There may be yet another reason, in addition to poaching and habitat loss, that giant pandas are in danger. Their digestive systems are not designed to eat bamboo and never have been. According to researchers in China, the bears still have the gut bacteria of a carnivorous animal predominated by bacteria such as Escherichia/Shigella and Streptococcus.
“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. The animals also do not have the genes for plant-digesting enzymes in their own genome. This combined scenario may have increased their risk for extinction,” said Zhihe Zhang, director of the Chengdu Research Base of Giant Panda Breeding, China in a statement.
Zhang is the lead author of a paper appearing in mBio®, the online open-access journal of the American Society for Microbiology.
“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,” said study coauthor Xiaoyan Pang, PhD, MSc, an associate professor in the School of Life Sciences and Biotechnology at Shanghai Jiao Tong University.
According to the researchers, giant pandas evolved from omniverous bears about two million years ago, but their digestive systems do not seem to have ever caught up. Currently, the animals spend about 14 hours a day eating. On average, an adult will consume 27.5 pounds of bamboo daily but can only digest about 17 percent of what they eat.
The researchers used a technique called 16S rRNA sequencing to analyze 121 fecal samples from 45 pandas. These included adult, juvenile and newborn pandas, and were collected during the spring, summer and autumn. The researchers found that the feces was composed primarily of undigested bamboo.
The analysis showed that the pandas, along with previously studied captive animals, had extremely low diversity in their gut bacteria. The overall structure of their digestive system, was closer to that of omnivorous or carnivorous bears. Additionally, the pandas didn’t have any plant-degrading bacteria like Ruminococcaceae and Bacteroides that tend to dominate the systems of herbivores.
The group is now planning a follow up study to more carefully examine how the pandas digestive systems handle the bamboo they ingest.
While giant panda’s are still considered endangered by the IUCN, Chinese conservation efforts appear to be working. According to a report released in February, harsh penalties for poaching and improved habitat protection have resulted in a 17 percent increase in the wild panda population in the last decade.
