1
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Penk SR, Sadana P, Archer LC, Pagano AM, Cattet MRL, Lunn NJ, Thiemann GW, Molnár PK. A body composition model with multiple storage compartments for polar bears ( Ursus maritimus). CONSERVATION PHYSIOLOGY 2023; 11:coad043. [PMID: 37346266 PMCID: PMC10281502 DOI: 10.1093/conphys/coad043] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 05/08/2023] [Accepted: 06/15/2023] [Indexed: 06/23/2023]
Abstract
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.
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Affiliation(s)
- Stephanie R Penk
- Corresponding author: Laboratory of Quantitative Global Change Ecology, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada. E-mail:
| | - Pranav Sadana
- Laboratory of Quantitative Global Change Ecology, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
- Department of Biology, University of Winnipeg, 515 Portage Ave, Winnipeg, Manitoba R3B 2E9, Canada
| | - Louise C Archer
- Laboratory of Quantitative Global Change Ecology, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
| | - Anthony M Pagano
- U.S. Geological Survey, Alaska Science Center, 4210 University Dr., Anchorage, AK 99508 USA
| | - Marc R L Cattet
- Fish and Wildlife Branch, Department of Environment, Government of Yukon, 10 Burns Road, Whitehorse, Yukon Y1A 4Y9, Canada
| | - Nicholas J Lunn
- Wildlife Research Division, Science and Technology Branch, Environment Canada and Climate Change Canada, 11455 Saskatchewan Dr., Edmonton, Alberta T6G 2E9, Canada
| | - Gregory W Thiemann
- Faculty of Environmental and Urban Change, York University, 4700 Keele St., Toronto, Ontario M3J 1P3, Canada
| | - Péter K Molnár
- Laboratory of Quantitative Global Change Ecology, Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5S 3B2 Canada
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2
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Togunov RR, Derocher AE, Lunn NJ, Auger-Méthé M. Drivers of polar bear behavior and the possible effects of prey availability on foraging strategy. MOVEMENT ECOLOGY 2022; 10:50. [PMID: 36384775 PMCID: PMC9670556 DOI: 10.1186/s40462-022-00351-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 11/09/2022] [Indexed: 06/05/2023]
Abstract
BACKGROUND Change in behavior is one of the earliest responses to variation in habitat suitability. It is therefore important to understand the conditions that promote different behaviors, particularly in areas undergoing environmental change. Animal movement is tightly linked to behavior and remote tracking can be used to study ethology when direct observation is not possible. METHODS We used movement data from 14 polar bears (Ursus maritimus) in Hudson Bay, Canada, during the foraging season (January-June), when bears inhabit the sea ice. We developed an error-tolerant method to correct for sea ice drift in tracking data. Next, we used hidden Markov models with movement and orientation relative to wind to study three behaviors (stationary, area-restricted search, and olfactory search) and examine effects of 11 covariates on behavior. RESULTS Polar bears spent approximately 47% of their time in the stationary drift state, 29% in olfactory search, and 24% in area-restricted search. High energy behaviors occurred later in the day (around 20:00) compared to other populations. Second, olfactory search increased as the season progressed, which may reflect a shift in foraging strategy from still-hunting to active search linked to a shift in seal availability (i.e., increase in haul-outs from winter to the spring pupping and molting seasons). Last, we found spatial patterns of distribution linked to season, ice concentration, and bear age that may be tied to habitat quality and competitive exclusion. CONCLUSIONS Our observations were generally consistent with predictions of the marginal value theorem, and differences between our findings and other populations could be explained by regional or temporal variation in resource availability. Our novel movement analyses and finding can help identify periods, regions, and conditions of critical habitat.
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Affiliation(s)
- Ron R. Togunov
- Institute for the Oceans and Fisheries, The University of British Columbia, V6T 1Z4 Vancouver, Canada
- Department of Zoology, The University of British Columbia, Vancouver, V6T 1Z4 Canada
| | - Andrew E. Derocher
- Department of Biological Sciences, University of Alberta, Edmonton, T6G 2E9 Canada
| | - Nicholas J. Lunn
- Wildlife Research Division, Science and Technology Branch, Environment and Climate Change Canada, Edmonton, T6G 2E9 Canada
| | - Marie Auger-Méthé
- Institute for the Oceans and Fisheries, The University of British Columbia, V6T 1Z4 Vancouver, Canada
- Department of Statistics, The University of British Columbia, Vancouver, V6T 1Z4 Canada
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3
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Griffen BD, Whiteman JP, Pullan S. Significance of autumn and winter food consumption for reproduction by Southern Beaufort Sea polar bears, Ursus maritimus. Polar Biol 2022. [DOI: 10.1007/s00300-022-03066-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
AbstractPolar bears (Ursus maritimus) in the southern Beaufort Sea experience long annual periods when preferred seal prey are scarce or are unavailable. Consumption of bowhead whale (Balaena mysticetus) carcasses from native Alaskan subsistence hunting is increasingly common for onshore polar bears, yet the energetic consequences of this consumption remain unclear. We use data on bears captured repeatedly over periods that encompassed autumn and winter, combined with calculations, to show that adult female bears likely consume an average of at least 4 seal equivalents during both autumn and winter periods and that considerable variation in energy intake exists across individual bears. We further show that subsistence-caught whale carcasses provide an upper threshold of > 4000 seal equivalents, which could potentially meet mean consumption needs of ~ 80% of the southern Beaufort Sea bear subpopulation during autumn and winter periods. Finally, we modify an existing model to show that observed mass changes over autumn and winter could substantially alter spring foraging habitat choice by females with cubs and the chance that a female with reduced energy reserves would abort a pregnancy or abandon cubs in favor of increasing her own survival; these behaviors could potentially influence population vital rates. Our study highlights the importance of mass dynamics over the autumn and winter months, points to the need for additional data on foraging and energetics over this period, and indicates that the recent declines in polar bear body condition in some subpopulations could have complex effects on reproduction.
