Vegetarian pandas have carnivore guts, may be on their way to extinction
The reason Pandas are always chewing and eating bamboo is that their digestive systems evolved from bears that ate both plants and meat.
Although Panda bears spend about 14 hours a day munching on bamboo shoots and leaves, sometimes consuming up to 12.5 kilograms a day, they only digest 17 percent of what they eat, according to a new study published in the American Society for Microbiology on Tuesday,
Their feces also mainly consist of fragments of undigested bamboo.
“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 lead study author Zhihe Zhang, director of the Chengdu Research Base of Giant Panda Breeding in China.
Pandas started eating bamboo about two million years ago, but the results of the study show that the bear’s digestive system has not properly adapted to their unique diet.
“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, an associate professor in the School of Life Sciences and Biotechnology at Shanghai Jiao Tong University.
Pang and his team examined 121 fecal samples from 45 giant pandas living on the Chengdu Research Base in spring, summer and late autumn over a year. All of the giant pandas showed extremely low gut microbiota diversity and an overall gut structure that evolved from non-panda plant eaters and which was similar to carnivorous and omnivorous bears.
The giant pandas did not have plant-digesting bacteria that are found in other herbivores and instead mainly had Escherichia/Shigella and Streptococcus, bacteria that digests meat.
They also found that the panda’s gut microbiota experienced significant seasonal variations, particularly among the Streptococcus and Lactobacillus bacteria. Pang said that a lack of bamboo shoots in late autumn is probably an important factor in gut bacteria fluctuations.
The authors conclude that the way the panda’s digestion tract has evolved means that it could be on its way to extinction.
“Although studies of its genetic diversity, population structure, and demographic history suggest that the giant panda is not a species at an evolutionary dead end, the peculiar characteristics of its gut microbiota may put it at high risk of extinction,” the study says.