Clemson University TigerPrints All Theses Theses 8-2018 Hatch Success and Population Modeling for the Critically Endangered Bog Turtle in North Carolina Michael Donald Knoerr Clemson University, [email protected] Follow this and additional works at: https://tigerprints.clemson.edu/all_theses Recommended Citation Knoerr, Michael Donald, "Hatch Success and Population Modeling for the Critically Endangered Bog Turtle in North Carolina" (2018). All Theses. 2930. https://tigerprints.clemson.edu/all_theses/2930 This Thesis is brought to you for free and open access by the Theses at TigerPrints. It has been accepted for inclusion in All Theses by an authorized administrator of TigerPrints. For more information, please contact [email protected]. HATCH SUCCESS AND POPULATION MODELING FOR THE CRITICALLY ENDANGERED BOG TURTLE IN NORTH CAROLINA A Thesis Presented to the Graduate School of Clemson University In Partial Fulfillment of the Requirements for the Degree Master of Science Wildlife and Fisheries Biology by Michael Donald Knoerr August 2018 Accepted by: Dr. Kyle Barrett, Committee Chair Dr. Beth Ross Dr. Cathy Jachowski ABSTRACT Recent literature suggests that several North Carolina bog turtle (Glyptemys muhlenbergii) populations are in decline, and many of these populations have few remaining individuals with low annual survival probability. Most populations appear dominated by older adults with few juveniles encountered; however, the proportion of juveniles encountered at two populations is dramatically higher. The reason for this variability is unknown. We conducted a nest monitoring study in 2016 and 2017 to test the hypothesis that nest survival patterns explain the observed population age structure. We collected the largest dataset yet compiled on the fate of naturally-incubated bog turtle eggs as well as the first study of its kind in North Carolina. Predation was the primary driver of nest failure across all sites. Populations with more juvenile encounters had substantially higher egg survival. These observations support the hypothesis that variation in egg survival may be linked to observed variation in recruitment patterns. We subsequently incorporated site-specific population parameters, including site-specific egg survival, into a stage-based matrix model to estimate population growth rates and to assess potential management scenarios for five bog turtle populations. Only two of the five populations modeled were stable or growing under current vital rates. Our results demonstrated that management scenarios targeting increased recruitment (especially a head-start scenario) may substantially contribute to some populations reaching stability. Population growth rates will likely be higher when recruitment augmentation coincides with wetland restoration efforts that increase survival and site fidelity at other life stages. ii DEDICATION I dedicate this thesis to my mother Nancy. You supported my love for turtles and nature early on. You gave me opportunities to pursue my passion, even when you didn’t fully understand it. You brought me camping in Michigan when I was 13 in search of beautiful rivers and the mythical wood turtle (the other Glyptemys). I promise that you will have a waterproof tent the next time we camp in the north woods. iii ACKNOWLEDGEMENTS This project stems from decades of field labor-a labor of love- by over a dozen individuals who are passionate about bog turtle conservation. It was these efforts that made my research a reality, as recapture data suggests several populations are in decline. I am indebted to the people that make up Project Bog Turtle, to Dennis Herman for his guidance, and to Annalee Tutterow and Dr. Shannon Pittman for their excellent work proceeding my own. My particular project gained traction via two key people, Gabrielle Graeter and Dr. Kyle Barrett. I am thankful to Gabrielle and the North Carolina Wildlife Resources Commission for supporting this project and trusting me to perform good science while working in North Carolina’s most important bog turtle populations. Dr. Kyle Barrett gave me the opportunity of a lifetime, and offered unwavering support. He also made me a substantially better scientist along the way. A special thanks to Adam Warwick and The Nature Conservancy for supporting this project and giving me access to their properties. Thank you to Michael Ogle and Zoo Knoxville for providing funding via the Bern Tryon Grant. Thank you to Sue Cameron and Mark Endries of the United States Fish & Wildlife Service for supporting our ongoing research. Thank you to Dr. JJ Apodaca for the guidance and for providing field equipment and technicians. Thank you to Rob Carmichael of the Wildlife Discovery Center for providing radio-telemetry gear. Thank you to Dr. Jeff Wilcox for helping us install hydrological wells in the heat of summer. Thank you to my committee members Dr. Beth Ross and Dr. Cathy Jachowski for your technical support. iv An enthusiastic thank you to my field technicians, lab-mates and volunteers. We are able to say something meaningful because of your efforts to collect a robust dataset. Your efforts, day and night, made all the difference. Thank you to: Michael Holden, Cody Davis, Kirsten Brown, Maria Alvarez, Amy Almond, Alison Cercy, Michael Frazier, Sam McCoy, Morgan Harris, Worth Pugh, Dr. Mike Osbourne, Katelyn Pollock, Jill Newman, Joel Mota, David Hutto, Ryan Lubbers, Bryan Suson, and Sam Silknetter. A special thank you to my wonderful fiancé Micaela Scobie who became an expert at finding bog turtles who tolerated my extended absences in the name of turtle conservation. v TABLE OF CONTENTS Page TITLE PAGE ....................................................................................................................... i ABSTRACT ........................................................................................................................ ii DEDICATION ................................................................................................................... iii ACKNOWLEDGEMENTS ............................................................................................... iv LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ......................................................................................................... viii Chapter I. HATCH SUCCESS OF THE BOG TURTLE, GLYPTEMYS MUHLENBERGII, IN NORTH CAROLINA....................................................1 Abstract ..............................................................................................................1 Introduction ........................................................................................................2 Study Area .........................................................................................................5 Methods..............................................................................................................7 Results ..............................................................................................................11 Discussion ........................................................................................................13 Management Implications ................................................................................18 Literature Cited ................................................................................................29 II. POPULATION MODELS REVEAL THE IMPORTANCE OF MANAGEMENT INTERVENTION FOR AN ENDANGERED TURTLE SPECIES ..........................................................................................................35 Abstract ............................................................................................................35 Introduction ......................................................................................................36 Study Area .......................................................................................................40 Methods............................................................................................................43 Results ..............................................................................................................50 Discussion ........................................................................................................52 Management Implications ................................................................................58 Literature Cited ................................................................................................72 vi LIST OF TABLES Table Page 1.1 AIC results for nest predation models ................................................................20 1.2 Egg fate ...............................................................................................................21 1.3 Nest temperature comparisons by site ................................................................22 1.4 Literature review of bog turtle egg survival .......................................................23 2.1 Stable stage distributions ....................................................................................60 2.2 Reproductive values ............................................................................................61 2.3 Elasticities ...........................................................................................................62 2.4 Survival estimates resulting in λ<1 for stable populations .................................63