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1. Grizzly and polar bears as nonconsumptive cultural keystone species

   https://doi.org/10.1139/facets-2020-0089  

   Clark, Douglas ; Artelle, Kyle ; Darimont, Chris ; Housty, William ; Tallio, Clyde ; Neasloss, Douglas ; Schmidt, Aimee ; Wiget, Andrew ; Turner, Nancy ( January 2021 , FACETS)

   Olive, Andrea (Ed.)

   Grizzly bears and polar bears often serve as ecological “flagship species” in conservation efforts, but although consumptively used in some areas and cultures they can also be important cultural keystone species even where not hunted. We extend the application of established criteria for defining cultural keystone species to also encompass species with which cultures have a primarily nonconsumptive relationship but that are nonetheless disproportionately important to well-being and identity. Grizzly bears in coastal British Columbia are closely linked to many Indigenous Peoples (including the Haíɫzaqv (Heiltsuk), Kitasoo/Xai’xais, and Nuxalk First Nations), where they are central to the identity, culture, and livelihoods of individuals, families, Chiefs, and Nations. Polar bears in Churchill, Manitoba, provide another example as a cultural keystone species for a mixed Indigenous and non-Indigenous community in which many of the livelihood benefits from the species are mediated by economic transactions in a globalized tourism market. We discuss context specificity and questions of equity in sharing of benefits from cultural keystone species. Our expanded definition of cultural keystone species gives broader recognition of the beyond-ecological importance of these species to Indigenous Peoples, which highlights the societal and ecological importance of Indigenous sovereignty and could facilitate the increased cross-cultural understanding critical to reconciliation. 

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2. Dietary ecology of Alaskan polar bears ( Ursus maritimus ) through time and in response to Arctic climate change

   https://doi.org/10.1111/gcb.15573  

   Petherick, Ansley S. ; Reuther, Joshua D. ; Shirar, Scott J. ; Anderson, Shelby L. ; DeSantis, Larisa R. G. ( April 2021 , Global Change Biology)

   Arctic climate change poses serious threats to polar bears (Ursus maritimus) as reduced sea ice makes seal prey inaccessible and marine ecosystems undergo bottom‐up reorganization. Polar bears’ elongated skulls and reduced molar dentition, as compared to their sister species the grizzly bear (Ursus arctos), are adaptations associated with hunting seals on sea ice and a soft, lipid‐rich diet of blubber and meat. With significant declines in sea ice, it is unclear if and how polar bears may be altering their diets. Clarifying polar bear dietary responses to changing climates, both today and in the past, is critical to proper conservation and management of this apex predator. This is particularly important when a dietary strategy may be maladaptive. Here, we test the hypothesis that hard‐food consumption (i.e., less preferred foods including bone), inferred from dental microwear texture analysis, increased with Arctic warming. We find that polar bears demonstrate a conserved absence of hard‐object feeding in Alaska through time (including approximately 1000 years ago), until the 21st century, consistent with a highly conserved and specialized diet of soft blubber and flesh. Notably, our results also suggest that some 21st‐century polar bears may be consuming harder foods (e.g., increased carcass utilization, terrestrial foods including garbage), despite having skulls and metabolisms poorly suited for such a diet. Prior to the 21st century, only polar bears with larger mandibles demonstrated increased hard‐object feeding, though to a much lower degree than closely related grizzly bears which regularly consume mechanically challenging foods. Polar bears, being morphologically specialized, have biomechanical constraints which may limit their ability to consume mechanically challenging diets, with dietary shifts occurring only under the most extreme scenarios. Collectively, the highly specialized diets and cranial morphology of polar bears may severely limit their ability to adapt to a warming Arctic.

    

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3. The acute physiological response of polar bears to helicopter capture

   https://doi.org/10.1002/jwmg.22238  

   Whiteman, John P. ; Harlow, Henry J. ; Durner, George M. ; Regehr, Eric V. ; Amstrup, Steven C. ; Pagano, Anthony M. ; Ben‐David, Merav ( April 2022 , The Journal of Wildlife Management)

