Data and code from: At the intersection of soundscapes and roads: Quantifying anthrophony’s influence on wildlife crossing structure use

Anthropogenic noise (anthrophony) can have significant negative effects on
wildlife, causing both physiological (i.e., increased stress hormone
production) and behavioral (i.e., altered anti-predator behaviors, space
use, or diel activity) changes in individuals. Roads are a major source of
anthrophony, often contributing the most to the anthrophony in rural
areas. Most efforts to reduce road effects on wildlife have focused on
decreasing road-associated mortality through the construction of wildlife
crossing structures (WCSs) with little consideration for the anthrophony
associated with these structures. Given the impacts of anthrophony on
wildlife behavior, the effectiveness of WCSs could be altered without
consideration towards noise pollution. Therefore, understanding how
anthrophony is structured in space and time and how it impacts WCS use is
an important aspect of assessing effectiveness of WCSs. We developed a
framework for assessing anthrophony at WCS using an array of autonomous
recording units to monitor overall acoustic conditions. We then examined
how wildlife crossing rates were associated with anthrophony using camera
traps. We monitored five underpass-style WCSs built in the Lower Rio
Grande Valley of South Texas, USA using camera traps and acoustic
recording units. We measured sound pressure level (SPL [dB]) and relative
level of anthrophony (using the normalized difference soundscape index
[NDSI]) at six positions around each WCS: two at elevation (road grade)
with the road surface (west and east), two at the WCS entrances, and two
in the middle of the WCSs. We then used SPL and NDSI to predict the
probability of a successful crossing by Virginia opossum (Didelphis
virginiana), a common, disturbance-tolerant mammal. While the relative
amount of anthrophony did not differ, smaller WCSs and those with less
traffic were up to 40 dB quieter than larger WCSs and those with more
traffic. Opossums spent more time at WCSs when it was quieter on average
and were more likely to successfully cross through a WCS when there was
less vehicle noise. Our study highlights the importance of considering
soundscapes in assessing WCS effectiveness and represents a framework that
can be used for further exploration of the impacts of anthrophony on WCS
use.