Grizzly bear

The grizzly bear, known scientifically as Ursus arctos horribilis, is a major subspecies of the brown bear.

While many people call them simply brown bears, the term grizzly specifically refers to certain North American populations. These animals are vital members of their ecosystems across North America. They are large, powerful mammals that have adapted to many different environments. Understanding the grizzly requires looking at their biology, their history, and their changing numbers in the wild.

To identify a grizzly bear, you can look for specific physical traits that set them apart from other animals like black bears. Adult grizzlies possess a prominent muscular hump on their shoulders. Their faces have a "dished in" profile, meaning the area between the eyes and nose curves inward. They also have short, rounded ears and a rump that sits lower than their shoulders.

Their claws are quite long, measuring about 2 to 4 inches, which makes them excellent at digging. Their fur color varies from blond to nearly black. However, they often have white or blond-tipped hair on their flanks and backs. This coloring is likely why early explorers used the term "grizzled" to describe them.

Biological processes like hibernation are essential for their survival. Grizzly bears hibernate for five to seven months every year, except in warmer climates like that of the extinct California grizzly.

During this period of deep rest, female bears give birth to their offspring. These newborn cubs are very small and weigh less than one pound. They stay in the den and consume milk from their mother to gain strength. This process allows them to grow significantly before the winter ends. This cycle of rest and nursing is a key part of their life history.

Classification of the grizzly has changed many times due to new scientific discoveries. In the 19th century, researchers actually classified the grizzly into 86 distinct species. By 1928, that number dropped to seven, and by 1953, scientists realized there was only one species.

Modern genetic testing has confirmed that the grizzly is a subspecies of the brown bear, Ursus arctos. Biologist R.L. Rausch helped clarify that North American grizzlies are part of this single species. While some scientists still debate how many subspecies exist, most modern research uses DNA to understand their relationships. This includes studying their genome, which contains 30,387 genes.

The evolutionary history of these bears began in Eurasia. Brown bears migrated to North America between 177,000 and 111,000 years ago.

Genetic evidence suggests they moved south during a period called MIS-5, roughly 92,000 to 83,000 years ago. This movement happened as an ice-free corridor opened up. Fossils found near Edmonton provide evidence of their presence around 26,000 years ago. After a local extinction in Beringia about 33,000 years ago, two lineages repopulated parts of Alaska and Canada. This complex movement shaped the populations we see today.

Today, there are approximately 60,000 wild grizzly bears in North America.

About 30,000 of these live in Alaska, which is the highest population in any single state or province. In Canada, there are roughly 29,000 bears, with many living in British Columbia. In the United States, about 1,000 live in the Northern Continental Divide in Montana. Another 1,000 inhabit the Greater Yellowstone Ecosystem. However, their range has shrunk significantly. They now occupy only about half of their historical territory. Many populations, such as the California grizzly, are now extinct due to hunting and habitat loss.

Grizzly bears are highly dependent on their specific habitats and food sources. Coastal populations in the Alaskan peninsula are often much larger than inland populations.

This is because coastal areas provide abundant food, such as salmon. In contrast, inland males might weigh significantly less than their coastal counterparts. In some areas, like the Admiralty Island National Monument, bears are very dense. There are 1,600 bears living on that 1,600-square-mile island. These variations in size and location show how closely the grizzly is tied to the land it inhabits.