Assessing Changes in Clusters of Wildlife Road Mortalities after the
Construction Wildlife Mitigation Structures
Abstract
Collisions with vehicles are a major threat to wildlife populations and
often occur in identifiable patterns. To reduce wildlife road
mortalities, mitigation structures including exclusionary fencing and
wildlife crossings are constructed. Openings in fencing at road
intersections may lead to concentration of road mortality hot spots at
openings leading to a belief that these gaps concentrate road
mortalities. However, it is also possible that hot spots existed at
these locations before construction indicating that road mortality
patterns have not changed with mitigation structure construction.
Therefore, to assess mitigation structure effectiveness, it is important
to examine both road mortality numbers and road mortality spatial
distribution. Wildlife road mortality data was collected on a 15-km
section of rural highway in Texas, USA before, during, and after the
construction of wildlife mitigation structures. We expected that the
number of road mortalities would decrease after construction compared to
before construction and that road mortalities would become more
concentrated around openings in the fence. We used ANOVA to compare
numbers of road mortalities and emerging hot spot analysis and
generalized linear modelling to assess changes in road mortality spatial
distribution. Road mortalities were not significantly different in the
before and after construction periods (p = 0.092). While there were no
significant changes in road mortality patterns with construction,
cluster intensity was greater when nearer to fence openings in all three
time periods. Emerging hot spot analysis provides an effective and easy
way to visualize road mortality patterns through time, however, due to
low numbers of mortalities in many road mortality studies, including
this one, the power of this analysis to detect significant changes in
road mortality may be limited. This technique can provide both
ecologists and transportation planners an effective tool for identifying
patterns that may warrant further investigation using traditional
statistical techniques.