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At least 1,369 records · Page 76Linked to original sources
USGS2016

A suspended dive-net technique for catching territorial divers

A variety of methods such as night-lighting and lift nets have been used to catch divers (Gavidae), although 24-hour daylight in the Arctic summer and the remote nature of field sites can make the use of these traditional methods impossible. Our research required capture of adult divers at remote locations in northern Alaska. Here we describe a suspended dive-net technique that we used to safely capture territorial White-billed Gavia adamsii and Pacific Divers G. pacifica and that is lightweight and easy to set up. We also were able to capture divers with chicks, and failed breeders, and suggest that this method could be used to catch other territorial aquatic diving birds, especially other diver species.

Ringing and Migration↗
USGS2017

Future of Pacific salmon in the face of environmental change: Lessons from one of the world's remaining productive salmon regions

Pacific salmon Oncorhynchus spp. face serious challenges from climate and landscape change, particularly in the southern portion of their native range. Conversely, climate warming appears to be allowing salmon to expand northwards into the Arctic. Between these geographic extremes, in the Gulf of Alaska region, salmon are at historically high abundances but face an uncertain future due to rapid environmental change. We examined changes in climate, hydrology, land cover, salmon populations, and fisheries over the past 30–70 years in this region. We focused on the Kenai River, which supports world-famous fisheries but where Chinook Salmon O. tshawytscha populations have declined, raising concerns about their future resilience. The region is warming and experiencing drier summers and wetter autumns. The landscape is also changing, with melting glaciers, wetland loss, wildfires, and human development. This environmental transformation will likely harm some salmon populations while benefiting others. Lowland salmon streams are especially vulnerable, but retreating glaciers may allow production gains in other streams. Some fishing communities harvest a diverse portfolio of fluctuating resources, whereas others have specialized over time, potentially limiting their resilience. Maintaining diverse habitats and salmon runs may allow ecosystems and fisheries to continue to thrive amidst these changes.

Alaska↗
USGS2009

Review of fish diversity in the Lake Huron basin

Lake Huron has a rich aquatic habitat diversity that includes shallow embayments, numerous tributaries, shallow mid-lake reef complexes, archipelagos, and profundal regions. These habitats provide support for warm, cool, and cold water fish communities. Diversity of fishes in Lake Huron reflects post-glaciation colonization events, current climate conditions, accidental and intentional introductions of non-indigenous species, and extinctions. Most extinction events have been largely associated with habitat alterations, exploitation of fisheries, and interactions with non-indigenous species. The most recent historical survey of extirpated and imperiled species conducted in the late 1970s identified 79 fish species in Lake Huron proper and about 50 additional species in tributaries. Of those 129 species, 20 are now considered extirpated or imperiled. Extirpated species include Arctic grayling, paddlefish, weed shiner, deepwater cisco, blackfin cisco, shortnose cisco, and kiyi. Six species have declined appreciably due to loss of clear-water stream habitat: the river redhorse, river darter, black redhorse, pugnose shiner, lake chubsucker, redside dace, eastern sand darter, and channel darter. While numerous agencies, universities, and other organizations routinely monitor nearshore and offshore fish distribution and abundance, there is a need for more rigorous examination of the distribution and abundance of less-common species to better understand their ecology. This information is critical to the development of management plans aimed at ecosystem remediation and restoration.

Conference Paper↗
USGS2011

Monitoring a boreal wildfire using multi-temporal Radarsat-1 intensity and coherence images

Twenty-five C-band Radarsat-1 synthetic aperture radar (SAR) images acquired from the summer of 2002 to the summer of 2005 are used to map a 2003 boreal wildfire (B346) in the Yukon Flats National Wildlife Refuge, Alaska under conditions of near-persistent cloud cover. Our analysis is primarily based on the 15 SAR scenes acquired during arctic growing seasons. The Radarsat-1 intensity data are used to map the onset and progression of the fire, and interferometric coherence images are used to qualify burn severity and monitor post-fire recovery. We base our analysis of the fire on three test sites, two from within the fire and one unburned site. The B346 fire increased backscattered intensity values for the two burn study sites by approximately 5–6 dB and substantially reduced coherence from background levels of approximately 0.8 in unburned background forested areas to approximately 0.2 in the burned area. Using ancillary vegetation information from the National Land Cover Database (NLCD) and information on burn severity from Normalized Burn Ratio (NBR) data, we conclude that burn site 2 was more severely burned than burn site 1 and that C-band interferometric coherence data are useful for mapping landscape changes due to fire. Differences in burn severity and topography are determined to be the likely reasons for the observed differences in post-fire intensity and coherence trends between burn sites.

