Date of Award
Master of Science (MS)
Forestry and Environmental Conservation
David Jachowski, Committee Chair
Swift foxes are endemic to the Great Plains of North America, but they were extirpated from the northern portion of their range by the mid-1900s. Despite several reintroductions to the Northern Great Plains, there is still a large range gap between the swift fox population along the Montana and Canada border, and the population in northeastern Wyoming and northwestern South Dakota. A better understanding of the resources swift foxes use and demography of the population at the edge of this range gap in northern Montana might help to managers to facilitate connectivity among populations. In Chapter 1, we collected fine-scale locational data from swift foxes fitted with Global Positioning System collars to examine movement and resource use patterns during winter of 2016-2017 in northeastern Montana. Our results suggest that swift foxes displayed three distinct movement patterns (i.e., resting, foraging, and travelling) during the winter. Distance to road decreased relative probability of use by 39-46% per kilometer across all movement states and individuals, whereas the influence of topographic roughness and distance to crop field varied among movement states and individuals. Overall, while our findings are based on data from three individuals, our study suggests that across movement states during the critical winter season, swift foxes are likely using topography and areas near roads to increase their ability to detect predators.
In Chapter 2, we estimated the home range size and evaluated third order resource selection of 22 swift foxes equipped with Global Positioning System tracking collars in northeastern Montana. Swift fox home ranges in our study were some of the largest ever recorded averaging (+/-SE) 42.0 km2 +/- 4.7. Our results indicate that both environmental and anthropogenic factors influenced resource use. At the population level, relative probability of use increased by 3.3% for every 5.0% increase in percent grasslands. Relative probability of use decreased by 7.9% and 7.4% for every kilometer away from nonpaved roads and gas well sites, respectively, and decreased by 2.9% and 11.3% for every one-unit increase in topographic roughness and every 0.05 increase in normalized difference vegetation index (NDVI). Overall, to reestablish connectivity among swift fox populations in Montana, our study suggests that managers should aim to maintain large corridors of contiguous grasslands a landscape-scale, a process that will likely require having to work with multiple property owners.
In the Northern Great Plains, a suite of carnivores has experienced a large decline in distribution and abundance since the 1800s. In Chapter 3, our objective was to estimate survival and reproductive rates of swift foxes in Montana and assess population viability. In addition, we evaluated support for nine different hypotheses of how several demographic and environmental factors influence survival. We found that adult and juvenile annual survival rates were 54% and 74%, respectively, and fecundity was 0.85. We found the most support for the hypothesis that the percentage of native grassland at the 1 km scale influenced survival and found that survival increased, on average, 2.1% for every 5% increase in grassland. The estimated population growth rate of this population was estimated to be 1.002, indicating that the population was likely to be stable. Our results suggest that this population is currently not likely acting as a source population (i.e. not producing a sufficient number of dispersers), which might be contributing to the lack of range expansion. The long-term success of swift fox recovery will likely be dependent on maintaining large tracts of contiguous grassland with abundant prey, which would be benefit not only the swift fox, but a suite of recovering carnivores.
Butler, Andrew Russell, "Behavioral and Population Ecology of Swift Foxes in Northeastern Montana" (2019). All Theses. 3133.