Bears exhibit a wide range of weights, with significant variation observed across different species. Factors like age, sex, season, and the availability of food sources all contribute to these differences in size. Understanding these influences provides insight into the diverse adaptations of bear populations globally.
Weight by Species
The average weight of a bear is highly dependent on its species. American black bears, a common North American species, have males weighing between 125 to 500 pounds, while females range from 90 to 300 pounds. Regional variations exist, with some male black bears on the East Coast reaching over 400 pounds.
Brown bears, which include grizzly bears and Kodiak bears, are considerably larger. Male brown bears can average around 478 pounds, and females average about 335 pounds. Inland grizzly males weigh between 400 to 790 pounds, with females between 290 and 400 pounds. Coastal brown bears, like those in Alaska, are even larger, with males weighing 800 to 1,200 pounds and females between 400 to 700 pounds.
Polar bears are among the largest bear species. Adult male polar bears weigh between 770 and 1,540 pounds, while females are smaller, weighing between 330 and 650 pounds.
Asian black bears are smaller than their American counterparts. Adult males weigh between 130 and 440 pounds, with an average of about 298 pounds, while females weigh 88 to 276 pounds. Giant pandas have adult males weighing up to 350 pounds, and females are smaller, ranging from 150 to 276 pounds. The smallest bear species is the sun bear, which weighs only 55 to 143 pounds.
Factors Affecting Weight
Several biological and environmental factors influence a bear’s weight. Age plays a role, with cubs being small at birth and growing to reach their adult size. For example, a black bear cub weighs about eight ounces at birth, while a brown bear cub may weigh up to one and a half pounds. Males take longer to reach their full size compared to females, reaching it by 10 to 12 years of age.
Sex is another determinant, as male bears are larger and heavier than females across most species. Male brown bears, for instance, are at least 30% larger than females. This difference is particularly pronounced in polar bears, where males can weigh four to six times more than females.
Seasonal changes also affect bear weight. Bears weigh the least in spring after emerging from their dens, having utilized fat reserves during the winter. They gain weight in late summer and fall to build fat reserves for hibernation. Brown bears can double their weight from spring to late fall, gaining up to 400 pounds of fat.
Diet and habitat directly impact a bear’s ability to gain and maintain weight. Areas with abundant food sources, such as coastal regions rich in salmon, support larger bear populations. For example, coastal brown bears are notably heavier than inland grizzlies due to their access to high-protein food. Availability of diverse food, including plants, berries, nuts, insects, and fish, helps bears grow.
Exceptional Bear Weights
Some individual bears attain remarkable sizes. The heaviest recorded wild male Kodiak bear weighed 1,656 pounds. A captive Kodiak bear named Clyde was estimated to have weighed nearly 2,400 pounds.
The largest polar bear ever recorded was a male shot in Kotzebue Sound, Alaska, in 1960, weighing 2,209 pounds.
For American black bears, the heaviest male on record was found in New Brunswick, weighing 902 pounds after being field-dressed, suggesting a live weight exceeding 1,000 pounds. Another notable black bear weighed 880 pounds in North Carolina.