Geomatics, Natural Hazards and Risk↗
USGS2019

Heightened immune system function in polar bears using terrestrial habitats

Climate change is altering the distribution of some wildlife species while warming temperatures are facilitating the northward expansion of pathogens, potentially increasing disease risk. Melting of Arctic sea ice is causing polar bears ( Ursus maritimus ) of the Southern Beaufort Sea (SBS) to increasingly spend summer on land, where they may encounter novel pathogens. Here, we tested whether SBS polar bears on shore during summer exhibited greater immune system activity than bears remaining on the sea ice. In addition, we tested whether the type of immune response correlated with body condition, because adaptive responses (slowly-developing defenses against specific pathogens) often require less energy than innate responses (rapid defenses not based on pathogen identity). After accounting for body condition, we found that polar bears on shore exhibited higher total white blood cell counts, neutrophils, and monocytes than bears on the ice, suggesting greater infections. Lymphocytes, eosinophils, basophils and globulins did not differ. C-reactive protein, an indicator of inflammation, also did not differ between habitats. Body condition was associated with variables indicative of both innate and adaptive immunity, suggesting that neither response was uniquely limited by energy resources. Our data indicate that as more polar bears spend longer periods of time on shore, they may experience more infections. We encourage continued health monitoring of this species and studies of the long-term fitness consequences from disease.

Physiological and Biochemical Zoology↗
USGS2016

Consequences of changes in vegetation and snow cover for climate feedbacks in Alaska and northwest Canada

Changes in vegetation and snow cover may lead to feedbacks to climate through changes in surface albedo and energy fluxes between the land and atmosphere. In addition to these biogeophysical feedbacks, biogeochemical feedbacks associated with changes in carbon (C) storage in the vegetation and soils may also influence climate. Here, using a transient biogeographic model (ALFRESCO) and an ecosystem model (DOS-TEM), we quantified the biogeophysical feedbacks due to changes in vegetation and snow cover across continuous permafrost to non-permafrost ecosystems in Alaska and northwest Canada. We also computed the changes in carbon storage in this region to provide a general assessment of the direction of the biogeochemical feedback. We considered four ecoregions, or Landscape Conservations Cooperatives (LCCs; including the Arctic, North Pacific, Western Alaska, and Northwest Boreal). We examined the 90 year period from 2010 to 2099 using one future emission scenario (A1B), under outputs from two general circulation models (MPI-ECHAM5 and CCCMA-CGCM3.1). We found that changes in snow cover duration, including both the timing of snowmelt in the spring and snow return in the fall, provided the dominant positive biogeophysical feedback to climate across all LCCs, and was greater for the ECHAM (+3.1 W m −2 decade −1 regionally) compared to the CCCMA (+1.3 W m −2 decade −1 regionally) scenario due to an increase in loss of snow cover in the ECHAM scenario. The greatest overall negative feedback to climate from changes in vegetation cover was due to fire in spruce forests in the Northwest Boreal LCC and fire in shrub tundra in the Western LCC (−0.2 to −0.3 W m −2 decade −1 ). With the larger positive feedbacks associated with reductions in snow cover compared to the smaller negative feedbacks associated with shifts in vegetation, the feedback to climate warming was positive (total feedback of +2.7 W m −2 decade regionally in the ECHAM scenario compared to +0.76 W m −2 decade regionally in the CCCMA scenario). Overall, increases in C storage in the vegetation and soils across the study region would act as a negative feedback to climate. By exploring these feedbacks to climate, we can reach a more integrated understanding of the manner in which climate change may impact interactions between high-latitude ecosystems and the global climate system.