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4
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Summer/fall diet and macronutrient assimilation in an Arctic predator. Oecologia 2022; 198:917-931. [PMID: 35412091 DOI: 10.1007/s00442-022-05155-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 03/28/2022] [Indexed: 10/18/2022]
Abstract
Free-ranging predator diet estimation is commonly achieved by applying molecular-based tracers because direct observation is not logistically feasible or robust. However, tracers typically do not represent all dietary macronutrients, which likely obscures resource use as prey proximate composition varies and tissue consumption can be specific. For example, polar bears (Ursus maritimus) preferentially consume blubber, yet diets have been estimated using fatty acids based on prey blubber or stable isotopes of lipid-extracted prey muscle, neither of which represent both protein and lipid macronutrient contributions. Further, additional bias can be introduced because dietary fat is known to be flexibly routed beyond short-term energy production and storage. We address this problem by simultaneously accounting for protein and lipid assimilation using carbon and nitrogen isotope compositions of lipid-containing prey muscle and blubber to infer summer/fall diet composition and macronutrient proportions from Chukchi Sea polar bear guard hair (n = 229) sampled each spring between 2008 and 2017. Inclusion of blubber (85-95% lipid by dry mass) expanded the isotope mixing space and improved separation among prey species. Ice-associated seals, including nutritionally dependent pups, were the primary prey in summer/fall diets with lower contributions by Pacific walruses (Odobenus rosmarus) and whales. Percent blubber estimates confirmed preferential selection of this tissue and represented the highest documented lipid assimilation for any animal species. Our results offer an improved understanding of summer/fall prey macronutrient usage by Chukchi Sea polar bears which likely coincides with a nutritional bottleneck as the sea ice minimum is approached.
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5
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Klappstein NJ, Potts JR, Michelot T, Börger L, Pilfold NW, Lewis MA, Derocher AE. Energy‐based step selection analysis: modelling the energetic drivers of animal movement and habitat use. J Anim Ecol 2022; 91:946-957. [DOI: 10.1111/1365-2656.13687] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 02/17/2022] [Indexed: 11/30/2022]
Affiliation(s)
| | - Jonathan R. Potts
- School of Mathematics and Statistics University of Sheffield, Hicks Building, Hounsfield Road Sheffield UK
| | - Théo Michelot
- Centre for Research into Ecological and Environmental Modelling University of St Andrews St Andrews UK
| | - Luca Börger
- Department of Biosciences Swansea University Swansea UK
- Centre for Biomathematics, College of Science Swansea University Swansea UK
| | - Nicholas W. Pilfold
- Conservation Science and Wildlife Health, San Diego Zoo Wildlife Alliance San Diego USA
| | - Mark A. Lewis
- Department of Biological Sciences University of Alberta Edmonton Canada
- Department of Mathematical and Statistical Sciences University of Alberta Edmonton Canada
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6
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Ross TR, Thiemann GW, Young BG, Ferguson SH. Complimentary diet analyses reveal intraspecific and temporal variation in ringed seal (Pusa hispida) foraging in the Canadian high arctic. Polar Biol 2022. [DOI: 10.1007/s00300-021-02999-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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7
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Lindsay JM, Laidre KL, Conn PB, Moreland EE, Boveng PL. Modeling ringed seal Pusa hispida habitat and lair emergence timing in the eastern Bering and Chukchi Seas. ENDANGER SPECIES RES 2021. [DOI: 10.3354/esr01140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Ringed seals Pusa hispida are reliant on snow and sea ice for denning, and a better understanding of ringed seal habitat selection and timing of emergence from snow dens (also called lairs) is needed to quantify and predict effects of climate change in the Arctic. We used generalized additive models to assess relationships between ringed seal counts, from spring aerial surveys in the Bering Sea (2012 and 2013) and Chukchi Sea (2016), and spatiotemporal covariates including survey date, remotely sensed snow and sea-ice values, and short-term weather data. We produced separate models for total ringed seal counts and for pup counts within each region. Our models showed that in both areas, total ringed seal counts increased over the course of the spring, especially after 15 May, indicating emergence from lairs and/or the onset of basking behavior. For the more northerly Chukchi Sea, we found a substantial unimodal effect of snow melt progression and a positive effect of snow depth on total ringed seal counts. In contrast, Bering Sea total ringed seal counts and pup counts in both regions were affected much more strongly by date than by habitat variables. Overall, our findings demonstrate that snow depth and melt play an important role in the timing of ringed seal den emergence, particularly in the Chukchi Sea, and suggest that ringed seal denning may be affected by continued shifts in melt and snow depth associated with climate change.
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Affiliation(s)
- JM Lindsay
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98105, USA
| | - KL Laidre
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98105, USA
- Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA 98105, USA
| | - PB Conn
- Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA 98115, USA
| | - EE Moreland
- Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA 98115, USA
| | - PL Boveng
- Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA 98115, USA
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8
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Togunov RR, Derocher AE, Lunn NJ, Auger‐Méthé M. Characterising menotactic behaviours in movement data using hidden Markov models. Methods Ecol Evol 2021. [DOI: 10.1111/2041-210x.13681] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ron R. Togunov
- Institute for the Oceans and Fisheries The University of British Columbia Vancouver BC Canada
- Department of Zoology The University of British Columbia Vancouver BC Canada
| | - Andrew E. Derocher
- Department of Biological Sciences University of Alberta Edmonton AB Canada
| | - Nicholas J. Lunn
- Department of Biological Sciences University of Alberta Edmonton AB Canada
- Wildlife Research Division, Science and Technology Branch Environment and Climate Change Canada Edmonton AB Canada
| | - Marie Auger‐Méthé
- Institute for the Oceans and Fisheries The University of British Columbia Vancouver BC Canada
- Department of Statistics University of British Columbia Vancouver BC Canada
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9
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Diet composition and body condition of polar bears (Ursus maritimus) in relation to sea ice habitat in the Canadian High Arctic. Polar Biol 2021. [DOI: 10.1007/s00300-021-02891-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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10
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Rode KD, Regehr EV, Bromaghin JF, Wilson RR, St Martin M, Crawford JA, Quakenbush LT. Seal body condition and atmospheric circulation patterns influence polar bear body condition, recruitment, and feeding ecology in the Chukchi Sea. GLOBAL CHANGE BIOLOGY 2021; 27:2684-2701. [PMID: 33644944 DOI: 10.1111/gcb.15572] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 02/10/2021] [Indexed: 06/12/2023]
Abstract
Polar bears (Ursus maritimus) are experiencing loss of sea ice habitats used to access their marine mammal prey. Simultaneously, ocean warming is changing ecosystems that support marine mammal populations. The interactive effects of sea ice and prey are not well understood yet may explain spatial-temporal variation in the response of polar bears to sea ice loss. Here, we examined the potential combined effects of sea ice, seal body condition, and atmospheric circulation patterns on the body condition, recruitment, diet, and feeding probability of 469 polar bears captured in the Chukchi Sea, 2008-2017. The body condition of ringed seals (Pusa hispida), the primary prey of females and subadults, was related to dietary proportions of ringed seal, feeding probability, and the body condition of females and cubs. In contrast, adult males consumed more bearded seals (Erignathus barbatus) and exhibited better condition when bearded seal body condition was higher. The litter size, number of yearlings per adult female, and the condition of dependent young were higher following winters characterized by low Arctic Oscillation conditions, consistent with a growing number of studies. Body condition, recruitment, and feeding probability were either not associated or negatively associated with sea ice conditions, suggesting that, unlike some subpopulations, Chukchi Sea bears are not currently limited by sea ice availability. However, spring sea ice cover declined 2% per year during our study reaching levels not previously observed in the satellite record and resulting in the loss of polar bear hunting and seal pupping habitat. Our study suggests that the status of ice seal populations is likely an important factor that can either compound or mitigate the response of polar bears to sea ice loss over the short term. In the long term, neither polar bears nor their prey are likely robust to limitless loss of their sea ice habitat.
