Behaviour and characteristics of mating polar bears (Ursus maritimus) in the Beaufort Sea, Canada

Biddlecombe, Brooke A.; Derocher, Andrew E.; Richardson, Evan S.; Stirling, Ian

doi:10.1007/s00300-019-02485-5

Cited by 6 publications

(5 citation statements)

References 64 publications

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“…The stress axis of male bears may be unique in that adult males often fast during the spring breeding season (Cherry, Derocher, Stirling, & Richardson, 2009) while acquiring and defending mates. Males frequently have fresh cuts and wounds during the spring breeding season as a result of contest competition for estrus females (Biddlecombe, Derocher, Richardson, & Stirling, 2019; Derocher et al., 2010) and therefore may be both nutritionally and physically stressed resulting in lower body condition, increased stress during the breeding season, and potential lower MCBC levels in the summer. In addition, differences in body composition and the resultant higher metabolic requirements of males mean that males cannot cope with fasting stress as well as females (Molnár et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

The stress of Arctic warming on polar bears

Boonstra

Bodner

Bosson

et al. 2020

Global Change Biology

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Arctic ecosystems are changing rapidly in response to climate warming. While Arctic mammals are highly evolved to these extreme environments, particularly with respect to their stress axis, some species may have limited capacity to adapt to this change. We examined changes in key components of the stress axis (cortisol and its carrier protein—corticosteroid binding globulin [CBG]) in polar bears (Ursus maritimus) from western Hudson Bay (N = 300) over a 33 year period (1983–2015) during which time the ice‐free period was increasing. Changing sea ice phenology limits spring hunting opportunities and extends the period of onshore fasting. We assessed the response of polar bears to a standardized stressor (helicopter pursuit, darting, and immobilization) during their onshore fasting period (late summer–autumn) and quantified the serum levels of the maximum corticosteroid binding capacity (MCBC) of CBG, the serum protein that binds cortisol strongly, and free cortisol (FC). We quantified bear condition (age, sex, female with cubs or not, fat condition), sea ice (breakup in spring–summer, 1 year lagged freeze‐up in autumn), and duration of fasting until sample collection as well as cumulative impacts of the latter environmental traits from the previous year. Data were separated into “good” years (1983–1990) when conditions were thought to be optimal and “poor” years (1991–2015) when sea ice conditions deteriorated and fasting on land was extended. MCBC explained 39.4% of the variation in the good years, but only 28.1% in the poor ones, using both biological and environmental variables. MCBC levels decreased with age. Changes in FC were complex, but more poorly explained. Counterintuitively, MCBC levels increased with increased time onshore, 1 year lag effects, and in poor ice years. We conclude that MCBC is a biomarker of stress in polar bears and that the changes we document are a consequence of climate warming.

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Section: Discussionmentioning

confidence: 99%

The stress of Arctic warming on polar bears

Boonstra

Bodner

Bosson

et al. 2020

Global Change Biology

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“…Because relationships between age and body size have been shown to differ between bears in the two subpopulations [ 77 ], we included population as a factor in all regressions. We also examined relationships between age and body length with direct body measures (skull width, girth, and body mass) within the defined sex and age groups to better understand how morphometric variation may contribute to the patterns we observed in CIs and with two calculated measures commonly used to represent body mass (calculated body mass [ 55 , 65 , 66 ] and storage energy) [ 10 ].…”

Section: Methodsmentioning

confidence: 99%

“…However, larger structural size alone may be advantageous for polar bears in part because large-bodied prey can be more effectively captured by larger predators [51,52]. Further, polar bears are sexually size dimorphic and larger males have an advantage in competition for mates [53][54][55]. Thus, structural size may be an important factor affecting fitness in polar bears.…”

Section: Introductionmentioning

confidence: 99%

Identifying reliable indicators of fitness in polar bears

et al. 2020

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Animal structural body size and condition are often measured to evaluate individual health, identify responses to environmental change and food availability, and relate food availability to effects on reproduction and survival. A variety of condition metrics have been developed but relationships between these metrics and vital rates are rarely validated. Identifying an optimal approach to estimate the body condition of polar bears is needed to improve monitoring of their response to decline in sea ice habitat. Therefore, we examined relationships between several commonly used condition indices (CI), body mass, and size with female reproductive success and cub survival among polar bears ( Ursus maritimus ) measured in two subpopulations over three decades. To improve measurement and application of morphometrics and CIs, we also examined whether CIs are independent of age and structural size–an important assumption for monitoring temporal trends—and factors affecting measurement precision and accuracy. Maternal CIs and mass measured the fall prior to denning were related to cub production. Similarly, maternal CIs, mass, and length were related to the mass of cubs or yearlings that accompanied her. However, maternal body mass, but not CIs, measured in the spring was related to cub production and only maternal mass and length were related to the probability of cub survival. These results suggest that CIs may not be better indicators of fitness than body mass in part because CIs remove variation associated with body size that is important in affecting fitness. Further, CIs exhibited variable relationships with age for growing bears and were lower for longer bears despite body length being related to cub survival and female reproductive success. These results are consistent with findings from other species indicating that body mass is a useful metric to link environmental conditions and population dynamics.

