No land animals live at the geographic North Pole itself, because there is no land there. The North Pole sits in the middle of the Arctic Ocean, covered by shifting sea ice, and the nearest coastline is hundreds of kilometers away. But the broader Arctic region surrounding it supports a surprising variety of life, from microscopic algae embedded in sea ice to polar bears, narwhals, and birds that log tens of thousands of kilometers in annual migrations. What ties these species together is a shared dependence on sea ice and a suite of physiological tricks for handling extreme cold, months of darkness, and unpredictable food supplies.
Sea Ice as the Foundation
Almost every Arctic animal depends, directly or indirectly, on sea ice. The reason starts small. Algae grow on the underside of sea ice and within its internal brine channels, forming the base of the Arctic marine food web. These ice algae bloom in spring as sunlight returns, and their productivity drives the timing of everything above them: zooplankton reproduction, fish spawning, and the feeding schedules of seals, whales, and seabirds. Research has shown that the impact of declining sea ice on this algal production is both large and complex, with cascading effects expected throughout the food web.1PubMed Central. Sea-ice algal phenology in a warmer Arctic When the ice shrinks or forms later in autumn, the entire calendar of Arctic life shifts with it.
Inside the ice itself, tiny invertebrates like rotifers, nematodes, and flatworms inhabit brine channels, some narrower than a human hair. These channels fluctuate in size with temperature and salinity, and the creatures living in them have evolved remarkable flexibility. Flatworms adjust their body dimensions to match the osmotic pressure of the surrounding brine, while rotifers can squeeze through passages just over half their body diameter.2Journal of Experimental Marine Biology and Ecology. Implications of brine channel geometry and surface area for the interaction of sympagic organisms in Arctic sea ice Narrow channels also serve as refuges from predators, creating a miniature food web with its own spatial dynamics hidden within frozen seawater.
The Mammals That Depend on Ice
Polar bears are the Arctic’s most recognizable predator, and their relationship with sea ice is existential. They hunt ringed seals and bearded seals from ice platforms, waiting at breathing holes or stalking across floes. Their fur provides insulation so effective that, despite subzero temperatures, it typically stays free of ice buildup. A recent study found that polar bear fur has specific anti-icing properties that prevent ice from bonding to the hairs even after swimming in frigid water.3PubMed Central. Anti-icing properties of polar bear fur This matters more than it might sound: ice accumulation on fur would destroy its insulating ability and force the bear to burn extra energy getting warm again.
Ringed seals, the polar bear’s primary prey, are themselves ice specialists. They maintain breathing holes through thick ice and build snow lairs above those holes to shelter their pups. Field studies in northwest Alaska found that pup lairs had snow depths averaging about 75 centimeters and were located near areas of significant ice deformation, which creates the ridges and drifts needed for a protective snow cover.4PubMed Central. Ringed seal (Pusa hispida) breeding habitat on the landfast ice in northwest Alaska during spring 1983 and 1984 Without enough snow and deformed ice, pups are exposed to predators and cold, so thin ice years hit ringed seal reproduction hard.
Pacific walruses use sea ice as a resting platform between foraging trips to the seafloor, where they vacuum up clams and other bottom-dwelling invertebrates. Tracking data shows that walruses spend the most time foraging and hauling out when only sea ice is available, which typically occurs during summer and early autumn over the continental shelf.5Journal of Mammalogy. Walrus haul-out and in water activity levels relative to sea ice availability in the Chukchi Sea When sea ice retreats beyond the shallow shelf, walruses face a difficult choice: haul out on increasingly crowded shorelines or swim longer distances to feeding grounds, burning energy they cannot easily replace.
Narwhals and the Deep Arctic Ocean
Narwhals spend their entire lives in Arctic and sub-Arctic waters, rarely venturing south of the sea-ice zone. They are among the deepest-diving marine mammals, plunging hundreds of meters to hunt Greenland halibut and other prey in total darkness. What makes narwhal foraging remarkable is how inefficient it appears to be. A study using specialized tags on three narwhals found that only about 20 to 25 percent of their dives were dedicated to foraging, and of those, just 8 to 14 percent resulted in a successful prey capture.6PubMed Central. Extremely low seasonal prey capture efficiency in a deep-diving whale, the narwhal The whales averaged only about 12 prey captures per day, despite producing hundreds of echolocation buzzes. How they meet their energy needs on such low catch rates remains an open question, though it suggests each successful catch must be calorically significant.
