Pandas and Bamboo: Species for a specialized diet

It’s hard to think about bamboo without thinking about the giant panda bear. And vice versa. Bamboo, for the most part, is an exotic specimen of Far Eastern extraction. And same goes for the panda. Together or separate, they are iconic symbols of the Orient. But you really can’t picture a panda bear without also imagining bamboo, because a panda bear can’t survive without bamboo. The diet of a panda bear, in fact, consists almost exclusively of bamboo. But with more than a thousand species to choose from, which kinds of bamboo does the giant panda prefer?

The giant panda (Ailuropoda melanoleuca) enjoys around 30 or 40 different species of bamboo, which make up about 99 percent of its diet. In recent decades their population has decreased, and so has their natural habitat. Living in a limited, mountainous area of central China, a few varieties of the genus Fargesia are the most common kinds of bamboo available. In captivity, pandas may have access to more options, and they seem to prefer Square bamboo, Thorny bamboo, Bissetii, Square bamboo and Water bamboo. They like to eat every part of the plant, but especially the fresh, tender shoots. Pandas have one of the most specialized diets of any animal, and this probably has something to do with their becoming an endangered species.

Eating habits and habitat of the giant panda

The evolution of the giant panda is a pretty interesting story. At one time, they surely covered a far wider area with a much larger population. But today the habitat of wild pandas encompasses just a small region of mountains in the central Chinese province of Sichuan. They also inhabit limited portions of the adjoining Shaanxi and Gansu provinces.

Pandas were listed as endangered in 1990, but their numbers appear to be on the rise. In 2016 they went from endangered to vulnerable, according to the classification of the International Union for Conservation of Nature. Today, wildlife experts believe there are something between 1,500 and 3,000 giant pandas living in the wild, in addition to nearly 300 living in captivity.

Biologically speaking, the panda is indeed a bear, and also a carnivore. Millions of years ago, they probably were far more carnivorous. Perhaps the majority of their prey went extinct, and other environmental changes must have taken place as well. But somehow these 250 lb. beasts, with teeth and digestive systems adapted for meat eating, ended up becoming almost entirely vegetarian. Whether in the wild or at the zoo, bamboo now comprises about 99 percent of their diet.

The other one percent

If a panda bear eats bamboo 99 percent of the time, you might have to wonder, what else do they eat?

The remaining one percent of a panda’s diet consists of assorted vegetation and the occasional rodent.

Given their size and speed, pandas don’t ordinarily have a lot of success exercising their carnivorous instincts to catch a mouse or a pika. But once in a while they get lucky.

In captivity, fresh apples seem to be one of their favorite vegetarian treats provided by their zookeepers.

Favorite species

In the wilderness, pandas typically roam about in elevations between 1,500-3,000 meters (5-10,000 feet). At this altitude, in central China, the most common species of bamboo they will find are members of the genus Fargesia, particularly species like F. robusta, F. dracocephala, F. rufa and F. nitida. These are also popular garden varieties, especially well suited for bamboo gardens in cold climates or shady areas. Incidentally, Fargesias are all clumping bamboos, which is something that many gardeners prefer.

Phyllostachys glauca, P. bissetii, Yushania brevipaniculata and Bashania fargesii are a few more species that giant pandas are likely to come across as they browse the mountainsides of Sichuan. These too are popular species for bamboo gardens in colder climates.

As they move to higher and lower elevations over the course of the year, the pandas will encounter a greater diversity of species. And this is important, as we shall see below.

Risks of over specialization

One of the secrets to the great success of humans, as a species, is our incredibly diverse and omnivorous diet. We can subsist on such an enormous variety of plants and animals, allowing us to thrive and survive in nearly any habitat this planet has to offer. A species like the great panda, on the other hand, enjoys no such luxury.

Relying on just one plant, bamboo, makes the panda a truly vulnerable species. Even if they have a few dozen species of bamboo to choose from, their mobility and adaptability are greatly restricted. And when each adult needs to eat around 40-80 pounds of bamboo a day, they will not risk wandering away from an area with an abundant supply.