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Affiliation(s)
- Karyn D Rode
- Alaska Science Center, U.S. Geological Survey, Anchorage, AK, USA
| | - Eric V Regehr
- Polar Science Center, University of Washington, Seattle, WA, USA
| | | | - Ryan R Wilson
- Marine Mammals Management, U.S. Fish and Wildlife Service, Anchorage, AK, USA
| | - Michelle St Martin
- Marine Mammals Management, U.S. Fish and Wildlife Service, Anchorage, AK, USA
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11
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Pagano AM, Williams TM. Physiological consequences of Arctic sea ice loss on large marine carnivores: unique responses by polar bears and narwhals. J Exp Biol 2021; 224:224/Suppl_1/jeb228049. [PMID: 33627459 DOI: 10.1242/jeb.228049] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Rapid environmental changes in the Arctic are threatening the survival of marine species that rely on the predictable presence of the sea ice. Two Arctic marine mammal specialists, the polar bear (Ursus maritimus) and narwhal (Monodon monoceros), appear especially vulnerable to the speed and capriciousness of sea ice deterioration as a consequence of their unique hunting behaviors and diet, as well as their physiological adaptations for slow-aerobic exercise. These intrinsic characteristics limit the ability of these species to respond to extrinsic threats associated with environmental change and increased industrial activity in a warming Arctic. In assessing how sea ice loss may differentially affect polar bears that hunt on the ice surface and narwhals that hunt at extreme depths below, we found that major ice loss translated into elevated locomotor costs that range from 3- to 4-fold greater than expected for both species. For polar bears this instigates an energy imbalance from the combined effects of reduced caloric intake and increased energy expenditure. For narwhals, high locomotor costs during diving increase the risk of ice entrapment due to the unreliability of breathing holes. These species-specific physiological constraints and extreme reliance on the polar sea ice conspire to make these two marine mammal specialists sentinels of climate change within the Arctic marine ecosystem that may foreshadow rapid changes to the marine ecosystem.
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Affiliation(s)
- Anthony M Pagano
- Institute for Conservation Research, San Diego Zoo Global, San Diego, CA 92027, USA
| | - Terrie M Williams
- University of California, Santa Cruz, Department of Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
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12
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Bourque J, Desforges JP, Levin M, Atwood TC, Sonne C, Dietz R, Jensen TH, Curry E, McKinney MA. Climate-associated drivers of plasma cytokines and contaminant concentrations in Beaufort Sea polar bears (Ursus maritimus). THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 745:140978. [PMID: 32738684 DOI: 10.1016/j.scitotenv.2020.140978] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 07/08/2020] [Accepted: 07/13/2020] [Indexed: 06/11/2023]
Abstract
Assessing polar bear (Ursus maritimus) immune function in relation to environmental stressors, including habitat change, nutritional stress, pathogen prevalence, and pollution, has been identified as critical for improved understanding of the species' health. The objectives of this study were two-fold: 1) to assess the role of climate-associated factors (habitat use, body condition) in explaining the plasma concentrations of contaminants in southern Beaufort Sea (SB) polar bears, and 2) to investigate how climate-associated factors, contaminant concentrations, and pathogen sero-prevalence influence the plasma concentrations of immune-signaling proteins called cytokines. A commercially available multiplex canine cytokine panel was validated for the quantification of five pro- and anti-inflammatory cytokines in polar bear plasma: tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), IL-8, IL-10, and interferon gamma-induced protein 10 (IP-10). This panel was then used to measure cytokine concentrations in 49 SB polar bears sampled in the springs of 2013 and 2014. Mean ∑PCBs (plasma), ∑OCs (plasma), and THg (hair) were 13.01 ± 1.52 ng g-1 w.w. (range: 0.17-52.63), 19.46 ± 1.17 ng g-1 w.w. (range: 6.63-45.82), and 0.49 μg g-1 d.w. (range: 0.99-15.18), respectively. Top models explaining variation in concentrations of plasma PCBs, plasma OC pesticides, and hair THg in SB polar bears included body mass index and/or habitat use (onshore versus offshore), with higher contaminant concentrations in leaner and/or offshore bears. Plasma cytokine concentrations were influenced most strongly by plasma PCBs and age, with little to no influence found for plasma OCs or hair THg concentrations, habitat use, or pathogen sero-prevalence. The lack of association between cytokines and these latter variables is likely due to a temporal disconnect between measured endpoints. The change of polar bear habitat use, feeding ecology, and body condition with ongoing climate warming is affecting exposure to contaminants and pathogens, with potential adverse consequences on a well-balanced immune system.
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Affiliation(s)
- Jennifer Bourque
- Wildlife and Fisheries Conservation Center, Department of Natural Resources and the Environment and Center for Environmental Sciences and Engineering, University of Connecticut, Storrs, CT, USA
| | - Jean-Pierre Desforges
- Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada
| | - Milton Levin
- Department of Pathobiology and Veterinary Sciences, University of Connecticut, Storrs, CT, USA
| | - Todd C Atwood
- US Geological Survey, Alaska Science Center, Anchorage, AK, USA
| | - Christian Sonne
- Department of Bioscience, Arctic Research Centre, Aarhus University, Roskilde 4000, Denmark
| | - Rune Dietz
- Department of Bioscience, Arctic Research Centre, Aarhus University, Roskilde 4000, Denmark
| | - Trine H Jensen
- Aalborg Zoo/Aalborg University, Mølleparkvej 63, 9000 Aalborg, Denmark
| | - Erin Curry
- Center for Conservation & Research of Endangered Wildlife, Cincinnati Zoo & Botanical Garden, Cincinnati, OH, USA
| | - Melissa A McKinney
- Wildlife and Fisheries Conservation Center, Department of Natural Resources and the Environment and Center for Environmental Sciences and Engineering, University of Connecticut, Storrs, CT, USA; Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, QC, Canada.
