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  • 1
    Online Resource
    Online Resource
    Stable isotope differences of polar bears in the Southern Beaufort Sea and Chukchi Sea
    Wiley ; 2022
    In:  The Journal of Wildlife Management Vol. 86, No. 5 ( 2022-07)
    Details
    In: The Journal of Wildlife Management, Wiley, Vol. 86, No. 5 ( 2022-07)
    Abstract: The life‐history, genetic, and habitat use differences between the 2 polar bear ( Ursus maritimus ) subpopulations in Alaska, USA, have been used to determine the geographic border separating them, but it has sparked a debate of the correct placement of the border for several years. Recently, the Southern Beaufort Sea (SBS) polar bear subpopulation has declined because of sea ice loss, while the Chukchi Sea (CS) subpopulation appears stable. To provide additional information about potential differences between the SBS and CS subpopulations, such as differences in prey sources, we used stable isotope analysis of carbon and nitrogen from bone collagen of polar bears in these 2 neighboring subpopulations. We analyzed polar bear bones from 112 individuals collected from 1954–2019. Our purpose was to determine if the SBS and CS subpopulations could be distinguished based on the stable isotope signatures of bone collagen. A difference 〉 1‰ in stable carbon isotope (δ 13 C) values suggests a change in carbon sources, such as nearshore to offshore, while a 3‰ change in stable nitrogen isotope (δ 15 N) values equates to a change of about 1 trophic level. Our study indicated a difference in δ 13 C values ( P  ≤ 0.001) but not δ 15 N values ( P  = 0.654) between the CS (−13.0 ± 0.3‰ and 22.0 ± 0.9‰, respectively) and SBS bears (−14.7 ± 1.3‰ and 22.2 ± 1.0‰, respectively). Our findings indicate that the 2 subpopulations are consuming similar high trophic level prey, while feeding in ecosystems with different δ 13 C baselines. We performed a logistic regression analysis using δ 13 C and δ 15 N values of the polar bears to predict their placement into these 2 subpopulations. Using Icy Cape, Alaska as the geographical boundary, the analysis correctly placed polar bears in their respective subpopulations 82% of the time. Overall accuracy of placement changed to 84% when using the current geographical boundary at Utqiaġvik, Alaska. We predicted samples collected from the Wainwright, Alaska region as 58% CS and 42% SBS polar bears. This suggests that the area between Wainwright and Icy Cape is a polar bear mixing zone that includes bears from both subpopulations. Bone collagen has a long‐term, potentially life‐long, stable isotope turnover rate, and our results could be used to determine the association of harvested polar bears to Alaska subpopulations, thus aiding in transboundary harvest quota management.
    Type of Medium: Online Resource
    ISSN: 0022-541X , 1937-2817
    URL: Issue
    URL: Article
    DOI: 10.1002/jwmg.v86.5
    DOI: 10.1002/jwmg.22225
    Language: English
    Publisher: Wiley
    Publication Date: 2022
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    SSG: 12
    SSG: 23
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  • 2
    Online Resource
    Online Resource
    Diet energy density estimated from isotopes in predator hair associated with survival, habitat, and population dynamics
    Wiley ; 2023
    In:  Ecological Applications Vol. 33, No. 2 ( 2023-03)
    Details
    In: Ecological Applications, Wiley, Vol. 33, No. 2 ( 2023-03)
    Abstract: Sea ice loss is fundamentally altering the Arctic marine environment. Yet there is a paucity of data on the adaptability of food webs to ecosystem change, including predator–prey interactions. Polar bears ( Ursus maritimus ) are an important subsistence resource for Indigenous people and an apex predator that relies entirely on the under‐ice food web to meet its energy needs. In this study, we assessed whether polar bears maintained dietary energy density by prey switching in response to spatiotemporal variation in prey availability. We compared the macronutrient composition of diets inferred from stable carbon and nitrogen isotopes in polar bear guard hair (primarily representing summer/fall diet) during periods when bears had low and high survival (2004–2016), between bears that summered on land versus pack ice, and between bears occupying different regions of the Alaskan and Canadian Beaufort Sea. Polar bears consumed diets with lower energy density during periods of low survival, suggesting that concurrent increased dietary proportions of beluga whales ( Delphinapterus leucas ) did not offset reduced proportions of ringed seals ( Pusa hispida ). Diets with the lowest energy density and proportions from ringed seal blubber were consumed by bears in the western Beaufort Sea (Alaska) during a period when polar bear abundance declined. Intake required to meet energy requirements of an average free‐ranging adult female polar bear was 2.1 kg/day on diets consumed during years with high survival but rose to 3.0 kg/day when survival was low. Although bears that summered onshore in the Alaskan Beaufort Sea had higher‐fat diets than bears that summered on the pack ice, access to the remains of subsistence‐harvested bowhead whales ( Balaena mysticetus ) contributed little to improving diet energy density. Because most bears in this region remain with the sea ice year round, prey switching and consumption of whale carcasses onshore appear insufficient to augment diets when availability of their primary prey, ringed seals, is reduced. Our results show that a strong predator–prey relationship between polar bears and ringed seals continues in the Beaufort Sea. The method of estimating dietary blubber using predator hair, demonstrated here, provides a new metric to monitor predator–prey relationships that affect individual health and population demographics.
