For years scientists have wondered whether pandas are a type of bear, raccoon, or something all their own. Through studying the genetic code (DNA) in pandas’ cells, scientists have confirmed the panda's relationship with bears. Giant pandas are similar to other bears in their general looks, the way they walk and climb, their skull characteristics, and, importantly, their social system and reproductive biology. It's necessary to know that pandas are bears, because the more we know about pandas, the better we can help them reproduce and survive.

Bamboo is the most important plant in a giant panda's life. Pandas live in cold and misty forests of conifers and bamboo high in the mountains of western China. They spend at least 12 hours each day eating bamboo. Because bamboo is so low in nutrients, pandas eat a lot of it daily. They grasp bamboo stalks using their five digits and a special bone that extends from their wrist, and use their teeth to peel off the tough outer layers to reveal the soft inner tissue of the stalk.

Strong jawbones and cheek muscles help pandas crush and chew the thick stalks with their flattened back teeth. A panda’s actual thumb lines up with its fingers—just like our big toe lines up with our other toes. So a panda has five digits plus an opposable “pseudo-thumb.” That little pseudo-thumb adeptly holds and manipulates bamboo and works almost as well as your thumb does.

Bamboo leaves are also on the menu, as pandas strip them off the stalks, wad them up, and eat them. Giant pandas have also been known to eat grasses, bulbs, fruits, some insects, and even rodents and carrion—pretty much whatever they can find. At the San Diego Zoo, pandas are offered bamboo, carrots, yams, apples, and special biscuits designed for leaf-eating animals (called leaf eater biscuits) that are made of grain and packed with all the vitamins and minerals pandas need.

Pandas are always associated with bamboo, but they need more than just bamboo to make a home. San Diego Zoo scientists have found that suitable panda habitat requires old-growth conifer forests with at least two species of bamboo and water access. Why is old-growth forest habitat important for pandas? It provides old, hollow logs and tree stumps large enough for panda dens, and it also provides shelter and nutrients for the bamboo growing there. The average panda’s home range is thought to be about 1.9 square miles (5 square kilometers), with male ranges larger than that of females. In areas where bamboo is not plentiful, the home range may be larger.

Pandas aren’t party animals by any stretch of the imagination. Like other bears, they spend most of the day eating and sleeping. Wild pandas are solitary by nature, and they take their own “space” seriously! Since a panda needs so much bamboo each day to survive, it only makes sense that two’s a crowd when it comes to the bamboo forest. If two pandas happen to cross paths, they’ll growl, swat, and lunge at each other, and maybe even bite each other. There are two exceptions to this less-than-welcoming attitude: the very brief mating season and mothers with cubs.

Once a young panda reaches a weight of about 110 pounds (50 kilograms) and is about 2½ years old, it is probably safe from predators. However, animals such as the golden cat, yellow-throated marten, dhole, and weasel prey on panda cubs and juveniles. Long ago, panda cubs were also prey to tigers and leopards, as their relatively slow gait on the ground made them easy pickings. To stay safe, solitary cubs scamper high in trees and remain there until their mother returns, spending hours and hours asleep up in those trees. When they are resting quietly in the branches, they can be hard to spot. Even the San Diego Zoo’s cubs can easily be overlooked when sleeping in trees that have been trimmed to allow for better viewing for our guests.

Today, pandas have fewer predators than they did historically. Tigers are generally not found in what remains of panda habitat, and leopards are found in reduced numbers. But the drive to remain safe is still the same and is seen even in pandas housed in zoos and breeding centers.

Pandas are arguably the most vocal of all the bear species. One of the most distinctive of the panda vocalizations is the “bleat.” This sounds similar to the sound a lamb or a goat kid would make, and it’s a friendly sound, a greeting. Pandas don't roar the way you think of a brown bear roaring. Other vocalizations include honks, huffs, barks, and growls. Young cubs are known to croak and squeal.

There are other ways pandas communicate, too. Both male and female pandas have a scent gland underneath their short tail that secretes a waxy substance used to leave scent marks. Pandas scent mark trees, rocks, bamboo, and bushes. The scent is pretty strong. Human noses can smell the stinky, waxy scent mark from about a foot away, but pandas are more sensitive to smell, so to them it's even stronger! We’ve discovered that a scent-marked tree or rock can serve as a community bulletin board, notifying pandas in the area what other pandas have been there and how long ago they left their scent mark. Another panda can detect the sex, age, reproductive condition, social status, and even individual identity of the scent maker—as well as how long that scent has been there.

Male pandas often perform “handstands” to leave scent marks. A handstand gets a panda’s rear end higher up the tree, so the scent mark will be higher, too. It seems that pandas are most interested in higher-placed scent marks; the panda with the highest scent mark is obviously the biggest—or at least the tallest—panda.

Although pandas are generally solitary as adults, they are exposed to the scents of other neighboring pandas that have crossed over their path days or weeks before. If a female is starting her estrus soon, it makes sense that she would need to advertise her status to any males that might be in the area. She scent marks, and a male that comes across her scent a few days later can recognize the change in her status via that scent mark. Our research in Wolong has confirmed that males are more interested in scent from a female who was known to be in estrus at the time she left the scent.

Once he has identified this change in a female’s status, a male remains closer to this female, assessing her status more frequently and keeping closer tabs on her so he can be present when she is for mating. This is important, as there is only a two- to three-day period that the female is receptive to breeding. When she is no longer receptive, the male moves on to find another willing female. He does not help raise any cubs born.

Pandas have a slow reproductive rate: mature females usually breed just once every two or three years. In the wild, a typical female panda may bear about five litters in her lifetime.

Giant pandas are only about the size of a stick of butter at birth, and they're hairless and helpless. The panda mother gives great care to her tiny cub, usually cradling it in one paw and holding it close to her chest. For several days after birth, the mother does not leave the den, not even to eat or drink!

The cub's eyes open at 50 to 60 days of age and by 10 weeks the cub begins to crawl. Its teeth appear by the time it is 14 weeks old and mother and cub spend much less time using their den. By 21 weeks, the cub is able to walk pretty well. At this time, the cub starts to play with its mother, and at 7 to 9 months of age it starts attempting to eat bamboo. The cub continues to nurse until about 18 months of age. At this time, the mother is ready to send the cub off on its own so she can prepare for her next cub.