A COMPARISON of WHITE-TAILED DEER RECRUITMENT RATES to RELATIVE PREDATOR ABUNDANCE in MARYLAND by Eric W. Ness a Thesis Submitte
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A COMPARISON OF WHITE-TAILED DEER RECRUITMENT RATES TO RELATIVE PREDATOR ABUNDANCE IN MARYLAND by Eric W. Ness A thesis submitted to the Faculty of the University of Delaware in partial fulfillment of the requirements for the degree of Master of Science in Wildlife Ecology Fall 2017 © 2017 Eric W. Ness All Rights Reserved A COMPARISON OF WHITE-TAILED DEER RECRUITMENT RATES TO RELATIVE PREDATOR ABUNDANCE IN MARYLAND by Eric W. Ness Approved: __________________________________________________________ Jacob L. Bowman, Ph.D. Professor in charge of thesis on behalf of the Advisory Committee Approved: __________________________________________________________ Jacob L. Bowman, Ph.D. Chair of the Department of Entomology and Wildlife Ecology Approved: __________________________________________________________ Mark W. Rieger, Ph.D. Dean of the College of Agriculture and Natural Resources Approved: __________________________________________________________ Ann Ardis, Ph.D. Senior Vice Provost for Graduate and Professional Education ACKNOWLEDGEMENTS I am grateful to all of those with whom I have had the pleasure to work, during this and other related projects. Both members of my committee, Brian Eyler and Kyle McCarthy, have provided me extensive personal and professional guidance and taught me a great deal about both scientific research and life in general. I would especially like to thank Dr. Jacob Bowman, the chairman of my committee. As my teacher and mentor, he has taught me more than I could ever give him credit for here. He has shown me, by his example, what a good scientist (and person) should be. I owe an enormous amount of gratitude to the faculty, staff, and fellow students within the department for making my experience so enjoyable. The guidance and hard work provided by Jacob Haus both in the lab and field has been immense. I am very thankful for the efforts of Harry Spiker, George Timko, Liz Tymkiw, Jessica Hicken, Katie Gundermann, and Kristen Van Neste for their assistance in the field. Nobody has been more important to me in the pursuit of this project than the members of my family. I would like to thank my parents; whose love and guidance are with me in whatever I pursue. They are the ultimate role models. Most importantly, I wish to thank my loving and supportive wife, Brenna, who provided unending inspiration, guidance, and extremely hard work in the field. iii TABLE OF CONTENTS LIST OF TABLES.............................................................................................................. v LIST OF FIGURES…....................................................................................................... vi ABSTRACT..................................................................................................................... vii Chapter 1 A COMPARISON OF WHITE-TAILED DEER RECRUITMENT RATES TO RELATIVE PREDATOR ABUNDANCE IN MARYLAND……………………1 1.1 Introduction....................................................................................................... 1 1.2 Study Area........................................................................................................ 5 1.3 Methods............................................................................................................. 6 1.3.1 Deer FLIR Survey........................................................................... 6 1.3.2 Predator Camera Survey................................................................. 8 1.3.3 Predator-Prey Relationship........................................................... 12 1.4 Results............................................................................................................. 13 1.4.1 Deer FLIR Survey......................................................................... 13 1.4.2 Predator Camera Survey............................................................... 14 1.4.3 Predator-Prey Relationship........................................................... 15 1.5 Discussion....................................................................................................... 16 1.5.1 Deer Density and Fawn Recruitment............................................ 16 1.5.2 Predator Density Estimation......................................................... 17 1.5.3 Predator-Prey Relationship........................................................... 21 1.6 Management Implications…………………..……………………….……… 22 TABLES..................................................................................................................... 23 FIGURES.................................................................................................................... 31 REFERENCES........................................................................................................... 38 iv LIST OF TABLES Table 1.1 Range and standard error (SE) of covariates within each camera buffer across 3 state forests within western Maryland. All calculations were made using ArcGIS 10.2 using the 2014 TIGER shapefile (a, b, c), or the 2011 USGS national landcover dataset (d, e, f)................................................. 23 Table 1.2 Summer survey top models for each of the 3 species to estimate density of each species on 3 state forests within western Maryland. Covariates are listed by model performance based on Akaike's information criterion adjusted for small n (AICc)...................................................................... 24 Table 1.3 Winter survey top models for each of the 3 species to estimate density of each species on 3 state forests within western Maryland. Covariates are listed by model performance based on Akaike's information criterion adjusted for small n (AICc)....................................................................... 25 Table 1.4 Density and fawn recruitment estimates of white-tailed deer obtained using road-based distance surveys using a FLIR device (FLIR) on 3 state forests within deer management region A, Maryland, USA..................... 26 Table 1.5 Camera survey detections of target species (black bear, bobcat, and coyote) per 100 camera trap nights at 3 state forests within western Maryland. 2015 and 2016 60-day survey from June-August. Winter 60- day survey from December, 2016-February, 2017. Black bear were excluded from the winter survey due to reduced activity……..………... 27 Table 1.6 Estimated predator density (individuals/km2), standard error (SE), 95% confidence interval (95%CI), and detection probability on 3 state forests in western Maryland obtained via camera survey June-August, 2015 and 2016…………………………………………………………………...… 28 Table 1.7 Estimated predator density (individuals/km2), standard error (SE), 95% confidence interval (95%CI), and detection probability on 3 state forests in western Maryland obtained via camera survey December, 2015-February, 2016. ......................................................................................................... 29 Table 1.8 Results of western Maryland mast survey performed by the Maryland Department of Natural Resources. Acorn abundance is expressed as an average number of acorns per branch from 2012-2016 (MDNR 2016)... 30 v LIST OF FIGURES Figure 1.1 Maryland deer management regions, 2015-2016. Region A consisted of Garrett, Allegany, and western Washington Counties. Region B consisted of the remainder of the state. .................................................................... 31 Figure 1.2 Study sites (from west to east: Potomac-Garret (1), Savage River (2), and Green Ridge (3) State Forests) locations used for FLIR surveys in 2015- 2016........................................................................................................... 32 Figure 1.3 Illustration of the camera grid within the Green Ridge State Forest study area 2015-2016. Each point represents a camera station and the circles around each represent the 8.04 km2 the cameras cover............................ 33 Figure 1.4 Illustration of camera site construction for optimal detections of mammals using a scent tree and camera tree…......................................................... 34 Figure 1.5 Example of three most likely predator-prey relationships present within Region A, Maryland.................................................................................. 35 Figure 1.6 Predator-prey relationship based on estimate of fawn recruitment and predator density from 2015 surveys.......................................................... 36 Figure 1.7 Predator-prey relationship based on estimate of fawn recruitment and predator density from 2016 surveys.......................................................... 36 Figure 1.8 Averaged results of FLIR (right axis) and camera surveys (left axis) for 2015 and 2016 surveys. Estimated recruitment (fawn) does not change between sites; however, estimated total predator density of black bear, bobcat, and coyote decreases from west to east........................................ 37 vi ABSTRACT In the late 1990s, Maryland’s deer management plan aimed to reduce and stabilize the state’s white-tailed deer (Odocoileus virginianus) population. While attempting to achieve this goal through liberalized seasons and bag limits, managers estimated a decreasing fawn recruitment rate and sought to better understand causes for these declines, particularly in the western portion of the state. Fawn recruitment may be impacted by several factors: predation, disease, starvation, malnutrition, parasite-load, and collisions with vehicles and farm machinery. My study’s goal