Study: Pandas can't properly digest bamboo

CHENGDU, China, May 19 (UPI) -- The combination of bacteria inside the guts of giant pandas isn't ideally suited to break down bamboo. Researchers say the iconic black-and-white bears (Ailuropoda melanoleuca) are inefficient when it comes to digesting their favorite food.

In analyzing the microorganisms that populate the giant panda's digestive system, a team of scientists found the panda's microbiota more closely resembles the guts of meat-eaters.

As detailed in a new research paper in the journal mBio, the panda's most common gut bacteria, from the genera Escherichia, Shigella and Streptococcus, aren't well-suited to break down fibrous chunks of bamboo. The research explains why pandas spend so long chewing the plant before swallowing.

"Unlike other plant-eating animals that have successfully evolved, anatomically specialized digestive systems to efficiently deconstruct fibrous plant matter, the giant panda still retains a gastrointestinal tract typical of carnivores," lead study author Zhihe Zhang, director of the Chengdu Research Base of Giant Panda Breeding, China, said in a press release.

More than just a headline-grabbing discovery, the new research is worrisome for conservationists hoping to bolster wild giant panda populations. Self-sustaining panda populations may simply be an impossibility.

"The animals also do not have the genes for plant-digesting enzymes in their own genome," Zhang said. "This combined scenario may have increased their risk for extinction."

Though not an exact replica, the giant panda's gut microbiome is more similar those of its closest carnivorous and omnivorous relatives than it is to non-panda plant-eaters. Specifically, its digestive system lacks microorganisms from the genera Ruminococcaceae and Bacteroides -- bacteria common in the guts of other herbivores.

"This result is unexpected and quite interesting, because it implies the giant panda's gut microbiota may not have well adapted to its unique diet, and places pandas at an evolutionary dilemma," explained co-author Xiaoyan Pang, a biologist at Shanghai Jiao Tong University.

The researchers say further research could help explain whether there are any unforeseen benefits to their seemingly ill-suited digestive microbiome.