The giant panda, a black-and-white bear, has a body typical of bears. It has black fur on its ears, eye patches, muzzle, legs, and shoulders. The rest of the animal's coat is white. Although scientists do not know why these unusual bears are black and white, some speculate that the bold coloring provides effective camouflage. In patches of dense bamboo, an immobile giant panda is nearly invisible, and virtually disappears among snow covered rocky outcrops on a mountain slope. This theory does not work, however, when considering that giant pandas have no natural enemies to hide from. Another thought is that the pattern may accentuate social signals in some way, or help giant pandas to identify one another from a distance so they can avoid socializing, as they are typically a solitary animal. Another theory suggests that the black absorbs heat while the white reflects it, helping giant pandas maintain an even temperature. Unfortunately, there is no one conclusive theory as to why giant pandas are black and white.
The giant panda has lived in bamboo forests for several million years. It is a highly specialized animal, with unique adaptations. The panda's thick, wooly coat keeps it warm in the cool forests of its habitat. Giant pandas have large molar teeth and strong jaw muscles for crushing tough bamboo. Many people find these chunky, lumbering animals to be cute, but giant pandas can be as dangerous as any other bear.
About the size of an American black bear, giant pandas stand between 2 and 3 feet (60 to 90 centimeters) tall at the shoulder (on all four legs), and reach 4 to 6 feet (1.2 to 1.8 meters) long. Males are larger than females, weighing up to 250 pounds (113 kilograms) in the wild. Females rarely reach 220 pounds (104 kilograms).
Giant pandas live in a few mountain ranges in central China, in Sichuan, Shaanxi, and Gansu provinces. They once lived in lowland areas, but farming, forest clearing, and other development now restrict giant pandas to the mountains.
Giant pandas live in broadleaf and coniferous forests with a dense understory of bamboo, at elevations between 5,000 and 10,000 feet. Torrential rains or dense mist throughout the year characterizes these forests, often shrouded in heavy clouds.
Giant pandas do not exhibit body characteristics that communicate visual signals. They have round, inexpressive faces. Their tails are stubs and therefore cannot flag signals to other giant pandas. They have no crest or mane to erect and their ears are not flexible enough to cock forward or flatten. It is thought that giant pandas never developed these visual accessories due in part to their habitat and solitary nature. Giant pandas live in dense, fog-enshrouded stands of bamboo that obstruct a direct line of sight and any potential visual communications. Giant pandas do occasionally vocalize when playing. During mating, they become very vocal, relying on extremely detailed vocalizations to express all shades of mood from amorous to angry.
Most of their communication is accomplished through scent marking throughout their habitat and territory. Giant pandas mark their territory by rubbing secretions from their anal glands onto tree trunks, rocks, or on the ground, usually along paths that they habitually tread. Scent marking alerts giant pandas in the vicinity to one another, and depending on who reads the mark, the scents may either separate giant pandas or help bring them together. Outside of breeding season, a scent mark that is unfamiliar is usually enough to send a potential intruder ambling away. During breeding season, however, a female's scent mark advertises her sexual readiness and draws males to her. A female is more likely to accept a male whose scent she recognizes and has encountered before.
Millions of Zoo visitors enjoy watching giant pandas eat. A panda usually eats while sitting upright, in a pose that resembles how humans sit on the floor. This posture leaves the front paws free to grasp bamboo stems with the help of a "pseudo thumb," formed by an elongated and enlarged wrist bone covered with a fleshy pad of skin. The panda also uses its powerful jaws and strong teeth to crush the tough, fibrous bamboo into bits.
A giant panda's digestive system is more similar to that of a carnivore than an herbivore, and so much of what is eaten is passed as waste. To make up for the inefficient digestion, a panda needs to consume a comparatively large amount of food—from 20 to 40 pounds of bamboo each day—to get all its nutrients. To obtain this much food means that a panda must spend 10 to 16 hours a day foraging and eating. The rest of its time is spent mostly sleeping and resting.
