panda

Giant pandas are members of the bear family, and resemble other bears in size and shape. In contrast, the red panda, which lives in the same habitat as the giant panda, is closely related to and resembles the raccoon. The black-and-white giant panda coat is recognizable to people all over the world. Its legs, ears, eye patches, and a band across the shoulders are black, while the rest of the coat is white. Pandas have large jaws and broad teeth, with an increased number of cusps that help them chew tough bamboo stalks. The wide jaw contributes to the large, round shape of the panda's head. The black eye patches create an illusion of very large eyes. These features, along with short legs, give the panda a cute, infantlike appearance to humans, which contributes to their enormous popularity. Another remarkable feature is the "thumb." Pandas have the same five digits of other bears, plus a sixth digit, an opposable thumb, which is actually a modified wrist bone (sesamoid). The thumb allows them to grasp bamboo with considerable dexterity.

Diet and Reproduction
Giant pandas are the most nearly herbivorous of the bears. Ninety-nine percent of their diet consists of bamboo. They also eat other plants and meat that they can scavenge, and will eat a variety of foods in captivity. However, pandas live in areas once covered by vast bamboo forests, and their jaws, teeth, paws, and behavior are all adapted to eating bamboo. Nonetheless, they have a short, simple digestive tract similar to those of other bears, a sign of their carnivorous ancestry, which is not well-adapted to digesting the leaves and fiber of bamboo. Accordingly, pandas can only digest 21 percent of the bamboo that they consume, whereas ruminants such as cows digest up to 60 percent of the plant material that they eat. Because of this inefficiency, pandas consume 12 to 15 percent of their body weight in bamboo each day, and must spend twelve to fourteen hours each day eating. Pandas mate in the spring between March and May, with cubs born in late summer. The total gestational period varies from 87 to 165 days. Cubs are born very small, between three and five ounces. Combined with hormonal data, these characteristics suggest that pandas have a delayed implantation. That is, after fertilization, the embryo remains free-floating in the uterus for several months before attaching to the uterine wall. After attachment, pregnancy is only about forty days, resulting in small newborns. Delayed implantation also occurs in some other bear species. Pandas have between one and three cubs at a time. However, they usually raise only one cub, which the mother nurtures intensively for several months.

Status and Distribution
The giant panda is an endangered species, with fewer than 1,500 individuals remaining. Panda habitat once covered an area of roughly 450,000 square miles in southeastern China, ranging from central China, to Hong Kong, into Burma and Vietnam. Today, they are found within only a 5,400-square-mile area. Even within this area, they are separated into many subpopulations, which prevents interbreeding. Within their range, pandas live at elevations above human settlements (four to eight thousand feet) to the upper edges of bamboo forest(ten to eleven thousand feet). The continuing expansion of human farms and villages has forced them from the lower elevations, which further contributes to the fragmentation of their populations. Small subpopulations are at a high risk for inbreeding, which reduces the genetic variability and individual fitness, placing panda survival in doubt. Because of the giant panda's endangered status and charismatic traits, extensive efforts are being made to prevent its extinction. It is considered a national treasure in China, and killing one is punishable by death. Western conservationists, including the World Wildlife Fund, which uses the panda as its symbol, are also aiding the preservation efforts. Captive panda breeding, mostly in China, has been a focus of these efforts. Unfortunately, breeding programs have never produced enough cubs to introduce into the wild, or even to sustain the captive populations. Still, many scientists and conservationists around the world are working to ensure a future for the giant panda.