Environmental Research Letters↗
USGS2018

Phenological mismatch in coastal western Alaska may increase summer season greenhouse gas uptake

High latitude ecosystems are prone to phenological mismatches due to climate change- driven advances in the growing season and changing arrival times of migratory herbivores. These changes have the potential to alter biogeochemical cycling and contribute to feedbacks on climate change by altering greenhouse gas (GHG) emissions of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) through large regions of the Arctic. Yet the effects of phenological mismatches on gas fluxes are currently unexplored. We used a three-year field experiment that altered the start of the growing season and timing of grazing to investigate how phenological mismatch affects GHG exchange. We found early grazing increased mean GHG emission to the atmosphere despite lower CH 4 emissions due to grazing-induced changes in vegetation structure that increased uptake of CO 2 . In contrast, late grazing reduced GHG emissions because greater plant productivity led to an increase in CO 2 uptake that overcame the increase in CH 4 emission. Timing of grazing was an important control on both CO 2 and CH 4 emissions, and net GHG exchange was the result of opposing fluxes of CO 2 and CH 4 . N 2 O played a negligible role in GHG flux. Advancing the growing season had a smaller effect on GHG emissions than changes to timing of grazing in this study. Our results suggest that a phenological mismatch that delays timing of grazing relative to the growing season, a change which is already developing along in western coastal Alaska, will reduce GHG emissions to the atmosphere through increased CO 2 uptake despite greater CH 4 emissions.

Environmental Research Letters↗
USGS2019

Cloud cover and delayed herbivory relative to timing of spring onset interact to dampen climate change impacts on net ecosystem exchange in a coastal Alaskan wetland

Rapid warming in northern ecosystems over the past four decades has resulted in earlier spring, increased precipitation, and altered timing of plant–animal interactions, such as herbivory. Advanced spring phenology can lead to longer growing seasons and increased carbon (C) uptake. Greater precipitation coincides with greater cloud cover possibly suppressing photosynthesis. Timing of herbivory relative to spring phenology influences plant biomass. None of these changes are mutually exclusive and their interactions could lead to unexpected consequences for Arctic ecosystem function. We examined the influence of advanced spring phenology, cloud cover, and timing of grazing on C exchange in the Yukon–Kuskokwim Delta of western Alaska for three years. We combined advancement of the growing season using passive-warming open-top chambers (OTC) with controlled timing of goose grazing (early, typical, and late season) and removal of grazing. We also monitored natural variation in incident sunlight to examine the C exchange consequences of these interacting forcings. We monitored net ecosystem exchange of C (NEE) hourly using an autochamber system. Data were used to construct daily light curves for each experimental plot and sunlight data coupled with a clear-sky model was used to quantify daily and seasonal NEE over a range of incident sunlight conditions. Cloudy days resulted in the largest suppression of NEE, reducing C uptake by approximately 2 g C m −2 d −1 regardless of the timing of the season or timing of grazing. Delaying grazing enhanced C uptake by approximately 3 g C m −2 d −1 . Advancing spring phenology reduced C uptake by approximately 1.5 g C m −2 d −1 , but only when plots were directly warmed by the OTCs; spring advancement did not have a long-term influence on NEE. Consequently, the two strongest drivers of NEE, cloud cover and grazing, can have opposing effects and thus future growing season NEE will depend on the magnitude of change in timing of grazing and incident sunlight.

Alaska↗
USGS2020

Multi-decadal patterns of vegetation succession after tundra fire on the Yukon-Kuskokwim Delta, Alaska

Alaska’s Yukon-Kuskokwim Delta (YKD) is one of the warmest parts of the Arctic tundra biome and tundra fires are common in its upland areas. Here we combine field measurements, Landsat observations, and quantitative cover maps for tundra plant functional types (PFTs) to characterize multi-decadal succession and landscape change after fire in lichen-dominated upland tundra of the YKD, where extensive wildfires occurred in 1971–1972, 1985, 2006–2007, and 2015. Unburned tundra was characterized by abundant lichens and low lichen cover was consistently associated with historical fire. While we observed some successional patterns that were consistent with earlier work in Alaskan tussock tundra, other patterns were not. In the landscape we studied, a large proportion of pre-fire moss cover and surface peat tended to survive fire, which favors survival of existing vascular plants and limits opportunities for seed recruitment. Although shrub cover was much higher in 1985 and 1971–1972 burns than in unburned tundra, tall shrubs (>0.5 m height) were rare and the PFT maps indicate high landscape-scale variability in the degree and persistence of shrub increase after fire. Fire has induced persistent changes in species composition and structure of upland tundra on the YKD, but the lichen-dominated fuels and thick surface peat appear to have limited the potential for severe fire and accompanying edaphic changes. Soil thaw depths were about 10 cm deeper in 2006–2007 burns than in unburned tundra, but were similar to unburned tundra in 1985 and 1971–1972 burns. Historically, repeat fire has been rare on the YKD, and the functional diversity of vegetation has recovered within several decades post-fire. Our findings provide a basis for predicting and monitoring post-fire tundra succession on the YKD and elsewhere.

