The Ursidae family, commonly known as bears, exhibits a wide range of sizes. There is no single, simple answer to the question of how much a bear weighs. An individual bear’s mass is influenced by its species, geographic location, and individual factors. This biological diversity results in a weight spectrum that ranges from human-sized animals to predators weighing nearly a ton. This article examines the weights across the family, from the largest to the smallest members.
The Heaviest Bears: Polar and Brown Species
The world’s heaviest bears are the Polar Bear (Ursus maritimus) and the largest subspecies of the Brown Bear (Ursus arctos). A full-grown male polar bear, or boar, typically weighs between 770 and 1,500 pounds, making it the largest land carnivore on average. Female polar bears, or sows, are significantly smaller, generally ranging from 330 to 650 pounds. The largest male polar bear documented was recorded at 2,209 pounds in Alaska in 1960.
Rivaling the polar bear are the Brown Bear subspecies found along North America’s coastlines, particularly the Kodiak bears. These coastal bears benefit from abundant salmon resources, allowing them to achieve large weights. Mature male Kodiak bears typically weigh between 600 and 1,400 pounds, with some individuals recorded at over 1,600 pounds. Females are about 30% lighter than males, usually falling into the 300 to 700-pound range.
The Most Common Bear: American Black Bear Weight
The American Black Bear (Ursus americanus) is the most widespread bear species in North America. Adult males commonly weigh between 125 and 500 pounds, though individuals in resource-rich areas can reach over 600 pounds. Females are lighter, typically ranging from 90 to 300 pounds.
The heaviest American Black Bear on record exceeded 800 pounds, but these weights are highly localized and not representative of the species’ average. This species is generally smaller than the Brown Bear, lacking the prominent shoulder hump and massive head structure.
Size Extremes: The Smallest Bear Species
The smallest member of the bear family is the Sun Bear (Helarctos malayanus). Native to the tropical forests of Southeast Asia, adult males typically weigh between 88 and 155 pounds. Females are smaller, with weights ranging from 55 to 110 pounds.
Another smaller species is the Spectacled Bear (Tremarctos ornatus), the only bear native to South America. Male Spectacled Bears usually weigh between 220 and 440 pounds. Females are substantially lighter, typically weighing 77 to 181 pounds.
How Sex and Season Influence Weight
An individual bear’s mass fluctuates based on sex and the time of year. The most significant factor contributing to weight variation is sexual dimorphism, the difference in size between males and females. In many species, including Polar and Brown Bears, adult males can be 50% to 100% heavier than adult females. This difference is driven by competition for mates, requiring males to be large to assert dominance.
Seasonal fluctuation causes significant changes in mass, particularly in species that hibernate. During the late summer and fall, bears enter a period of excessive eating known as hyperphagia to build up fat reserves for winter denning. A coastal Brown Bear can gain up to 70% of its spring body mass before entering its den. Polar Bears can also increase their mass by up to 50% to sustain them through periods of poor hunting. The stored fat is metabolized during hibernation, leading to weight loss that can approach 30 to 40% of their fall body weight by spring.