Integrated Population Modeling Provides the First Empirical Estimates of Vital Rates and Abundance for Polar Bears in the Chukchi Sea

Hunting quotas are used to manage populations of game species in order to ensure sustainable exploitation. However, unpredictable climatic events may interact with hunting. We established a population model for European hares (Lepus europaeus) in Lower Austria. We compared the sustainability of voluntary quotas used by hunters—which are derived from hare-specific guidelines—with the actual numbers of hares shot and our recommended quotas for hares, which have been derived from climate and population modeling. We used population modeling based on vital rates and densities to adjust our recommended quotas in order to achieve sustainable harvest. The survival of age classes 1 and 3 had the highest impact on the population growth rate. Population viability analysis showed that a recommended quota with a harvest rate of 10% was sustainable for population densities of 45 hares/km2, and that the threshold for hunting should be raised from 10 hares/km2 so that hare populations with <15 hares/km2 are not hunted. The recommended quota outperformed the voluntary hunting quota, since more hares could be harvested sustainably. Age Class 1 survival was strongly linked with weather: a single year with unfavorable weather conditions (low precipitation) negatively affected population densities. Game species, including the European hare, face increasingly frequent weather extremes due to climate change, so hunting quotas need to be sensitive to frequent population fluctuations.

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Geographic variation of PCB congeners in polar bears (Ursus maritimus) from Svalbard east to the Chukchi Sea

Polar Biology ◽

10.1007/s003000000201 ◽

2001 ◽

Vol 24 (4) ◽

pp. 231-238 ◽

Cited By ~ 60

Author(s):

M. Andersen ◽

E. Lie ◽

A.E. Derocher ◽

S.E. Belikov ◽

A. Bernhoft ◽

...

Keyword(s):

Geographic Variation ◽

Chukchi Sea ◽

Ursus Maritimus ◽

Polar Bears ◽

Pcb Congeners

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Polar Bear (Ursus maritimus) Behavior near Icebreaker Operations in the Chukchi Sea, 1991

ARCTIC ◽

10.14430/arctic4566 ◽

2016 ◽

Vol 69 (2) ◽

Cited By ~ 2

Author(s):

Mari A. Smultea ◽

Jay Brueggeman ◽

Frances Robertson ◽

Dagmar Fertl ◽

Cathy Bacon ◽

...

Keyword(s):

Climate Change ◽

Human Activity ◽

Polar Bear ◽

Chukchi Sea ◽

Group Behavior ◽

Ursus Maritimus ◽

The Arctic ◽

Polar Bears ◽

Running Away ◽

Significant Difference

Increasing interactions of polar bears (Ursus maritimus) with human activity, combined with impacts of climate change, are of critical concern for the conservation of the species. Our study quantifies and describes initial reactions and behaviors of polar bears observed from an icebreaker during summer 1991 at two exploratory drilling sites (near sites drilled in 2015) located in the Chukchi Sea 175 km and 312 km west of Barrow, Alaska. Polar bear behavior was described using continuous sampling of six predetermined focal group behavior states (walking, running, swimming, resting, feeding or foraging, unknown) and six behavioral reaction events (no reaction, walking away, running away, approaching, vigilance [i.e., watching], unknown). Forty-six bears in 34 groups were monitored from the Robert LeMeur (an Arctic Class 3 icebreaker) for periods of five minutes to 16.1 hours. Significantly more bear groups reacted to icebreaker presence (79%) than not (21%), but no relationship was found between their reactions and distance to or activity of the icebreaker. Reactions were generally brief; vigilance was the most commonly observed reaction, followed by walking or running away for short (< 5 minutes) periods and distances (< 500 m). Eleven percent of bear groups approached the vessel. No significant difference was found between reactions when cubs were present and those when cubs were absent. Despite the limited sample sizes, these findings are relevant to assessing potential impacts of resource development and shipping activities on polar bears, especially given the sparsity of such information in the face of growing human activity in the Arctic offshore areas. Overall, climate change is leading to longer and more extensive open-water seasons in the Arctic and therefore to increasing marine traffic—more vessels (including icebreakers) for a longer time each year over a wider area.

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Invariant polar bear habitat selection during a period of sea ice loss

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.0380 ◽

2016 ◽

Vol 283 (1836) ◽

pp. 20160380 ◽

Cited By ~ 12

Author(s):

Ryan R. Wilson ◽

Eric V. Regehr ◽

Karyn D. Rode ◽

Michelle St Martin

Keyword(s):

Habitat Selection ◽

Sea Ice ◽

Polar Bear ◽

Chukchi Sea ◽

Population Level ◽

Polar Bears ◽

Population Declines ◽

Before And After ◽

Productive Water ◽

Primary Driver

Climate change is expected to alter many species' habitat. A species' ability to adjust to these changes is partially determined by their ability to adjust habitat selection preferences to new environmental conditions. Sea ice loss has forced polar bears ( Ursus maritimus ) to spend longer periods annually over less productive waters, which may be a primary driver of population declines. A negative population response to greater time spent over less productive water implies, however, that prey are not also shifting their space use in response to sea ice loss. We show that polar bear habitat selection in the Chukchi Sea has not changed between periods before and after significant sea ice loss, leading to a 75% reduction of highly selected habitat in summer. Summer was the only period with loss of highly selected habitat, supporting the contention that summer will be a critical period for polar bears as sea ice loss continues. Our results indicate that bears are either unable to shift selection patterns to reflect new prey use patterns or that there has not been a shift towards polar basin waters becoming more productive for prey. Continued sea ice loss is likely to further reduce habitat with population-level consequences for polar bears.