Alaska↗
USGS2020

Satellite and airborne remote sensing of gross primary productivity in boreal Alaskan lakes

In terrestrial and marine ecosystems, remote sensing has been used to estimate gross primary productivity (GPP) for decades, but few applications exist for shallow freshwater ecosystems.Here we show field-based GPP correlates with satellite and airborne lake color across a range of optically and limnologically diverse lakes in interior Alaska. A strong relationship between in situ GPP derived from stable oxygen isotopes (δ 18 O) and space-based lake color from satellites (e.g. Landsat-8, Sentinel-2 and CubeSats) and airborne imagery (AVIRIS-NG) demonstrates the potential power of this technique for improving spatial and temporal monitoring of lake GPP when coupled with additional field validation measurements across different systems. In shallow waters clear enough for sunlight to reach lake bottoms, both submerged vegetation (macrophytes and algae) and phytoplankton likely contribute to GPP. The stable isotopes and remotely sensed shallow lake color used here integrate both components. These results demonstrate the utility of lake color as a feasible means for mapping lake GPP from remote sensing. This novel methodology estimates GPP from remote sensing in shallow lakes by combining field measurements of oxygen isotopes with airborne, satellite and CubeSat imagery. This use of lake color for providing insight into ecological processes of shallow lakes is recommended, especially for remote arctic and boreal landscapes.

Alaska↗
USGS2020

Patterns and isotopic composition of greenhouse gases under ice in lakes of interior Alaska

Arctic and boreal lake greenhouse gas emissions (GHG) are an important component of regional carbon (C) budgets. Yet the magnitude and seasonal patterns of lake GHG emissions are poorly constrained, because sampling is limited in these remote landscapes, particularly during winter and shoulder seasons. To better define patterns of under ice GHG content (and emissions potential at spring thaw), we surveyed carbon dioxide (CO 2 ) and methane (CH 4 ) concentrations and stable isotopic composition during winter of 2017 in 13 lakes in the arid Yukon Flats Basin of interior Alaska, USA. Partial pressures of CO 2 and CH 4 ranged over three orders of magnitude, were positively correlated, and CO 2 exceeded CH 4 at all but one site. Shallow, organic matter-rich lakes located at lower elevations tended to have the highest concentrations of both gases, though CH 4 content was more heterogeneous and only abundant in oxygen-depleted lakes, while CO 2 was negatively correlated to oxygen content. Isotopic values of CO 2 spanned a narrow range (−10‰ to −23‰) compared to CH 4 , which ranged over 50‰ (−19‰ to −71‰), indicating CH 4 source pathways and sink strength varied widely between lakes. Miller-Tans and Keeling plots qualitatively suggested two groups of lakes were present; one with isotopically enriched source CH 4 possibly more dominated by acetoclastic methanogenesis, and one with depleted signatures suggesting a dominance of the hydrogenotrophic production. Overall, regional lake differences in winter under ice GHG content appear to track landscape position, oxygen, and organic matter content and composition, causing patterns to vary widely even within a relatively small geographic area of interior Alaska.

Alaska↗
USGS2020

Subsea permafrost carbon stocks and climate change sensitivity estimated by expert assessment

The continental shelves of the Arctic Ocean and surrounding seas contain large stocks of organic matter (OM) and methane (CH 4 ), representing a potential ecosystem feedback to climate change not included in international climate agreements. We performed a structured expert assessment with 25 permafrost researchers to combine quantitative estimates of the stocks and sensitivity of organic carbon in the subsea permafrost domain (i.e. unglaciated portions of the continental shelves exposed during the last glacial period). Experts estimated that the subsea permafrost domain contains ~560 gigatons carbon (GtC; 170–740, 90% confidence interval) in OM and 45 GtC (10–110) in CH 4 . Current fluxes of CH 4 and carbon dioxide (CO 2 ) to the water column were estimated at 18 (2–34) and 38 (13–110) megatons C yr −1 , respectively. Under Representative Concentration Pathway (RCP) RCP8.5, the subsea permafrost domain could release 43 Gt CO 2 -equivalent (CO 2 e) by 2100 (14–110) and 190 Gt CO 2 e by 2300 (45–590), with ~30% fewer emissions under RCP2.6. The range of uncertainty demonstrates a serious knowledge gap but provides initial estimates of the magnitude and timing of the subsea permafrost climate feedback.

