Compare the location variations of the black bear and the grizzly.
The black bear can be found almost anywhere in the US.
All of these charachteristics can vary with the sex and age of the bear; for example, a young grizzlies' ears may appear larger because they're still growing. Body position, behavior, and light conditions can effect appearance; For example, a black bear engaged in digging may appear to have a shoulder hump.
Size is also not a reliable indicator of species. Most people overestimate the size of grizzlies. A typical adult female grizzly bear weighs 200-350 pounds and an adult male between 300-600 pounds. An Adult male black bear can easily weigh as much or more than a female grizzly, and definitely more than a young or sub-adult grizzly of either sex.
Telling the two species apart is important for both you and the protected grizzly; look at shoulders, face, ears, and claws because color and size are not reliable for identification.
The future of the grizzly depends on you. Killing a grizzly bear in the lower 48 states, is both a federal and state offense that can bring criminal and civil penalties of up to $50,000 and a year in jail. Rewards are available for information leading to an arrest and or conviction.
Grizzlies CAN be found outside "recovery zones".