Cooperative Fish and Wildlife Research Units Program: Pennsylvania
Education, Research and Technical Assistance for Managing Our Natural Resources

Evidence indicating a decline in muskrat populations in the United States during the past 40 years has led to speculation in regard to factors influencing muskrat survival. In order to understand population dynamics and survival, it is important to first understand the ecology of local populations. We investigated the dwelling structure use, movements, home range, and survival of radio-tagged muskrats (n = 17) in an urban wetland complex in central Pennsylvania. We 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. Muskrats shared an average of nine lodging structures and on average 68% of a muskrat’s home range overlapped other muskrat home ranges. We used four home range estimators (Kernel Density Estimator (KDE) _href, KDE_{ad hoc}, KDE_plug-in, and Local Convex Hull estimator) to assess the ability of each estimator in representing muskrat home ranges. The KDE_plug-in that constrained the estimate of home range to habitat boundaries provided the more appropriate home range size for muskrats in a linear-non-linear habitat matrix. We also calculated overwinter survival estimates using known-fate models in Program MARK®. Our top model indicated 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). Our model suggests that snowfall may be an important factor in muskrat survival. Our study provides novel data on muskrat ecology in Pennsylvania as well as preliminary evidence for future investigations of climate’s impact on muskrat survival during the winter months.