The grizzly bear either eats itself to enormous weight or it starves almost to nothing. In summer and autumn they build up their body fat on fish, carrion, ripe fruit, nuts and berries. The following three months the bears hibernate and nurse their young the body.  Their weight drops by a quarter. Their cubs are born blind, naked and weigh 500 g. The female has cubs every other year and could produce one to four cubs but mostly two. The mother defends its cubs fiercely if she thinks they are threatened

Grizzly bears mate during spring and early summer and the fertilised egg starts to grow almost immediately. Then it stops, being no more than tiny ball of cells. It moves freely and stays like that for about 5 months. When she is getting ready for hibernation in October and November it starts to grow again. All this it is making sure that the female grizzly eats as much as possible and build up her fat store which is necessary for her and her cubs to survive the lean period of the winter.

When they emerge from their den in the spring the young cubs start to play games. Chasing each others, having a wrestling match and trying to stalk each other. All these games are necessary for young cubs to learn to survive later in adult life and also to build up their strength.

Their mother also teaches them to handle food. Introduces them to fish when she takes them to the river in summer and shows them to catch the salmon when they head up stream to their breeding ground.

Mother also has to teach them to be independent. After she has given her cubs all the loving care, one day the mother chases them up the tree as she always done when there was danger. This time it is different because she walks away. She makes them understood they have to face the world on their own.

This must seem cruel after all the love and devotion she gave them. However, when they manage to survive they must leave their mother and their mother's territory because they all end up with food shortage. If that happened mother and cubs would not survive. They have to go and find a territory of their own to make sure a good breeding continues.

To mark their boundaries of their territory the grizzly bear rolls in its urine. When they go up and down their path from their den to the feeding ground, they stand on their hind legs and rub against trees this leaves their scent and hairs as their mark. The odour stays there for a long time and it gives information of the status, sex and even the mood the animal was in.