title: Calling at the highway: The spatiotemporal constraint of road noise on Pacific chorus frog communication.
abstract: Loss of acoustic habitat due to anthropogenic noise is a key environmental stressor for vocal amphibian species, a taxonomic group that is experiencing global population declines. The Pacific chorus frog (Pseudacris regilla) is the most common vocal species of the Pacific Northwest and can occupy human-dominated habitat types, including agricultural and urban wetlands. This species is exposed to anthropogenic noise, which can interfere with vocalizations during the breeding season. We hypothesized that Pacific chorus frogs would alter the spatial and temporal structure of their breeding vocalizations in response to road noise, a widespread anthropogenic stressor. We compared Pacific chorus frog call structure and ambient road noise levels along a gradient of road noise exposures in the Willamette Valley, Oregon, USA. We used both passive acoustic monitoring and directional recordings to determine source level (i.e., amplitude or volume), dominant frequency (i.e., pitch), call duration, and call rate of individual frogs and to quantify ambient road noise levels. Pacific chorus frogs were unable to change their vocalizations to compensate for road noise. A model of the active space and time ("spatiotemporal communication") over which a Pacific chorus frog vocalization could be heard revealed that in high-noise habitats, spatiotemporal communication was drastically reduced for an individual. This may have implications for the reproductive success of this species, which relies on specific call repertoires to portray relative fitness and attract mates. Using the acoustic call parameters defined by this study (frequency, source level, call rate, and call duration), we developed a simplified model of acoustic communication space-time for this species. This model can be used in combination with models that determine the insertion loss for various acoustic barriers to define the impact of anthropogenic noise on the radius of communication in threatened species. Additionally, this model can be applied to other vocal taxonomic groups provided the necessary acoustic parameters are determined, including the frequency parameters and perception thresholds. Reduction in acoustic habitat by anthropogenic noise may emerge as a compounding environmental stressor for an already sensitive taxonomic group.
authors.affiliation: Department of Fisheries and Wildlife Oregon State University Corvallis OR USA; ARCS Foundation Scholar Arcata CA USA.
authors.forename: Danielle V
authors.initials: DV
authors.lastname: Nelson
authors.affiliation: Bioacoustics Research Program Cornell Lab of Ornithology Cornell University Ithaca NY USA; Cooperative Institute for Marine Resources Oregon State University and NOAA Pacific Marine Environmental Laboratory Newport OR USA.
authors.forename: Holger
authors.initials: H
authors.lastname: Klinck
authors.affiliation: Department of Integrated Biology Oregon State University Corvallis OR USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Carbaugh-Rutland
authors.affiliation: Department of Fisheries and Wildlife Oregon State University Corvallis OR USA.
authors.forename: Codey L
authors.initials: CL
authors.lastname: Mathis
authors.affiliation: Department of Natural Resources and the Environment University of Connecticut Storrs CT USA.
authors.forename: Anita T
authors.initials: AT
authors.lastname: Morzillo
authors.affiliation: Department of Fisheries and Wildlife Oregon State University Corvallis OR USA.
authors.forename: Tiffany S
authors.initials: TS
authors.lastname: Garcia
keywords: acoustic; amphibian; anthropogenic; communication; road noise; spatiotemporal