    Type of Medium: Online Resource
    ISSN: 1051-0761 , 1939-5582
    URL: Issue
    URL: Article
    DOI: 10.1002/eap.v33.2
    DOI: 10.1002/eap.2751
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2010123-5
    SSG: 12
    SSG: 23
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  • 3
    Online Resource
    Online Resource
    A novel method to measure steroid hormone concentrations in walrus bone from archaeological, historical, and modern time periods using liquid chromatography/tandem mass spectrometry
    Wiley ; 2018
    In:  Rapid Communications in Mass Spectrometry Vol. 32, No. 23 ( 2018-12-15), p. 1999-2023
    Details
    In: Rapid Communications in Mass Spectrometry, Wiley, Vol. 32, No. 23 ( 2018-12-15), p. 1999-2023
    Abstract: A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was validated and utilized to measure and analyze four steroid hormones related to stress and reproduction in individual samples from a novel tissue, Pacific walrus ( Odobenus rosmarus divergens , herein walrus) bone. This method determines steroid hormone concentrations in the remote walrus population over millennia from archaeological ( 〉 200 bp ), historical (200–20 bp ), and modern (2014–2016) time periods. Methods Lipids were extracted from walrus bone collected from these periods using methanol before LC/MS/MS analysis. Isotopically labeled internal standards for each target hormone were added to every sample. Analytical and physiological validations were performed. Additionally, a tissue comparison was done among paired walrus bone, serum, and blubber samples. A rapid resolution liquid chromatography system coupled to a QqQ mass spectrometer was used to analyze all samples after derivatization for progesterone, testosterone, cortisol, and estradiol concentrations. Multiple reaction monitoring was used for MS analysis and data were acquired in positive electrospray ionization mode. Results Progesterone, testosterone, cortisol, and estradiol were linear along their respective standard calibration curves based on their R 2 values (all  〉  0.99). Accuracy ranged from 93–111% for all hormones. The recovery of extraction, recovery of hormones without matrix effect, was 92–101%. The overall process efficiency of our method for measuring hormones in walrus bone was 93–112%. Progesterone and testosterone concentrations were not affected by reproductive status among adult females and males, respectively. However, estradiol was different among pregnant and non‐pregnant adult females. Overall, steroid hormones reflect a long‐term reservoir in cortical bone. This method was also successfully applied to walrus bone as old as 3585 bp . Conclusions LC/MS/MS analysis of bone tissue (0.2–0.3 g) provides stress and reproductive data from elusive walruses that were alive thousands of years ago. Based on physiological validations, tissue comparison, and published literature, steroid hormone concentrations measured in walrus cortical bone could represent an accumulated average around a 10–20‐year time span. By investigating how stress and reproductive physiology may have changed over the past ~3000 years based on bone steroid hormone concentrations, this method will help answer how physiologically resilient walruses are to climate change in the Arctic.