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13
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Laidre KL, Atkinson SN, Regehr EV, Stern HL, Born EW, Wiig Ø, Lunn NJ, Dyck M, Heagerty P, Cohen BR. Transient benefits of climate change for a high-Arctic polar bear (Ursus maritimus) subpopulation. GLOBAL CHANGE BIOLOGY 2020; 26:6251-6265. [PMID: 32964662 DOI: 10.1111/gcb.15286] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 05/18/2020] [Indexed: 06/11/2023]
Abstract
Kane Basin (KB) is one of the world's most northerly polar bear (Ursus maritimus) subpopulations, where bears have historically inhabited a mix of thick multiyear and annual sea ice year-round. Currently, KB is transitioning to a seasonally ice-free region because of climate change. This ecological shift has been hypothesized to benefit polar bears in the near-term due to thinner ice with increased biological production, although this has not been demonstrated empirically. We assess sea-ice changes in KB together with changes in polar bear movements, seasonal ranges, body condition, and reproductive metrics obtained from capture-recapture (physical and genetic) and satellite telemetry studies during two study periods (1993-1997 and 2012-2016). The annual cycle of sea-ice habitat in KB shifted from a year-round ice platform (~50% coverage in summer) in the 1990s to nearly complete melt-out in summer (<5% coverage) in the 2010s. The mean duration between sea-ice retreat and advance increased from 109 to 160 days (p = .004). Between the 1990s and 2010s, adult female (AF) seasonal ranges more than doubled in spring and summer and were significantly larger in all months. Body condition scores improved for all ages and both sexes. Mean litter sizes of cubs-of-the-year (C0s) and yearlings (C1s), and the number of C1s per AF, did not change between decades. The date of spring sea-ice retreat in the previous year was positively correlated with C1 litter size, suggesting smaller litters following years with earlier sea-ice breakup. Our study provides evidence for range expansion, improved body condition, and stable reproductive performance in the KB polar bear subpopulation. These changes, together with a likely increasing subpopulation abundance, may reflect the shift from thick, multiyear ice to thinner, seasonal ice with higher biological productivity. The duration of these benefits is unknown because, under unmitigated climate change, continued sea-ice loss is expected to eventually have negative demographic and ecological effects on all polar bears.
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Affiliation(s)
- Kristin L Laidre
- Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, USA
- Greenland Institute of Natural Resources, Nuuk, Greenland
| | - Stephen N Atkinson
- Wildlife Research Section, Department of Environment, Government of Nunavut, Igloolik, NU, Canada
| | - Eric V Regehr
- Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, USA
| | - Harry L Stern
- Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, USA
| | - Erik W Born
- Greenland Institute of Natural Resources, Nuuk, Greenland
| | - Øystein Wiig
- Natural History Museum, University of Oslo, Oslo, Norway
| | - Nicholas J Lunn
- Environment and Climate Change Canada, University of Alberta, Edmonton, AB, Canada
| | - Markus Dyck
- Wildlife Research Section, Department of Environment, Government of Nunavut, Igloolik, NU, Canada
| | - Patrick Heagerty
- Department of Biostatistics, University of Washington, Seattle, WA, USA
| | - Benjamin R Cohen
- Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, USA
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14
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Boucher NP, Derocher AE, Richardson ES. Spatial and temporal variability in ringed seal ( Pusa hispida) stable isotopes in the Beaufort Sea. Ecol Evol 2020; 10:4178-4192. [PMID: 32489588 PMCID: PMC7246210 DOI: 10.1002/ece3.6186] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 02/14/2020] [Accepted: 02/17/2020] [Indexed: 12/02/2022] Open
Abstract
Arctic ecosystem dynamics are shifting in response to warming temperatures and sea ice loss. Such ecosystems may be monitored by examining the diet of upper trophic level species, which varies with prey availability. To assess interannual variation in the Beaufort Sea ecosystem, we examined spatial and temporal trends in ringed seal (Pusa hispida) δ13C and δ15N in claw growth layers grown from 1964 to 2011. Stable isotopes were correlated with climate indices, environmental conditions, seal population productivity, and geographic location. Sex and age did not influence stable isotopes. Enriched 13C was linked to cyclonic circulation regimes, seal productivity, and westward sampling locations. Higher δ15N was linked to lower sea surface temperatures, a higher percentage of pups in the subsistence harvest, and sample locations that were eastward and further from shore. From the 1960s to 2000s, ringed seal niche width expanded, suggesting a diversification of diet due to expansion of prey and/or seal space use. Overall, trends in ringed seal stable isotopes indicate changes within the Beaufort Sea ecosystem affected by water temperatures and circulation regimes. We suggest that continued monitoring of upper trophic level species will yield insights into changing ecosystem structure with climate change.
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Affiliation(s)
- Nicole P. Boucher
- Department of Biological SciencesUniversity of AlbertaEdmontonABCanada
| | | | - Evan S. Richardson
- Wildlife Research Division, Science and Technology BranchEnvironment and Climate Change CanadaWinnipegMBCanada
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15
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Galicia MP, Thiemann GW, Dyck MG. Correlates of seasonal change in the body condition of an Arctic top predator. GLOBAL CHANGE BIOLOGY 2020; 26:840-850. [PMID: 31465583 DOI: 10.1111/gcb.14817] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 07/26/2019] [Indexed: 06/10/2023]
Abstract
Climate-driven sea ice loss has led to changes in the timing of key biological events in the Arctic, however, the consequences and rate of these changes remain largely unknown. Polar bears (Ursus maritimus) undergo seasonal changes in energy stores in relation to foraging opportunities and habitat conditions. Declining sea ice has been linked to reduced body condition in some subpopulations, however, the specific timing and duration of the feeding period when bears acquire most of their energy stores and its relationship to the timing of ice break-up is poorly understood. We used community-based sampling to investigate seasonality in body condition (energy stores) of polar bears in Nunavut, Canada, and examined the influence of sea ice variables. We used adipose tissue lipid content as an index of body condition for 1,206 polar bears harvested from 2010-2017 across five subpopulations with varying seasonal ice conditions: Baffin Bay (October-August), Davis Strait and Foxe Basin (year-round), Gulf of Boothia and Lancaster Sound (August-May). Similar seasonal patterns were found in body condition across subpopulations with bears at their nadir of condition in the spring, followed by fat accumulation past break-up date and subsequent peak body condition in autumn, indicating that bears are actively foraging in late spring and early summer. Late season feeding implies that even minor advances in the timing of break-up may have detrimental effects on foraging opportunities, body condition, and subsequent reproduction and survival. The magnitude of seasonal changes in body condition varied across the study area, presumably driven by local environmental conditions. Our results demonstrate how community-based monitoring of polar bears can reveal population-level responses to climate warming in advance of detectable demographic change. Our data on the seasonal timing of polar bear foraging and energy storage should inform predictive models of the effects of climate-mediated sea ice loss.
