The Pennsylvania State University The Graduate School USING A MULTI-FACETED APPROACH TO ASSESS ECOLOGICAL COMPONENTS AFFECTING MUSKRAT (ONDATRA ZIBETHICUS) POPULATIONS A Thesis in Wildlife and Fisheries Science by Laken Samantha Ganoe © 2019 Laken Samantha Ganoe Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science December 2019 The thesis of Laken Samantha Ganoe was reviewed and approved* by the following: W. David Walter Adjunct Assistant Professor of Wildlife Ecology Thesis Advisor Duane R. Diefenbach Adjunct Professor of Wildlife Ecology Justin D. Brown Assistant Teaching Professor of Veterinary and Biomedical Sciences Matthew J. Lovallo Wildlife Biologist at the Pennsylvania Game Commission Special Signatory David Eissenstat Interim Head of the Department of Ecosystem Science and Management *Signature are on file in the Graduate School ii ABSTRACT The muskrat (Ondatra zibethicus) is a prominent and wide-spread furbearer in North America. Historically valued for their waterproof pelts and abundance of capture, muskrats have been trapped for their fur in North America for centuries. However, evidence of a decline of muskrat harvest since 1970 has been observed across the United States. Theories as to why populations declined include habitat loss, increased flooding events, predation, environmental contamination, and disease. Two of these theories, environmental contamination and disease, can directly affect the physical health of individual muskrat. Disease transmission between individual muskrats and muskrat populations may be influenced by various components of muskrat ecology (e.g. semi-colonial behavior). Therefore, it is important to not only understand the prevalence of specific pathogens, diseases, and contaminants that muskrats are exposed to, but also to understand the role that muskrat ecology plays in population health. To address these knowledge gaps, I employed a multifaceted approach to define pathogens, diseases and contaminants of muskrats, including: 1) retrospective study of published data on muskrat diseases in North America; 2) review of diagnostic data on muskrats in the Eastern United States in combinations with active surveys of diseases and pathogens of trapper-killed muskrats throughout Pennsylvania, and 3) a telemetry study in Pennsylvania to characterize survival and ecological factors of muskrats that may influence disease transmission. In Chapter 1, I conducted a literature review on muskrat parasites, pathogens, and disease across their natural range. This review was comprised of 129 articles from 1915 to 2019. Reports included were from 27 U.S. states and 9 Canadian provinces, and cover the following disease etiologies: parasites, bacteria, viruses, and contaminants. Several notable diseases and pathogens causing mortality in muskrats were cysticercosis, tularemia (Francisella tularensis), and iii Tyzzer’s disease (Clostridium piliforme). I identified gaps in the literature, specifically relating to biotoxin poisoning and impacts of both agricultural and chemical contamination on muskrat health. The retrospective study provided a basis for further investigations in this study. In Chapter 2, I built upon previous literature based on passive surveillance which was comprised of reviewing diagnostic cases of muskrats from the Southeastern Cooperative Wildlife Disease Study. Aside from trauma, the main causes of mortality in the diagnostic cases were Tyzzer’s disease and cysticercosis. These commonalities, along with existing knowledge gaps identified during the retrospective study, provided me with the foundation for components to examine using active surveillance. I collected 380 muskrat carcasses from across Pennsylvania to examine exposure to bacterial (C. piliforme, F. tularensis) and parasite (Toxoplasma gondii, Babesia spp., intestinal parasites) infections as well as heavy metal contamination. I detected Tyzzer’s disease, sarcosystosis, and toxoplasmosis at low prevalence. I failed to detect tularemia, babesiosis, or cadmium, arsenic, and mercury contamination. Parasite burdens were typical of historic reports, however younger muskrats had larger burdens than older muskrats which is contradictory to what was observed in Pennsylvania in 1966. The Northcentral and Northwest regions had higher parasite burdens than all of the southern regions combined (P<0.03). I also documented the first positive detection of Versteria mustelae infection in muskrats using genetic sequencing. In addition, I found no relationships between heavy metal concentrations and landscape features, and only zinc concentrations varied by sex. In Chapter 3, I investigated the dwelling structure use, movements, home range, and survival of radio-tagged muskrats (n = 17) in an urban wetland complex in central Pennsylvania. I used locations collected from intensive radio telemetry monitoring to determine number of lodging structures used, hourly movement, and size and percent area overlap of home ranges. I iv observed muskrats sharing large amounts of space within home ranges (68% of each individual home range) with other muskrats. I also determined that of four home range estimators (Kernel Density Estimator (KDE) href, KDEad hoc, KDEplug-in, and Local Convex Hull estimator), KDEplug- in provided the more appropriate home range size for muskrats in a linear-non-linear habitat matrix. I also calculated overwinter survival estimates using Known Fate models in Program MARK®. My top model showed a positive effect of the average weekly precipitation on survival with an overwinter survival estimate of 0.59 (SE = 0.16). The main cause of muskrat mortality was mink (n = 6). My model suggests that snowfall may be an important factor in muskrat survival. Using a multi-faceted approach, I was able to 1) find gaps in knowledge on muskrat health and key pathogens and disease causing mortality, 2) define the prevalence of historic pathogens and disease in the current muskrat populations in Pennsylvania, as well as define some relationships between muskrat health, sex, and heavy metal contamination, and 3) document the semi-colonial nature of muskrats which may influence disease transmission, while also distinguishing KDEplug-in as the most appropriate estimator to use in movement studies on muskrats in a linear-non-linear habitat matrix. This project provides the groundwork for future investigations of muskrat population health. v Table of Contents LIST OF TABLES ........................................................................................................................ vii LIST OF FIGURES ..................................................................................................................... viii ACKNOWLEDGEMENTS ............................................................................................................ x Chapter 1: A retrospective study of pathogens, diseases, and contaminants of muskrats (Ondatra zibethicus) .................................................................................................................... 1 Abstract .................................................................................................................................... 2 Introduction ............................................................................................................................. 2 Materials and methods ............................................................................................................. 4 Results ..................................................................................................................................... 5 Discussion .............................................................................................................................. 25 References ............................................................................................................................. 29 Chapter 2: Passive and active surveillance for disease of muskrat (Ondatra zibethicus) ......... 48 Abstract .................................................................................................................................. 49 Introduction ........................................................................................................................... 49 Materials and Methods .......................................................................................................... 51 Results ................................................................................................................................... 55 Discussion .............................................................................................................................. 57 Literature Cited ...................................................................................................................... 64 Chapter Three: Ecology of an isolated muskrat population during regional population declines ................................................................................................................................................... 81 Abstract .................................................................................................................................. 82 Study Area ............................................................................................................................. 85 Methods ................................................................................................................................. 86 Results ..................................................................................................................................