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Microsatellite DNA and mitochondrial DNA variation in polar bears (Ursus maritimus) from the Beaufort and Chukchi seas, Alaska

Canadian Journal of Zoology ◽

10.1139/z06-039 ◽

2006 ◽

Vol 84 (5) ◽

pp. 655-660 ◽

Cited By ~ 20

Author(s):

M.A. Cronin ◽

S.C. Amstrup ◽

K.T. Scribner

Keyword(s):

Mitochondrial Dna ◽

Microsatellite Dna ◽

Chukchi Sea ◽

Genetic Data ◽

Beaufort Sea ◽

Ursus Maritimus ◽

Polar Bears ◽

Dna Variation ◽

Movement Data ◽

Mtdna Haplotype

Radiotelemetry data have shown that polar bears ( Ursus maritimus Phipps, 1774 ) occur in separate subpopulations in the Chukchi Sea and the southern Beaufort Sea. However, segregation is not absolute, and there is overlap of ranges of animals in each subpopulation. We used genetic variation at eight microsatellite DNA loci and mitochondrial DNA (mtDNA) to further assess the degree of spatial structure of polar bears from the Chukchi and southern Beaufort seas. Microsatellite allele frequencies and mtDNA haplotype frequencies of bears from the southern Beaufort and Chukchi seas did not differ significantly. Lack of differentiation at both maternally inherited mtDNA and bi-parentally inherited microsatellite loci suggests that gene flow between the two areas is mediated by both sexes. The genetic data indicate that polar bears in the southern Beaufort and Chukchi seas compose one interbreeding population. However, there is considerable fidelity to ranges in each area, particularly by adult females. The combined genetic and movement data suggest that polar bears could be managed as Beaufort Sea and Chukchi Sea subpopulations of a combined southern Beaufort Sea and Chukchi Sea population.

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Using simulation to evaluate wildlife survey designs: polar bears and seals in the Chukchi Sea

Royal Society Open Science ◽

10.1098/rsos.150561 ◽

2016 ◽

Vol 3 (1) ◽

pp. 150561 ◽

Cited By ~ 6

Author(s):

Paul B. Conn ◽

Erin E. Moreland ◽

Eric V. Regehr ◽

Erin L. Richmond ◽

Michael F. Cameron ◽

...

Keyword(s):

Chukchi Sea ◽

Superior Performance ◽

Polar Bears ◽

Arctic Regions ◽

Aerial Surveys ◽

Model Configuration ◽

Simulation Based ◽

Survey Designs ◽

Different Levels ◽

Allocation Strategies

Logistically demanding and expensive wildlife surveys should ideally yield defensible estimates. Here, we show how simulation can be used to evaluate alternative survey designs for estimating wildlife abundance. Specifically, we evaluate the potential of instrument-based aerial surveys (combining infrared imagery with high-resolution digital photography to detect and identify species) for estimating abundance of polar bears and seals in the Chukchi Sea. We investigate the consequences of different levels of survey effort, flight track allocation and model configuration on bias and precision of abundance estimators. For bearded seals (0.07 animals km −2 ) and ringed seals (1.29 animals km −2 ), we find that eight flights traversing ≈7840 km are sufficient to achieve target precision levels (coefficient of variation (CV)<20%) for a 2.94×10 5 km 2 study area. For polar bears (provisionally, 0.003 animals km −2 ), 12 flights traversing ≈11 760 km resulted in CVs ranging from 28 to 35%. Estimators were relatively unbiased with similar precision over different flight track allocation strategies and estimation models, although some combinations had superior performance. These findings suggest that instrument-based aerial surveys may provide a viable means for monitoring seal and polar bear populations on the surface of the sea ice over large Arctic regions. More broadly, our simulation-based approach to evaluating survey designs can serve as a template for biologists designing their own surveys.

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Environmental stochasticity: empirical estimates of prairie vole survival with implications for demographic models

Canadian Journal of Zoology ◽

10.1139/z06-037 ◽

2006 ◽

Vol 84 (5) ◽

pp. 635-642 ◽

Cited By ~ 9

Author(s):

Aaron W. Reed ◽

Norman A. Slade

Keyword(s):

Survival Rates ◽

Natural Populations ◽

Environmental Stochasticity ◽

Population Projections ◽

Time Lags ◽

Vital Rates ◽

Prairie Voles ◽

Demographic Models ◽

Empirical Estimates ◽

Cross Correlations

A rich theory exists regarding the potential impact of correlations among vital rates on population projections derived from demographic models. However, relatively little is known about the magnitude of correlations among vital rates in natural populations, particularly in mammals. We used 30 years of mark–recapture data from a population of prairie voles ( Microtus ochrogaster (Wagner, 1842)) to test for differences in survival among mass classes and sexes, in correlations among vital rates, in correlations between vital rates and environmental factors, and in autocorrelation in vital rates. Estimated monthly survival rates did not differ significantly among mass classes and there were no significant cross-correlations among mass classes. Survival of large prairie voles increased in mild winters (i.e., warm temperatures and low snowfall). Survival rates of medium and large voles were negatively autocorrelated at time lags of 9–12 months, and survivals of large voles were positively autocorrelated for time lags of <3 months. These autocorrelations were not explained by patterns of temperature or precipitation. The observed degree of autocorrelation in vital rates is sufficient to affect projections from demographic models, particularly in short-lived taxa that require seasonal or monthly estimation of vital rates.

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