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Forward-looking infrared image of two polar bear dens in the snow bank on the south shore of an Alaskan coastal island. Also note hotspots created by exposed tundra and warmth radiating up from sea ice with a thin covering of snow. https://doi.org/10.1371/journal.pone.0222744.g002
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Denned polar bears (Ursus maritimus) are invisible under the snow, therefore winter-time petroleum exploration and development activities in northern Alaska have potential to disturb maternal polar bears and their cubs. Previous research determined forward looking infrared (FLIR) imagery could detect many polar bear maternal dens under the snow, bu...
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... potential targets in this environment (e.g. cracks in sea ice, exposed soil, large rocks, or some manmade objects like abandoned 55-gallon steel drums) collect and reradiate heat differently than snow covered ground, and can emit thermal signals similar to those from dens (Fig 2). Hotspots with the "right" signature [9], detected during surveys, were marked as putative maternal dens. ...
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... The other emerging opportunity for passive detection is forward-looking infrared radar (Smith et al., 2020), which can detect the infrared signatures of animals that might be otherwise unobserved or unobservable by operators. Recent advances pair this detection technique with machine-learning to process the datastream to reduce the probability of false positives. ...
HeliCat Canada members operating in mountain caribou range have been collecting and reporting wildlife sightings data since 2010, resulting in more than 3,750 spatially referenced sightings of animals and tracks by the end of the 2022 operating season. Mountain caribou, mountain goats, and wolverine have been the most commonly recorded species, with caribou observations generally declining over time, mountain goat sightings showing no trend, and observations of wolverines and their tracks increasing. No reaction and Unconcerned are the most common responses of caribou and mountain goats to encounters with helicopters or skiers. Behavioural responses are generally stronger at shorter encounter distances, but responses remain variable, with some animals still showing No reaction or an Unconcerned response to close encounters. Recorded responses to skiers tend to be stronger than to helicopters, particularly among caribou. The number and proportion of Alarmed or Very alarmed responses to encounters was higher in early years of monitoring but has been stable since about 2014. Evidence suggesting that HeliCat activities are causing population declines of mountain caribou or mountain goats is lacking. Opportunities to further reduce risk include: improved habitat mapping, expanded monitoring and reporting, telemetry data sharing, and passive detection of wildlife. However, the benefits of all of these approaches are also currently associated with a variety of limitations.
... In the context of distance sampling, counts obtained from visual surveys on aerial platforms assume perfect detection along either the transect line or the distance at which left truncation is specified (Laake et al. 2008). We used a vertical-looking infrared (VLIR) platform coupled with highresolution color video in an attempt to meet this assumption more readily than when sampling with observers counting from the sides of fixed-wing aircraft (Caughley andGrice 1982, Fleming andTracey 2008) or when using forwardlooking infrared (FLIR) cameras that increase distance and vegetative obstruction between the thermographer and animals (Bernatas and Nelson 2004, Storm et al. 2011, Smith et al. 2020). Vertical-looking infrared permits detection of deer directly beneath the aerial platform (Kissell and Nimmo 2011). ...
Density estimates for animal populations often inform conservation and management decisions. Many methods to estimate animal density exist but deciding between competing alternatives traditionally has depended upon assessing multiple factors (e.g., precision, total cost, area sampled) independently and often in an ad hoc manner. Cost‐effectiveness analysis is a tool that economists use to decide objectively between competing alternatives. We extend cost‐effectiveness analysis to simultaneously integrate precision and per‐area cost of sampling when selecting between competing techniques used to estimate animal density both after a single application of a method and across several applications of capital equipment. Our extension allows for weighting of factors that may vary with the objectives and constraints of decision makers. We apply our extension of cost‐effectiveness analysis to a case study in which population density of white‐tailed deer (Odocoileus virginianus) was estimated in 3 large management units in Indiana, USA, using 3 competing distance‐sampling methods: fecal‐pellet, camera‐trap, and aerial sampling. The unweighted cost effectiveness of aerial sampling with color and infrared sensors was usually superior after a single application of each method and was always superior across several applications in differing landscapes. Pellet sampling was the most cost effective after a single application of each method in an agriculturally‐dominated management unit. Although camera sampling has increased in popularity, the cost effectiveness of camera sampling was poorer than the other 2 methods, even when allowing for potential future innovations to streamline data processing. Cost‐effectiveness analysis can be useful when selecting among competing methods for monitoring animal populations of conservation and management importance. The same principles used in our cost‐effectiveness analysis can be used to decide between competing alternatives related to any ecological monitoring in addition to density estimation. Management requiring estimates of density must decide between the many density‐estimation methods that are currently available. We present a simple extension of cost‐effectiveness analysis to help guide this decision.
... One major advantage of these vehicles is the capability of flying at much lower altitudes compared to crewed aircraft, which helps to increase video quality and thus reduce misidentification and perception errors . If battery life is of no concern, some researchers have even reduced altitude upon detection of a potential heat signature in non-forested habitats, and honed in for more certain confirmation (Smith et al., 2020). Furthermore, crewed aerial vehicle accidents account for 66% of wildlife biologist deaths while on the job (Sasse, 2003). ...
