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Jagielski PM, Dey CJ, Gilchrist HG, Richardson ES, Semeniuk CA. Polar bear foraging on common eider eggs: estimating the energetic consequences of a climate-mediated behavioural shift. Anim Behav 2021. [DOI: 10.1016/j.anbehav.2020.11.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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2
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Reimer JR, Mangel M, Derocher AE, Lewis MA. Modeling optimal responses and fitness consequences in a changing Arctic. GLOBAL CHANGE BIOLOGY 2019; 25:3450-3461. [PMID: 31077520 DOI: 10.1111/gcb.14681] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2019] [Accepted: 04/29/2019] [Indexed: 06/09/2023]
Abstract
Animals must balance a series of costs and benefits while trying to maximize their fitness. For example, an individual may need to choose how much energy to allocate to reproduction versus growth, or how much time to spend on vigilance versus foraging. Their decisions depend on complex interactions between environmental conditions, behavioral plasticity, reproductive biology, and energetic demands. As animals respond to novel environmental conditions caused by climate change, the optimal decisions may shift. Stochastic dynamic programming provides a flexible modeling framework with which to explore these trade-offs, but this method has not yet been used to study possible changes in optimal trade-offs caused by climate change. We created a stochastic dynamic programming model capturing trade-off decisions required by an individual adult female polar bear (Ursus maritimus) as well as the fitness consequences of her decisions. We predicted optimal foraging decisions throughout her lifetime as well as the energetic thresholds below which it is optimal for her to abandon a reproductive attempt. To explore the effects of climate change, we shortened the spring feeding period by up to 3 weeks, which led to predictions of riskier foraging behavior and higher reproductive thresholds. The resulting changes in fitness may be interpreted as a best-case scenario, where bears adapt instantaneously and optimally to new environmental conditions. If the spring feeding period was reduced by 1 week, her expected fitness declined by 15%, and if reduced by 3 weeks, expected fitness declined by 68%. This demonstrates an effective way to explore a species' optimal response to a changing landscape of costs and benefits and highlights the fact that small annual effects can result in large cumulative changes in expected lifetime fitness.
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Affiliation(s)
- Jody R Reimer
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, AB, Canada
| | - Marc Mangel
- Institute of Marine Sciences and Department of Applied Mathematics and Statistics, University of California, Santa Cruz, Santa Cruz, California
- Department of Biology, University of Bergen, Bergen, Norway
| | - Andrew E Derocher
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Mark A Lewis
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, AB, Canada
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3
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Wilder JM, Vongraven D, Atwood T, Hansen B, Jessen A, Kochnev A, York G, Vallender R, Hedman D, Gibbons M. Polar bear attacks on humans: Implications of a changing climate. WILDLIFE SOC B 2017. [DOI: 10.1002/wsb.783] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- James M. Wilder
- U.S. Fish and Wildlife Service, Marine Mammals Management; 1011 E. Tudor Road Anchorage AK 99503 USA
| | - Dag Vongraven
- Norwegian Polar Institute, Fram Center; N-9296 Tromsø Norway
| | - Todd Atwood
- U.S. Geological Survey, Alaska Science Center; 4210 University Road Anchorage AK 99508 USA
| | - Bob Hansen
- Government of Nunavut; Igloolik NU X0A 0L0 Canada
| | - Amalie Jessen
- Government of Greenland, Department of Wildlife and Agriculture; P.O. Box 269 3900 Nuuk Greenland
| | - Anatoly Kochnev
- Russian Academy of Sciences, Far East Branch, Institute of Biological Problems of the North, Mammals Ecology Lab; 18 Portovaya Street 685000 Magadan Russia
| | - Geoff York
- Polar Bears International; PO Box 3008 Bozeman MT 59772 USA
| | - Rachel Vallender
- Canadian Wildlife Service, Environment Canada; 351 St. Joseph Boulevard Gatineau QC K1A 0H3 Canada
| | - Daryll Hedman
- Manitoba Conservation and Water Stewardship; Northeast Region, Box 28 Thompson MB R8N 1N2 Canada
| | - Melissa Gibbons
- Wapusk National Park and Manitoba North National Historic Sites, Parks Canada; Box 127 Churchill MB R0B 0E0 Canada
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Dey CJ, Richardson E, McGeachy D, Iverson SA, Gilchrist HG, Semeniuk CAD. Increasing nest predation will be insufficient to maintain polar bear body condition in the face of sea ice loss. GLOBAL CHANGE BIOLOGY 2017; 23:1821-1831. [PMID: 27614094 DOI: 10.1111/gcb.13499] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 07/11/2016] [Accepted: 08/07/2016] [Indexed: 06/06/2023]
Abstract
