Grizzly Bear

More Information

Grizzly bears are a North American subspecies of brown bear. They vary greatly in size, based on age, sex, and season. Inland-based adult males can weigh up to 600 pounds, while adult females may max out at 350 pounds; coastal or island males can get up to 1,000 pounds. They grow throughout their life and can be distinguished from American black bears by their shoulder hump, rounded ears, and an angle to their facial profile where their muzzle begins.

They live in many different habitats, including forests, grasslands, tundra, and wetlands, and seek food using a very powerful sense of smell. Grizzlies are generally solitary, except around a shared food source or during breeding season. These bears may have multiple mates in a single season, and litters may include cubs with different fathers. Gestation lasts 6–8 weeks and litters have one to three cubs. Cubs are born in winter and stay with their mother for two or more winters. They reach sexual maturity around 4 years old.

Did You Know?

• Female grizzly bears experience delayed implantation after mating. Fertilized embryos do not develop until her fat reserves are enough to sustain her and nursing cubs over the winter.
• In the fall, grizzlies eat to gain weight rapidly. This ensures they can live off their fat stores and go months without feeding, drinking, or excreting while denning for the winter. However, they do not experience true hibernation. They go into torpor, which allows them to become active more quickly if disturbed.
• Grizzlies once inhabited areas from Alaska to Mexico and east to Missouri. As they were considered pests for 150 years, they were hunted, trapped, or poisoned and their numbers dropped. In 1975 these bears were given protection under the Endangered Species Act—and populations in some areas, including those around Yellowstone National Park and in northern Montana, have grown significantly. However, climate change remains a challenge.