Polar Bear: The Arctic's Apex Predator
A Thousand Kilograms of Arctic Hunter
A male polar bear walking across Arctic ice can weigh up to a metric ton. His fur, which appears white, is actually transparent -- each hair is a hollow tube that scatters light. His skin is black, absorbing the sunlight that reaches it after passing through the fur. His feet are the size of dinner plates, spreading weight across thin ice.
He is the largest land carnivore on Earth. He hunts primarily seals through ice up to a meter thick. He swims for days in water just above freezing. He tolerates -40 degrees Celsius without difficulty but overheats at temperatures above 10 degrees.
He depends absolutely on sea ice. And the sea ice is disappearing.
Size and Strength
Males:
- Weight: 350-680 kg typical, 1,002 kg record
- Length: 2.4-3 m standing upright
- Shoulder height: 1.3-1.5 m on all fours
Females:
- Weight: 150-300 kg
- Smaller in all dimensions
- Take on pregnancy and cub-raising responsibility alone
Polar bears are larger than Kodiak brown bears, which are the second-largest bears. Their elongated bodies help with swimming and moving across ice; their enormous paws distribute weight on thin ice without breaking through.
Built for Cold
Every aspect of polar bear biology is adapted to Arctic extremes.
Fur structure:
Polar bear fur appears white but is actually transparent. Each hair is a hollow tube that scatters visible light, giving the fur its white appearance. Beneath the fur, polar bear skin is black -- absorbing the sunlight that penetrates the fur.
The fur provides:
- Thermal insulation (hollow shafts trap air)
- Light scattering (creates white appearance)
- Waterproofing (dense undercoat sheds water)
- Buoyancy (trapped air helps with swimming)
Blubber:
A 10 cm layer of blubber beneath the skin provides additional insulation and stores energy. During good hunting seasons, polar bears accumulate thick fat reserves that sustain them through fasting periods.
Feet:
Paws are approximately 30 cm wide -- large enough to distribute weight across thin ice. Fur between pads provides traction and insulation. Small bumps called papillae function like snow tires on ice.
Metabolism:
Polar bears have surprisingly efficient metabolism. They can fast for 4-8 months during poor hunting seasons, surviving on stored fat. Females pregnant during fall ice loss fast throughout the 8-month denning period while giving birth and nursing.
Hunting Seals
Polar bears are specialized seal hunters.
Primary prey:
- Ringed seals (most common)
- Bearded seals (larger, more valuable)
- Occasional walruses, belugas, seabirds
Hunting technique:
The primary hunting method is stationary ambush at seal breathing holes. Seals must surface through ice holes to breathe every 20-30 minutes. The bear waits motionless beside a hole, sometimes for hours.
When a seal surfaces, the bear strikes with one paw, kills it with a bite to the head or neck, and drags the body onto the ice.
Success rate:
About 2 percent of hunting attempts succeed. This sounds discouraging but each successful kill provides 30-50 kg of seal meat and blubber -- enough to sustain a bear for a week or longer.
Fat preference:
Polar bears eat primarily the blubber, sometimes leaving the muscle tissue. Blubber provides 9 calories per gram -- more than twice what protein provides. The calorie-dense blubber is essential for surviving long Arctic winters.
Abandoned seal carcasses provide food for Arctic foxes, gulls, and other scavengers. Polar bear hunting supports significant scavenger populations.
Sea Ice Dependence
Polar bears cannot survive without sea ice.
Why ice matters:
- Hunting platform (cannot catch seals in open water)
- Travel surface (access to distant feeding areas)
- Breeding habitat (some populations den on ice)
- Resting platforms (between hunts)
The crisis:
Arctic sea ice has declined 40 percent since 1979. Ice forms later each autumn and melts earlier each spring. Polar bears now have shorter hunting seasons and longer forced fasting periods.
Population impacts:
Western Hudson Bay polar bears have declined 30 percent since 1990. Body condition has deteriorated -- modern bears are thinner than bears from the 1980s. Cub survival rates have fallen.
Population models suggest loss of 30-70 percent of polar bears by 2050 if current climate trends continue.
Swimming
Polar bears are excellent swimmers, though swimming has limits.
Capabilities:
- Swimming speed: 10 km/h
- Endurance: 100+ km typical, 687 km record
- Can submerge for 2 minutes at a time
- Front paws provide most propulsion
Why they swim:
- Crossing between ice floes
- Reaching seals on floating ice
- Escaping from threats (rarely)
- Searching for new hunting grounds
Risk of drowning:
As sea ice fragments, polar bears must swim longer distances between ice floes. Some have drowned during extended swims when unable to reach land or solid ice. Climate change increases this risk significantly.
Reproduction
Polar bear reproduction is slow, making population recovery difficult.
Breeding cycle:
- Mating: April-May on sea ice
- Delayed implantation: embryo pauses development
- Den entry: October-November
- Cubs born: November-December
- Cubs emerge: March-April
- Maternal care: 2-3 years
Cubs:
Cubs are born tiny (less than 1 kg) after short gestation. They are blind, nearly hairless, and helpless. The mother nurses them in the den while fasting herself.
By den emergence in spring, cubs weigh 10-15 kg and are ready to follow mother onto the ice for hunting. They remain with her 2-3 years, learning hunting techniques before dispersing.
Reproductive rate:
- First birth: age 5-6 years
- Litter size: 1-3 cubs (usually 2)
- Interbirth interval: 3-5 years
- Maximum lifetime reproduction: 15-20 cubs
Conservation
Current conservation focuses on both direct and indirect threats.