Climate change can influence interspecific interactions by differentially affecting species-specific phenology. In seasonal ice environments, there is evidence that polar bear predation of Arctic bird eggs is increasing because of earlier sea ice breakup, which forces polar bears into nearshore terrestrial environments where Arctic birds are nesting. Because polar bears can consume a large number of nests before becoming satiated, and because they can swim between island colonies, they could have dramatic influences on seabird and sea duck reproductive success. However, it is unclear whether nest foraging can provide an energetic benefit to polar bear populations, especially given the capacity of bird populations to redistribute in response to increasing predation pressure. In this study, we develop a spatially explicit agent-based model of the predator-prey relationship between polar bears and common eiders, a common and culturally important bird species for northern peoples. Our model is composed of two types of agents (polar bear agents and common eider hen agents) whose movements and decision heuristics are based on species-specific bioenergetic and behavioral ecological principles, and are influenced by historical and extrapolated sea ice conditions. Our model reproduces empirical findings that polar bear predation of bird nests is increasing and predicts an accelerating relationship between advancing ice breakup dates and the number of nests depredated. Despite increases in nest predation, our model predicts that polar bear body condition during the ice-free period will continue to decline. Finally, our model predicts that common eider nests will become more dispersed and will move closer to the mainland in response to increasing predation, possibly increasing their exposure to land-based predators and influencing the livelihood of local people that collect eider eggs and down. These results show that predator-prey interactions can have nonlinear responses to changes in climate and provides important predictions of ecological change in Arctic ecosystems.
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Affiliation(s)
- Cody J Dey
- Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada
| | - Evan Richardson
- Environment and Climate Change Canada, Science and Technology Branch, Wildlife Research Division, CW405 Biological Sciences BLDG, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - David McGeachy
- Environment and Climate Change Canada, Science and Technology Branch, Wildlife Research Division, CW405 Biological Sciences BLDG, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - Samuel A Iverson
- Environment and Climate Change Canada, Canadian Wildlife Service, 335 River Road, Ottawa, ON, K1A 0H3, Canada
| | - Hugh G Gilchrist
- Environment and Climate Change Canada, National Wildlife Research Center, 1125 Colonel By Drive, Ottawa, ON, K1A 0H3, Canada
| | - Christina A D Semeniuk
- Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada
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5
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Coogan SCP, Raubenheimer D. Might macronutrient requirements influence grizzly bear–human conflict? Insights from nutritional geometry. Ecosphere 2016. [DOI: 10.1002/ecs2.1204] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Affiliation(s)
- Sean C. P. Coogan
- Charles Perkins Centre School of Biological Sciences University of Sydney Level 4 East Building D17 Sydney New South Wales 2006 Australia
| | - David Raubenheimer
- Faculty of Veterinary Science Charles Perkins Centre School of Biological Sciences University of Sydney Level 4 East Building D17 Sydney New South Wales 2006 Australia
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Rode KD, Wilson RR, Regehr EV, St. Martin M, Douglas DC, Olson J. Increased Land Use by Chukchi Sea Polar Bears in Relation to Changing Sea Ice Conditions. PLoS One 2015; 10:e0142213. [PMID: 26580809 PMCID: PMC4651550 DOI: 10.1371/journal.pone.0142213] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 10/19/2015] [Indexed: 11/21/2022] Open
Abstract
Recent observations suggest that polar bears (Ursus maritimus) are increasingly using land habitats in some parts of their range, where they have minimal access to their preferred prey, likely in response to loss of their sea ice habitat associated with climatic warming. We used location data from female polar bears fit with satellite radio collars to compare land use patterns in the Chukchi Sea between two periods (1986–1995 and 2008–2013) when substantial summer sea-ice loss occurred. In both time periods, polar bears predominantly occupied sea-ice, although land was used during the summer sea-ice retreat and during the winter for maternal denning. However, the proportion of bears on land for > 7 days between August and October increased between the two periods from 20.0% to 38.9%, and the average duration on land increased by 30 days. The majority of bears that used land in the summer and for denning came to Wrangel and Herald Islands (Russia), highlighting the importance of these northernmost land habitats to Chukchi Sea polar bears. Where bears summered and denned, and how long they spent there, was related to the timing and duration of sea ice retreat. Our results are consistent with other studies supporting increased land use as a common response of polar bears to sea-ice loss. Implications of increased land use for Chukchi Sea polar bears are unclear, because a recent study observed no change in body condition or reproductive indices between the two periods considered here. This result suggests that the ecology of this region may provide a degree of resilience to sea ice loss. However, projections of continued sea ice loss suggest that polar bears in the Chukchi Sea and other parts of the Arctic may increasingly use land habitats in the future, which has the potential to increase nutritional stress and human-polar bear interactions.
