Because of their wide range across multiple continents, there are many subspecies of brown bear. The term “grizzly bear” is typically applied to the populations of smaller inland bears, as opposed to individuals living along the coast. The largest subspecies in North America is the Kodiak bear, found only on the Kodiak Archipelago in Alaska. This population has remained genetically isolated since the last ice age, making them one of the most distinct subspecies. Although brown bears used to be native to this region, these animals were unfortunately extirpated from most of the continental U.S., including California and Oregon.

Despite their reputation as fierce predators, brown bears are highly omnivorous; they’ve been recorded to eat more types of food than any other bear species. Their diet is dependent on the season and where an individual bear lives. For example, Yellowstone bears have diets consisting of around 50% meat, whereas the diet of bears in the nearby Glacier National Park consists of only 11% meat. Surprisingly, brown bears also eat vast numbers of insects. Some consume over 40,000 moths in a single day during the summer, allowing them to derive almost half of their yearly food supply from tiny insects! Even when hunting, they typically pursue rodents and other small mammals. Despite their preference for smaller prey, brown bears are capable of killing large game such as moose, elk, caribou, and bison. Because their diets can vary so widely, brown bears can also vary greatly in size. In regions where food quality is typically poor, mature bears can weigh as little as 160 pounds. On the Kodiak Archipelago, where salmon is available for much of the year, bears range in weight from 260-1400 pounds! On average, though, most brown bears fall in the range of 300-500 pounds. Brown bears can change size seasonally as well, sometimes doubling their weight in preparation for winter. Although brown bears aren’t true hibernators, they do sleep through much of the winter, requiring large fat stores to sustain them.

Brown bears are highly intelligent, possessing one of the highest brain to body ratios of any living carnivore. This comes in handy because many adult behaviors are learned, rather than innate. This means that cubs must learn from their mothers how to find the highest quality foods, when foods are available seasonally, how and where to dig dens, and how to defend themselves. This is likely why bear cubs remain with their mother for up to 4.5 years. Although they are primarily solitary, brown bears will gather in large numbers if enough food is available, such as during a salmon run.