    Type of Medium: Online Resource
    ISSN: 0951-4198 , 1097-0231
    URL: Issue
    URL: Article
    DOI: 10.1002/rcm.v32.23
    DOI: 10.1002/rcm.8272
    Language: English
    Publisher: Wiley
    Publication Date: 2018
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    detail.hit.zdb_id: 58731-X
    SSG: 11
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  • 4
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    Online Resource
    Carbon sources and trophic relationships of ice seals during recent environmental shifts in the Bering Sea
    Wiley ; 2016
    In:  Ecological Applications Vol. 26, No. 3 ( 2016-04), p. 830-845
    Details
    In: Ecological Applications, Wiley, Vol. 26, No. 3 ( 2016-04), p. 830-845
    Abstract: Dramatic multiyear fluctuations in water temperature and seasonal sea ice extent and duration across the Bering–Chukchi continental shelf have occurred in this century, raising a pressing ecological question: Do such environmental changes alter marine production processes linking primary producers to upper trophic‐level predators? We examined this question by comparing the blubber fatty acid (FA) composition and stable carbon isotope ratios of individual FA (δ 13 C FA ) of adult ringed seals ( Pusa hispida ), bearded seals ( Erignathus barbatus ), spotted seals ( Phoca largha ), and ribbon seals ( Histriophoca fasciata ), collectively known as “ice seals,” sampled during an anomalously warm, low sea ice period in 2002–2005 in the Bering Sea and a subsequent cold, high sea ice period in 2007–2010. δ 13 C FA values, used to estimate the contribution to seals of carbon derived from sea ice algae (sympagic production) relative to that derived from water column phytoplankton (pelagic production), indicated that during the cold period, sympagic production accounted for 62–80% of the FA in the blubber of bearded seals, 51–62% in spotted seals, and 21–60% in ringed seals. Moreover, the δ 13 C FA values of bearded seals indicated a greater incorporation of sympagic FAs during the cold period than the warm period. This result provides the first empirical evidence of an ecosystem‐scale effect of a putative change in sympagic production in the Western Arctic. The FA composition of ice seals showed clear evidence of resource partitioning among ringed, bearded, and spotted seals, and little niche separation between spotted and ribbon seals, which is consistent with previous studies. Despite interannual variability, the FA composition of ringed and bearded seals showed little evidence of differences in diet between the warm and cold periods. The findings that sympagic production contributes significantly to food webs supporting ice seals, and that the contribution apparently is less in warm years with low sea ice, raise an important concern: Will the projected warming and continuing loss of seasonal sea ice in the Arctic, and the associated decline of organic matter input from sympagic production, be compensated for by pelagic production to satisfy both pelagic and benthic carbon and energy needs?
    Type of Medium: Online Resource
    ISSN: 1051-0761 , 1939-5582
    URL: Article
    DOI: 10.1890/14-2421
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 2010123-5
    SSG: 12
    SSG: 23
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  • 5
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    Online Resource
    Evaluating tooth strontium and barium as indicators of weaning age in Pacific walruses
    Wiley ; 2020
    In:  Methods in Ecology and Evolution Vol. 11, No. 12 ( 2020-12), p. 1626-1638
    Details
    In: Methods in Ecology and Evolution, Wiley, Vol. 11, No. 12 ( 2020-12), p. 1626-1638
    Abstract: Lactation length and weaning age provide important information about maternal investment, which can reflect the health and nutritional status of the mother, as well as broader reproductive strategies in mammals. Calcium‐normalized strontium (Sr) and barium (Ba) concentrations in the growth layers of mammalian teeth differ for nursing animals and those consuming non‐milk foods, thus can be used to estimate age‐at‐weaning. To date, this approach has been used only for terrestrial animals, and almost exclusively for primates. The goal of this study was to determine whether Sr and Ba concentrations in the cementum of Pacific walrus Odobenus rosmarus divergens teeth can be used to estimate weaning age. Teeth from 107 walruses were analysed using laser ablation inductively coupled plasma mass spectrometry, and calcium‐normalized 88 Sr and 137 Ba concentrations were quantified. For most walruses, both Sr and Ba concentrations exhibited rapid changes in early life. Ba concentrations matched closely with expected patterns in the published literature, rapidly declining from high to low concentrations (typically from ~10 ppm to ~5 ppm). In contrast, Sr exhibited a pattern opposite to that presented in studies of terrestrial mammals, appearing nearly identical to Ba (typically declining from ~400 ppm to ~200 ppm). To explain these findings, we present conceptual models of the factors generating weaning signals in Sr and Ba for terrestrial mammals, as well as a new, hypothetical model for walruses. Both a visual and mathematical approach to weaning age estimation indicated a median weaning age of walruses at the end of the second year of life (in the second dark layer of the tooth cementum), with many walruses estimated to have weaned in their third year of life, and a smaller group weaning in their fourth or fifth year. This is later than expected, given a published estimate of walrus weaning at 18–24 months. These results do not conclusively support the use of tooth Sr and Ba for estimating weaning age in walruses, and further research is warranted to better understand the drivers of the observed patterns of Ba and Sr accumulation in walrus teeth.
    Type of Medium: Online Resource
    ISSN: 2041-210X , 2041-210X
    URL: Issue
    URL: Article
    DOI: 10.1111/mee3.v11.12
    DOI: 10.1111/2041-210X.13482
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2528492-7
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