The grizzly bear (Ursus arctos horribilis) is one of North America’s most powerful and recognizable apex predators. This subspecies of the brown bear ranges from the contiguous United States up through Alaska and Canada. The sheer size of these animals leads to curiosity about the largest individual ever documented. Finding a definitive record involves navigating anecdotal accounts and the difficulty of accurately weighing massive, wild animals.
The Specific Record Holder
The largest reliably documented instance of monumental size is tied to a skull discovered near Lone Mountain, Alaska, in 1976. This massive specimen was not weighed directly, but its dimensions placed it far beyond the average. The skull measured 27 and 13/16 inches, a measurement scientists use to estimate the bear’s overall body mass.
Experts concluded the bear responsible for this record-setting skull likely weighed approximately 1,200 pounds during the fall feeding period. This enormous size suggests the bear was a coastal brown bear, often casually grouped with inland grizzlies. The finding highlights a challenge in wildlife record-keeping, as verifiable measurements often require a hunter kill or scientific capture, making skull size the most durable record.
Clarifying Grizzly Bear Size Limitations
Understanding the size of the Lone Mountain record requires distinguishing between the true inland grizzly and its larger coastal relatives. While the public often uses “grizzly bear” broadly, the Ursus arctos horribilis designation technically applies only to those living inland. These interior populations, such as those in Yellowstone or the Rocky Mountains, typically have a maximum weight closer to 800 to 900 pounds for a large male.
The true giants are the coastal brown bears, which include the Kodiak bear (Ursus arctos middendorffi) and the bears of the Alaska Peninsula (Ursus arctos gyas). These coastal populations are distinct due to their incredibly rich diet. They routinely exceed 1,000 pounds, with some individuals verified at weights nearing 1,500 pounds, placing them among the largest land carnivores on Earth.
Environmental Factors Driving Exceptional Size
The attainment of exceptional size depends on a combination of genetic predisposition and environmental abundance. Large male bears possess the necessary genetics to grow beyond the average, but they cannot achieve their full potential without a hyper-caloric diet. This is particularly true during hyperphagia, the intense feeding phase bears undergo in the late summer and fall to store fat reserves for hibernation.
Coastal regions provide the perfect conditions for maximizing size, primarily through the seasonal availability of high-protein, high-fat Pacific salmon runs. An inland grizzly relies on a more varied diet of vegetation, small mammals, and occasional large prey, which provides fewer concentrated calories. The consistent, dense caloric intake from salmon allows coastal bears to accumulate hundreds of pounds of fat, translating directly to the potential for record-breaking body mass.