Pandas are among the least-motivated animals on Earth, and by any objective measure should not exist: The majestic beasts are so inept at something as primal as breeding that U.S. zoologists had to resort to showing them “panda porn” in order to get them in the mood. Now, new research out of the Chinese Academy of Sciences and Shanghai Jiao Tong University finds yet another way pandas routinely spit in the face of Charles Darwin: Their gut bacteria is unable to fully digest bamboo, practically the only thing they eat.
“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,” said lead study author Zhihe Zhang, director of the Chengdu Research Base of Giant Panda Breeding, in southwest China’s Sichuan Province, in a statement. “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.”
Pandas – the only carnivore too lazy to act like one. As it is, bamboo isn’t particularly nutritious – pandas tear through it by the truck load, thanks to their powerful jaws. In order to consume enough calories, pandas spend upwards of 14 hours each day noshing on bamboo. Part of that is due to its low nutritional value, but analysis of panda feces reveals another reason for the tremendous volume: Pandas can only digest about 17% of what they eat. Most of their droppings consist of undigested bamboo fibers
Zhang and his colleagues used a technique called 16S rRNA sequencing to evaluate 121 fecal samples from 45 giant pandas living in China’s Sichuan Province, including 24 adults, 16 juveniles and five unweaned cubs. Despite their insistence on eating bamboo, the pandas had remarkably low gut bacteria diversity, and lacked bacteria crucial for plant digestion like Ruminococcaceae and Bacteroides. Instead, their stomachs more closely resembled those of carnivores and omnivorous bears.
“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,” added study coauthor Xiaoyan Pang, an associate professor in the School of Life Sciences and Biotechnology at Shanghai Jiao Tong University.
Pandas, the researchers say, started eating bamboo almost exclusively a whopping 21 million years ago, and they’re still bad at it. Pandas – is there anything they do right?