... Geographic coordinates of all other objects or animals can then be compared to those of the target individuals, and used to count misidentification errors (Corcoran et al., 2019). Other researchers have reduced the altitude of an uncrewed aircraft (Bushaw et al., 2019;Smith et al., 2020), or circled a crewed aircraft (Gillette et al., 2015), to confirm IR heat signatures as the target species. Circling or altitude-reduction strategies may not be feasible for large-scale spatial sampling of common species, as time expenditures would drastically increase. ...
Aerial vehicles equipped with infrared thermal sensors facilitate quick density estimates of wildlife, but detection error can arise from the thermal sensor and viewer of the infrared video. We reviewed published research to determine how commonly these sources of error have been assessed in studies using infrared video from aerial platforms to sample wildlife. The number of annual articles pertaining to aerial sampling using infrared thermography has increased drastically since 2018, but past studies inconsistently assessed sources of imperfect detection. We illustrate the importance of accounting for some of these types of error in a case study on white-tailed deer Odocoileus virginianus in Indiana, USA, using a simple double-observer approach. In our case study, we found evidence of false negatives associated with the viewer of infrared video. Additionally , we found that concordance between the detections of two viewers increased when using a red-green-blue camera paired with the infrared thermal sensor, when altitude decreased and when more stringent criteria were used to classify thermal signatures as deer. We encourage future managers and ecologists recording infrared video from aerial platforms to use double-observer methods to account for viewer-induced false negatives when video is manually viewed by humans. We also recommend combining infrared video with red-green-blue video to reduce false positives, applying stringent verification standards to detections in infrared and red-green-blue video and collecting data at lower altitudes over snow when needed.
... Local-scale variables are average values for a 50-km radius around each den location (snow depth) or a 50-km radius around the nearest point on the coast (for all sea ice concentration variables). surveys based on imperfect and unknown detection probability, such as those using forward looking infrared sensors (FLIR;Smith et al. 2020). ...
Although polar bears (Ursus maritimus) of the Southern Beaufort Sea (SBS) subpopulation have commonly created maternal dens on sea ice in the past, maternal dens on land have become increasingly prevalent as sea ice declines. This trend creates conditions for increased human–bear interactions associated with local communities and industrial activity. Maternal denning is a vulnerable period in the polar bear life cycle, and den disturbance could lead to den abandonment, cub mortality, and negative population impacts. We used published long‐term data to parameterize a Bayesian hierarchical model of annual land den abundance during 2000–2015, in 4 regions of northern Alaska, USA, with current or potential future oil and gas activity. We also estimated long‐term (1982–2015) shifts in the spatial distribution of land dens within and among regions using kernel density estimation and assessed the influence of local and regional sea ice and snow conditions on den site selection using a random forest resource selection function. Our objectives were to quantify current den distribution and abundance, test for distributional shifts over time, and investigate if those shifts could be attributed to environmental variables related to den habitat. We estimated that between 2000 and 2015, the SBS contained a median 123 dens in a typical year, of which 68 occurred on land. The region between the Colville and Canning rivers, where most current oil and gas activity occurred, also contained the largest fraction of land dens. Overall, land dens were disproportionately concentrated on barrier islands and on land within 30 km of the coast. The probability of dens occurring on land varied from 1982–1999 to 2000–2015 in all regions, and the overall distribution of land dens shifted west between those periods. This regional‐scale change in den distribution was predictable based on spatial and temporal heterogeneity in snow and sea ice conditions within 50 km of individual den locations. Land denning is likely to become increasingly common with continued sea ice loss, and our results and modeling framework could be used to design additional mitigation strategies for reducing the risk of incidental take due to den disturbance. The distribution of land‐based polar bear maternal dens in the Southern Beaufort Sea subpopulation shifted westward over 3 decades (1982–2015). In recent years land dens were most abundant in the region between the Colville and Canning rivers, where most current oil and gas activity occurs but were concentrated on barrier islands and land within a few kilometers of the coast. Understanding the likely distribution of maternal dens can help local communities and industry reduce the risk of accidental den disturbance.
... Previous studies have evaluated the effectiveness of IR surveys to detect polar bear and grizzly bear (Ursus arctos) dens using handheld (Robinson et al. 2014 rates for polar bear dens ranged from an average of 45% to nearly 90% under optimal survey conditions ). Comparison of these 2 studies is not straightforward, however, as the detection estimate by Smith et al. (2020) was derived from a single industry-led, fixed-wing aircraft survey with a flight crew naïve to the presence of, or location of, dens. The estimate from Amstrup et al. (2004), on the other hand, was derived from 67 helicopter flights over 23 dens whose general locations were known to flight crews. ...