Environmental Research Letters↗
USGS1997

Ephemeral lekking behavior in the buff-breasted sandpiper, Tryngites subruficollis

We studied male reproductive behavior of the buff-breasted sandpiper Tryngites subruficoills for three yean on a 16-km 2 study site in northern Alaska to document variation in male lekking behavior and to explore the causes of that variation. During the breeding season, about 75% of males on the study area displayed on leks, with the remainder displaying solitarily. Leks averaged between 2.3 and 3.0 males each (maximum size = 20). Most leks (69%) were present in only one year and about one-tenth were active all three years. Half of the leks were active for only one survey (maximum of 3-4 days) in a given year. Individual male behavior varied substantially, from remaining at a tingle lek for most of the breeding season or attending multiple leks during the season, to displaying solitarily or displaying both on leks and solitarily. Some males (30% or fewer) displayed near nests during the later part of the breeding season, perhaps attempting to copulate with females during egg-laying. The pro-portion of males that displayed on leks remained consistently high throughout the breeding season despite changes in the operational sex ratio and in the intensity of male-male competition. However, the absolute number of males (lekking and solitary) in the study area was positively correlated with the number of fertile females during both breeding seasons. We suggest that buff-breasted sandpipers may be unusual among lek-breeding birds in that males have the option of leaving areas when the number of fertile females becomes depressed and flying to new areas where breeding opportunities are still available. Breeding opportunities may be especially variable in the high arctic because of uneven snow accumulation and differential melt-off that can delay breeding by two or more weeks. This interpretation suggests that the mating system of the buff-breasted sandpiper must be viewed at a much larger scale than what has typically been used in mating system studies.

Alaska↗
USGS2026

Growth, movement, and survival of precocial shorebird chicks are constrained by their environment.

Young animals are often less mobile than adults, while also having high energetic demands. They may therefore be more vulnerable to local-scale changes in environmental conditions. In particular, when 1 sex must grow more rapidly than the other to achieve a larger adult size, that sex may experience especially dramatic reductions in growth and survival in the face of suboptimal environmental conditions. In order to investigate the flexibility of individuals in response to local-scale environmental variation during development, we studied the sex-specific growth, movement, and survival of Hudsonian Godwit ( Limosa haemastica ) chicks—a sexually dimorphic, precocial shorebird that breeds in the sub-Arctic and exhibits a male-skewed adult sex ratio. We found that female chicks—which must grow to a larger adult size—reached their maximum growth rates at a later age, but had similar growth rates to males before that and survived equally well to 21 days. We also found that, irrespective of sex, chicks had reduced movement rates when they were young and/or temperatures were cold, and only weakly increased their movement rates when invertebrate abundances remained low across an entire week. Early in life, godwit chicks may therefore be constrained from increasing their foraging efforts by local environmental conditions, forcing females to sustain higher growth rates late in the season past the local resource peak. Such sex-specific vulnerabilities could lead to lower early-life survival and, in turn, skewed adult sex ratios, which have important implications for population dynamics and persistence.

Behavioral Ecology↗
USGS2014

Capturing migration phenology of terrestrial wildlife using camera traps

Remote photography, using camera traps, can be an effective and noninvasive tool for capturing the migration phenology of terrestrial wildlife. We deployed 14 digital cameras along a 104-kilometer longitudinal transect to record the spring migrations of caribou ( Rangifer tarandus ) and ptarmigan ( Lagopus spp.) in the Alaskan Arctic. The cameras recorded images at 15-minute intervals, producing approximately 40,000 images, including 6685 caribou observations and 5329 ptarmigan observations. The northward caribou migration was evident because the median caribou observation (i.e., herd median) occurred later with increasing latitude; average caribou migration speed also increased with latitude (r 2 = .91). Except at the northernmost latitude, a northward ptarmigan migration was similarly evident (r 2 = .93). Future applications of this method could be used to examine the conditions proximate to animal movement, such as habitat or snow cover, that may influence migration phenology.