To further complicate the picture, many species of bamboo undergo what’s called gregarious flowering, or synchronous flowering. This means that massive quantities of a given species flowers at the same time. And when they do so, the plants all die off, and need another 4-8 years to reestablish.

This has happened with Fargesia nitida (sometimes called Arrow bamboo, but not to be confused with Pseudosasa japonica) and other Fargesias on a number of occasions in the last few decades, directly resulting in the starvation of hundreds of pandas. When other species of bamboo are available, the pandas can still manage to find food. But mass flowering and the subsequent collapse in food supply will always present a challenge.

This phenomenon remains somewhat poorly understood, due to the tremendous variety of bamboo species and the infrequency with which they bloom. Some bamboo varieties will flower once every 120 years, while others flower every 20 to 40 years. In some cases every member of the species will flower and die off. But sometimes only those plants in a certain region will flower together and die.

Other species of bamboo flower independently (not synchronously). And not all types of bamboo die after flowering. As you can imagine, keeping track of which bamboo is which, and which one flowered when, over the span of centuries, can become something of a record keeping nightmare.

Commercial bamboo as a threat to pandas

People who are aware of the plight of the giant panda, and its ever shrinking habitat, often raise concerns around the issue of over harvesting bamboo for flooring, textiles and building material. If the giant panda is in danger of extinction because of a shortage of bamboo, then doesn’t the use of this resource put the panda population at even great risk?

Because pandas are so localized to the mountains of central China, where they eat a small variety of bamboo species, primarily Fargesias, they are NOT affected by the commercial cultivation of bamboo for flooring and textiles. Phyllostachys edulis, commonly known as Moso bamboo, is the singular species grown in China for the production of bamboo clothing, flooring, cutting boards and other popular applications. Pandas are not interested in this species of timber bamboo, and so its cultivation does not endanger their survival.

So if you’re using bamboo as an alternative to slow-growing hardwood or pesticide-rich cotton, feeling good about the remarkable sustainability of this miraculous grass, you can rest easy knowing you’re not encroaching on panda habitat.

Bamboo parts preferred by pandas

Amazingly enough, pandas — with their terribly restricted diet — actually eat every part of the bamboo plant. The plants, the leaves, the stalks and the roots of bamboo are all acceptable to the panda bear palate. It’s not hard to see that the leaves of a bamboo plant would be easier to consume than the woody poles. But the poles are actually higher in protein.

The favorite portions, however, are the soft, fresh bamboo shoots, which announce the beginning of every growing season. Although people sometimes make tea from the bamboo leaves, we also know that the tender shoots are the best part to eat. In addition to being more soft and digestible, they also have the greatest nutritional value.

In general, bamboo doesn’t pack a lot of protein, especially relative to the diet of most carnivores. As a result, the pandas need to eat about a third of their body weight in bamboo every day in order to get their fill.

Finding bamboo to feed pandas in captivity

For the 50 panda bears (more or less) living in zoos outside of China, obtaining an adequate supply of bamboo can be a challenge. Even in China, zookeepers have to make arrangements to bring bamboo to the few hundred pandas they have living in captivity.

The Wolong Nature Reserve, in the heart of Sichuan Province, is a protected area covering 200,000 hectares with thousands of species of biodiversity, including about 150 individual pandas. Besides protecting the pandas, the reserve has also made a concerted effort to propagate bamboo, both for the local panda population as well as those living in zoos. Their bamboo grove focusses on five species: Chimonobambusa Quadrangularis (Square Bamboo), Bambusa Sinospinosa (Thorny Bamboo), Plyllostachys Bissetii, Dendrocalamus Latiflorus (Mei-Nung Bamboo), and Fargesia Robusta.

The COVID-19 situation has also made life difficult for pandas. The two bears living in the Calgary Zoo have been suffering a bamboo shortage as a result of the travel and shipping restrictions related to the virus. As of now (summer 2020), the zoo is trying to return Er Shun and Da Mao back to their homeland.

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PHOTO CREDIT: Giant panda chowing down on bamboo stalks (Unsplash)