Polar bears and Kodiak bears are the two heaviest bears alive, and which one is bigger depends on how you measure. Polar bears are usually described as the largest bear species, and the heaviest wild bear on record was a polar bear. But the weights of typical adult males overlap: about 775 to 1,300 pounds for polar bears and 600 to 1,400 pounds for Kodiak bears. Alaska's wildlife agency calls Kodiak bears the largest bears in the world, with big males reaching 1,500 pounds.
Polar bear vs Kodiak bear at a glance
| — | Polar bear | Kodiak bear |
|---|---|---|
| Scientific name | Ursus maritimus | Ursus arctos middendorffi (a brown bear subspecies) |
| Adult male weight | 775-1,300 lb (350-600 kg) | 600-1,400 lb (272-635 kg) |
| Adult female weight | 330-650 lb (150-290 kg) | 300-700 lb (136-318 kg) |
| Height on all fours | 3.3-5 ft (1-1.5 m) at the shoulder | 3-5 ft (0.9-1.5 m) |
| Standing on hind legs | Large males over 10 ft (3 m) | Up to about 10 ft (3 m) |
| Range | Circumpolar Arctic, on and around sea ice | Kodiak Archipelago, Alaska, only |
| Population | About 26,000 | About 3,500 |
| Main food | Ringed and bearded seals | Salmon (about 64% of the diet) and plants (about 26%) |
| Conservation status | Vulnerable (IUCN); protected under the U.S. Endangered Species Act | Brown bear species is Least Concern (IUCN); Kodiak population has very low genetic diversity |
| Lifespan in the wild | Commonly cited as 25-30 years | Oldest known wild female reached 34 |
Weights come from Polar Bears International and the U.S. Fish and Wildlife Service. They are ranges, and individual bears vary with age, sex, season and food supply. For the heaviest polar bear on record, see polar bear vs grizzly size.
Size and appearance
Polar bears have a long neck, a relatively small head and white-looking fur. Their paws can be up to 30 cm (nearly 12 inches) across, with claws longer than 5 cm (2 inches) for gripping seals and ice. Two layers of fur hold in so much heat that adult males can overheat when running.
Kodiak bears have the broad head and shoulder hump of other brown bears, with dense brown fur. The Boone and Crockett Club's world-record bear, a Kodiak, had a skull measuring 30.75 inches (length plus width). Fish and Wildlife Service data show Kodiak males weighing up to 1,400 pounds, while Alaska Fish and Game puts the upper end at 1,500.
Where they live
Polar bears roam the Arctic Ocean and its coasts in Canada, Greenland, Norway, Russia and Alaska. They depend on sea ice as a platform for hunting seals. About 26,000 bears live in 19 subpopulations, and shrinking sea ice is the main long-term threat.
Kodiak bears live only on the Kodiak Archipelago in Alaska, including Kodiak Island and nearby islands. They use nearly every habitat there, from coastal salt marshes and salmon streams to forests, mountains and tundra. The population is about 3,500. The bears have been isolated from other brown bears for roughly 12,000 years, since the end of the last ice age.
The two species' ranges do not overlap. A Kodiak bear and a polar bear would never meet in the wild.
What they eat
Polar bears eat mostly meat. Ringed seals are their main prey, followed by bearded seals. They sometimes take larger animals such as walruses and belugas, and scavenge whale remains. When hunting is good, a bear may eat only the seal's fat and skin.
Kodiak bears are omnivores. The Fish and Wildlife Service reports that salmon makes up about 64% of their diet and plants about 26%. They also occasionally eat marine mammals, birds and eggs, rodents and invertebrates. Alaska Fish and Game adds that Kodiak bears eat more grasses, plants and berries than meat.
Life cycle and behavior
Both species are mostly solitary, and both give birth in dens in winter.
- Polar bears mate on the sea ice from about April through June. Cubs are born in a maternity den around December or January, weighing about a pound, and leave the den in March or April. They stay with their mother for just over two years. Adult males compete hard for females and are roughly twice the size of females.
- Kodiak bears mate in May and June. Cubs are born in the den in January or February and usually come out in May or June. Litters are typically two or three cubs, and most stay with their mother for about three years. Some males skip denning altogether and stay active through winter.
Swimming and speed
Polar bears are strong swimmers, using their front paws as paddles and their hind legs to steer. The longest recorded swim is 687 km (426 miles) over nine days. See can polar bears swim for details.
Kodiak bears live on land and fish in streams. Alaska Fish and Game says brown bears can run up to 40 mph in short bursts, and Montana wildlife officials give 35 mph for grizzlies.
Conservation
The IUCN lists the polar bear as Vulnerable, with sea-ice loss the main threat. In the United States, polar bears are protected under both the Endangered Species Act and the Marine Mammal Protection Act.
The IUCN rates the brown bear species as a whole Least Concern, which covers Kodiak bears as a subspecies. The Fish and Wildlife Service notes that the Kodiak population has the lowest genetic diversity of any recorded North American brown bear population, which is a conservation concern.
Safety around either bear
Both bears are dangerous at close quarters. A 2017 review of 73 recorded polar bear attacks on people between 1870 and 2014 found that almost all involved males, usually young, and that most happened when sea ice was at its lowest and bears were hungry. Alaska Fish and Game says that living with bears requires keeping human food and garbage secured, and that how a person behaves in an encounter often shapes the outcome. In either bear's territory, follow local guidance and keep a wide distance.