Polar Bear Biology, Adaptations, and Conservation

Vocabulary practice flashcards covering polar bear morphology, physiological adaptations, reproduction, diet, hunting strategies, and environmental threats.

Marine mammal criteria (polar bears)

living on marine pack ice, feeding primarily on marine prey, possessing swimming adaptations, and depending directly on the marine environment for survival.

Male polar bear dimensions

Body size reaching up to $3\,\text{m}$ in length and weighing between $400\text{--}600\,\text{kg}$.

Female polar bear dimensions

Body size reaching up to $2\,\text{m}$ in length and weighing between $200\text{--}350\,\text{kg}$.

Annual ice pack

Sea ice that melts and refreezes each year, representing the primary habitat where most of the world's polar bears live.

Polar bear geographic distribution

The Arctic range where two-thirds ($\frac{2}{3}$) of the global polar bear population is concentrated in North America and Greenland across approximately $19$ geographic populations.

Guard hair and undercoat

The two protective fur layers of a polar bear that provide thermal insulation against severe Arctic winter temperatures averaging $-35^\circ\text{C}$ down to $-45^\circ\text{C}$ ($-49^\circ\text{F}\text{ to } -31^\circ\text{F}$).

Black skin (polar bears)

The epidermal pigmentation layer underneath a polar bear's dense fur that assists in absorbing and retaining solar heat.

Blubber layer

A dense layer of subcutaneous fat approximately $11\,\text{cm}$ thick that insulates polar bears against freezing Arctic conditions and stores vital energy reserves.

Paw adaptations (polar bears)

Large, partially webbed paws that evenly distribute body weight across snow and thin ice while functioning as paddles during swimming.

Nictitating membrane

A clear, protective third eyelid in polar bears that shields the eyes from snow blindness and allows underwater vision.

Ringed seal

The primary prey species of polar bears, typically ambushed at ice breathing holes or hunted in snow birth lairs.

Bearded seal

A large Arctic seal species that serves as a common dietary component of polar bears alongside ringed, harp, and hooded seals.

Harp seal

A seal species native to the northern Arctic waters that forms part of the polar bear's carnivorous marine mammal diet.

Hooded seal

An Arctic seal species known for the male's inflatable nasal sac, hunted by polar bears as part of their marine diet.

Still-hunting / Breathing hole ambush

A hunting technique where a polar bear waits quietly beside a seal breathing hole or ocean ice channel to ambush surfacing seals.

Induced ovulation

A physiological mechanism where mating during the spring or seal pupping season triggers ovulation in female polar bears.

Delayed implantation

A reproductive phenomenon in which fertilized eggs delay implantation for approximately $4\,\text{months}$, contributing to an $8\text{-month}$ gestation period where embryonic development occupies only the latter half.

Maternal denning

The reproductive behavior in which a pregnant bear doubles her body weight, enters a maternity den, fasts for $3\text{--}4\,\text{months}$, and gives birth (typically to twins weighing approximately $2.2\,\text{lbs}$).

Starvation-induced hibernation

A temporary metabolic depression that polar bears can enter to conserve energy when deprived of food during critical nutritional stress.

Polar bear conservation status (2008)

The formal protection listing designating polar bears as 'Threatened' under the ESA and 'Vulnerable' under the IUCN Red List, with the global population counted at approximately $26{,}000$ in $2015$.

Climate change impacts (polar bears)

Habitat disruption caused by earlier melting of annual ice, leading to severed migration routes, stranded bears, increased drowning risks, and elevated human-bear conflicts.

Polar bear harvest regulations

The regional policies governing polar bear hunting: permitted only for native populations in the US; managed under quota-based trophy/sport hunting in Canada; banned completely in Norway and Russia; and universally permitted in defense of human life or property.

Hormone-mimicking pollutants

Chemical contaminants that accumulate and biomagnify in polar bear adipose tissue, potentially disrupting normal endocrine function and reproduction.

Non-invasive hair sampling

A biological monitoring method highlighted by researcher Thea Østergaard Bechshøft using polar bear hair to evaluate mercury, persistent organic pollutants, and chronic stress hormones without needing invasive organ or blood samples.

Tundra Buggy

A specially constructed high-clearance passenger vehicle used to conduct polar bear observation tourism safely across the tundra in Churchill, Canada.