   Many wildlife species are live captured, sampled, and released; for polar bears (Ursus maritimus) capture often requires chemical immobilization via helicopter darting. Polar bears reduce their activity for approximately 4 days after capture, likely reflecting stress recovery. To better understand this stress, we quantified polar bear activity (via collar‐mounted accelerometers) and body temperature (via loggers in the body core [T_abd] and periphery [T_per]) during 2–6 months of natural behavior, and during helicopter recapture and immobilization. Recapture induced bouts of peak activity higher than those that occurred during natural behavior for 2 of 5 bears, greater peak T_perfor 3 of 6 bears, and greater peak T_abdfor 1 of 6 bears. High body temperature (>39.0°C) occurred in T_perfor 3 of 6 individuals during recapture and 6 of 6 individuals during natural behavior, and in T_abdfor 2 of 6 individuals during recapture and 3 of 6 individuals during natural behavior. Measurements of T_abdand T_percorrelated with rectal temperatures measured after immobilization, supporting the use of rectal temperatures for monitoring bear response to capture. Using a larger dataset (n = 66 captures), modeling of blood biochemistry revealed that maximum ambient temperature during recapture was associated with a stress leukogram (7–26% decline in percent lymphocytes, 12–21% increase in percent neutrophils) and maximum duration of helicopter operations had a similar but smaller effect. We conclude that polar bear activity and body temperature during helicopter capture are similar to that which occurs during the most intense events of natural behavior; high body temperature, especially in warm capture conditions, is a key concern; additional study of stress leukograms in polar bears is needed; and additional data collection regarding capture operations would be useful.

    

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

   https://doi.org/10.1002/ece3.5053  

   Pagano, Anthony M. ; Williams, Terrie M. ( March 2019 , Ecology and Evolution)

   Measures of energy expenditure can be used to inform animal conservation and management, but methods for measuring the energy expenditure of free‐ranging animals have a variety of limitations. Advancements in biologging technologies have enabled the use of dynamic body acceleration derived from accelerometers as a proxy for energy expenditure. Although dynamic body acceleration has been shown to strongly correlate with oxygen consumption in captive animals, it has been validated in only a few studies on free‐ranging animals. Here, we use relationships between oxygen consumption and overall dynamic body acceleration in resting and walking polar bearsUrsus maritimusand published values for the costs of swimming in polar bears to estimate the total energy expenditure of 6 free‐ranging polar bears that were primarily using the sea ice of the Beaufort Sea. Energetic models based on accelerometry were compared to models of energy expenditure on the same individuals derived from doubly labeled water methods. Accelerometer‐based estimates of energy expenditure on average predicted total energy expenditure to be 30% less than estimates derived from doubly labeled water. Nevertheless, accelerometer‐based measures of energy expenditure strongly correlated (r² = 0.70) with measures derived from doubly labeled water. Our findings highlight the strengths and limitations in dynamic body acceleration as a measure of total energy expenditure while also further supporting its use as a proxy for instantaneous, detailed energy expenditure in free‐ranging animals.

    

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5. The post-emergence period for denning polar bears: phenology and influence on cub survival

   https://doi.org/10.1093/jmammal/gyae010  

   Andersen, Erik M. ; Wilson, Ryan R. ; Rode, Karyn D. ; Durner, George M. ; Atwood, Todd C. ; Gustine, David D. ; Wang, ed., Guiming ( March 2024 , Journal of Mammalogy)

   Among polar bears (Ursus maritimus), only parturient females den for extended periods, emerging from maternal dens in spring after having substantially depleted their energy reserves during a fast that can exceed 8 months. Although den emergence coincides with a period of increasing prey availability, polar bears typically do not depart immediately to hunt, but instead remain at the den for up to a month. This delay suggests that there are likely adaptive advantages to remaining at the den between emergence and departure, but the influence of the timing and duration of this post-emergence period on cub survival has not been evaluated previously. We used temperature and location data from 70 denning bears collared within the Southern Beaufort Sea and Chukchi Sea subpopulations to estimate the phenology of the post-emergence period. We evaluated the influence of various spatial and temporal features on duration of the post-emergence period and evaluated the potential influence of post-emergence duration on litter survival early in the spring following denning. For dens that likely contained viable cubs at emergence (n = 56), mean den emergence occurred on 16 March (SE = 1.4 days) and mean departure on 24 March (SE = 1.6 days), with dates typically occurring later in the Chukchi Sea relative to Southern Beaufort Sea and on land relative to sea ice. Mean duration of the post-emergence period was 7.9 days (SE = 1.4) for bears that were observed with cubs later in the spring, which was over 4 times longer than duration of those observed without cubs (1.9 days). Litter survival in the spring following denning (n = 31 dens) increased from 0.5 to 0.9 when duration of the post-emergence period increased by ~4 days and other variables were held at mean values. Our limited sample size and inability to verify cub presence at emergence suggests that future research is merited to improve our understanding of this relationship. Nonetheless, our results highlight the importance of the post-emergence period in contributing to reproductive success and can assist managers in developing conservation and mitigation strategies in denning areas, which will be increasingly important as human activities expand in the Arctic.

    

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