Giant pandas reach breeding maturity between four and eight years of age. They may be reproductive until about age 20. Female pandas ovulate only once a year, in the spring. A short period of two to three days around ovulation is the only time she is able to conceive. Calls and scents draw males and females to each other.
Female giant pandas give birth between 95 and 160 days after mating. Although females may give birth to two young, usually only one survives. Giant panda cubs may stay with their mothers for up to three years before striking out on their own. This means a wild female, at best, can produce young only every other year; in her lifetime, she may successfully raise only five to eight cubs. The giant pandas' naturally slow breeding rate prevents a population from recovering quickly from illegal hunting, habitat loss, and other human-related causes of mortality. At birth, the cub is helpless, and it takes considerable effort on the mother's part to raise it. A newborn cub weighs three to five ounces and is about the size of a stick of butter. Pink, hairless, and blind, the cub is 1/900th the size of its mother. Except for a marsupial (such as the kangaroo or opossum), a giant panda baby is the smallest mammal newborn relative to its mother's size.
Cubs do not open their eyes until they are six to eight weeks of age and are not mobile until three months. A cub may nurse for eight to nine months. A cub is nutritionally weaned at one year, but not socially weaned for up to two years.
In the wild, giant pandas typically nap between feedings for two to four hours at a time, snoozing on their side, back, or belly, either sprawled or curled up. While a giant panda is resting, it continues to defecate. The number of droppings at a rest site can be used to gauge the relative amount of time a giant panda spent at that site. During a short rest of less than two hours, there are five to ten droppings. Eleven to 25 droppings often accompany rests lasting longer than two hours. Most rest periods are two to four hours in duration but may increase to six or more hours during the summer months.
Scientists aren't sure how long giant pandas live in the wild, but they are sure it's shorter than lifespans in zoos. Chinese scientists have reported zoo pandas as old as 35. The Smithsonian National Zoo's Hsing-Hsing died at age 28 in 1999.
An estimated 1,600 giant pandas remain in the wild. The largest threat to giant panda survival is habitat destruction. People in need of food and income have cleared forests for agriculture and timber. This logging has fragmented a once continuous habitat, leaving small groups of pandas isolated from each other. When populations become small, they are extremely susceptible to extinction due to environmental or genetic influences, such as drought or inbreeding. Small populations cannot rebound the same way large populations do; as groups of pandas become more isolated, it is more likely that reproduction, disease resistance, and population stability will be threatened.
As per the Zoo's original agreement with the China Wildlife Conservation Association, any cub born to Mei and Tian would be sent to a breeding center in one of the panda reserves in China sometime after the cub turned two years old. In April 2007, it was determined that Tai Shan would remain at the Zoo an additional two years past his second birthday, which was July 9, 2007. This extension allowed Tai Shan to become an adolescent bear in front of his fans. What's more, Zoo scientists were able to continue their studies of his growth and development to document changes during this little-known stage of a panda's life. On February 2010, Tai Shan was sent back to China, per the loan agreement, to a breeding center in Bifengxia, China. The new loan, which was agreed upon in 2010, states that any cub born at Zoo will stay for four years.
Zoo scientists began giant panda research when Ling-Ling and Hsing-Hsing arrived at the Zoo in 1972. A history and timeline of giant pandas at the Zoo can be found here. Much has been learned since that time but there still remains much more to learn. With the arrival of Tian Tian and Mei Xiang, the Zoo has developed a ten-year research plan that will hopefully culminate in a growing, thriving population of giant pandas. Some research areas will repeat behavioral observation studies on Tian Tian and Mei Xiang in order to increase sample size and determine whether a behavior pattern is common to giant pandas or particular to an individual. In other areas, such as reproductive biology, the advanced techniques scientists use today largely did not exist when Ling-Ling and Hsing-Hsing were alive. Also, opportunities for research and conservation initiatives in the wild, including the potential for increasing the wild giant panda population in China through reintroduction, are greater today than at any time in the past. However, these plans and initiatives will be costly to carry out, as will China's official National Plan for the Conservation of Giant Pandas and Their Habitats.