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Affiliation(s)
- Karyn D. Rode
- U.S. Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, Alaska, 99508, United States of America
- * E-mail:
| | - Ryan R. Wilson
- United States Fish and Wildlife Service, Marine Mammals Management, 1011 E Tudor Road, Anchorage, Alaska, 99503, United States of America
| | - Eric V. Regehr
- United States Fish and Wildlife Service, Marine Mammals Management, 1011 E Tudor Road, Anchorage, Alaska, 99503, United States of America
| | - Michelle St. Martin
- United States Fish and Wildlife Service, Marine Mammals Management, 1011 E Tudor Road, Anchorage, Alaska, 99503, United States of America
| | - David C. Douglas
- U.S. Geological Survey, Alaska Science Center, 250 Egan Drive, Juneau, Alaska, 99801, United States of America
| | - Jay Olson
- Brigham Young University, Plant and Wildlife Sciences, 5049 LSB, Provo, Utah, 84602, United States of America
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Miller S, Wilder J, Wilson RR. Polar bear–grizzly bear interactions during the autumn open-water period in Alaska. J Mammal 2015. [DOI: 10.1093/jmammal/gyv140] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Erlenbach JA, Rode KD, Raubenheimer D, Robbins CT. Macronutrient optimization and energy maximization determine diets of brown bears. J Mammal 2014. [DOI: 10.1644/13-mamm-a-161] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Iverson SA, Gilchrist HG, Smith PA, Gaston AJ, Forbes MR. Longer ice-free seasons increase the risk of nest depredation by polar bears for colonial breeding birds in the Canadian Arctic. Proc Biol Sci 2014; 281:20133128. [PMID: 24500172 PMCID: PMC3924086 DOI: 10.1098/rspb.2013.3128] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Northern polar regions have warmed more than other parts of the globe potentially amplifying the effects of climate change on biological communities. Ice-free seasons are becoming longer in many areas, which has reduced the time available to polar bears (Ursus maritimus) to hunt for seals and hampered bears’ ability to meet their energetic demands. In this study, we examined polar bears’ use of an ancillary prey resource, eggs of colonial nesting birds, in relation to diminishing sea ice coverage in a low latitude region of the Canadian Arctic. Long-term monitoring reveals that bear incursions onto common eider (Somateria mollissima) and thick-billed murre (Uria lomvia) nesting colonies have increased greater than sevenfold since the 1980s and that there is an inverse correlation between ice season length and bear presence. In surveys encompassing more than 1000 km of coastline during years of record low ice coverage (2010–2012), we encountered bears or bear sign on 34% of eider colonies and estimated greater egg loss as a consequence of depredation by bears than by more customary nest predators, such as foxes and gulls. Our findings demonstrate how changes in abiotic conditions caused by climate change have altered predator–prey dynamics and are leading to cascading ecological impacts in Arctic ecosystems.
