Bamboo Preference Study
The Giant Panda Bamboo Preference Study, completed in 2001 at the National Zoo, determined what kind of bamboo Mei Xiang and Tian Tian prefer. During the study, they were fed five times a day. Most meals consisted of yellow grove bamboo, fruit, vegetables, and leaf-eater biscuits. On 18 trial days, their final feeding consisted of a random pair of three species of bamboo―arrow, black, and bissetii. Both arrow and black bamboo were new to them.
When Mei Xiang and Tian Tian entered their rooms at night, researchers watched to determine which types of bamboo were eaten first. In the morning, leftovers were cleaned out of the rooms and weighed to assess exactly how much bamboo was consumed.
The Pandas’ Preferences
In the first hour of exposure, both pandas demonstrated a significant preference for arrow bamboo—they spent more time feeding on arrow bamboo than on the other two species. By morning, Tian had eaten more arrow bamboo than the other two species, indicating a strong preference, while Mei ate about the same amount of bissetii and arrow bamboo. This is the first study to document bamboo preferences in captive giant pandas.
How Pandas Eat Bamboo
Bamboo makes up to 99 percent of the giant panda’s diet. Bamboo isn't very nutritious, so pandas spend up to 16 hours a day eating as much as 40 pounds. Anything that helps speed up the time it takes them to prepare bamboo increases efficiency.
Giant pandas—and red pandas—have a special adaptation to help them grasp bamboo stems, or culms. An oversized wrist bone serves as thumb, which pandas use to hold bamboo against their palm so they can manipulate a stalk of bamboo and strip the branches and leaves with their teeth to create a bundle of leaves. Then, they use the pseudo thumb and forepaw to hold the bundle and eat from it in smaller bites. They are also able to manipulate the culm to strip the exterior to get at the palatable pith.
What we know about bamboo nutrition indicates that leaves are more digestible by giant pandas than culms or branches. Like their wild counterparts, the Zoo’s giant pandas preferred the leaves of each species of bamboo to the culm or a combination of branches and leaves.
How the Three Bamboo Species Differ
Arrow bamboo has larger leaves and thinner, less woody culms than the other two species, which belong to the same genus. In addition, the leaves of both bissetii and black bamboo radiate from many small, forking branches that are attached to the culm. Arrow bamboo’s leaves grow in the same direction from a single branch attached to the culm, which may make it easier for pandas to strip the leaves and create a bundle of leaves. These differences could affect handling time and foraging efficiency, which is why the researchers had hypothesized that arrow bamboo would be the preferred species.
To researchers closely examined how the pandas were able to strip the leaves and create a bundle in their mouth and learned that the arrow bamboo required significantly fewer bites and less time for the pandas to create a bundle of leaves in their mouths than it did for the other two species. Therefore, the researches concluded, the pandas were able to handle and process arrow bamboo more efficiently than the other two species.
Pandas in the Wild
Giant pandas in the wild feed on as many as 42 different bamboo species. However, some studies have shown that pandas in the wild feed primarily on one or two particular species even when several other species of bamboo were common. The reasons for the pandas’ preferences are unknown. They may be favoring the bamboo they can consume most efficiently. With continued research, we hope to learn a great deal more about these fascinating animals.