They adapt by changing the thickness of there fur. They also have different fat and blubber content for which ever climate they live in. They have different surface areas. Big for hot climates and small for cold climates.
Migration and hibernation
They hibernate for the long period of cold weather
Well they grow more fur so they can cope with the cold weather and their fur changes a reddish brown colour for camouflage against trees.
They either hibernate or camouflage with the fur and also protect themselves from the cold by the fur