The great hump behind a grizzly’s head is solid muscle, enabling it to overturn 50-kg rocks with its front paws, or kill an elk with a single blow.
During its winter sleep the grizzly loses about 1 kg of bodyweight each day. Some grizzlies emerge from their sleep 50% lighter.
Grizzlies once ranged across the USA, with numbers as high as 50,000-100,000; but as their terrain has been taken over by humans, their numbers have fallen to 6000-8000.
Most grizzlies are dark brown in color, but regional coloring ranges from black to very pale yellow.
Despite their great size, grizzlies are nimble enough to catch squirrels and mice, and can reach a speed of over 55 km/h when charging.
Native Americans had great respect for the grizzly, and apologized before killing it, sometimes laying out ceremonial clothes for it to wear when it entered the spirit world. Mammals
Grizzlies are immensely strong. They have been known to bite through cast iron, bend rifle barrels, and open up cars like sardine cans in search of food.
Originating in China, the ancestors of the modern grizzly crossed land bridges from Asia to North America some 40,000 years ago.
Grizzlies often enter their winter dens just ahead of a snowstorm, so that the snow covers up their fresh tracks and seals them in for their long winter sleep.
Alaskan grizzlies feed heavily on migrating salmon.
Grizzly mothers give birth to their cubs in their dens in winter, and go on to look after them for anything up to a further 4- 5 years. During these early years their mothers teach them to forage and hunt and protect them from predators.
The huge Kodiak grizzly bear of the Alaskan coastal islands can reach a height of 3 m on its hind legs, and weigh up to 1500 pounds.