Jens Ammon
Coyote Home Range Distribution
In this exercise we analyze the habitat use patterns of seven different coyotes near the Dougway Proving Grounds in the west desert region of Utah. GPS data were collected on each coyote over the course of a year via coordinate transmitting collars. The point location data was then processed into home range boundaries for each coyote, a visualization of the area where the coyote spends most of its time. Two methods of calculating territories were used, the simpler Minimum Convex Polygons method and the more complex Kernel Density Estimate method.
The left map is an example of the Minimum Convex Polygon method of creating home range boundaries. This method connects the outermost points of a group of point locations in a way that only creates flat or convex boundaries. While this area is quick to calculate with ArcGIS tools and can be useful for defining the overall area for a study, it overestimates the area actually used by the species in question.
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Map Creation Process
- Import point location data subdivided into different study groups if necessary.
- Use the Minimum Bounding Geometry tool to create the boundaries for the desired attributes.
- Adjust symbology as necessary
The right map is an example of the Kernel Density Estimates method of creating home range boundaries. This method creates a heat-map style point density visualization by summing "piles of sand" created for each data point. While the kernel method takes more steps to calculate, it gives more detailed land use information such as core habitat and edge habitat.
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Map Creation Process
- Import point location data subdivided into different study groups if necessary.
- Use the Kernel Density tool to create a continuous point density raster.
- Use the Extract Values to Points tool to link the value from the raster back to the point file
- Reclassify the points into the desired core habitat density value and fringe habitat density value
- Use the Raster to Polygon tool to create polygons of the core and fringe habitat zones.
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** NOTE: these steps could be repeated for each coyote, but an automated python script was used here to avoid repetition.
Landcover Utilization vs Availability
In order to analyze which landcover types are preferred by the coyotes, the landcover utilized by the coyotes was compared to what landcover was available to them. First calculated was how much of each landcover type was available in the coyote's home range. This calculation was done by clipping a Landfire landcover raster to just the home range extents of the coyotes. Second calculated was how much of each landcover type was utilized by the coyotes. This calculation was done by using the Extract Values to Points tool to determine what landcover types the GPS locations are located on. These extracted landcover types were then summarized as shown in the table below. Finally, the Preference Ratio was calculated by comparing the actual count of each landcover use type to the expected count of each landcover if there was no preference by the coyotes.
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The most utilized land cover type correlates to the landcover type most available to the coyotes (most area available = most utilized). However, the most preferred landcover type was the Inter-Mountain Basins Greasewood Flat (highest Preference Ratio).