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“…Sexual dimorphism is exhibited in polar bears, with males being about twice as large in mass and roughly one-sixth larger in body length compared to females (Derocher et al, 2010;Biddlecomb et al, 2019). Males reach sexual maturity around three years old, though they typically do not breed until several years later, while females are sexually mature and begin mating at approximately four to six years old (Biddlecomb et al, 2019). As solitary animals, polar bears only seek out members of the opposite sex during breeding season (Owen et al, 2015), after which they return to their respective home ranges.…”

Section: Polar Bear Ecologymentioning

confidence: 99%

“…Pregnant females den during the winter months (November to April; Ramsay and Stirling, 1988) and give birth to one to two cubs, which they will nurse without access to food, producing milk exclusively from their fat stores (Stirling and McEwan, 1975;Molnár et al, 2010;Whiteman et al, 2018). Cubs will stay with their mothers for approximately two and a half years, during which time they rely heavily on their mothers for food and protection as they grow and learn how to hunt and defend themselves (Derocher et al, 2010;Whiteman et al, 2018;Biddlecomb et al, 2019). This puts additional energetic stress on female bears compared to males, and has resulted in many females with cubs resorting to feeding on alternative prey sources (i.e.…”

Section: Polar Bear Ecologymentioning

confidence: 99%

Illuminating the Historical Ecology of Polar Bears (Ursus Maritimus) from the Lancaster Sound Subpopulation, Nunavut, using Stable Isotope Analysis

Landry¹

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Polar bears (Ursus maritimus) are among the Arctic species that are most threatened by climate change. However, little is known about the ecology of polar bears over extended temporal intervals (>50 years). The goal of my thesis is to determine whether historic polar bears from the Lancaster Sound subpopulation underwent ecological shifts in response to a changing Arctic climate throughout the 20 th century (1950s-1970s) using stable isotope analysis. Historic polar bears did not undergo significant dietary shifts, remaining apex predators. The consistent reliance on seals and whales as their primary prey indicates continued access to optimal hunting conditions (i.e., sea ice). There is evidence that suggests environmental changes occurred from 1950-1970. This thesis offers novel insights into the historical ecology of polar bears, and provides a long-term isotopic baseline for polar bear ecology that will enable future studies to assess ongoing ecological changes of modern polar bears.iii ACKNOWLEDGEMENTS First and foremost, I would like to acknowledge that Carleton University is located on the traditional unceded territory of the Algonquin Anishnaabeg People, and that the specimens used in this project were collected from the traditional territory of the Inuit. As settlers, we must make the collective commitment to make the promise and the challenge of Truth and Reconciliation real in our communities, to honour the Treaty Rights of all Indigenous Peoples, and bring justice for murdered and missing Indigenous women and girls across the country.I would like to thank my thesis supervisors, Dr. Danielle Fraser and Dr. Root Gorelick. I can say with absolute certainty that this thesis would not exist in its current form without their guidance and endless support. I would especially like to thank Dr.Fraser for reading every single draft of my thesis without fail, and always offering helpful comments and suggestions. I would not be the scientist I am today without Dr. Fraser's influence -she is one of the most talented and passionate scientists I have met, and I am extremely grateful to have her as my mentor. I thank the members of my defense committee, Dr. Clément Bataille, Dr. Joseph Bennett, and Dr. Rachel Buxton, for their support throughout my degree and helpful commentary on my thesis. I would also like to thank the following people for their contributions to this study: Dr. Kamal Khidas for providing access to the Zoology Collections and polar bear specimens at the Canadian Museum of Nature; Roger D. Bull for granting access to the Laboratory of Molecular Biodiversity; Dr. Seth Newsome and Dr. Nicu-Viorel Atudorei for conducting stable isotope analyses at the University of New Mexico; Marisa Gilbert for her aid in coordinating sample shipment and ordering laboratory materials; and Dr. iv Catherine Cullingham for chairing my defense. I thank my friends, family, and labmatesfor providing me with never-ending kindness, love, and support, throughout the completion of my degree and beyond. I especially thank my frien...

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Behaviour and characteristics of mating polar bears (Ursus maritimus) in the Beaufort Sea, Canada

Cited by 6 publications

References 64 publications

The stress of Arctic warming on polar bears

The stress of Arctic warming on polar bears

Identifying reliable indicators of fitness in polar bears

Illuminating the Historical Ecology of Polar Bears (Ursus Maritimus) from the Lancaster Sound Subpopulation, Nunavut, using Stable Isotope Analysis

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