Pandas have adapted to their habitat by evolving a body shape, a digestive system and behavior patterns to accommodate a diet consisting almost exclusively of bamboo. Their fur has evolved to conform to the climate, landscape and foliage of their habitat. Because of the hilly terrain and lack of severity of the weather, they do not hibernate like other bears but instead move to lower elevations in winter.
Pandas inhabit mountainous forests full of stands of bamboo grass, and bamboo makes up 90 to 99 percent of their diet. Because bamboo provides little energy or protein, they spend 12 to 16 hours a day eating prodigious amounts of bamboo. An adult panda, depending upon its size, consumes 20 to 80 pounds of bamboo a day. Because much of the bamboo is indigestible cellulose, the digestive tracts of pandas are short and straight, and they defecate many times a day. Their paws have developed five fingers and wrist extensions that function as opposable thumbs to help them grasp bamboo. Their round faces are due to large molars and strong jaw muscles they have developed to chew bamboo, and their size is due to the low metabolic rate caused by their diet. Pandas are sedentary and docile largely due to the lack of energy their bamboo diet gives them.
The thick fur of pandas keeps them warm in the cool mountainous forests in which they roam. Their coloration affords camouflage in the dappled light and shadow of the forests and the stark contrast of dark rocks and bright snow.