Giant Panda

Scientists still debate why pandas are black and white, but one influential study offers a layered answer. Researchers compared panda fur with that of 195 other carnivore species and 39 bear subspecies. They concluded that the white face, neck, belly, and rump probably help pandas hide in snowy habitats, while the black arms and legs help them blend into shade. Pandas cannot hibernate, so they stay active year-round, moving through very different surroundings. The head markings appear to serve a different purpose. Dark ears may convey ferocity to predators, and the eye patches may help pandas recognize one another or signal aggression toward rivals. These explanations are still hypotheses, but together they suggest the coat works as both camouflage and communication.

The panda’s false thumb is not a true digit at all. It is an enlarged wrist bone, a modified sesamoid, covered by a fleshy pad of skin. Together with the panda’s five regular digits, it lets the animal grip bamboo stalks and manipulate them almost as well as a human thumb would. Scientists think this feature evolved because the panda’s real first digit is not opposable and lines up with the other digits. Pandas often sit upright while feeding, using their front paws to hold a stem steady. For an animal that spends many hours a day eating bamboo, this simple adaptation turns a wrist bone into an effective tool for handling food.

Bamboo makes up about 99 percent of a panda’s diet, yet it offers little energy, so pandas spend 10 to 16 hours a day foraging and eating. A typical adult eats roughly 12 to 15 kg (26 to 33 lb) a day, and some sources report up to 38 kg (84 lb) of shoots. Pandas also keep the short, straight digestive system of a carnivore, so food passes through quickly, limiting how much microbes can break down. To compensate, pandas rely on volume and on saving energy. Their field metabolic rate is among the lowest recorded for mammals, comparable to that of sloths. They also avoid steep slopes and limit social contact to conserve energy.

Giant pandas are generally solitary, and each adult guards a defined range. Females in particular do not tolerate other females in their territory. Pandas communicate largely through scent. They rub a waxy secretion from a gland under the tail onto trees, rocks, and bamboo, often along regularly used paths, and other pandas can read a marker’s sex, age, reproductive condition, and social status. Males sometimes do handstands to leave marks higher up, which signals a larger animal. These messages help neighbors avoid each other, and when two adults do meet, they typically growl, swat, and lunge. Still, ranges are not completely separate. Some pandas form local groups of 7 to 15 animals, and male ranges overlap almost completely within a group.

Female pandas can breed only once a year, during a fertile window of roughly two to three days, somewhere between March and May. Before that, a female advertises her condition through scent marks, and she may chirp when she is in estrus, drawing males to her. Males stay close to a female so they are present when she becomes receptive. They size up rivals by scent and body size, and larger mature males have the advantage in fights. Roars and growls are typical of hostile encounters. After mating, the male leaves and takes no part in raising the cub. Mature females usually breed only once every two or three years. Pandas reach sexual maturity at four to eight years old.

Panda cubs are born pink, blind, and toothless, weighing roughly 90 to 140 g (3 to 5 oz), about the size of a stick of butter. Their mother cradles them and nurses them six to 14 times a day. Within one to two weeks, gray skin appears where black fur will grow, and the adult color pattern is fully formed after about a month. Cubs open their eyes at around six to eight weeks and begin to crawl at 75 to 80 days. They start eating small amounts of bamboo around six months, though milk remains their main food for most of the first year. Cubs usually stay with their mother for 18 months to two years, until she sends them off.