Arctic Foxes and the Scavenging Economy
Arctic foxes are one of the few land predators that venture out onto sea ice, sometimes traveling hundreds of kilometers from shore. In winter, they scavenge the carcasses of seals killed by polar bears, picking apart the remains that bears leave behind after eating the fat-rich blubber.7PubMed. Variability in marine resources affects arctic fox population dynamics This marine scavenging supplements their primary diet of lemmings, and the availability of seal carcasses can influence fox population cycles. In good lemming years, foxes thrive on land. In bad lemming years, the sea ice scavenging network becomes a critical lifeline, linking the fates of polar bears, seals, and foxes into a single chain.
Arctic foxes also undergo one of the most dramatic seasonal coat changes of any mammal. Their fur shifts from brown or grey in summer to solid white in winter, a biannual moult driven primarily by changing day length. Over 20 species of birds and mammals in the Northern Hemisphere undergo this kind of complete seasonal color change, and across species, the main function is camouflage against snow.8PubMed Central. Function and underlying mechanisms of seasonal colour moulting in mammals and birds: what keeps them changing in a warming world? For the Arctic fox, white fur provides both hunting concealment and protection from predators like golden eagles. As snow cover shrinks in some regions, white-coated foxes on brown ground become conspicuous, a mismatch that researchers are watching closely.
Reindeer and Life on the Tundra
Reindeer (called caribou in North America) are the dominant large herbivore of the Arctic tundra. In summer they graze on grasses, sedges, and shrubs. In winter, when the tundra is buried under snow, they switch heavily to lichens, pawing through snow to reach them. The nutritive value of lichens varies considerably by species, and a reindeer’s ability to digest them depends on what it has been eating recently. Studies of captive reindeer that had not eaten lichens showed very low digestibility of common reindeer lichen, while animals with regular lichen access digested it much more effectively, indicating that gut microbes need time to adjust to this unusual food source.9The Lichenologist. Nutritive value of terricolous lichens for reindeer in winter
Reindeer also show a striking adaptation to the extreme light cycles of the Arctic. During the months of continuous daylight in summer and continuous darkness in winter, their bodies essentially disconnect the production of melatonin from their internal circadian clock. Instead of maintaining a steady daily rhythm year-round, their melatonin signal is driven directly by the light-dark cycle for just a few weeks in spring and autumn, when day and night actually alternate.10PubMed. Adaptations for life in the Arctic: evidence that melatonin rhythms in reindeer are not driven by a circadian oscillator but remain acutely sensitive to environmental photoperiod This allows them to remain active around the clock during the summer feeding season, a major advantage when you need to pack on weight before winter.
How Arctic Bodies Handle the Cold
One of the most elegant adaptations shared by Arctic mammals and birds is countercurrent heat exchange in their limbs. Arteries carrying warm blood from the core run in close contact with veins returning cold blood from the feet, flippers, or legs. Heat transfers from the outgoing arterial blood to the incoming venous blood before it ever reaches the extremity, so the animal’s feet can operate at near-freezing temperatures while its core stays warm. This arrangement has been documented in Arctic dogs, reindeer, seagulls, and seals.11Journal of Experimental Biology. Adaptations to polar life in mammals and birds – Section: Physiological defences The result is that a reindeer standing on snow at minus 30 degrees barely loses heat through its hooves.
For animals that hibernate, such as Arctic ground squirrels, staying warm through the winter involves a different strategy. These squirrels are the only Arctic mammal that hibernates underground, dropping their body temperature to below freezing for stretches. When they periodically arouse from torpor to rewarm, they rely on brown adipose tissue, a type of fat that generates heat chemically rather than through shivering. Research shows that utilization of the key heat-generating protein in brown fat peaks during winter and tapers off after the final spring arousal.12PubMed Central. Non-shivering thermogenesis is differentially regulated during the hibernation season in Arctic ground squirrels This system lets the squirrel rewarm from near-zero body temperatures without the violent muscle contractions of shivering, which would cost far more energy.
Seabirds like thick-billed murres face a different thermal challenge: spending long periods in cold water. Murres dive to catch fish, and their metabolic rate while diving can spike to well over double their resting rate. Studies of both common and thick-billed murres found that their metabolic rates increased linearly as water temperature dropped, with murres apparently relying on ramping up internal heat production rather than improving insulation to compensate.13PubMed Central. Diving metabolism and thermoregulation in common and thick-billed murres Preening after diving caused even larger metabolic spikes, presumably because wet feathers conduct heat away from the body faster until they are properly rearranged.
