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ABSTRACT DOES EXCLUDING A TOP MESOPREDATOR INDUCE A TROPHIC CASCADE? EFFECTS AND DIET OF AN OMNIVOROUS PREDATOR IN A RESTORED PRAIRIE Kirstie Savage, M.S. Department of Biological Sciences Northern Illinois University, 2018 Dr. Holly P Jones, Thesis Director Predators can shape prey communities through consumptive and non-consumptive interactions. By inducing fear of predation, predators can cause changes to prey foraging behavior that can negatively impact prey reproduction and body-condition. Furthermore, both consumptive (density-mediated) and non-consumptive (trait-mediated) predator-prey interactions can cascade down the food web to have indirect impacts of vegetation (trophic cascade). As we continue to lose apex predators and undergo land change, understanding how the new top dogs shape prey communities and restorations is increasingly important. Through utilizing predator- exclosure fences, mark-recapture analysis, plant biomass and stable isotopes we evaluated the role of coyotes as top mesopredator in a restored grassland. Results indicate that coyotes do not have strong impacts on small mammal population dynamics or cause non-consumptive impacts to small mammal reproduction. In addition, they do not induce a trophic cascade in a restored prairie. However, coyotes appear to be having a positive impact on Peromyscus spp. body condition. I also found that coyotes eat C4 grasses in the highest proportion, although I suspect this to be driven by corn and corn product consumption, and that they have both individualistic and seasonal diets. The lack of an impact on prairie communities and a diet comprised largely of C4 grasses indicate that coyotes may not be filling the role of apex predator and exerting strong top-down control in restored prairie communities. However, given the short time frame of my study and small sample sizes I obtained, more research may be necessary to conclusively determine if coyotes function as an apex mesopredator in restored prairie systems. NORTHERN ILLINOIS UNIVERSITY DEKALB, ILLINOIS MAY 2018 DOES EXCLUDING A TOP MESOPREDATOR INDUCE A TROPHIC CASCADE: EFFECTS AND DIET OF AN OMNIVOROUS PREDATOR IN A RESTORED PRAIRIE BY KIRSTIE SAVAGE ©2018 Kirstie Savage A THESIS SUBMITTED TO THE GRADUATE SCHOOL IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE MASTER OF SCIENCE DEPARTMENT OF BIOLOGICAL SCIENCES Thesis Director: Holly P. Jones ACKNOWLEDGEMENTS I would like to acknowledge The Nature Conservancy and Nachusa Grasslands for allowing me to conduct research and have fences built in their renowned tallgrass prairie. I would also like to acknowledge the organizations that funded my graduate research, Friends of Nachusa Grasslands, Prairie Biotic Research Inc., and the Northern Illinois University Graduate School. Thank you to Bill Kleiman, Cody Considine, the seasonal crew, stewards and volunteers at Nachusa for all their help with my project and for making Nachusa the remarkable place that it is. I am so grateful to the ReFuGE team, Jones lab, field assistants, and volunteers for all the time they spent helping and supporting me both in the field and lab. Their friendships have been invaluable through this process. I would like to thank my committee members, Nick Barber and Rich King, for all their assistance, guidance, and support with fieldwork, statistics, classes, IACUC procedures and my overall success as a graduate student. I am overwhelmingly grateful to my family for their patience, sacrifice and assistance throughout this whole process. Nothing was better than having you two in the field with me. Finally, a very special thank you to my advisor, Dr. Holly Jones, whose understanding of who I am, what I needed, and brilliance as an advisor and woman in science made this all possible. DEDICATION This thesis and all the sacrifices and hard work that were necessary to accomplish it are dedicated to my husband, Danny, daughter, Maple, and son to be. You’re my world. TABLE OF CONTENTS Page LIST OF TABLES .................................................................................................................. v LIST OF FIGURES ................................................................................................................ vi LIST OF APPENDICES ......................................................................................................... viii Chapter 1. INTRODUCTION ………………………....................................................................... 1 2. PRAIRIE COMMUNTITIES ………………………...................................................... 5 Methods ………………………................................................................................... 9 Results ………………………..................................................................................... 21 Discussion ………………………............................................................................... 39 3. COYOTE DIET …………….………………………...................................................... 45 Methods ………………………................................................................................... 50 Results ………………………..................................................................................... 68 Discussion ………………………............................................................................... 73 4. DISCUSSION ...…………….………………………...................................................... 80 LITERATURE CITED …….………………………........................................................... 83 LIST OF TABLES Table Page 1: Small mammal sampling sessions by year ............................................................... 13 2: Target species and identifying information .............................................................. 14 3: Non-target species and identifying information ....................................................... 15 4: Unique captured and recaptured small mammals by trapping session; species ordered by frequency of capture. I define unique as each individual caught per trapping session; this could include some overlaps from different trapping sessions (i.e., across months) ……………………………………………………………………………................... 24 5: Total number of unique species captured per site (X after site name indicates exclosure grids) for 2017 ............................................................................................................... 25 6: Total number of unique species captured per site (X after site name indicates exclosure grids) for 2016............................................................................................................... 26 7: Summary statistics for linear mixed effects models……………………………….. 26 8: Description of coyote samples ................................................................................. 51 9: Coyote prey sample methods of collection, preparation, and groupings for analysis ................................................................................................................... 54 10: Models run for coyote diet analysis ……………………....................................... 65 11: Individual coyote diet broken down by sources. Values represent the median proportion ……………………..................................................................................... 66 12: Mean and standard deviation δ15N and δ13C values for grouped sources used for seasonal coyote diet analysis ........................................................................................ 66 LIST OF FIGURES Figures Page 1: Map of trapping grid locations at Nachusa Grasslands ............................................ 11 2: Trapping grid set up, traps are located on black dots spaced 15m apart .................. 12 3: Bivariate plot of all individuals used in body condition measurement .................... 20 4: Small mammal abundance by treatment/Species ……………………..................... 27 5: Small mammal reproduction by treatment ……..……………………..................... 28 6: Peromyscus abundance by treatment/Microtus abundance by treatment …………. 29 7: Peromyscus reproduction by treatment /Microtus reproduction by treatment ……. 30 8: Small mammal diversity by treatment ……………………………………………. 31 9: Small mammal community composition measured through NMDS ………..……. 32 10: Body condition measured using the scaled mass index …………………………. 33 11: Reproductive body condition measured using the scaled mass index …………... 34 12: Time series comparing BCI between treatments through trapping sessions in 2017 35 13: Time series comparing difference in new captures for Microtus ochragaster, Peromscus maniculatus, and Peromyscus leucopus for control (left) and exclosure (right) treatments …………………………………………………………………………..... 36 14: Forb/Grass aboveground biomass (g) by treatment …..…………………………. 37 15: a) Plotted sources to visualize for grouping b) Dietary items grouped for seasonal analysis, black dots represent consumers 1-3 segmented values c) Dietary items groups for individual dietary analysis ……………………………………………………….. 63 16: Proportion of dietary items for individual coyotes 1-4 showing differences in diet among individuals …………………………………………………………………… 69 vii 17: Proportion of dietary items through time for coyote 1 showing individual seasonal diet ………………………………………………………………………………….... 70 18: Boxplots comparing δ15N and δ13C values by gender for visual inspection of potential differences …………………………………………………………………………… 71 CHAPTER 1 INTRODUCTION Top-down control is an important limitation in ecological systems. Apex predators, being primarily carnivores, are known to exert top-down control, and their impacts can
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