The giant panda's body makes it an efficient connoisseur of bamboo. Giant pandas learn to climb trees at about 6 months of age to forage, nest and avoid predators. They can eat 40 species of bamboo, though they usually stick to about 10 varieties. Eating a mostly plant-based diet despite having a carnivore's digestive system requires they eat more to make up for the wasteful nature of a digestive system more suited to processing meat than vegetation. They forage for about 14 hours a day and sleep pretty much the rest of the time. Cubs spend several hours playing as well as sleeping and eating. Pandas have strong paws equipped with a kind of opposable thumbs that allow them to hold the bamboo stalk while eating. They eat sitting up like a human or lying on their backs like an otter.