Factors Influencing the Efficacy of Forward-Looking Infrared in Polar Bear Den Detection

Robinson, Rusty; Smith, Tom S.; Larsen, Randy T.; Kirschhoffer, BJ

doi:10.1093/biosci/biu095

Cited by 8 publications

(29 citation statements)

References 7 publications

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“…Estimates of FLIR efficacy also reflect only those dens that are available to be detected. Depth of snow covering a den can significantly affect the probability that FLIR will be able to detect a den (Robinson et al 2014). Using artificial dens of varying depth, Robinson et al (2014) observed that dens with snow depth >100 cm were not detectable with handheld FLIR devices.…”

Section: Den Detectionmentioning

confidence: 99%

“…Depth of snow covering a den can significantly affect the probability that FLIR will be able to detect a den (Robinson et al 2014). Using artificial dens of varying depth, Robinson et al (2014) observed that dens with snow depth >100 cm were not detectable with handheld FLIR devices. Although Amstrup et al (2004) was able to detect all dens at least once during their multiple surveys, all dens surveyed had snow depths <100 cm.…”

Section: Den Detectionmentioning

confidence: 99%

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Seismic Survey Design and Effects on Maternal Polar Bear Dens

Wilson

Durner

2019

J Wildl Manag

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Large‐scale industrial activities can have negative effects on wildlife populations. Some of these effects, however, could be reduced with effective planning prior to development. The Coastal Plain of the Arctic National Wildlife Refuge, in northeastern Alaska, USA, is an important maternal denning area for polar bears (Ursus maritimus). Recent legislation has opened the area for potential oil and gas development. As a result, there is interest in conducting winter seismic surveys across the area that could disturb denning female polar bears and lead to decreased cub survival. We sought to demonstrate how different seismic survey designs, with and without aerial den detection surveys, could affect the level of potential effect on denning polar bears during spring (Feb–Apr). We developed 5 hypothetical seismic survey designs for a portion of the Coastal Plain ranging from no spatial or temporal restrictions on activities to explicit consideration of when and where operations can occur. We evaluated how many dens might be disturbed by seismic surveys and the average distance activity came within simulated polar bear dens. Survey design had a large effect on the estimated number of dens that could be disturbed; the scenario with the highest spatial and temporal specificity reduced the number of dens disturbed by >90% compared to the scenario with no restrictions on when and where activity could occur. The use of an aerial den detection survey prior to seismic activity further reduced the number of dens disturbed by 68% across all scenarios. The scenario with the highest spatial and temporal specificity always had the lowest level of disturbance for all scenarios with and without the aerial survey included. Our study suggests that large reductions in the probability of disturbance can occur through careful planning on the timing and distribution of proposed activities even when surveys are planned in areas with a high density of polar bear dens. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

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Section: Den Detectionmentioning

confidence: 99%

Section: Den Detectionmentioning

confidence: 99%

Seismic Survey Design and Effects on Maternal Polar Bear Dens

Wilson

Durner

2019

J Wildl Manag

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“…Aerial and handheld FLIR camera platforms have been evaluated to detect occupied and human-made artificial polar bear and grizzly bear dens (Amstrup et al, 2004;Robinson, Smith, Larsen, & Kirschhoffer, 2014;Shideler & Perham, 2013). Each of these previous studies revealed limitations on the effectiveness of FLIR cameras under varying ambient conditions that may influence odds of detection (detection).…”

Section: Introductionmentioning

confidence: 99%

Effects of environmental conditions on the use of forward‐looking infrared for bear den detection in the Alaska Arctic

Pedersen

Brinkman

Shideler

et al. 2020

Conservat Sci and Prac

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Industrial off-road activity in winter overlaps denning habitat of polar bear (Ursus maritimus) and grizzly bear (Ursus arctos) in the North Slope oilfields of Alaska (United States). To prevent disturbance of dens, managers have used forward-looking infrared (FLIR) cameras to detect dens, but the effectiveness of FLIR under different environmental conditions is unresolved. Our objective was to evaluate the effects of environmental variables on FLIR-based techniques for arctic bear den detection. Using a FLIR-equipped unmanned aircraft system (UAS), we conducted observations of artificial polar bear (APD) and grizzly bear (AGD) dens from horizontal and vertical perspectives between December 2016 and April 2017. We recorded physical characteristics of artificial dens and weather conditions present during each observation. We captured 291 images and classified each as detection or nondetection based on the number of pixels representative of a den "hot spot." We used logistic regression to model the effects of four weather variables on the odds of detection (detection). We found that UAS-FLIR detects APDs two times better than AGDs, and that for both species detections are four times more likely from the vertical than horizontal perspective. Lower air temperature and wind speed, and the absence of precipitation and sunlight increased detection for APDs. A 1 C increase in air temperature lowered detection by 12% for APDs and by 8% for AGDs. We recommend that UAS-FLIR surveys be conducted early in the denning season, on cold, clear days, with calm winds, in the absence of sunlight (e.g., civil twilight). Our study further refines the application of FLIR techniques for arctic bear den detection and offers practical recommendations for optimizing detection. Putative den locations should be confirmed by a secondary method to minimize disturbance as anthropogenic activity continues in the Arctic.

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“…We arranged dens linearly relative to one another and we separated each by approximately 7.6 m. We configured dens to mimic the internal dimensions of an average single‐chambered polar bear den (79 cm height, 148 cm length, and 127 cm width, Durner et al 2003). Similar to Robinson et al (2014), we used a 200‐watt ceramic heater in each den to simulate the heat generated by a denning polar bear. To assess the influence of snow depth and denning stage on noise reception, we varied 2 characteristics of the den configuration: roof thickness and the presence of an egress opening.…”

Section: Methodsmentioning

confidence: 99%

“…Study site near Milne Point, Alaska, USA, where we made acoustics measurements inside 4 artificial polar bear snow dens in 2010. Robinson et al [2014] provides details on den excavation). We arranged dens linearly relative to one another and we separated each by approximately 7.6 m. We configured dens to mimic the internal dimensions of an average singlechambered polar bear den (79 cm height, 148 cm length, and 127 cm width, Durner et al 2003).…”

Section: Methods Artificial Dens and Noise Measurementsmentioning

confidence: 99%

Estimating the Audibility of Industrial Noise to Denning Polar Bears

Owen

Pagano

Wisdom³

et al. 2020

J Wildl Manag

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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.

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Factors Influencing the Efficacy of Forward-Looking Infrared in Polar Bear Den Detection

Cited by 8 publications

References 7 publications

Seismic Survey Design and Effects on Maternal Polar Bear Dens

Seismic Survey Design and Effects on Maternal Polar Bear Dens

Effects of environmental conditions on the use of forward‐looking infrared for bear den detection in the Alaska Arctic

Estimating the Audibility of Industrial Noise to Denning Polar Bears

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