Vegetation and vantage point influence visibility across diverse ecosystems: implications for animal ecology

Visual information can influence animal behavior and habitat use in
diverse ways. Visibility is the property that relates 3D habitat structure
to accessibility of visual information. Despite the importance of
visibility in animal ecology, this property remains largely unstudied. Our
objective was to assess how habitat structure from diverse environments
and animal position within that structure can influence visibility. We
gathered terrestrial lidar data (1 cm at 10 m) in four ecosystems (forest,
shrub-steppe, prairie, and desert) to characterize viewsheds (i.e.,
estimates of visibility based on spatially explicit sightlines) from
multiple vantage points. Both ecosystem-specific structure and animal
position influenced potential viewsheds. Generally, as height of the
vantage point above the ground increased, viewshed extent also increased,
but the relationships were not linear.  In low-structure
ecosystems (prairie, shrub-steppe, and desert), variability in viewsheds
decreased as vantage points increased to heights above the vegetation
canopy. In the forest, however, variation in viewsheds was highest at
intermediate heights, and markedly lower at the lowest and highest vantage
points. These patterns are likely linked to the amount, heterogeneity, and
distribution of vegetation structure occluding sightlines. Our work is the
first to apply a new method that can be used to estimate viewshed
properties relevant to animals (i.e., viewshed extent and variability). We
demonstrate that these properties differ across terrestrial landscapes in
complex ways that likely influence many facets of animal ecology and
behavior.