Grizzly bears normally avoid humans but when threatened can charge at running speeds of up to 56km/h (35mph) and are able to outrun a horse over short distances!
Grizzly bears are omnivores, feeding mainly on fish, ants, grubs, moths, honey, grasses, sedges, mushrooms and carrion. They will even eat beached whales and winter-killed animals.
On rare occasions they have been known to kill elk and foxes.
Grizzlies in the northern regions tend to be larger as they obtain larger amounts of protein in their diet which they attain from the salmon streams.
These bears have a greater sense of smell than hound dogs and can smell carrion up to 29km (18 miles) away!
Before going into hibernation a grizzly bear can build up to 200 kg (440 pounds) of fat. Hibernation dens are normally dug on north-facing slopes to allow snow-cover for the entrances.
Mating occurs late spring to early summer. After mating the female grizzly bear will only fall pregnant once she has accumulated enough fat reserves and is ready for hibernation. The delayed pregnancy is referred to as “delayed implantation” whereby the fertilized eggs wait in the womb until ideal conditions are met before development takes place.
If the mother does not accumulate enough fat for the winter, the eggs may not implant.
A grizzly bears' claws can measure up to 4 inches in length!
The weight of the Grizzly bear varies quite considerably from the northern to southern territories with adults weighing from 90kg (200 pounds) to 370kg (820 pounds).
Grizzly bears live to around 25 - 30 years.