Abstract
Polar bears (Ursus maritimus) rely on sea ice for hunting marine mammal prey. Declining sea ice conditions associated with climate warming have negatively affected polar bears, especially in the southern portion of their range. At higher latitudes, the transition from multi-year ice to thinner annual ice has been hypothesized to increase biological productivity and potentially improve polar bear foraging conditions. To investigate this possibility, we used quantitative fatty acid signature analysis to characterize the diet composition of 148 polar bears in two high-latitude subpopulations from 2012 to 2014: (1) Viscount Melville Sound, where little is known about marine mammal ecology, and (2) Northern Beaufort Sea, a subpopulation considered stable with comparatively more ecological data. We used adipose tissue lipid content as an index of body condition. To characterize long-term habitat conditions, we examined trends in sea ice metrics from 1979 to 2014 in both regions. Although the diets of bears in both subpopulations were dominated by ringed seal (Pusa hispida, mean biomass consumption = 45%), bears in Viscount Melville Sound showed higher proportional consumption of beluga whale (Delphinapterus leucas; mean biomass consumption = 37%) than any other polar bear subpopulation studied to date. Although the three-year duration of our study precludes long-term insights, relatively lighter sea ice conditions in Viscount Melville Sound were associated with reduced consumption of preferred prey (i.e., ringed seal), especially among female polar bears. Further, polar bears in Viscount Melville sound were in poorer body condition than those in the Northern Beaufort Sea. Our results do not indicate that declining sea ice has had any positive effect on polar bear foraging at high-latitudes.
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References
Ackman RG, Eaton CA (1966) Some commercial Atlantic herring oils; fatty acid composition. Fish Res Board Canada 23:991–1006. https://doi.org/10.1139/f66-092
Amstrup SC (2003) The Polar Bear—Ursus maritimus. In: Feldhamer GA, Thompson BC, Chapman JA (eds) Wild Mammals of North America: biology, management, and conservation. Johns Hopkins University Press, Baltimore, pp 587–610
Bowen WD (1997) Role of marine mammals in aquatic ecosystems. Mar Ecol Prog Ser 158:267–274. https://doi.org/10.3354/meps158267
Boyd I, Murray A (2001) Monitoring a marine ecosystem using responses of upper trophic level predators. J Anim Ecol 70:747–760. https://doi.org/10.1046/j.0021-8790.2001.00534.x
Brockerhoff H, Hoyle RJ, Hwang PC (1967) Incorporation of fatty acids of marine origin into triglycerides and phospholipids of mammals. Biochim Biophys Acta 144:541–548. https://doi.org/10.1016/0005-2760(67)90043-4
Bromaghin JF (2017) qfasar: quantitative fatty acid signature analysis with R. Methods Ecol Evol. https://doi.org/10.1111/2041-210X.12740
Bromaghin J, McDonald T, Stirling I et al (2015) Polar bear population dynamics in the southern Beaufort Sea during a period of sea ice decline. Ecol Appl 25:634–651. https://doi.org/10.1890/14-1129.1
Bromaghin JF, Budge SM, Thiemann GW, Rode KD (2017) Simultaneous estimation of diet composition and calibration coefficients with fatty acid signature data. Ecol Evol. https://doi.org/10.1002/ece3.3179
Budge SM, Iverson SJ, Koopman HN (2006) Studying trophic ecology in marine ecosystems using fatty acids: a primer on analysis and interpretation. Mar Mammal Sci 22:759–801. https://doi.org/10.1111/j.1748-7692.2006.00079.x
Calvert W, Ramsay MA (1998) Evaluation of age determination of polar bears by counts of cementum growth layer groups. Ursus 10:449–453
