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grid_hr() provides a simple grid-based approach to
estimating animal home-range size. Rather than estimating a continuous
utilization distribution, the method overlays the observed locations
with a regular spatial grid and defines the home range as the set of
cells containing at least one location.
The estimated home-range area therefore depends on the chosen grid-cell area and cell shape. This makes the spatial resolution of the analysis an explicit and interpretable parameter rather than an implicit property of a smoothing procedure. The function can represent spatial variation in space-use intensity by displaying the number of locations recorded in each occupied cell.
In addition to estimating home-range size, grid_hr() can
represent how space-use intensity changes with distance from the centre
of the home range. This radial representation is based on the idea that
a home range is not necessarily used uniformly: the intensity with which
animals use space may increase, decrease, or vary in more complex ways
from the centre toward the periphery.
grid_hr(
gibbons,
cell_area = 2000,
fill_by = "locations",
show_legend = TRUE,
title = "Space-use intensity of a gibbon group (0.2-ha hexagons)"
)
#>
#> ----------------------------------------
#> Grid-based home-range analysis: Space-use intensity of a gibbon group (0.2-ha hexagons)
#> ----------------------------------------
#> Locations: 18098
#> Cell shape: hex
#> Cell area: 2000 square meters
#> Fill method: locations
#> Used cells: 159
#> Home-range area: 318000 square meters
#> Home-range area: 31.8 ha
#> ----------------------------------------For the radial representation, occupied cells are assigned to concentric radial rings according to their distance from the centre of the home range. For each ring, space-use intensity is calculated as the number of locations recorded in the ring divided by the number of occupied cells in that ring. The resulting values describe a radial space-use profile, showing how intensively different parts of the home range are used relative to their distance from the centre.
grid_hr(
gibbons,
cell_area = 2000,
fill_by = "radial",
show_legend = TRUE,
title = "Radial space-use intensity of a gibbon group (0.2-ha hexagons)"
)
#>
#> ----------------------------------------
#> Grid-based home-range analysis: Radial space-use intensity of a gibbon group (0.2-ha hexagons)
#> ----------------------------------------
#> Locations: 18098
#> Cell shape: hex
#> Cell area: 2000 square meters
#> Fill method: radial
#> Used cells: 159
#> Home-range area: 318000 square meters
#> Home-range area: 31.8 ha
#> ----------------------------------------This radial representation provides a way to examine how space use is organized from the centre toward the periphery of the home range. Although spatial variation in space-use intensity can be visualized directly from the number of locations in each grid cell, the radial approach summarizes this variation according to distance from the centre, providing a profile of how use changes across the home range.
These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
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