Alaska↗
USGS2023

A body composition model with multiple storage compartments for polar bears (Ursus maritimus)

Climate warming is rapidly altering Arctic ecosystems. Polar bears ( Ursus maritimus ) need sea ice as a platform from which to hunt seals, but increased sea-ice loss is lengthening periods when bears are without access to primary hunting habitat. During periods of food scarcity, survival depends on the energy that a bear has stored in body reserves, termed storage energy, making this a key metric in predictive models assessing climate change impacts on polar bears. Here, we developed a body composition model for polar bears that estimates storage energy while accounting for changes in storage tissue composition. We used data of dissected polar bears ( n = 31) to link routinely collected field measures of total body mass and straight-line body length to the body composition of individual bears, described in terms of structural mass and two storage compartments, adipose and muscle. We then estimated the masses of metabolizable proteins and lipids within these storage compartments, giving total storage energy. We tested this multi-storage model by using it to predict changes in the lipid stores from an independent dataset of wild polar bears ( n = 36) that were recaptured 8–200 days later. Using length and mass measurements, our model successfully predicted direct measurements of lipid changes via isotopic dilutions (root mean squared error of 14.5 kg). Separating storage into two compartments, and allowing the molecular composition of storage to vary, provides new avenues for quantifying energy stores of individuals across their life cycle. The multi-storage body composition model thus provides a basis for further exploring energetic costs of physiological processes that contribute to individual survival and reproductive success. Given bioenergetic models are increasingly used as a tool to predict individual fitness and population dynamics, our approach for estimating individual energy stores could be applicable to a wide range of species.

Article↗
USGS2023

Serum virome of southern Beaufort Sea polar bears (Ursus maritimus) during a period of rapid climate change

Climate change affects the behavior, physiology and life history of many Arctic wildlife species. It can also influence the distribution and ecology of infectious agents. The southern Beaufort Sea (SB) subpopulation of polar bears ( Ursus maritimus ) has experienced dramatic behavioral changes due to retreating sea ice and other climate-related factors, but the effects of these changes on physiology and infection remain poorly understood. Using serum from polar bears sampled between 2004 and 2015 and metagenomic DNA sequencing, we identified 48 viruses, all of the family Anelloviridae . Anelloviruses are small, ubiquitous infectious agents with circular single-stranded DNA genomes that are not known to cause disease but, in humans, covary in diversity and load with immunological compromise. We therefore examined the usefulness of anelloviruses as biomarkers of polar bear physiological stress related to climate and habitat use. Polar bear anelloviruses sorted into two distinct clades on a phylogenetic tree, both of which also contained anelloviruses of giant pandas ( Ailuropoda melanoleuca ), another ursid. Neither anellovirus diversity nor load were associated with any demographic variables, behavioral factors or direct physiological measures. However, pairwise genetic distances between anelloviruses were positively correlated with pairwise differences in sampling date, suggesting that the polar bear “anellome”is evolving over time. These findings suggest that anelloviruses are not a sensitive indicator of polar physiological stress, but they do provide a baseline for evaluating future changes to polar bear viromes.

Alaska↗
USGS2019

Reference intervals for blood-based biochemical analytes of southern Beaufort Sea polar bears

Accurate reference intervals (RI) for commonly measured blood-based analytes are essential for health monitoring programs. Baseline values for a panel of analytes can be used to monitor physiologic and pathophysiologic processes such as organ function, electrolyte balance, and protein catabolism. Our reference population includes 651 serum samples from polar bears (Ursus maritimus) from the southern Beaufort Sea subpopulation sampled in Alaska, USA, between 1983 - 2016. To establish RI for 13 biochemical analytes, we defined specific criteria for characterizing the reference population and relevant subgroups. To account for differences in seasonal life history characteristics, we determined separate RI for the spring and fall seasons, when prey availability and energetic requirements of bears differ. We established RI for five subgroups in spring based on sex, age class, and denning status, and three subgroups in fall based on sex and age class in females. Alkaline phosphatase activities were twice as high in subadult as in adult polar bears in spring (zmales = 4.08, Pmales < 0.001, zfemales = 3.90, Pfemales < 0.001), and did not differ between seasons. Denning females had significantly higher glucose concentrations than non-denning females (z = 4.94, P < 0.001), possibly reflecting differences in energy expenditure during lactation. Ten of the 13 analytes differed significantly between seasons in either males or females; however, the physiologic importance of these differences may be minimal. Establishing these RI allows for temporal monitoring of polar bear health in the southern Beaufort Sea and may prove useful for assessing and monitoring additional polar bear subpopulations in a changing Arctic environment.

Alaska↗