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Affiliation(s)
- Samuel A Iverson
- Department of Biology, Carleton University, , Ottawa, Ontario, Canada, Environment Canada-National Wildlife Research Centre, Ottawa, Ontario, Canada
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Fitzgerald KT. Polar bears: the fate of an icon. Top Companion Anim Med 2013; 28:135-42. [PMID: 24331553 DOI: 10.1053/j.tcam.2013.09.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Polar bears are one of the most iconic animals on our planet. Worldwide, even people who would never see one are drawn to these charismatic arctic ice hunters. They are the world's largest terrestrial carnivore, and despite being born on land, they spend most of their lives out on the sea ice and are considered a marine mammal. Current global studies estimate there are around 20,000 animals in some 19 discrete circumpolar populations. Aside from pregnant females denning in the winter months to give birth, the white bears do not hibernate. They spend their winters on the sea ice hunting seals, an activity they are spectacularly adapted for. Research on these animals is incredibly difficult because of the inhospitable surroundings they inhabit and how inaccessible they make the bears. For many years, the sum of our understanding of the natural history of polar bears came from tracks, scats, the remains of their kills, abandoned dens, and anecdotal observations of native hunters, explorers, and early biologists. Nonetheless, the last 40 years have seen a much better picture of their biology emerge thanks to, first, dedicated Canadian researchers and, later, truly international efforts of workers from many countries. Veterinarians have contributed to our knowledge of the bears by delivering and monitoring anesthesia, obtaining blood samples, performing necropsies, investigating their reproduction, conducting radiotelemetry studies, and examining their behavior. Recently, new technologies have been developed that revolutionize the study of the lives and natural history of undisturbed polar bears. These advances include better satellite radiotelemetry equipment and the development of remote-controlled miniature devices equipped with high-definition cameras. Such new modalities provide dramatic new insights into the life of polar bears. The remarkable degree of specialized adaptation to life on the sea ice that allowed the bears to be successful is the very reason that the bears are so vulnerable to the effects of climate change. Polar bears have few alternatives if their habitat (the sea ice) and their access to their ringed seal prey rapidly disappear. Predictions that polar bears may be able to adjust and sustain themselves on alternative food sources are not based on reality. Spring breakup of the sea ice is happening much earlier as well as fall freezeup is getting later, thereby prolonging the open water period that the bears are shore bound. If trends continue and the ice continues to disappear, the effect on polar bears would be devastating. Veterinarians must stay involved in polar bear studies and in multidisciplinary conservation studies dealing with threatened and endangered species worldwide. On account of their training, veterinarians can offer a unique skill set that can provide access to a number of technologies critical to conservation efforts. The oath veterinarians take on graduation from veterinary school charges them to be sworn to the "conservation of animal resources" and in the education of the public. We are only as good as the oaths we keep.
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Affiliation(s)
- Kevin T Fitzgerald
- VCA Alameda East Veterinary Hospital, Denver, CO, USA; Board of Directors, Denver Zoo, Denver, CO, USA.
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Castro de la Guardia L, Derocher AE, Myers PG, Terwisscha van Scheltinga AD, Lunn NJ. Future sea ice conditions in Western Hudson Bay and consequences for polar bears in the 21st century. GLOBAL CHANGE BIOLOGY 2013; 19:2675-87. [PMID: 23716301 DOI: 10.1111/gcb.12272] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Accepted: 04/19/2013] [Indexed: 05/25/2023]
Abstract
The primary habitat of polar bears is sea ice, but in Western Hudson Bay (WH), the seasonal ice cycle forces polar bears ashore each summer. Survival of bears on land in WH is correlated with breakup and the ice-free season length, and studies suggest that exceeding thresholds in these variables will lead to large declines in the WH population. To estimate when anthropogenic warming may have progressed sufficiently to threaten the persistence of polar bears in WH, we predict changes in the ice cycle and the sea ice concentration (SIC) in spring (the primary feeding period of polar bears) with a high-resolution sea ice-ocean model and warming forced with 21st century IPCC greenhouse gas (GHG) emission scenarios: B1 (low), A1B (medium), and A2 (high). We define critical years for polar bears based on proposed thresholds in breakup and ice-free season and we assess when ice-cycle conditions cross these thresholds. In the three scenarios, critical years occur more commonly after 2050. From 2001 to 2050, 2 critical years occur under B1 and A2, and 4 under A1B; from 2051 to 2100, 8 critical years occur under B1, 35 under A1B and 41 under A2. Spring SIC in WH is high (>90%) in all three scenarios between 2001 and 2050, but declines rapidly after 2050 in A1B and A2. From 2090 to 2100, the mean spring SIC is 84 (±7)% in B1, 56 (±26)% in A1B and 20 (±13)% in A2. Our predictions suggest that the habitat of polar bears in WH will deteriorate in the 21st century. Ice predictions in A1B and A2 suggest that the polar bear population may struggle to persist after ca. 2050. Predictions under B1 suggest that reducing GHG emissions could allow polar bears to persist in WH throughout the 21st century.
