Mammals with large home ranges, low reproductive rates, and small body sizes are most vulnerable to roads: A meta-analysis

In a previous meta-analysis, mammals with large home ranges, low
reproductive rates, and large body sizes were found to respond most
negatively to roads. However, due to correlations among these traits, it
is not known whether these responses were due to a subset or all three
traits. We conducted a multiple meta-regression of the effects of species
traits on mammal responses to roads, using data from 92 studies, to
determine whether an analysis with a larger sample size and controlling
for correlations among traits will support the previous findings. The
results reinforce the findings that mammals with larger home ranges and
lower reproductive rates respond more negatively to roads. Surprisingly,
we found that when controlling for the effects of home range size and
reproductive rate, larger mammals respond less negatively to roads than
smaller mammals. We speculate that the positive effect of body size is due
to driver avoidance of collisions with larger mammals and/or differences
in road attraction and car avoidance behaviors of larger vs. smaller
species that allow larger mammals to extract benefits of roads while
avoiding oncoming vehicles. We also found high variability of individual
responses to roads, above what could be explained by the species traits
model, most likely due to site and/or species-specific characteristics.
Synthesis and applications: Road mitigation for mammals should ideally be
informed by site level knowledge and generally involve prioritizing
species with the combination of larger home ranges, lower reproductive
rates, and smaller body sizes. To protect these vulnerable mammals from
roads, we should maintain low road densities and install small-mesh
mitigation fencing along roads. This differs from current road mitigation
efforts which are typically targeted towards large mammals (e.g.,
large-mesh fencing along roads) and are often ineffective for smaller
mammals.