Maternal Denning Phenology and Substrate Selection of Polar Bears (Ursus Maritimus) in the Southern Beaufort and Chukchi Seas
Maternal Denning Phenology and Substrate Selection of Polar Bears (Ursus Maritimus) in the Southern Beaufort and Chukchi Seas

Author: Jay Wesley Olson

Publisher:

Published: 2015

Total Pages: 60

ISBN-13:

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Loss of sea ice due to global warming may affect the phenology and distribution of polar bear (Ursus maritimus) denning by altering access to denning habitats. We examined trends in the selection of maternal denning substrate (land versus sea-ice denning) in the southern Beaufort Sea (SB), addressing the potential influence of summer land-use and fall sea-ice conditions on substrate selection. We developed an algorithm based on statistical process control methods to remotely identify denning bears and estimate denning phenology from temperature sensor data collected on collars deployed 1985-2013 in the SB and Chukchi Sea (CS). We evaluated cub survival relative to den entrance, emergence, and duration, and examined differences in the phenology of land and sea-ice dens. Land denning in the SB was more common during years when ice retreated farther from the coast and off the continental shelf in September. All SB bears that occupied land prior to denning subsequently denned on land; however, only 29% of denning bears that summered on sea ice denned on land. Den entrance and duration in the SB and CS were similar, although CS bears emerged later. Land dens were occupied longer than those on ice. Bears later observed with cubs remained in dens 23 days longer and emerged from denning 17 days later on average than bears that denned but were subsequently observed without cubs, suggesting that den exit dates are related to cub survival. The increase in land-based denning in the SB when sea ice retreated farther from shore, along with the positive correlation between fall land-use and land denning, suggest that further sea-ice declines may result in continued increases of onshore denning. Growing numbers of denning females along the coast may increase the potential for human-bear interactions.

Ethology and Behavioral Ecology of Sea Otters and Polar Bears
Ethology and Behavioral Ecology of Sea Otters and Polar Bears

Author: Randall W. Davis

Publisher: Springer Nature

Published: 2021-07-03

Total Pages: 366

ISBN-13: 3030667960

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Sea otters and polar bears are carnivorous marine mammals that still resemble their terrestrial ancestors. Compared with Cetacea (whales and dolphins), Sirenia (dugongs and manatees), and Pinnipedia (seals, sea lions, and walrus), they are less adapted for an aquatic life and the most recently evolved among marine mammals. Sea otters are amphibious but seldom come ashore, and polar bears primarily occur on sea ice or along the shore. When at sea, both species spend most of their time swimming at the surface or making short, shallow dives when foraging or pursuing prey. Indeed, polar bears rarely pursue seals in water. Nevertheless, polar bears are powerful swimmers and will stalk seals from the water. As with many other large carnivores, they are solitary hunters. Although sea otters are gregarious and form aggregations at sea called rafts, they are primarily asocial. Except during mating, the principal interaction among sea otters occurs between a female and offspring during the six-month dependency period. In large carnivores (e.g., wolves and lions) that feed on ungulates, sociality and cooperation are favored because of the need to capture large prey and defend carcasses. Polar bears, which are the largest terrestrial carnivore, are solitary hunters of seals and are neither gregarious nor social. Males and females briefly associate during courtship and mating. During this time, males aggressively compete for females. At other times, males generally avoid each other except for aggregations of males that form while summering on land, and females with cubs avoid males, which are known for infanticide. As with sea otters, the interaction of polar bears outside of mating occurs between a female and her offspring during the 2-3 year dependency period. This interaction is critically important when altricial cubs are born in the winter den. This book provides new insight into the ethology and behavioral ecology of sea otters and polar bears. Each chapter reviews the discoveries of previous studies and integrates recent research using new techniques and technology. The authors also address historic and current anthropogenic challenges for their survival as climate change alters entire marine ecosystems.

Identifying Shifts in Maternity Den Phenology and Habitat Characteristics of Polar Bears (Ursus Maritimus) in Baffin Bay and Kane Basin
Identifying Shifts in Maternity Den Phenology and Habitat Characteristics of Polar Bears (Ursus Maritimus) in Baffin Bay and Kane Basin

Author: Erica D. Escajeda

Publisher:

Published: 2016

Total Pages: 77

ISBN-13:

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The phenology and habitat selection of polar bear (Ursus maritimus) maternity dens may change over time in response to shifting environmental conditions. This study compared satellite telemetry data on 40 adult females from the Baffin Bay subpopulation collected from 2009–2015, and 16 adult females from the Kane Basin subpopulation collected from 2012–2015 to previously published data on maternity and shelter dens from 1991–1997 in order to look for shifts in maternity den site characteristics and phenology. Sea ice has decreased markedly in the two study regions since the early 1990s. Our specific objectives were to: 1) identify den entry and exit dates using temperature and location data from satellite radio collars; 2) compute denning duration and compare the results to historical data from the 1990s; and 3) characterize and compare maternal den site habitat attributes between the two time periods. Comparison of the Baffin Bay maternity dens (1990s n = 8 dens; 2000s n = 16 dens) from the two periods revealed that mean denning duration shortened in the 2000s by an average of 27 days (mean = 167.1 days, SD = 27.6 days) compared to the 1990s (mean = 194.1 days, SD = 21 days). Delayed den entry in the fall was the primary reason for the shorter denning durations observed in the later decade (1990s median entry date = 28 August; 2000s median entry date = 3 October). Maternity dens in Baffin Bay differed significantly in elevation and slope (p = 0.003), with bears in the 2000s using denning areas at higher elevation and steeper slopes than in the 1990s. No significant difference in den phenology or habitat characteristics was found among the Kane Basin subpopulation. These results suggest significant changes in maternity den phenology and denning habitat selection in Baffin Bay over the past two decades. Shifts in the timing of melting sea ice and the absence of suitable snow conditions may explain the observed changes. This study offers a successful example of the use of satellite telemetry in detecting shifts in phenology and habitat selection for species that occupy remote habitats.

Polar Bears
Polar Bears

Author: IUCN/SSC Polar Bear Specialist Group. Working Meeting

Publisher: IUCN

Published: 2006

Total Pages: 202

ISBN-13: 9782831709598

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These proceedings provide an overview of the ongoing research and management activities on polar bears in the circumpolar arctic. Together with the previous 13 proceedings, they provide an historic record of international efforts in protecting, studying and managing polar bears. With recent documentation of how warmer arctic climate might affect the sea ice habitat of polar bears, the predictions of even warmer climate in the next decades, and documentation of effects on polar bears subpopulations, an evaluation of the red list status of polar bear subpopulations was followed by an increased conservation designation of vulnerable. In the complexity of possible interactions between climate change, local harvest, and in some areas high levels of pollutants, an increased level of international cooperation was advocated.