Cavalieri D, Parkinson C, Gloersen P, Zwally HJ (1996) Sea ice concentrations from Nimbus-7 SMMR and DMSP SSM. Boulder, Colorado
Chambellant M, Stirling I, Gough WA, Ferguson SH (2012) Temporal variations in Hudson Bay ringed seal (Phoca hispida) life-history parameters in relation to environment. J Mammal 93:267–281. https://doi.org/10.1644/10-MAMM-A-253.1
Derocher AE, Wiig Ø (1999) Infanticide and cannibalism of juvenile polar bears (Ursus maritimus) in Svalbard. Arctic 52:307–310
Derocher A, Wiig Ø, Andersen M (2002) Diet composition of polar bears in Svalbard and the western Barents Sea. Polar Biol 25:448–452. https://doi.org/10.1007/s00300-002-0364-0
Derocher AE, Lunn NJ, Stirling I (2004) Polar Bears in a Warming Climate. Integr Comp Biol 44:163–176. https://doi.org/10.1093/icb/44.2.163
Derocher AE, Andersen M, Wiig Ø (2005) Sexual dimorphism of polar bears. J Mammal 86:895–901. https://doi.org/10.1644/1545-1542(2005)86%5b895:SDOPB%5d2.0.CO;2
Derocher AE, Andersen M, Wiig Ø, Aars J (2010) Sexual dimorphism and the mating ecology of polar bears (Ursus maritimus) at Svalbard. Behav Ecol Sociobiol 64:939–946. https://doi.org/10.1007/s00265-010-0909-0
Durner GM, Laidre KL, York GS (2018) Polar bears: proceedings of the 18th working meeting of the IUCN/SSC polar bear specialist group, 7-11 June 2016, Anchorage, Alaska. Gland, Switzerland and Cambridge.
Ferguson SH, Stirling I, McLoughlin P (2005) Climate change and ringed seal (Phoca hispida) recruitment in Western Hudson Bay. Mar Mammal Sci 21:121–135. https://doi.org/10.1111/j.1748-7692.2005.tb01212.x
Florko KRN, Thiemann GW, Bromaghin JF (2020) Drivers and consequences of apex predator diet composition in the Canadian Beaufort Sea. Oecologia 194:51–63
Folch J, Lees M, Sloane Stanley G (1957) A simple method for the isolation and purification of total lipides from animal tissues. J Biol Chem 226:497–509
Galicia MP, Thiemann GW, Dyck MG, Ferguson SH (2015) Characterization of polar bear (Ursus maritimus) diets in the Canadian High Arctic. Polar Biol 38:1983–1992. https://doi.org/10.1007/s00300-015-1757-1
Galicia MP, Thiemann GW, Dyck MG et al (2016) Dietary habits of polar bears in Foxe Basin, Canada: possible evidence of a trophic regime shift mediated by a new top predator. Ecol Evol 6:6005–6018. https://doi.org/10.1002/ece3.2173
Harwood LA, Kingsley MCS (2013) Trends in the offshore distribution and relative abundance of Beaufort Sea belugas, 1982–1985 vs 2007–2009. Arctic 66:247–256
Harwood LA, Smith TG (2002) Whales of the Inuvialuit settlement region in Canada’s Western Arctic: an overview and outlook. Arctic 24:77–93
Harwood LA, Smith TG, Melling H et al (2012) Ringed seals and sea ice in Canada’s western Arctic: harvest-based monitoring 1992-2011. Arctic 65:377–390
Harwood LA, Smith TG, Auld JC et al (2015a) Seasonal movements and diving of ringed seals, Pusa hispida, in the Western Canadian Arctic, 1999–2001 and 2010–11. Arctic 68:193–209. https://doi.org/10.14430/arctic4479
Harwood LA, Smith TG, George JC et al (2015b) Change in the Beaufort Sea ecosystem: diverging trends in body condition and/or production in five marine vertebrate species. Prog Oceanogr 136:263–273. https://doi.org/10.1016/j.pocean.2015.05.003
Harwood LA, Smith TG, Alikamik J et al (2020) Long-term, harvest-based monitoring of ringed seal body condition and reproduction in Canada’s Western Arctic: an update through 2019. Arctic 73:206–220
Hazen EL, Jorgensen S, Rykaczewski RR et al (2012) Predicted habitat shifts of Pacific top predators in a changing climate. Nat Clim Chang 3:234–238. https://doi.org/10.1038/nclimate1686
