Estimating the Audibility of Industrial Noise to Denning Polar Bears

Abstract

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.

Behavioral response of polar bears to aircraft activity on the northern coast of Alaska

“…Ringed seals were 8 times more likely to exhibit an escape response to a helicopter than a fixed‐wing aircraft (Born et al 1999). These previous studies noted that the differences in response may be related noise disturbance, with helicopters generally being louder (higher dB levels) and generating lower frequencies (Hz) that can be detected by wildlife at greater distances as compared to fixed‐wing aircraft (Born et al 1999, Owen et al 2021). Also, most research‐related polar bear captures occur from a helicopter, and the acute physiological response of polar bears to helicopter capture are similar to the most intense events of natural behavior (Whiteman et al 2022).…”

“…Arctic, climate change, disturbance, human-wildlife conflict, Marine Mammal Protection Act, Ursus maritimus Anthropogenic expansion into the Arctic has steadily increased over the last several decades, and the trajectory of industrial and commercial activity is forecasted to expand in this region as Arctic sea ice continues to diminish (Van Hemert et al 2015, Nevalainen et al 2017, Owen et al 2021. In response to unreliable sea ice conditions, some species that rely on sea ice are adjusting aspects of their life-history strategies (Atwood et al 2016a, b).…”

Classifying the effects of human disturbance on denning polar bears

“…Differences in den (e.g. snow ceiling thickness; Owen et al 2021) and snow characteristics (e.g. density, snow water equivalent; Ishida 1965, Blix & Lentfer 1992) affect propagation of sound and vibration and likely also contribute to bear responses to human activity.…”

Wolverines (Gulo gulo) in the Arctic: Revisiting distribution and identifying research and conservation priorities amid rapid environmental change

“…Exploratory surveys for mineral or petroleum deposits, which typically deploy high-energy seismic pulses into tundra, can have footprints covering 10% of the landscape (Raynolds et al 2020 ). Mitigating the impacts of over-snow travel and/or associated seismic pulses has received considerable attention for polar bears ( Ursus maritimus ) and ringed seals, which have similar reproductive phenology and denning requirements (Kelly et al 2010 ; Wilson and Durner 2020 ; Owen et al 2021 ). Observations of wolverine den abandonment following interaction with humans indicate that this species may be susceptible to these disturbances (Glass et al In press ).…”