................................35 Table 7: Rate and frequency of movements of individual coachwhips from 7 July to 10 September. Overall movement rate (OMR) is calculated as the sum of the distances moved divided by the total number of days. Actual movement rate (AMR) was calculated as the sum of the distances moved divided by the number of days movement occurred. OMR and AMR were re-calculated using the meander ratio (mr) described by Secor (1995) to offer comparability. Frequency of movement, minimum and maximum movements are listed................................................................................................... 36 Table 8: Home range (ha) for all individuals. Individual is the snake and the utilization distribution is the percentage of locations in the home range. MCP is the minimum convex polygon method, HM is the harmonic mean method and the ADK is the adaptive kernel method for calculating home range. A grid cell size of 50 was used for the HM and ADK method ...............................................................37 V Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 9: Percent of home range greater than 80% of maximum and the number of locations to reach this point ...................................................... 39 Table 8: Comparison of movement rates by Masticophis in the Mojave Desert (Secor 1995) and Texas. The Texas population