The polar regions, characterized by extreme cold, extended darkness, and scarce resources, are two of the planet’s most challenging environments. The Arctic is a frozen ocean surrounded by continents, while the Antarctic is a continent of ice surrounded by ocean. Animals in these regions have evolved unique biological and behavioral strategies to manage body temperature and energy, allowing them to exploit resources that briefly flourish during the short summer months.
Physiological Adaptations for Polar Survival
Survival relies on minimizing heat loss and efficiently producing internal heat. Many polar mammals and birds use thick insulation, such as the dense, multi-layered fur of the Arctic fox or the plumage of a king eider duck, which traps warm air near the skin. Marine animals, like whales and seals, rely on a substantial layer of blubber, which acts as an effective insulator and an energy reserve for fasting periods.
Thermoregulation in extremities, such as feet and flippers, is managed by countercurrent heat exchange. Arteries carrying warm blood from the core pass next to veins returning cold blood from the periphery. This arrangement transfers heat from the artery to the vein before it is lost, keeping the core warm while the limbs operate at a cooler temperature just above freezing.
Metabolic adjustments manage energy throughout the year during periods of food scarcity. Some smaller Arctic mammals, like the Arctic ground squirrel, enter true hibernation, drastically lowering their body temperature and metabolic rate. Other animals, such as muskoxen and Arctic foxes, undergo a seasonal reduction in their basal metabolic rate by up to 30% during winter to conserve energy without entering deep sleep.
Wildlife of the Arctic Region
The Arctic is home to land and sea creatures, many of which move between the sea ice and the terrestrial tundra. The apex predator is the Polar Bear (Ursus maritimus), classified as a marine mammal due to its dependence on sea ice for hunting ringed and bearded seals. Polar bears often use “still-hunting,” waiting for hours near a seal’s breathing hole, or aglu, in the ice.
On the tundra, the Caribou (Rangifer tarandus) undertake one of the longest terrestrial migrations, moving between summer calving grounds and winter foraging areas. Their large, concave hooves function like snowshoes and are used to dig through the snowpack to access lichens, their main winter food source. The Muskox (Ovibos moschatus) is another large herbivore, surviving the cold with a shaggy outer layer and a dense woolly undercoat called qiviut.
Smaller terrestrial species include the Arctic Fox (Vulpes lagopus), whose coat changes color seasonally for camouflage against the snow in winter and the tundra in summer. Lemmings remain active beneath the snowpack in the subnivean zone, which provides insulation. In the marine environment, the Beluga Whale (Delphinapterus leucas) and the Narwhal (Monodon monoceros) are year-round residents. The Narwhal is specialized for life among the pack ice with its distinctive long tusk.
Wildlife of the Antarctic Region
The Antarctic landmass lacks permanent terrestrial mammals; its ecosystem revolves around the abundant Southern Ocean. The most recognizable inhabitants are the Penguins, including the Emperor Penguin (Aptenodytes forsteri), the only species to breed through the harsh Antarctic winter. Male Emperor Penguins endure months of fasting and temperatures down to -50°C, incubating a single egg on their feet in dense huddles.
The waters surrounding the continent are patrolled by seals. The Weddell Seal (Leptonychotes weddellii) is the world’s southernmost-ranging mammal. The Leopard Seal (Hydrurga leptonyx) is a predator known for its powerful jaws and a diet that includes krill, fish, and other seals, often preying on penguins near the ice edge. It ambushes penguins as they enter or exit the water, shaking them vigorously to dismember the carcass.
The Antarctic Krill (Euphausia superba), a small crustacean, forms swarms and provides the primary food source for nearly all other large animals. Krill support vast populations of baleen whales, such as the Blue Whale and Humpback Whale, which migrate to the Southern Ocean during the summer to feed on the seasonal bloom. This marine-centric structure underscores the region’s dependence on the productivity of the cold, nutrient-rich circumpolar currents.