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Affiliation(s)
| | | | - Markus G Dyck
- Wildlife Research Station, Department of Environment, Government of Nunavut, Igloolik, NU, Canada
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16
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Reimer JR, Caswell H, Derocher AE, Lewis MA. Ringed seal demography in a changing climate. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2019; 29:e01855. [PMID: 30672632 DOI: 10.1002/eap.1855] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 10/09/2018] [Accepted: 11/13/2018] [Indexed: 06/09/2023]
Abstract
Climate change is affecting species' distributions and abundances worldwide. Baseline population estimates, against which future observations may be compared, are necessary if we are to detect ecological change. Arctic sea ice ecosystems are changing rapidly and we lack baseline population estimates for many ice-associated species. Provided we can detect them, changes in Arctic marine ecosystems may be signaled by changes in indicator species such as ringed seals (Pusa hispida). Ringed seal monitoring has provided estimates of survival and fertility rates, but these have not been used for population-level inference. Using matrix population models, we synthesized existing demographic parameters to obtain estimates of historical ringed seal population growth and structure in Amundsen Gulf and Prince Albert Sound, Canada. We then formalized existing hypotheses about the effects of emerging environmental stressors (i.e., earlier spring ice breakup and reduced snow depth) on ringed seal pup survival. Coupling the demographic model to ice and snow forecasts available from the Coupled Model Intercomparison Project resulted in projections of ringed seal population size and structure up to the year 2100. These projections showed median declines in population size ranging from 50% to 99%. Corresponding to these projected declines were substantial changes in population structure, with increasing proportions of ringed seal pups and adults and declining proportions of juveniles. We explored if currently collected, harvest-based data could be used to detect the projected changes in population stage structure. Our model suggests that at a present sample size of 100 seals per year, the projected changes in stage structure would only be reliably detected by mid-century, even for the most extreme climate models. This modeling process revealed inconsistencies in existing estimates of ringed seal demographic rates. Mathematical population models such as these can contribute both to understanding past population trends as well as predicting future ones, both of which are necessary if we are to detect and interpret future observations.
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Affiliation(s)
- Jody R Reimer
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta , T6G 2E9, Canada
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, T6G 2G1, Canada
| | - Hal Caswell
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, 1090, The Netherlands
| | - Andrew E Derocher
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta , T6G 2E9, Canada
| | - Mark A Lewis
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta , T6G 2E9, Canada
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, T6G 2G1, Canada
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17
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Reimer JR, Brown H, Beltaos-Kerr E, de Vries G. Evidence of intraspecific prey switching: stage-structured predation of polar bears on ringed seals. Oecologia 2018; 189:133-148. [PMID: 30456487 PMCID: PMC6323094 DOI: 10.1007/s00442-018-4297-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Accepted: 11/08/2018] [Indexed: 11/25/2022]
Abstract
Prey switching is a phenomenon in which a predator disproportionately consumes the most abundant prey type, and switches to preferentially consume another prey type if the first becomes relatively rare. This concept may be expanded outside of its usual usage describing switching between prey species (interspecific), to describe switching between prey stages within a given species (intraspecific). Polar bears (Ursus maritimus) are thought to seek out naive ringed seal (Pusa hispida) pups in the spring, but how that may change in years with low seal productivity is unknown. We addressed two main questions: If polar bears typically select for ringed seals’ pups, how does this change in years with reduced ringed-seal productivity? How does polar bear predation during years with low ringed-seal productivity impact the ringed seal population? We created a matrix population model for ringed seals to get an estimate of each stage’s availability to polar bears in the spring. These estimates of availability were combined with existing studies on the ages of seals consumed by polar bears in years of both high and low ringed seal productivity. Our results suggest that polar bears typically strongly select for ringed seal pups, but switch to disproportionately select older ringed seals in years with low pup availability. The effects of this on ringed seal population growth appear negligible. Non-intuitive results on the effect of prey switching on the prey population emphasize the importance of considering environmental sequences rather than individual years.
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Affiliation(s)
- Jody R Reimer
- Department of Biological Sciences, University of Alberta, Edmonton, Canada. .,Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Canada.
| | - Hannah Brown
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Canada
| | - Elaine Beltaos-Kerr
- Department of Mathematics and Statistics, MacEwan University, Edmonton, Canada
| | - Gerda de Vries
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Canada
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18
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Rode KD, Wilson RR, Douglas DC, Muhlenbruch V, Atwood TC, Regehr EV, Richardson ES, Pilfold NW, Derocher AE, Durner GM, Stirling I, Amstrup SC, St Martin M, Pagano AM, Simac K. Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity. GLOBAL CHANGE BIOLOGY 2018; 24:410-423. [PMID: 28994242 DOI: 10.1111/gcb.13933] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 08/02/2017] [Indexed: 05/27/2023]
Abstract
The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally. Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears (Ursus maritimus) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983-1999 and 2000-2016 and was related to an index of ringed seal body condition. This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems.
