Estimating the energy expenditure of free‐ranging polar bears using tri‐axial accelerometers: A validation with doubly labeled water

Pagano, Anthony M.; Williams, Terrie M.

doi:10.1002/ece3.5053

Cited by 45 publications

(52 citation statements)

References 88 publications

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“…S3). This is consistent with previous studies in the same region (Mauritzen et al 2001, 2002, Hamilton et al 2017, Tartu et al 2018 and other regions (Stirling & Parkinson 2006, Pagano & Williams 2019. There were large interindividual variations within ecotypes suggesting that individual polar bears differ in their habitat use.…”

Section: Discussionsupporting

confidence: 92%

“…Polar bears with different spatial strategies have different energy requirements (Mauritzen et al 2001, Pagano & Williams 2019, Blévin et al 2020. Studies on the Southern Beaufort Sea and Chukchi Sea populations suggest that energy requirements are tightly related to movement patterns (Ware et al 2017, Pagano et al 2018, and it has been recently shown that spatial strategy influences energy requirements for polar bears of the Barents Sea population (Blévin et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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Space-use strategy affects energy requirements in Barents Sea polar bears

Blanchet

Aars

Andersen

et al. 2020

Mar. Ecol. Prog. Ser.

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Polar bears Ursus maritimus are currently facing rapid environmental changes with loss of sea ice and shifts in their prey distribution. Two distinct ecotypes exist in the Barents Sea, where sea ice is decreasing at the highest rate in the Arctic. Coastal bears remain within the Archipelago of Svalbard year-round, whereas offshore bears follow the marginal ice zone (MIZ). We explored these 2 ecotypes’ habitat use, activity and energy needs as well as seasonal variation within these parameters. During the period from 2011-2018, adult female polar bears were equipped with GPS collars and activity sensors (n = 84); 46 of these were equipped with conductivity switches to record aquatic behaviour. Offshore bears travelled longer distances at a higher speed on land and at sea away from land and had a higher activity rate compared to coastal bears. This translated into higher overall energy expenditure. Offshore bears also undertook more distant and energetically costly trips from land to the MIZ, swimming in open water. Both ecotypes showed similar seasonal patterns of activity and movement consistent with their life history linked to sea ice phenology. Despite higher energy expenditure, the offshore strategy seemed to be as profitable as the coastal one as females had marginally better spring body condition, likely due to their specialized high caloric diet of seals throughout the year. However, both ecotypes are currently experiencing habitat changes. Future studies should aim to predict how rapidly declining sea ice in the Barents Sea may challenge polar bears energetically during the coming decades.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Space-use strategy affects energy requirements in Barents Sea polar bears

Blanchet

Aars

Andersen

et al. 2020

Mar. Ecol. Prog. Ser.

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“…The use of doubly labelled water (DLW) remains one of the best techniques for estimating metabolic rates under natural conditions (Nagy et al , 1999; Shaffer, 2011), but it can be infeasible for many species because it typically requires an animal to be captured twice within a period of days to weeks (Speakman, 1997). Metabolic rates of captive animals are thus increasingly used to fill the metabolic data gap and are particularly useful for the ability to isolate the costs of discrete activities and physiological or life history events that can then be applied to estimate the energy requirements of wild populations (Williams et al , 2007; Thometz et al , 2014; Pagano and Williams, 2019). Captive studies cannot, however, mimic the complex behaviour exhibited by free-ranging animals.…”

