Despite its taxonomic classification as a carnivoran, the giant panda's diet is primarily herbivorous, consisting almost exclusively of bamboo. However, the giant panda still has the digestive system of a carnivore, as well as carnivore-specific genes, and thus derives little energy and little protein from consumption of bamboo. Its ability to digest cellulose is ascribed to the microbes in its gut. Pandas are born with sterile intestines, and require bacteria obtained from their mother's feces to digest vegetation. The giant panda is a "highly specialized" animal with "unique adaptations", and has lived in bamboo forests for millions of years. The average giant panda eats as much as 9 to 14 kg (20 to 30 lb) of bamboo shoots a day to compensate for the limited energy content of its diet. Ingestion of such a large quantity of material is possible because of the rapid passage of large amounts of indigestible plant material through the short, straight digestive tract.