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Affiliation(s)
- Karyn D Rode
- U.S. Geological Survey, Alaska Science Center, Anchorage, AK, USA
| | - Ryan R Wilson
- U.S. Fish and Wildlife Service, Marine Mammals Management, Anchorage, AK, USA
| | - David C Douglas
- U.S. Geological Survey, Alaska Science Center, Juneau, AK, USA
| | | | - Todd C Atwood
- U.S. Geological Survey, Alaska Science Center, Anchorage, AK, USA
| | - Eric V Regehr
- U.S. Fish and Wildlife Service, Marine Mammals Management, Anchorage, AK, USA
| | - Evan S Richardson
- Wildlife Research Division, Science and Technology Branch, Environment Canada, Edmonton, AB, Canada
| | - Nicholas W Pilfold
- Institute for Conservation Research, San Diego Zoo Global, Escondido, CA, USA
| | - Andrew E Derocher
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - George M Durner
- U.S. Geological Survey, Alaska Science Center, Anchorage, AK, USA
| | - Ian Stirling
- Wildlife Research Division, Science and Technology Branch, Environment Canada, Edmonton, AB, Canada
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Steven C Amstrup
- Polar Bears International, Bozeman, MT, USA
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY, USA
| | - Michelle St Martin
- U.S. Fish and Wildlife Service, Marine Mammals Management, Anchorage, AK, USA
| | - Anthony M Pagano
- U.S. Geological Survey, Alaska Science Center, Anchorage, AK, USA
| | - Kristin Simac
- U.S. Geological Survey, Alaska Science Center, Anchorage, AK, USA
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19
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McKinney MA, Atwood TC, Pedro S, Peacock E. Ecological Change Drives a Decline in Mercury Concentrations in Southern Beaufort Sea Polar Bears. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:7814-7822. [PMID: 28612610 DOI: 10.1021/acs.est.7b00812] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We evaluated total mercury (THg) concentrations and trends in polar bears from the southern Beaufort Sea subpopulation from 2004 to 2011. Hair THg concentrations ranged widely among individuals from 0.6 to 13.3 μg g-1 dry weight (mean: 3.5 ± 0.2 μg g-1). Concentrations differed among sex and age classes: solitary adult females ≈ adult females with cubs ≈ subadults > adult males ≈ yearlings > cubs-of-the-year ≈ 2 year old dependent cubs. No variation was observed between spring and fall samples. For spring-sampled adults, THg concentrations declined by 13% per year, contrasting recent trends observed for other Western Hemispheric Arctic biota. Concentrations also declined by 15% per year considering adult males only, while a slower, nonsignificant decrease of 4.4% per year was found for adult females. Lower THg concentrations were associated with higher body mass index (BMI) and higher proportions of lower trophic position food resources consumed. Because BMI and diet were related, and the relationship to THg was strongest for BMI, trends were re-evaluated adjusting for BMI as the covariate. The adjusted annual decline was not significant. These findings indicate that changes in foraging ecology, not declining environmental concentrations of mercury, are driving short-term declines in THg concentrations in southern Beaufort Sea polar bears.
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Affiliation(s)
- Melissa A McKinney
- Wildlife and Fisheries Conservation Center, Department of Natural Resources and the Environment and Center for Environmental Sciences and Engineering, University of Connecticut , Storrs, Connecticut 06269, United States
| | - Todd C Atwood
- United States Geological Survey, Alaska Science Center , Anchorage, Alaska 99508, United States
| | - Sara Pedro
- Wildlife and Fisheries Conservation Center, Department of Natural Resources and the Environment and Center for Environmental Sciences and Engineering, University of Connecticut , Storrs, Connecticut 06269, United States
| | - Elizabeth Peacock
- United States Geological Survey, Alaska Science Center , Anchorage, Alaska 99508, United States
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20
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Windscapes and olfactory foraging in a large carnivore. Sci Rep 2017; 7:46332. [PMID: 28402340 PMCID: PMC5389353 DOI: 10.1038/srep46332] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 03/16/2017] [Indexed: 11/08/2022] Open
Abstract
The theoretical optimal olfactory search strategy is to move cross-wind. Empirical evidence supporting wind-associated directionality among carnivores, however, is sparse. We examined satellite-linked telemetry movement data of adult female polar bears (Ursus maritimus) from Hudson Bay, Canada, in relation to modelled winds, in an effort to understand olfactory search for prey. In our results, the predicted cross-wind movement occurred most frequently at night during winter, the time when most hunting occurs, while downwind movement dominated during fast winds, which impede olfaction. Migration during sea ice freeze-up and break-up was also correlated with wind. A lack of orientation during summer, a period with few food resources, likely reflected reduced cross-wind search. Our findings represent the first quantitative description of anemotaxis, orientation to wind, for cross-wind search in a large carnivore. The methods are widely applicable to olfactory predators and their prey. We suggest windscapes be included as a habitat feature in habitat selection models for olfactory animals when evaluating what is considered available habitat.
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21
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McKinney MA, Atwood TC, Iverson SJ, Peacock E. Temporal complexity of southern Beaufort Sea polar bear diets during a period of increasing land use. Ecosphere 2017. [DOI: 10.1002/ecs2.1633] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Melissa A. McKinney
- Department of Natural Resources and the Environment and Center for Environmental Sciences and Engineering; University of Connecticut; Storrs Connecticut 06269 USA
| | - Todd C. Atwood
- US Geological Survey; Alaska Science Center; Anchorage Alaska 99508 USA
| | - Sara J. Iverson
- Department of Biology; Dalhousie University; Halifax Nova Scotia B3H 4R2 Canada
| | - Elizabeth Peacock
- US Geological Survey; Alaska Science Center; Anchorage Alaska 99508 USA
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22
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Pilfold NW, Hedman D, Stirling I, Derocher AE, Lunn NJ, Richardson E. Mass Loss Rates of Fasting Polar Bears. Physiol Biochem Zool 2016; 89:377-88. [DOI: 10.1086/687988] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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23
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Pongracz JD, Derocher AE. Summer refugia of polar bears (Ursus maritimus) in the southern Beaufort Sea. Polar Biol 2016. [DOI: 10.1007/s00300-016-1997-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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24
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Tartu S, Bourgeon S, Aars J, Andersen M, Ehrich D, Thiemann GW, Welker JM, Routti H. Geographical Area and Life History Traits Influence Diet in an Arctic Marine Predator. PLoS One 2016; 11:e0155980. [PMID: 27196700 PMCID: PMC4873193 DOI: 10.1371/journal.pone.0155980] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 05/06/2016] [Indexed: 11/22/2022] Open
Abstract
Global changes are thought to affect most Arctic species, yet some populations are more at risk. Today, the Barents Sea ecoregion is suffering the strongest sea ice retreat ever measured; and these changes are suspected to modify food access and thus diet of several species. Biochemical diet tracers enable investigation of diet in species such as polar bears (Ursus maritimus). We examined individual diet variation of female polar bears in Svalbard, Norway, and related it to year, season (spring and autumn), sampling area and breeding status (solitary, with cubs of the year or yearlings). Sampling areas were split according to their ice cover: North-West (less sea ice cover), South-East (larger amplitude in sea ice extent) and North-East/South-West (NESW) as bears from that zone are more mobile among all regions of Svalbard. We measured fatty acid (FA) composition in adipose tissue and carbon (δ13C) and nitrogen (δ15N) stable isotopes in plasma and red blood cells. Females feeding in the North-West area had lower δ15N values than those from the NESW. In South-East females, δ13C values were lower in autumn compared to spring and females seemed less selective in their diet as depicted by large variances in stable isotope values. Considering the differences in FA composition and stable isotope values, we suggest that females from the North-West and South-East could ingest a higher proportion of avian prey. With regard to breeding status, solitary females had higher δ15N values and smaller variance in their stable isotopic values than females with cubs, suggesting that solitary females were more selective and prey on higher trophic level species (i.e. seals). Overall, our results indicate that prey availability for Svalbard polar bears varies according to geographical area and prey selectivity differs according to breeding status. Our findings suggest that complex changes in sea ice and prey availability will interact to affect Svalbard polar bear feeding patterns and associated nutrition.