Higdon JW, Ferguson SH (2012) Environmental conditions and beluga whale entrapment events in the Husky Lakes, NWT. Canada/Inuvialuit Fisheries Joint Management Committee Report 2012. Canada/Inuvialuit Fisheries Joint Management Committee Report 2012
Hornby CA, Hoover C, Iacozza J et al (2016) Spring conditions and habitat use of beluga whales (Delphinapterus leucas) during arrival to the Mackenzie River Estuary. Polar Biol 39:2319–2334. https://doi.org/10.1007/s00300-016-1899-9
Iverson SJ, Lang SL, Cooper MH (2001) Comparison of the Bligh and Dyer and Folch methods for total lipid determination in a broad range of marine tissue. Lipids 36:1283–1287. https://doi.org/10.1007/s11745-001-0843-0
Iverson SJ, Field C, Bowen WD, Blanchard W (2004) Quantitative fatty acid signature analysis: a new method of estimating predator diets. Ecol Monogr 74:211–235. https://doi.org/10.1890/02-4105
Kingsley MCS, Stirling I, Calvert W (1985) The distribution and abundance of seals in the Canadian High Arctic, 1980–1982. Can J Fish Aquat Sci 42:1189–1210. https://doi.org/10.1139/f85-147
Laidre KL, Atkinson SN, Regehr EV et al (2020) Transient benefits of climate change for a high-Arctic polar bear (Ursus maritimus) subpopulation. Glob Chang Biol 26:6251–6265. https://doi.org/10.1111/gcb.15286
Lindsay R, Schweiger A (2015) Arctic sea ice thickness loss determined using subsurface, aircraft, and satellite observations. Cryosph. https://doi.org/10.5194/tc-9-269-2015
Lowry LF, Burns JJ, Nelson RR (1987) Polar bear, Ursus maritimus, predation on belugas, Delphinapterus leucas, in the Bering and Chukchi Seas. Can Field-Nat 101:141–146
McKinney MA, Atwood T, Dietz R et al (2014) Validation of adipose lipid content as a body condition index for polar bears. Ecol Evol 4:516–527. https://doi.org/10.1002/ece3.956
McKinney M, Atwood T, Iverson SJ, Peacock E (2017) Temporal complexity of southern Beaufort Sea polar bear diets during a period of increasing land use. Ecosphere 8: https://doi.org/10.1002/ecs2.1633
McLaren IA (1958) The biology of the ringed seal (Phoca hispida Schreher) in the eastern Canadian Arctic. Fish Res Board Canada 118:1–97
Nguyen L, Pilfold NW, Derocher AE et al (2017) Ringed seal (Pusa hispida) tooth annuli as an index of reproduction in the Beaufort Sea. Ecol Indic 77:286–292
Obbard ME, Cattet MRL, Howe EJ et al (2016) Trends in body condition in polar bears (Ursus maritimus) from the Southern Hudson Bay subpopulation in relation to changes in sea ice. Arct Sci. https://doi.org/10.1152/ajplung.00521.2007
Paine RT (1966) Food web complexity and species diversity. Am Nat 100:65–75
Pilfold NW, Derocher AE, Stirling I et al (2012) Age and sex composition of seals killed by Polar bears in the Eastern Beaufort sea. PLoS ONE 7:2–8. https://doi.org/10.1371/journal.pone.0041429
Pilfold NW, Derocher AE, Richardson E (2014) Influence of intraspecific competition on the distribution of a wide-ranging, non-territorial carnivore. Glob Ecol Biogeogr 23:425–435. https://doi.org/10.1111/geb.12112
Pond CM (1992) An evolutionary and functional view of mammalian adipose tissue. Proc Nutr Soc 51:367–377. https://doi.org/10.1079/PNS19920050
Regehr EV, Lunn NJ, Amstrup SC, Stirling I (2007) Effects of earlier sea ice breakup on survival and population size of polar bears in Western Hudson Bay. J Wildl Manage 71:2673–2683. https://doi.org/10.2193/2006-180
Reimer JR, Caswell H, Derocher AE, Lewis MA (2019) Ringed seal demography in a changing climate. Ecol Appl 29: https://doi.org/10.1002/eap.1855
Richard PR, Martin AR, Orr JR (2001) Summer and autumn movements of belugas of the Bastern Beaufort Sea stock. Arctic 54:223–236
