Den phenology and reproductive success of polar bears in a changing climate

Rode, Karyn D.; Olson, Jay; Eggett, Dennis L.; Douglas, David C.; Durner, George M.; Atwood, Todd C.; Regehr, Eric V.; Wilson, Ryan R.; Smith, Tom S.; Martin, Michelle St.

doi:10.1093/jmammal/gyx181

Cited by 32 publications

(50 citation statements)

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“…Because seismic surveys in Arctic regions occur in winter so that potential effects on tundra are minimized (National Research Council 2003), they overlap temporally with the period when female polar bears are in maternal dens giving birth and raising altricial young (Rode et al 2018). Disturbance to denning females before they give birth is not thought to cause significant effects to fitness because bears can re-den elsewhere (Amstrup 1993, Linnell et al 2000.…”

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confidence: 99%

“…cubs from the harsh winter environment before they are capable of effective thermoregulation (Blix and Lentfer 1979). The consequences of disturbance post-birth can cause den abandonment or early emergence, leading to decreased cub survival (Elowe and Dodge 1989, Amstrup and Gardner 1994, Rode et al 2018. Conversely, in the absence of abandonment, a severely disturbed denning bear may experience a prolonged (i.e., 2-3 weeks) elevated heart rate, which could increase energetic costs (Evans et al 2016), and thereby reduce maternal energy stores necessary for cub production (Atkinson and Ramsay 1995).…”

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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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Seismic Survey Design and Effects on Maternal Polar Bear Dens

Wilson

Durner

2019

J Wildl Manag

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“…Thus, despite an initial greater energetic cost to move to land in the summer, our results suggest there is an overall energetic benefit to summer land‐use rather than remaining on the receding sea ice. This overall energetic benefit may be reflected in the greater reproductive success of females denning on land relative to females denning on the sea ice (Rode et al ). However, because our accelerometers stopped recording prior to sea ice return, we were unable to evaluate the difference in energetic costs between habitats in the late autumn and winter.…”

Section: Discussionmentioning

confidence: 99%

The seasonal energetic landscape of an apex marine carnivore, the polar bear

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Atwood

Durner

et al. 2020

Ecology

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Divergent movement strategies have enabled wildlife populations to adapt to environmental change. In recent decades, the Southern Beaufort Sea subpopulation of polar bears (Ursus maritimus) has developed a divergent movement strategy in response to diminishing sea ice where the majority of the subpopulation (73–85%) stays on the sea ice in summer and the remaining bears move to land. Although declines in sea ice are generally considered a challenge to energy balance in polar bears residing in some regions of the Arctic, little quantitative data exists concerning the seasonal energy expenditures of this apex marine carnivore. We used GPS satellite collars with tri‐axial accelerometers and conductivity sensors to measure the location, behavior, and energy expenditure of five adult female polar bears in the southern Beaufort Sea across seasons of sea ice breakup and minimum extent. Using a Bayesian mixed‐effects model, we found that energy expenditure was influenced by month, ocean depth, and habitat type (sea ice or land). Total energy expenditure from May through September ranged from 37.7 to 47.2 mJ/kg for individual bears. Bears that moved to land expended 7% more energy on average from May through September than bears that remained on the receding sea ice. In August, when bears were moving from the sea ice to land or moving north with the receding pack ice, bears that moved to land spent 7% more time swimming and expended 22% more energy. This means the immediate cost of moving to land exceeded the cost of remaining on the receding summer pack ice. These findings suggest a physiological reason why the majority of the Southern Beaufort Sea subpopulation continues to inhabit a diminishing summer ice platform. However, bears that moved to land spent 29% more time in preferred hunting habitats over the continental shelf than bears that remained on the sea ice. Bears on land also had access to subsistence‐harvested bowhead whale carcasses. Hence, our findings indicate there may be a greater overall energetic benefit to move to land in this region, which suggests that the use of the diminishing summer sea ice may be functioning as an ecological trap.

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“…From the data in Table A1 we can assume that the proportion of adult females with coy (PAFC0) represents the proportion of females that denned in a given winter minus any litters that were lost between den emergence and subsequent capture that spring and minus females that emerged from dens without cubs. The results of Rode et al (2018) provide an estimate of the proportion of females denning in the Southern Beaufort Sea (SBS) population that were observed with ≥1 coy ≤100 days after emergence. We relied on data from 2000 onward for adult female bears in the SBS population that had known denning status and that were recaptured ≤100 days after emergence (Rode et al 2018) to correspond with the timeframe of the capture data.…”

Section: New Calculation Methodsmentioning

confidence: 99%

“…The results of Rode et al (2018) provide an estimate of the proportion of females denning in the Southern Beaufort Sea (SBS) population that were observed with ≥1 coy ≤100 days after emergence. We relied on data from 2000 onward for adult female bears in the SBS population that had known denning status and that were recaptured ≤100 days after emergence (Rode et al 2018) to correspond with the timeframe of the capture data. There were 43 observations in this dataset, and of those, 30 were captured with ≥1 coy.…”

Section: New Calculation Methodsmentioning

confidence: 99%

Erratum

2020

J Wildl Manag

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ERRATUM Wilson, R. R., and G. M. Durner. 2020. Seismic survey design and effects on maternal polar bear dens. Journal of Wildlife Management 84:201-212.Since the publication of this manuscript, readers have noted 2 errors in our analysis. Here, we describe the errors and the changes to the supplemental code that will remedy them. The changes do not affect either the resulting expected number of maternal polar bear dens in the 1002 Area (20 dens) or the relative effects of the scenarios explored in the original manuscript.The first error is that we inadvertently stated that the forward looking infrared (FLIR) survey simulations only represented a single FLIR survey. In reality, the analysis assumed 2 independent FLIR surveys occurred before simulated seismic activity occurred. Thus, when we reference a single FLIR survey in the text, this represents 2 FLIR surveys prior to seismic activity in the simulations. To evaluate the results for a single FLIR survey, readers can simply modify line 41 of the R code (file jwmg21800-sup-0006-missed.dens.funcAnalysis.R in the Supporting Information) to read p2 = 0 and re-run the analysis.

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Den phenology and reproductive success of polar bears in a changing climate

Cited by 32 publications

References 54 publications

Seismic Survey Design and Effects on Maternal Polar Bear Dens

Seismic Survey Design and Effects on Maternal Polar Bear Dens

The seasonal energetic landscape of an apex marine carnivore, the polar bear

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