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Affiliation(s)
- Sabrina Tartu
- Norwegian Polar Institute, Fram Centre, Tromsø, Norway
- * E-mail:
| | - Sophie Bourgeon
- Norwegian Polar Institute, Fram Centre, Tromsø, Norway
- UiT-The Arctic University of Norway, Department of Arctic and Marine Biology, Tromsø, Norway
| | - Jon Aars
- Norwegian Polar Institute, Fram Centre, Tromsø, Norway
| | | | - Dorothee Ehrich
- UiT-The Arctic University of Norway, Department of Arctic and Marine Biology, Tromsø, Norway
| | | | - Jeffrey M. Welker
- Department of Biological Sciences, University of Alaska Anchorage, Anchorage, Alaska, United States of America
- University Center in Svalbard, Longyearbyen, Svalbard, Norway
| | - Heli Routti
- Norwegian Polar Institute, Fram Centre, Tromsø, Norway
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25
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26
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Saadi Y, Yanto ITR, Herawan T, Balakrishnan V, Chiroma H, Risnumawan A. Ringed Seal Search for Global Optimization via a Sensitive Search Model. PLoS One 2016; 11:e0144371. [PMID: 26790131 PMCID: PMC4720396 DOI: 10.1371/journal.pone.0144371] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 11/17/2015] [Indexed: 11/18/2022] Open
Abstract
The efficiency of a metaheuristic algorithm for global optimization is based on its ability to search and find the global optimum. However, a good search often requires to be balanced between exploration and exploitation of the search space. In this paper, a new metaheuristic algorithm called Ringed Seal Search (RSS) is introduced. It is inspired by the natural behavior of the seal pup. This algorithm mimics the seal pup movement behavior and its ability to search and choose the best lair to escape predators. The scenario starts once the seal mother gives birth to a new pup in a birthing lair that is constructed for this purpose. The seal pup strategy consists of searching and selecting the best lair by performing a random walk to find a new lair. Affected by the sensitive nature of seals against external noise emitted by predators, the random walk of the seal pup takes two different search states, normal state and urgent state. In the normal state, the pup performs an intensive search between closely adjacent lairs; this movement is modeled via a Brownian walk. In an urgent state, the pup leaves the proximity area and performs an extensive search to find a new lair from sparse targets; this movement is modeled via a Levy walk. The switch between these two states is realized by the random noise emitted by predators. The algorithm keeps switching between normal and urgent states until the global optimum is reached. Tests and validations were performed using fifteen benchmark test functions to compare the performance of RSS with other baseline algorithms. The results show that RSS is more efficient than Genetic Algorithm, Particles Swarm Optimization and Cuckoo Search in terms of convergence rate to the global optimum. The RSS shows an improvement in terms of balance between exploration (extensive) and exploitation (intensive) of the search space. The RSS can efficiently mimic seal pups behavior to find best lair and provide a new algorithm to be used in global optimization problems.
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Affiliation(s)
- Younes Saadi
- Department of Information Systems, University of Malaya, 50603 Pantai Valley, Kuala Lumpur, Malaysia
| | - Iwan Tri Riyadi Yanto
- Department of Computer Science, University of Ahmad Dahlan, Jalan Kapas n 9, Yogyakarta, 55165, Indonesia
| | - Tutut Herawan
- Department of Information Systems, University of Malaya, 50603 Pantai Valley, Kuala Lumpur, Malaysia
| | - Vimala Balakrishnan
- Department of Information Systems, University of Malaya, 50603 Pantai Valley, Kuala Lumpur, Malaysia
| | - Haruna Chiroma
- Department of Computer Science, Federal College of Education, (Technical), Gombe, Nigeria
| | - Anhar Risnumawan
- Department of Information Systems, University of Malaya, 50603 Pantai Valley, Kuala Lumpur, Malaysia
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27
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Auger‐Méthé M, Derocher AE, Plank MJ, Codling EA, Lewis MA. Differentiating the Lévy walk from a composite correlated random walk. Methods Ecol Evol 2015. [DOI: 10.1111/2041-210x.12412] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marie Auger‐Méthé
- Department of Biological Sciences University of Alberta Edmonton Canada
| | | | - Michael J. Plank
- Department of Mathematics and Statistics University of Canterbury Christchurch New Zealnd
| | - Edward A. Codling
- Department of Mathematical Sciences University of Essex Colchester UK
| | - Mark A. Lewis
- Department of Biological Sciences University of Alberta Edmonton Canada
- Centre for Mathematical Biology Department of Mathematical and Statistical Sciences University of Alberta Edmonton Canada
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28
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Pilfold NW, Derocher AE, Stirling I, Richardson E. Multi-temporal factors influence predation for polar bears in a changing climate. OIKOS 2015. [DOI: 10.1111/oik.02000] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Andrew E. Derocher
- Dept of Biological Sciences; Univ. of Alberta; Edmonton, AB T6G 2E9 Canada
| | - Ian Stirling
- Dept of Biological Sciences; Univ. of Alberta; Edmonton, AB T6G 2E9 Canada
- Wildlife Research Division; Science and Technology Branch, Environment Canada; Edmonton, AB T6G 2E9 Canada
| | - Evan Richardson
- Wildlife Research Division; Science and Technology Branch, Environment Canada; Edmonton, AB T6G 2E9 Canada
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29
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Pavlova V, Nabe-Nielsen J, Dietz R, Svenning JC, Vorkamp K, Rigét FF, Sonne C, Letcher RJ, Grimm V. Field metabolic rate and PCB adipose tissue deposition efficiency in East Greenland polar bears derived from contaminant monitoring data. PLoS One 2014; 9:e104037. [PMID: 25101837 PMCID: PMC4125222 DOI: 10.1371/journal.pone.0104037] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 07/09/2014] [Indexed: 11/19/2022] Open
Abstract
Climate change will increasingly affect the natural habitat and diet of polar bears (Ursus maritimus). Understanding the energetic needs of polar bears is therefore important. We developed a theoretical method for estimating polar bear food consumption based on using the highly recalcitrant polychlorinated biphenyl (PCB) congener, 2,2′,4,4′,55-hexaCB (CB153) in bear adipose tissue as an indicator of food intake. By comparing the CB153 tissue concentrations in wild polar bears with estimates from a purposely designed individual-based model, we identified the possible combinations of field metabolic rates (FMR) and CB153 deposition efficiencies in East Greenland polar bears. Our simulations indicate that if 30% of the CB153 consumed by polar bear individuals were deposited into their adipose tissue, the corresponding FMR would be only two times the basal metabolic rate. In contrast, if the modelled CB153 deposition efficiency were 10%, adult polar bears would require six times more energy than that needed to cover basal metabolism. This is considerably higher than what has been assumed for polar bears in previous studies though it is similar to FMRs found in other marine mammals. An implication of this result is that even relatively small reductions in future feeding opportunities could impact the survival of East Greenland polar bears.