Rode KD, Amstrup SC, Regehr EV (2010) Reduced body size and cub recruitment in polar bears associated with sea ice decline. Ecol Appl 20:768–782. https://doi.org/10.1890/08-1036.1
Rode KD, Peacock E, Taylor M et al (2012) A tale of two polar bear populations: ice habitat, harvest, and body condition. Popul Ecol 54:3–18. https://doi.org/10.1007/s10144-011-0299-9
Rode KD, Regehr EV, Bromaghin JF et al (2021) Seal body condition and atmospheric circulation patterns influence polar bear body condition, recruitment, and feeding ecology in the Chukchi Sea. Glob Chang Biol. https://doi.org/10.1111/gcb.15572
Sciullo L, Thiemann GW, Lunn NJ (2016) Comparative assessment of metrics for monitoring the body condition of polar bears in western Hudson Bay. J Zool 300:45–58. https://doi.org/10.1111/jzo.12354
Sciullo L, Thiemann GW, Lunn NJ et al (2017) Intraspecific and temporal variability in the diet composition of female polar bears in a seasonal sea ice regime. Arct Sci 3:672–688. https://doi.org/10.1139/as-2017-0004
Smith TG, Harwood LA (2001) Observations of neonate ringed seals, Phoca hispida, after early break-up of the sea ice in Prince Albert Sound, Northwest Territories, Canada, spring 1998. Polar Biol 24:215–219. https://doi.org/10.1007/s003000000198
Smith TG, Sjare B (1990) Predation of belugas and narwhals by polar bears in nearshore areas of the Canadian High Arctic. Arctic 43:99–102. https://doi.org/10.14430/arctic1597
Stern HL, Laidre KL (2016) Sea-ice indicators of polar bear habitat. Cryosph 10:2027–2041
Stewart C, Iverson S, Field C (2014) Testing for a change in diet using fatty acid signatures. Environ Ecol Stat 21:775–792
Stirling I (2002) Polar bears and seals in the eastern Beaufort Sea and Amundsen Gulf: a synthesis of population trends and ecological relationships over three decades. Arctic 55:59–76
Stirling I, Derocher AE (1993) Possible impacts of climatic warming on polar bears. Arctic 46:240–245
Stirling I, Derocher AE (2012) Effects of climate warming on polar bears: a review of the evidence. Glob Chang Biol 18:2694–2706. https://doi.org/10.1111/j.1365-2486.2012.02753.x
Stirling I, Spencer C, Andriashek D (1989) Immobilization of polar bears (Ursus maritimus) with Telazol® in the Canadian Arctic. J Wildl Dis 25:159–168. https://doi.org/10.7589/0090-3558-25.2.159
Stirling I, Andriashek D, Calvert W (1993) Habitat preferences of polar bears in the Western Canadian Arctic in late winter and spring. Polar Rec (Gr Brit) 29:13–24. https://doi.org/10.1017/S0032247400023172
Stirling I, Lunn NJ, Iacozza J (1999) Long-term trends in the population ecology of polar bears in western Hudson Bay in relation to climatic change. Arctic 52:294–306
Stirling I, McDonald TL, Richardson ES et al (2011) Polar bear population status in the northern Beaufort Sea, Canada, 1971–2006. Ecol Appl 21:859–876. https://doi.org/10.1890/10-0849.1
Stroeve JC, Kattsov V, Barrett A et al (2012) Trends in Arctic sea ice extent from CMIP5, CMIP3 and observations. Geophys Res Lett 39:1–7. https://doi.org/10.1029/2012GL052676
Thiemann GW, Budge SM, Iverson SJ (2004) Determining blubber fatty acid composition: a comparison of in situ direct and traditional methods. Mar Mammal Sci 20:284–295. https://doi.org/10.1111/j.1748-7692.2004.tb01157.x
Thiemann GW, Iverson SJ, Stirling I (2006) Seasonal, sexual and anatomical variability in the adipose tissue of polar bears (Ursus maritimus). J Zool 269:65–76. https://doi.org/10.1111/j.1469-7998.2006.00084.x
Thiemann GW, Budge SM, Iverson SJ, Stirling I (2007) Unusual fatty acid biomarkers reveal age- and sex-specific foraging in polar bears (Ursus maritimus). Can J Zool 85:505–517. https://doi.org/10.1139/Z07-028