Direct threats:
- Oil and gas development in Arctic
- Shipping traffic increases
- Pollution from industrial activity
- Illegal hunting (limited)
- Human-bear conflicts in Arctic communities
Indirect threats:
- Climate change (primary threat): sea ice loss
- Food chain disruption
- Changing prey availability
Protection:
- CITES Appendix II trade restrictions
- National protection in Russia, Canada, US, Norway, Greenland
- Quota hunting in some regions (primarily indigenous)
- Research and monitoring programs
Climate change cannot be addressed through polar bear conservation alone -- it requires global reduction in greenhouse gas emissions. Polar bears have become a symbol of climate change impacts, though this symbolism does not translate directly into climate action.
The Symbol
Polar bears have become the iconic image of climate change.
A polar bear stranded on a small ice floe in open water has appeared in countless news stories, documentaries, and political campaigns about global warming. The image is powerful because polar bears cannot adapt to ice loss -- unlike many species that might shift ranges or change behavior, polar bears simply die when ice is not available.
The symbolism has limits. Polar bears alone will not drive climate policy. But they remain among the most visible indicators of how specific species face specific consequences of rising temperatures.
Whatever happens to the climate over coming decades, polar bears will be among the first major species to demonstrate the results. Their current trajectory is downward. Reversing it requires addressing climate change at scales much larger than polar bear conservation can accomplish alone.
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Frequently Asked Questions
How big are polar bears?
Adult male polar bears (Ursus maritimus) weigh 350-680 kg and stand 2.4-3 meters when rearing on hind legs. The largest verified polar bear weighed 1,002 kg. Females are smaller at 150-300 kg. This makes polar bears the largest land carnivore on Earth, slightly larger than Kodiak brown bears. They have distinctive long necks, small ears, and black skin covered by white fur that actually consists of hollow transparent hairs that scatter light. Their fur appears yellowish-white or cream in natural lighting. Beneath the fur is a 10 cm blubber layer providing insulation and energy storage. Their enormous paws (30 cm wide) distribute weight on thin ice and function as paddles for swimming. Their sense of smell can detect seals through a meter of ice and snow from several kilometers away.
How do polar bears survive Arctic cold?
Polar bears are built for extreme cold. Their hollow hair shafts trap air for insulation and reflect sunlight into their black skin underneath, which absorbs heat efficiently. A 10 cm blubber layer provides additional insulation and stores energy. They have specialized feet with fur between pads and small bumps (papillae) that provide traction on ice. Their slow metabolism compared to other bears helps conserve energy in food-scarce Arctic environments. They can tolerate temperatures down to -40 degrees C without difficulty, actually showing signs of overheating at temperatures above 10 degrees. Their compact body shape (relative to surface area) minimizes heat loss. During swimming, they can paddle continuously for hours in water just above freezing -- individuals have been tracked swimming 687 km in a single journey. They rely heavily on sea ice as a hunting platform and can travel hundreds of kilometers across drifting ice floes.
Why are polar bears endangered?
Polar bears are listed as Vulnerable by the IUCN, with populations declining due to climate change causing sea ice loss. Arctic sea ice covers 40 percent less area than it did 40 years ago. Polar bears hunt seals almost exclusively on sea ice -- they cannot catch seals in open water. Less ice means less hunting opportunity, less fat storage, and less reproductive success. Some populations (Western Hudson Bay) have declined 30 percent since 1990. Scientific projections suggest polar bears may lose 30-70 percent of their population by 2050 if current climate trends continue. Current global population is estimated at 22,000-31,000 individuals distributed across 19 subpopulations. Direct hunting for subsistence and sport historically reduced populations, but modern hunting is regulated and sustainable. The primary threat is ice loss from warming Arctic temperatures. Without sea ice, polar bears cannot survive as a species regardless of other conservation efforts.
What do polar bears eat?
Polar bears eat primarily ringed seals and bearded seals, with occasional walruses, beluga whales, and seabirds. A mature polar bear kills approximately 50-75 seals per year and requires about 2 kg of fat per day to maintain body weight. They hunt by waiting motionless beside seal breathing holes in sea ice, striking when seals surface to breathe. This technique requires enormous patience -- a single hunt can take hours of stationary waiting. Successful hunts are rare (only about 2 percent of attempts succeed), but each successful kill provides abundant calories from the seal's blubber. Polar bears eat primarily the blubber and leave the meat, providing food for Arctic foxes, gulls, and other scavengers. Without sea ice, they cannot hunt seals effectively. Stranded polar bears occasionally eat birds, eggs, and scavenged carcasses, but these alternatives cannot sustain them. They can fast for 4-8 months when ice conditions are poor, but extended fasting causes population declines.
How many polar bears are left?
Approximately 22,000-31,000 polar bears remain worldwide, distributed across 19 distinct subpopulations spanning Canada, Greenland, Norway, Russia, and the United States (Alaska). Canadian populations hold about 60 percent of all polar bears. Some subpopulations are stable (Southern Beaufort Sea), some are growing (Foxe Basin), and some are declining rapidly (Western Hudson Bay). Assessing populations is difficult because polar bears range across vast Arctic areas. Scientific estimates have wide uncertainty ranges but most indicate either stability or decline. The long-term outlook depends primarily on Arctic sea ice conditions. If current climate warming continues, multiple subpopulations could become extinct within 50 years even if other threats are eliminated. Several indigenous Arctic communities continue traditional polar bear hunting under strict quotas. International protection under CITES Appendix II restricts trade in polar bear parts. Conservation organizations focus on addressing climate change as the primary long-term threat to the species.