Smooth Green Snake (Opheodrys vernalis): A Technical Conservation Assessment Prepared for the USDA Forest Service, Rocky Mountain Region, Species Conservation Project November 27, 2006 Alan J. Redder1, Brian E. Smith, Ph.D.2, and Douglas A. Keinath1 with life cycle model by Dave McDonald3 and Takeshi Ise3 1Wyoming Natural Diversity Database, University of Wyoming, P.O. Box 3381, Laramie, WY 82071 2Black Hills State University, 1200 University Street Unit 9044 Spearfish, SD 57799-9044 3Department of Zoology and Physiology, University of Wyoming, P.O. Box 3166, Laramie, WY 82071 Peer Review Administered by Society for Conservation Biology Redder, A.J., B.E. Smith, and D.A. Keinath. (2006, November 27). Smooth Green Snake (Opheodrys vernalis): a technical conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Available: http: //www.fs.fed.us/r2/projects/scp/assessments/smoothgreensnake.pdf [date of access]. ACKNOWLEDGMENTS We wish to thank the personnel of the state Natural Heritage Programs and wildlife management agencies in Colorado, Kansas, Nebraska, South Dakota, Utah, and Wyoming and various North American natural history museums for providing current and historical distribution and natural history data for smooth green snake occurrences in USDA Forest Service Region 2. Discussions with many biologists from these and other states provided essential background for the interpretation of these data and the status of local smooth green snake populations. Geoff Hammerson provided data for Colorado and excellent smooth green snake photographs. We thank the two anonymous reviewers for their many helpful suggestions and criticisms. We are especially grateful to the USDA Forest Service technical editor, Gary Patton, and his staff for their patient guidance and assistance in the improvement of this assessment. AUTHORS’ BIOGRAPHIES Alan J. Redder is currently the Data Manager at the Wyoming Natural Diversity Database at the University of Wyoming in Laramie, WY. He received his M.A. in Zoology and Physiology in 1994 and his M.S. in Statistics in 1998, both from the University of Wyoming. His research interests include the biogeography of reptiles and amphibians in western North America, the statistical analysis and presentation of complex biological data, and the philosophy and history of evolutionary theory. Dr. Brian Smith is an associate professor in biology at Black Hills State University. His areas of research expertise include herpetology, biostatistics, and landscape ecology. He has conducted herpetological research in the Philippines, Peru, Guam, Costa Rica, Guatemala, and the Caribbean. He has also worked on the herpetofauna of Louisiana, Texas, New Mexico, and Arizona, and he spent four years working in the Department of Herpetology at the Dallas Zoo. For the last 10 years, he has been working on reptiles and amphibians in the Badlands and Black Hills of western South Dakota and in the Bear Lodge Mountains in northeastern Wyoming. Dr. Smith received his B.S. from Washington State University in 1980, his M.S. from Louisiana State University in 1983, and his Ph.D. from the University of Texas at Arlington in 1996. Doug Keinath is the Senior Zoologist for the Wyoming Natural Diversity Database, a research unit of the University of Wyoming and a member of the Natural Heritage Network. He has been researching Wyoming’s wildlife for the past nine years and has 11 years experience in conducting technical and policy analyses for resource management professionals. His broader scope of research focuses on bat and small mammal ecology, survey, and monitoring at the population and landscape scales, and more recently on the spatially explicit predictive distribution modeling of sensitive elements (i.e., animals, plants, communities) of the Rocky Mountain West. Mr. Keinath earned a B.S. in Interdisciplinary Engineering (1993; magna cum laude) and a B.S. in Natural Resource Management (1993; with Distinction) from the University of Michigan. In 2000 he earned a M.S. in Wildlife Biology from the University of Wyoming. COVER PHOTO CREDIT Smooth green snake (Opheodrys vernalis). Photograph by G.A. Hammerson. Used with permission. 2 3 SUMMARY OF KEY COMPONENTS FOR CONSERVATION OF THE SMOOTH GREEN SNAKE Although widely distributed in North America, and in numerous disjunct populations in the Great Plains and Rocky Mountain states, the status of the smooth green snake (Opheodrys vernalis) is poorly known in the Rocky Mountain Region of the USDA Forest Service. This species is known from scattered locations near streams in Nebraska and eastern South Dakota, but otherwise it may be rare in South Dakota, Nebraska, and Wyoming outside of the Black Hills and Bear Lodge Mountains. There are some indications that it is declining in numbers and geographical extent. However, the only protection provided in Region 2 is by the states of Wyoming, Colorado, and Nebraska where it is protected by state law, prohibiting commercial collection and limiting collection to individual use. The smooth green snake is threatened through the direct and indirect consequences of habitat destruction from cattle grazing, logging, dewatering of streams, road building, pesticide use, and development, particularly in meadows, riparian areas, and mountain foothills. Smooth green snakes are at risk of mass mortality at communal den sites due to destruction, freezing, or flooding of dens. As with all snake species, the smooth green snake is susceptible to direct anthropogenic mortality from roads and human encounters. Populations could also decline because of reductions in invertebrate prey due to drought and other climatic extremes, or management actions such as the application of pesticides. The loss of habitat and dispersal corridors, and the resulting isolation of populations, put this species at risk of reduced genetic variability, loss of recolonization or rescue potential through connection with other populations, and eventually local extinction. This snake’s small body size, moderate reproductive output, high hatchling and juvenile mortality, and low probability of dispersal out of occupied habitats exacerbate its sensitivity to environmental variability. The smooth green snake is generally found in grassy habitats and foothills habitats. In some locations in the Black Hills and Bear Lodge Mountain it can be abundant in moist grass and understory habitats and along forest/ meadow ecotones. The protection and preservation of currently occupied riparian and wet meadow habitats and their associated habitat mosaics in the Great Plains of eastern South Dakota and Nebraska, the Black Hills, Bear Lodge Mountains, and southern and central Rocky Mountains are essential to provide for the long-term survival of smooth green snakes in the West. Xerification of meadow habitats in all parts of the range due to climate change and/or exhaustion of surface water and groundwater supplies for irrigation and urban use are threats that will only increase in the future. Studies of the effects of anthropogenic threats (e.g., pesticide use, roads, impoundments, heavy equipment use, water pollution, cattle grazing) on smooth green snakes and approaches for ameliorating those effects are needed. The lack of data about most aspects of the biology of smooth green snakes (e.g., local taxonomic and population status, abundance, population trends, genetics of isolated populations, detailed life history data, response to threats) is a serious impediment when considering detailed management options for this species. This deficiency could be corrected by a region-wide survey and long-term monitoring of smooth green snakes in conjunction with other herpetological survey efforts. 2 3 TABLE OF CONTENTS ACKNOWLEDGMENTS ..............................................................................................................................................2 AUTHORS’ BIOGRAPHIES .........................................................................................................................................2 COVER PHOTO CREDIT .............................................................................................................................................2 SUMMARY OF KEY COMPONENTS FOR CONSERVATION OF THE SMOOTH GREEN SNAKE....................3 LIST OF TABLES AND FIGURES ...............................................................................................................................6 INTRODUCTION ..........................................................................................................................................................7 Goal............................................................................................................................................................................7 Scope..........................................................................................................................................................................7 Uncertainty.................................................................................................................................................................7 Publication on the World Wide Web ..........................................................................................................................7 Peer Review ...............................................................................................................................................................7 MANAGEMENT STATUS AND NATURAL HISTORY .............................................................................................8