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12
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Robbins CT, Lopez-Alfaro C, Rode KD, Tøien Ø, Nelson OL. Hibernation and seasonal fasting in bears: the energetic costs and consequences for polar bears. J Mammal 2012. [DOI: 10.1644/11-mamm-a-406.1] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Stirling I, Derocher AE. Effects of climate warming on polar bears: a review of the evidence. GLOBAL CHANGE BIOLOGY 2012; 18:2694-706. [PMID: 24501049 DOI: 10.1111/j.1365-2486.2012.02753.x] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 04/09/2012] [Accepted: 04/09/2012] [Indexed: 05/25/2023]
Abstract
Climate warming is causing unidirectional changes to annual patterns of sea ice distribution, structure, and freeze-up. We summarize evidence that documents how loss of sea ice, the primary habitat of polar bears (Ursus maritimus), negatively affects their long-term survival. To maintain viable subpopulations, polar bears depend on sea ice as a platform from which to hunt seals for long enough each year to accumulate sufficient energy (fat) to survive periods when seals are unavailable. Less time to access to prey, because of progressively earlier breakup in spring, when newly weaned ringed seal (Pusa hispida) young are available, results in longer periods of fasting, lower body condition, decreased access to denning areas, fewer and smaller cubs, lower survival of cubs as well as bears of other age classes and, finally, subpopulation decline toward eventual extirpation. The chronology of climate-driven changes will vary between subpopulations, with quantifiable negative effects being documented first in the more southerly subpopulations, such as those in Hudson Bay or the southern Beaufort Sea. As the bears' body condition declines, more seek alternate food resources so the frequency of conflicts between bears and humans increases. In the most northerly areas, thick multiyear ice, through which little light penetrates to stimulate biological growth on the underside, will be replaced by annual ice, which facilitates greater productivity and may create habitat more favorable to polar bears over continental shelf areas in the short term. If the climate continues to warm and eliminate sea ice as predicted, polar bears will largely disappear from the southern portions of their range by mid-century. They may persist in the northern Canadian Arctic Islands and northern Greenland for the foreseeable future, but their long-term viability, with a much reduced global population size in a remnant of their former range, is uncertain.
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Affiliation(s)
- Ian Stirling
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9
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Whiteman JP, Greller KA, Harlow HJ, Felicetti LA, Rode KD, Ben-David M. Carbon isotopes in exhaled breath track metabolic substrates in brown bears (Ursus arctos). J Mammal 2012. [DOI: 10.1644/11-mamm-s-178.1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Predicting climate change impacts on polar bear litter size. Nat Commun 2011; 2:186. [PMID: 21304515 PMCID: PMC3105343 DOI: 10.1038/ncomms1183] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Accepted: 01/11/2011] [Indexed: 11/23/2022] Open
Abstract
Predicting the ecological impacts of climate warming is critical for species conservation. Incorporating future warming into population models, however, is challenging because reproduction and survival cannot be measured for yet unobserved environmental conditions. In this study, we use mechanistic energy budget models and data obtainable under current conditions to predict polar bear litter size under future conditions. In western Hudson Bay, we predict climate warming-induced litter size declines that jeopardize population viability: ∼28% of pregnant females failed to reproduce for energetic reasons during the early 1990s, but 40–73% could fail if spring sea ice break-up occurs 1 month earlier than during the 1990s, and 55–100% if break-up occurs 2 months earlier. Simultaneously, mean litter size would decrease by 22–67% and 44–100%, respectively. The expected timeline for these declines varies with climate-model-specific sea ice predictions. Similar litter size declines may occur in over one-third of the global polar bear population. Predicting ecological impacts of climate change is complicated, because key biological parameters are unknown for future conditions. Using a mechanistic energy budget model to relate sea ice to polar bear reproduction, Molnár et al. predict decreases in litter size with anticipated changes in sea ice.
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