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Affiliation(s)
- Viola Pavlova
- Aarhus University, Department of Bioscience, Section for Marine Mammal Research, Roskilde, Denmark
- * E-mail:
| | - Jacob Nabe-Nielsen
- Aarhus University, Department of Bioscience, Section for Marine Mammal Research, Roskilde, Denmark
- Aarhus University, Arctic Research Centre, Aarhus, Denmark
| | - Rune Dietz
- Aarhus University, Department of Bioscience, Section for Marine Mammal Research, Roskilde, Denmark
- Aarhus University, Arctic Research Centre, Aarhus, Denmark
| | - Jens-Christian Svenning
- Aarhus University, Department of Bioscience, Section for Ecoinformatics and Biodiversity, Aarhus, Denmark
| | - Katrin Vorkamp
- Aarhus University, Arctic Research Centre, Aarhus, Denmark
- Aarhus University, Department of Environmental Science, Section for Environmental Chemistry and Toxicology, Roskilde, Denmark
| | - Frank Farsø Rigét
- Aarhus University, Department of Bioscience, Section for Marine Mammal Research, Roskilde, Denmark
| | - Christian Sonne
- Aarhus University, Department of Bioscience, Section for Marine Mammal Research, Roskilde, Denmark
- Aarhus University, Arctic Research Centre, Aarhus, Denmark
| | - Robert J. Letcher
- Ecotoxicology and Wildlife Division, Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Carleton University, Ottawa, Ontario, Canada
| | - Volker Grimm
- Helmholtz Centre for Environmental Research - UFZ, Department of Ecological Modelling, Leipzig, Germany
- University of Potsdam, Institute for Biochemistry and Biology, Potsdam, Germany
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30
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Rode KD, Regehr EV, Douglas DC, Durner G, Derocher AE, Thiemann GW, Budge SM. Variation in the response of an Arctic top predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations. GLOBAL CHANGE BIOLOGY 2014; 20:76-88. [PMID: 23913506 DOI: 10.1111/gcb.12339] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 07/20/2013] [Indexed: 06/02/2023]
Abstract
Polar bears (Ursus maritimus) have experienced substantial changes in the seasonal availability of sea ice habitat in parts of their range, including the Beaufort, Chukchi, and Bering Seas. In this study, we compared the body size, condition, and recruitment of polar bears captured in the Chukchi and Bering Seas (CS) between two periods (1986-1994 and 2008-2011) when declines in sea ice habitat occurred. In addition, we compared metrics for the CS population 2008-2011 with those of the adjacent southern Beaufort Sea (SB) population where loss in sea ice habitat has been associated with declines in body condition, size, recruitment, and survival. We evaluated how variation in body condition and recruitment were related to feeding ecology. Comparing habitat conditions between populations, there were twice as many reduced ice days over continental shelf waters per year during 2008-2011 in the SB than in the CS. CS polar bears were larger and in better condition, and appeared to have higher reproduction than SB bears. Although SB and CS bears had similar diets, twice as many bears were fasting in spring in the SB than in the CS. Between 1986-1994 and 2008-2011, body size, condition, and recruitment indices in the CS were not reduced despite a 44-day increase in the number of reduced ice days. Bears in the CS exhibited large body size, good body condition, and high indices of recruitment compared to most other populations measured to date. Higher biological productivity and prey availability in the CS relative to the SB, and a shorter recent history of reduced sea ice habitat, may explain the maintenance of condition and recruitment of CS bears. Geographic differences in the response of polar bears to climate change are relevant to range-wide forecasts for this and other ice-dependent species.
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Affiliation(s)
- Karyn D Rode
- Marine Mammals Management, U. S. Fish and Wildlife Service, 1011 E Tudor Road, Anchorage, AK, 99502, USA
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Pilfold NW, Derocher AE, Stirling I, Richardson E. Polar bear predatory behaviour reveals seascape distribution of ringed seal lairs. POPUL ECOL 2013. [DOI: 10.1007/s10144-013-0396-z] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Andrew E. Derocher
- Department of Biological SciencesUniversity of AlbertaT6G 2E9EdmontonCanada
| | - Ian Stirling
- Department of Biological SciencesUniversity of AlbertaT6G 2E9EdmontonCanada
- Wildlife Research DivisionScience and Technology Branch, Environment CanadaT6H 3S5EdmontonCanada
| | - Evan Richardson
- Department of Biological SciencesUniversity of AlbertaT6G 2E9EdmontonCanada
- Wildlife Research DivisionScience and Technology Branch, Environment CanadaT6H 3S5EdmontonCanada
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