25-30 years in the wild, up to 50 years in captivity
Length up to 8 feet 7 inches; height at shoulder 53 inches; weight 300-1,153 lbs. Grizzlies vary greatly in color from cream through cinnamon and brown to black. They also have a distinguishing shoulder hump of flesh and muscle. It is not stored fat. The name "grizzly" comes from the silver-tipped guard hairs that appear around the bear's face in autumn, giving it a grizzled appearance.
Behavior: Grizzlies are most active during dawn and dusk. During midday they make daybeds and nap. Their eyesight is poor, however, their ability to smell is extraordinary (they can scent something as much as 15 miles away) . They can run at speeds of 15 to 20 miles per hour over rugged terrain. They can sit up, stand and walk upright for a few paces, and have a good sense of balance. Unlike other bears, grizzlies cannot climb trees. They have five non-retractable, sharp, curved claws that help them catch their food. The teeth are heavy, with flattened molars. They do not cut and tear as well as true carnivores. Food has to be chewed and crushed instead of being cut into pieces. The jaws are powerful. A single bear can devour 60 to 70 fish in one hour. They normally live alone, but will congregate to feed with others when there is an abundance of food.
Reproduction: North American bears usually mate in the spring and the females den in the fall. If the female is in peak condition (with enough stored fat) when she goes into her winter den, the embryo will start to develop. If the female is not in peak condition, her body will reabsorb the embryo and not give birth that year. During hibernation the female will usually give birth to 2 cubs, which suckle and sleep until spring. When they awaken the female immediately starts searching for food, and teaching the cubs how to survive. They will remain with her for 2.5 to 3 years. At that time she chases them off and is once again ready to mate. The mating season is only 2 weeks long. She may mate with several males during that period. Other than during the mating season, these bears lead solitary lives. The only other time their paths cross without fighting is when food is in abundance, such as when fishing for salmon during the summer salmon run.