Thiemann GW, Iverson SJ, Stirling I (2008a) Polar bear diets and Arctic marine food webs: insights from fatty acid analysis. Ecol Monogr 78:591–613. https://doi.org/10.1890/07-1050.1
Thiemann GW, Iverson SJ, Stirling I (2008b) Variation in blubber fatty acid composition among marine mammals in the Canadian Arctic. Mar Mammal Sci 24:91–111. https://doi.org/10.1111/j.1748-7692.2007.00165.x
Thiemann GW, Iverson SJ, Stirling I, Obbard ME (2011) Individual patterns of prey selection and dietary specialization in an Arctic marine carnivore. Oikos 120:1469–1478. https://doi.org/10.1111/j.1600-0706.2011.19277.x
Wang M, Overland JE (2015) Projected future duration of the sea-ice-free season in the alaskan arctic. Prog Oceanogr. https://doi.org/10.1016/j.pocean.2015.01.001
Wilmers CC, Getz WM (2005) Gray wolves as climate change buffers in Yellowstone. PLoS Biol 3: https://doi.org/10.1371/journal.pbio.0030092
Acknowledgements
We are particularly grateful to the Inuvialuit Game Council and Inuvialuit hunters for collecting adipose tissue samples from polar bears harvested during their subsistence hunts. Thanks to the researchers, field assistants, and helicopter personnel that assisted in the safe capture and handling of polar bears. We are thankful for financial support from Natural Sciences and Engineering Research Council (NSERC) Discovery Grant, Kenneth M. Molson Foundation, Environment and Climate Change Canada, Northern Scientific Training Program, Nunavut Wildlife Management Board Nunavut Wildlife Research Trust, Government of the Northwest Territories, Polar Continental Shelf Program, Inuvialuit Implementation Funds, World Wildlife Fund, and York University, Faculty of Graduate Studies. We thank Marsha Branigan and Jodie Pongracz (Government of Northwest Territories) for organizing and facilitating sample collection and providing ecological insights on the Beaufort Sea ecosystem. We thank D. McGeachy (Environment and Climate Change Canada) for a summary analysis of sea ice metrics, S. Budge and C. Barry (Dalhousie University) for conducting gas chromatography, L. Harwood (Fisheries and Oceans Canada) and J. Alikamik for ringed seal adipose tissue samples, and S. Ferguson (Fisheries and Oceans Canada) and J. Higdon (Higdon Wildlife Consulting) for access to beluga entrapment reports. We thank L. Adams, A. Fischbach (USGS Alaska Science Center), A. Derocher (University of Alberta), R. Dietz (Aarhus University) and two anonymous reviewers for their helpful comments on an earlier version of this manuscript. Any use of trade, firm, or product names is for descriptive purposes only and does not constitute endorsement by the U.S. Government. This article is a U.S. Government work and is in the public domain in the U.S.A. This article was reviewed and approved under the U.S. Geological Survey, Fundamental Science Practices policy (http://www.usgs.gov/fsp).
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KRNF and GWT conceived and formulated the ideas, ESR provided data, KRNF processed tissue samples, KRNF and JFB analysed the data, KRNF and GWT wrote the manuscript, and JFB and ESR provided editorial advice and ecological insights.
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Florko, K.R.N., Thiemann, G.W., Bromaghin, J.F. et al. Diet composition and body condition of polar bears (Ursus maritimus) in relation to sea ice habitat in the Canadian High Arctic. Polar Biol 44, 1445–1456 (2021). https://doi.org/10.1007/s00300-021-02891-8
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DOI: https://doi.org/10.1007/s00300-021-02891-8