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Oil and gas activities on Alaska's North Slope overlap spatially with polar bear (Ursus maritimus) maternal denning habitat and temporally with the peri‐partum and emergence periods. Noise associated with these activities can be substantial and concerns regarding the effects on polar bears have been acknowledged. But the secluded and ephemeral nature of subnivean maternal dens renders the measurement of behavioral and physiological responses of bears to noise exposure challenging, except for rare cases when disturbance‐prompted den abandonment has been documented. These limitations, coupled with the uncertainty associated with the synergistic effects of anthropogenic activities on bears in a rapidly changing Arctic, prompt the need to develop predictive models of disturbance to ensure management guidelines effectively mitigate disturbance. Towards this end, we characterized noise propagation from 9 sources (2 aircraft, 2 over‐tundra tracked vehicles, 4 wheeled on‐road vehicles, and humans walking) used to support industrial activities around artificial snow dens near Milne Point, Alaska, USA, in March–April 2010. We built dens in 4 configurations to mimic variability in den roof thickness and to evaluate differences in noise propagation from when the den was closed compared to being open, similar to den emergence. We integrated these data with an existing polar bear audiogram and developed models to predict auditory‐detection probabilities as a function of distance from the den. Within a closed den, aircraft had high probabilities (detection probability ≥75%) of being detected by polar bears at distances ≤1.6 km and ground‐based sources had high probabilities of detection at distances ≤0.8 km. On average, closed dens reduced noise levels by 15 decibels (dB) relative to open dens. Our findings indicate that although polar bear snow dens effectively attenuate acoustic sound pressure levels, noise from some industrial support vehicles was likely to be detected farther from dens than previously documented. These results reinforce the importance of maintaining buffer zones around polar bear dens to minimize the potential for den disturbance. © 2020 The Wildlife Society.

Under the National Environmental Policy Act, authors must address environmental impacts of various anthropogenic actions on wildlife. One such impact of increasing awareness and concern is effect noise on wildlife, both during construction and operation of the project. However, biologists often have difficulty in understanding the fundamentals of acoustics and noise analysts often have difficulty in understanding the biological implications of increased noise on wildlife. As a result, inappropriate weighting metrics (such as A-weighted decibel) or time descriptors (e.g., community noise equivalent level) are often used erroneously to assess noise impacts on wildlife. Noise exposure thresholds on wildlife exist for marine mammals and fish, as mandated by the National Marine Fisheries Service. However, no such thresholds exist for terrestrial wildlife. This talk provides specific examples of how noise impacts on wildlife have been assessed using GIS-based technology, industry-accepted noise propagation models, and peer-reviewed literature in the absence of management guidelines. Examples include assessing construction noise impacts on the California coastal gnatcatcher in southern California, aircraft noise impacts on sage grouse in central California, and helicopter disturbance on caribou in Alaska.

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