Polar bears are widely believed to be the largest bear species on Earth, commanding attention with their imposing size and adaptations to the Arctic. However, determining the largest bear is nuanced, requiring a closer look at different species.
Comparing the Largest Bears
While polar bears are colossal, the Kodiak bear, a brown bear subspecies found exclusively on Alaska’s Kodiak Archipelago, often surpasses them in mass. Adult male polar bears weigh between 300 and 800 kilograms (660–1,760 pounds) and measure 200–250 centimeters (6.6–8.2 feet) in length. They stand 130–160 centimeters (4.3–5.2 feet) tall at the shoulder, reaching over 3 meters (10 feet) on their hind legs.
Kodiak bears achieve greater weights. Mature male Kodiak bears average 477–534 kilograms (1,052–1,177 pounds), with some individuals reaching up to 680 kilograms (1,500 pounds) during peak feeding. The largest recorded wild male Kodiak bear weighed 751 kilograms (1,656 pounds). These bears stand about 133 centimeters (4 feet 4 inches) at the shoulder on all fours and can exceed 3 meters (10 feet) standing upright. While polar bears may be taller on average, large Kodiak bears can outweigh and sometimes exceed the height of average polar bears, making the Kodiak bear the largest land carnivore by mass.
Factors Influencing Bear Size
The substantial size of both polar and Kodiak bears links to their diets and environmental pressures. Polar bears are specialized carnivores, feeding almost exclusively on ice-living seals. They target species like ringed and bearded seals, consuming energy-rich blubber to build thick fat reserves. This high-fat diet provides the caloric intake necessary to sustain their large body mass and insulates against extreme Arctic cold.
Kodiak bears, conversely, are omnivores with a diverse, seasonally fluctuating diet. While they consume vegetation, salmon forms a significant portion of their diet, especially during spawning season. Abundant, protein-rich salmon runs in their island habitat allow them to accumulate fat reserves, contributing to their impressive size.
Larger body sizes in colder climates are explained by Bergmann’s Rule, an ecological principle for warm-blooded animals. This rule states that individuals of a species in colder regions are larger than those in warmer regions. A larger body has a smaller surface area-to-volume ratio, losing heat less rapidly than a smaller body. This is an adaptation for surviving frigid environments. Both Arctic polar bears and subarctic Kodiak bears benefit from this principle, conserving body heat and storing energy efficiently.