The need to balance economic development with impacts to Arctic wildlife has been a prominent subject since petroleum exploration began on the North Slope of Alaska, USA, in the late 1950s. The North Slope region includes polar bears (Ursus maritimus) of the southern Beaufort Sea subpopulation, which has experienced a long‐term decline in abundance. Pregnant polar bears dig dens in snow drifts during winter and are vulnerable to disturbance, as den abandonment and mortality of neonates may result. Maternal denning coincides with the peak season of petroleum exploration and construction, raising concerns that human activities may disrupt denning. To minimize disturbance of denning polar bears, aerial infrared (AIR) surveys are routinely used to search for dens within planned industry activity areas and that information is used to implement mitigation. Aerial infrared surveys target the heat signature emanating from dens. Despite use by industry for >15 years, the efficacy of AIR and the factors that impact its ability to detect dens remains uncertain. Here, we evaluate AIR using artificial dens and observers naïve to locations to estimate detection probability and its relationship with covariates including weather variables, den characteristics, infrared sensor and altitude, and survey order to identify potential evidence of in‐flight observer learning occurring between surveys. In December 2019 we constructed 14 dens (each with an artificial heat source), and 11 control sites (disturbed sites without dens). Between December 2019 and January 2020, 3 survey crews flew 6 independent AIR surveys within the vicinity of dens and control sites and video‐recorded AIR imagery. Observers identified putative dens either in flight or during post‐flight review of recordings. We assessed detection probability with a simple Bayesian model using 3 subsets of data: 1) all detection/non‐detection data; 2) detection/non‐detection data restricted to instances where sample sites were confirmed to have been properly scanned by AIR during post‐study verification (i.e., when den locations were known); and 3) all dens visible on the recorded imagery during post‐study verification, even if they were not seen during the survey or during post‐flight review. Subsets 1 and 2 most closely resembled den surveys flown for oil and gas industry and had detection probabilities of 0.15 (95% CI = 0.08–0.23) and 0.24 (95% CI = 0.13–0.37), respectively. Detection probability was 0.41 (95% CI = 0.25–0.58) for subset 3. Higher wind speeds and larger den volume negatively influenced detection probability. Our low detection rate compared to previous studies could partially be the result of differences in study design, such as survey flight patterns. Our results suggest that AIR, as it is currently used, is unlikely to detect most polar bear dens in surveyed areas. Resource managers who use AIR should consider a suite of additional methods (e.g., habitat mapping, probabilistic den distribution, AIR methodology improvements) for minimizing impacts of industry on denning polar bears. We evaluated the efficacy of aerial infrared surveys using artificial dens and observers naïve to den locations to estimate den detection probability. Our results suggest that aerial infrared surveys are unlikely to detect most polar bear dens in surveyed areas. Resource managers who use AIR should consider additional methods for minimizing impacts of industry on denning polar bears.
Climate-induced sea-ice loss represents the greatest threat to polar bears (Ursus maritimus Phipps, 1774), and utilizing drones to characterize behavioural responses to sea-ice loss is valuable for forecasting polar bear persistence. In this manuscript, we review previously published literature and draw on our own experience of using multirotor aerial drones to study polar bear behaviour in the Canadian Arctic. Specifically, we suggest that drones can minimize human–bear conflicts by allowing users to observe bears from a safe vantage point; produce high-quality behavioural data that can be reviewed as many times as needed and shared with multiple stakeholders; and foster knowledge generation through co-production with northern communities. We posit that in some instances drones may be considered as an alternative tool for studying polar bear foraging behaviour, interspecific interactions, human–bear interactions, human safety and conflict mitigation, and den-site location at individual-level small spatial scales. Finally, we discuss flying techniques to ensure ethical operation around polar bears, regulatory requirements to consider, and recommend that future research focus on understanding polar bears’ behavioural and physiological responses to drones and the efficacy of drones as a deterrent tool for safety purposes.
Captive polar bears (Ursus maritimus) are well-documented as being prone to behavioural disorders and, as a result, their welfare is the cause of increasing concern. There is therefore a need for an evidence-based approach to the assessment of the welfare of this species and identification of valid welfare indicators is the first step towards achieving this. To this end, a critical evaluation of peer-reviewed literature was undertaken. Searches of Web of Science and Scopus took place in May 2020 for publications relevant to the welfare of captive polar bears which met inclusion criteria. Further, validity of extracted indicators was assessed via investigation of evidence of content, construct and criterion validity along with strength of evidence at publication-level. Database searches and snow-balling unearthed 46 publications included for review. Identified indicators were sorted into nine behavioural, four physiological (based on physiological or biological sampling) and five physical (based on visual inspection) categories. Among behavioural indicators, the strongest evidence of validity was found for abnormal behaviour. For the physiological indicators, validity was only established for faecal glucocorticoid metabolite concentration. Content validity was assumed for all physical indicators. Generalisability and strength of evidence was generally compromised by low sample sizes and experimental limitations, and only a small number of papers investigated welfare indicators directly, resulting in a paucity of validated indicators. Potential welfare indicators that warrant further validation are highlighted. Overall, this review provides an overview of current valid and promising welfare indicators along with identified gaps in knowledge, relevant for the provision of a methodology for assessing and monitoring welfare of captive polar bears.
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.