Fish That Make Their Own Antifreeze
Arctic waters hover near minus 1.8 degrees Celsius, cold enough to freeze the blood of most fish. Several species of Arctic cod have solved this problem by producing antifreeze glycoproteins, molecules that bind to tiny ice crystals in the blood and prevent them from growing. What makes these proteins scientifically fascinating is that they evolved from scratch. Genomic studies have shown that antifreeze glycoprotein genes in codfishes arose from noncoding DNA, sequences that originally had no function, roughly 13 to 18 million years ago as the Northern Hemisphere cooled.14Molecular Biology and Evolution. De Novo Gene Evolution of Antifreeze Glycoproteins in Codfishes Revealed by Whole Genome Sequence Data Researchers traced the origin to a nine-nucleotide element in noncoding DNA that duplicated over and over to build the repetitive protein-coding sequence that exists today.15PubMed Central. Molecular mechanism and history of non-sense to sense evolution of antifreeze glycoprotein gene in northern gadids Species exposed to more severe freezing conditions tend to carry more copies of the gene, suggesting that having extra copies provides a stronger antifreeze effect.
Birds of the High Arctic
Arctic terns hold the record for the longest known animal migration. Tracking studies using miniature geolocators confirmed that some individuals travel more than 80,000 kilometers annually, breeding in the high Arctic during the northern summer and then flying to the Southern Ocean for the austral summer. Along the way, they exploit a previously unknown stopover area in the North Atlantic and ride prevailing wind systems to reduce flight costs.16PubMed Central. Tracking of Arctic terns Sterna paradisaea reveals longest animal migration By chasing summer in both hemispheres, Arctic terns experience more daylight over a year than any other animal.
At the other extreme of mobility, ivory gulls spend virtually their entire lives associated with sea ice, rarely venturing far from the ice edge. Tracking studies found that about half of ivory gull positions were within 41 kilometers of the ice edge, and roughly 80 percent were on relatively concentrated sea ice.17PubMed Central. Living on the edge of a shrinking habitat: the ivory gull, Pagophila eburnea, an endangered sea-ice specialist In winter, ivory gulls from across the Arctic converge on the Davis Strait and Labrador Sea, where they scavenge polar bear kills, feed on leftovers from seal whelping patches, and prey on ice-associated fish and invertebrates along the pack ice edge.18PLoS ONE. Annual Movement Patterns of Endangered Ivory Gulls: The Importance of Sea Ice As sea ice declines, ivory gulls are losing both their foraging habitat and their food supply simultaneously, and their conservation outlook remains poor as long as that trend continues.
What Climate Change Means for Arctic Species
The Arctic is warming roughly two to four times faster than the global average, and the animals described above are already feeling the consequences. One of the clearest case studies involves polar cod, a small fish that sits at the center of the Arctic marine food web, connecting ice algae and zooplankton to seals, whales, and seabirds. A biophysical model of polar cod early life stages predicts a strong link between larval survival and sea-ice cover, suggesting that continued ice loss and warming could trigger recruitment collapse in some of their key nursery areas.19PubMed Central. Polar cod in jeopardy under the retreating Arctic sea ice
The threat is not just about temperature. As ice retreats, boreal species are expanding northward and competing with or preying on Arctic natives. Atlantic cod, a larger and more aggressive predator, now increasingly overlaps with polar cod in the Barents Sea. Modeling shows that the predation effect of Atlantic cod on polar cod was strongest in years with low summer ice cover and low stocks of capelin, their other main prey.20Progress in Oceanography. Changes in prey-predator interactions in an Arctic food web under climate change In other words, the same warming that weakens polar cod’s breeding success also invites new predators into its habitat.
These pressures ripple upward. Fewer polar cod mean less food for ringed seals, which means less prey for polar bears. Thinner ice means fewer and shallower snow lairs for seal pups. Less ice algae means less zooplankton at the right time for fish to feed on. The Arctic food web is tightly coupled, so a disruption at any level tends to propagate. For species like the ivory gull, which are already endangered and tied to a shrinking habitat, the margin for adaptation is narrow. The Arctic will still have animal life as the climate shifts, but the community that exists there is likely to look quite different by mid-century, with boreal generalists replacing some of the ice-dependent specialists that define the region today.