A Comparative Study of Hunted vs. Unhunted Populations of the Twin-Spotted Rattlesnake David B. Prival, Matthew J. Goode, Don E. Swann, Cecil R. Schwalbe, Michael J. Schroff, and Robert J. Steidl Wildlife and Fisheries Science, School of Renewable Natural Resources, University of Arizona, Tucson, Arizona 85721 FINAL REPORT IIPAM I97040 30 September 1999 Heritage Program Arizona Game and Fish Department 2221 West Greenway Road Phoenix, Arizona 85023 DISCLAIMER The findings, opinions, and recommendations in this report are those of the investigators who have received partial or full funding from the Arizona Game and Fish Department Heritage Fund. The findings, opinions, and recommendations do not necessarily reflect those of the Arizona Game and Fish Commission or the Department, or necessarily represent official Department policy or management practice. For further information, please contact the Arizona Game and Fish Department. TWIN-SPOTTED RATTLESNAKE STUDY PRIVAL ET AL. EXECUTIVE SUMMARY............................................................................................................1 INTRODUCTION ..........................................................................................................................2 Wildlife Trade ..................................................................................................................................2 Evolutionary History ........................................................................................................................3 Distribution Within Arizona.............................................................................................................4 Potential Threats...............................................................................................................................4 Study Objectives...............................................................................................................................5 Study Area........................................................................................................................................5 Duration of Study .............................................................................................................................6 ECOLOGY......................................................................................................................................6 METHODS.......................................................................................................................................6 Population Size and Density.........................................................................................................6 Morphology ..................................................................................................................................8 Growth ..........................................................................................................................................8 Survival.........................................................................................................................................8 Diet ...............................................................................................................................................8 Reproduction.................................................................................................................................8 Habitat...........................................................................................................................................9 Radiotelemetry and Activity Patterns ...........................................................................................9 RESULTS.......................................................................................................................................10 Population Size and Density.......................................................................................................11 Size .............................................................................................................................................11 Sex and Age................................................................................................................................12 Growth ........................................................................................................................................14 Survival Estimates ......................................................................................................................16 Diet .............................................................................................................................................16 Reproduction...............................................................................................................................19 Habitat.........................................................................................................................................21 Movements .................................................................................................................................21 Home Range Sizes......................................................................................................................24 Intensive Observation Periods ....................................................................................................24 Winter Activity ...........................................................................................................................25 DISCUSSION ................................................................................................................................25 Population Size and Density.......................................................................................................25 Size Differences Between Areas.................................................................................................26 Growth ........................................................................................................................................27 Size Relationships of Montane Rattlesnakes ..............................................................................27 Survival Estimates ......................................................................................................................28 Diet .............................................................................................................................................29 Reproduction...............................................................................................................................30 Habitat.........................................................................................................................................31 Movements .................................................................................................................................32 Winter Activity ...........................................................................................................................32 TWIN-SPOTTED RATTLESNAKE COLLECTING..............................................................33 METHODS.....................................................................................................................................33 Historical.....................................................................................................................................33 63 TWIN-SPOTTED RATTLESNAKE STUDY PRIVAL ET AL. Remote Sensing ..........................................................................................................................33 Surveillance ................................................................................................................................33 Incidental Observations ..............................................................................................................34 Habitat Destruction.....................................................................................................................34 RESULTS.......................................................................................................................................35 Historical.....................................................................................................................................35 Review of Specimens..................................................................................................................37 Interviews ...................................................................................................................................37 Current Collecting ......................................................................................................................39 Habitat Destruction.....................................................................................................................39 DISCUSSION ................................................................................................................................43 Historical.....................................................................................................................................43 Current Collecting ......................................................................................................................45 Crotalus pricei and the Pet Trade...............................................................................................45 Future of Collecting at Barfoot...................................................................................................46