Section: Introductionmentioning

confidence: 99%

Factors affecting energy expenditure in a declining fur seal population

McHuron

Sterling

Costa

et al. 2019

Conservation Physiology

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Quantifying metabolic rates and the factors that influence them is key to wildlife conservation efforts because anthropogenic activities and habitat alteration can disrupt energy balance, which is critical for reproduction and survival. We investigated the effect of diving behaviour, diet and season on field metabolic rates (FMR) and foraging success of lactating northern fur seals (Callorhinus ursinus) from the Pribilof Islands during a period of population decline. Variation in at-sea FMR was in part explained by season and trip duration, with values that ranged from 5.18 to 9.68 W kg−1 (n = 48). Fur seals experienced a 7.2% increase in at-sea FMR from summer to fall and a 1.9% decrease in at-sea FMR for each additional day spent at sea. There was no effect of foraging effort, dive depth or diet on at-sea FMR. Mass gains increased with trip duration and were greater in the fall compared with summer, but were unrelated to at-sea FMR, diving behaviour and diet. Seasonal increases in at-sea FMR may have been due to costs associated with the annual molt but did not appear to adversely impact the ability of females to gain mass on foraging trips. The overall high metabolic rates in conjunction with the lack of any diet-related effects on at-sea FMR suggests that northern fur seals may have reached a metabolic ceiling early in the population decline. This provides indirect evidence that food limitation may be contributing to the low pup growth rates observed in the Pribilof Islands, as a high metabolic overhead likely results in less available energy for lactation. The limited ability of female fur seals to cope with changes in prey availability through physiological mechanisms is particularly concerning given the recent and unprecedented environmental changes in the Bering Sea that are predicted to have ecosystem-level impacts.

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“…We calculated ODBA as the absolute sum of dynamic acceleration across the three axes (Wilson et al ). For swimming movements, we used the mean swimming metabolic rate determined by Griffen () (2.75 mL O 2 ·g ‐1 ·h ‐1 ) as described by Pagano and Williams (). To evaluate potential differences in energy expenditure between bears that moved to land and those that stayed on the sea ice, we used two‐sample t ‐tests in R, which are considered to retain suitable statistical power at low sample sizes (de Winter ).…”

Section: Methodsmentioning

confidence: 99%

The seasonal energetic landscape of an apex marine carnivore, the polar bear

Pagano

Atwood

Durner

et al. 2020

Ecology

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Divergent movement strategies have enabled wildlife populations to adapt to environmental change. In recent decades, the Southern Beaufort Sea subpopulation of polar bears (Ursus maritimus) has developed a divergent movement strategy in response to diminishing sea ice where the majority of the subpopulation (73–85%) stays on the sea ice in summer and the remaining bears move to land. Although declines in sea ice are generally considered a challenge to energy balance in polar bears residing in some regions of the Arctic, little quantitative data exists concerning the seasonal energy expenditures of this apex marine carnivore. We used GPS satellite collars with tri‐axial accelerometers and conductivity sensors to measure the location, behavior, and energy expenditure of five adult female polar bears in the southern Beaufort Sea across seasons of sea ice breakup and minimum extent. Using a Bayesian mixed‐effects model, we found that energy expenditure was influenced by month, ocean depth, and habitat type (sea ice or land). Total energy expenditure from May through September ranged from 37.7 to 47.2 mJ/kg for individual bears. Bears that moved to land expended 7% more energy on average from May through September than bears that remained on the receding sea ice. In August, when bears were moving from the sea ice to land or moving north with the receding pack ice, bears that moved to land spent 7% more time swimming and expended 22% more energy. This means the immediate cost of moving to land exceeded the cost of remaining on the receding summer pack ice. These findings suggest a physiological reason why the majority of the Southern Beaufort Sea subpopulation continues to inhabit a diminishing summer ice platform. However, bears that moved to land spent 29% more time in preferred hunting habitats over the continental shelf than bears that remained on the sea ice. Bears on land also had access to subsistence‐harvested bowhead whale carcasses. Hence, our findings indicate there may be a greater overall energetic benefit to move to land in this region, which suggests that the use of the diminishing summer sea ice may be functioning as an ecological trap.

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Estimating the energy expenditure of free‐ranging polar bears using tri‐axial accelerometers: A validation with doubly labeled water

Cited by 45 publications

References 88 publications

Space-use strategy affects energy requirements in Barents Sea polar bears

Space-use strategy affects energy requirements in Barents Sea polar bears

Factors affecting energy expenditure in a declining fur seal population

The seasonal energetic landscape of an apex marine carnivore, the polar bear

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