Bamboo: What’s in it for the Pandas.
Research Associate, Memphis Zoo Conservation & Research
The giant panda (Ailuropoda melanoleuca) is classified within the bear family (Ursidae). Although giant pandas have the digestive tract of a carnivore, they subsist on an almost entirely bamboo-based diet, a woody, fibrous plant in the grass family (Granidae). In spite of this exclusive diet, pandas are very selective with their actual bamboo consumption. A giant panda will alternate which bamboo plant part it consumes (leaf, stalk, or shoot) depending upon time of year. Similar to pandas in the wild, giant pandas in U.S. Zoos typically switch from eating the leaves of the bamboo plant to eating the stalks (culm) in late winter into spring, and bamboo shoots (new growth) in the spring when available.
Currently, the cause of this selection remains unknown, and as a result, the actual dietary needs of a giant panda are not fully understood. Health conditions caused by dietary deficiencies continue to be an issue in captive pandas and gastrointestinal disorders are the number one cause of death.
The Memphis Zoo is researching the chemical constituents of bamboo in an attempt to describe the driving force behind panda bamboo plant part selection. Nutrient composition in the different plant parts of bamboo is being examined over time in an effort to track nutrient fluctuations that correlate with the pandas’ foraging behavior. Bamboo samples were collected once monthly several years, and nutrients such as fiber, ash, and protein have been analyzed for leaf, culm, and shoots of several bamboo species.
In conjunction with this bamboo nutrition research, Memphis Zoo biologists have developed a giant panda behavior ethogram, an observational method used to systematically document panda behavioral data. Our pandas are recorded on video using several cameras in each holding area. Both live and recorded feeds can be viewed, and two separate data collections are used to characterize overall activity budgets and foraging budgets. The overall behavior is collected using recorded data in 12 hour blocks, and specific behaviors such as foraging, resting, moving, and drinking are noted every half hour.
Foraging budgets are collected on live feeds in 20 minute blocks, and specific foraging behaviors such as eating leaf versus culm are noted every 30 seconds. Additional data on specific feeding behavior (such as biting vs. chewing) are also taken for future studies. These foraging data are analyzed to show the dietary shifts in bamboo plant parts by the Memphis Zoo pandas (Figure 1, 20 minute data shown), and are then correlated with the bamboo nutrition research.
Figure 1. Female giant panda (Ya Ya) plant part selection (leaf vs. culm) assessed from 20 minute foraging data collection. Pandas eat primarily culm in the spring (shaded brown) and switch back to leaf between May and June (shaded green). *Other Budget = other plant parts, plant part unknown, drink, budget unknown.
The panda behavioral data are meticulously recorded by highly trained Memphis Zoo Docents. Four individuals have been involved in this research project for up to eight years, offering a consistent data set that is statistically checked for accuracy. These docents, namely BL Gocinski (Myers), F Maury, M Himmelreich, and S Beard, were authors on a recent paper describing panda foraging behavior in the peer-reviewed journal Zoo Biology (2010, Volume 29, pp. 470-483). A data set of this breadth would not be possible without their dedication, precision, and persistence, and the data have been used in behavior, nutrition, and other panda studies by Memphis Zoo graduate students and researchers. The information they learn from involvement in this project is also used as an educational resource for the public.
In summary, with the help of Memphis Zoo Docents, we have quantified the giant pandas’ selective foraging behaviors and related this consumption information to specific seasonal changes in the nutrition of bamboo plant parts. What we have found is that the Memphis Zoo pandas:
- Favor culm at the time of year when dietary fiber and lignin are lower
- Favor leaves at the time of year when ash and lignin are lower
- Favor young shoots when available, which are higher in protein and fat, and lower in fiber, ash, and lignin than mature bamboo.
A better understanding of the nutritional requirements for giant pandas will enhance the captive management of this species and also broaden the knowledge of the biology of wild pandas.