Giant pandas are unable to properly digest food, a new study reveals. Evidence of this surprising conclusion was found by researchers examining scat from the iconic Asian creatures.

Panda poop from 45 animals of all ages living in captivity was studied by researchers over the course of an entire year. Strands of RNA collected from the scat was the compared with samples of other animals, including herbivores, omnivores and meat-eaters. Bacteria within the guts of the animals appear to be geared toward a meat-eating diet, which is surprising, considering the fact that pandas are herbivores.

Researchers found that the bacteria microbiome in panda guts lacks the genetic diversity typically seen in vegetarian animals. The microorganisms inside the panda digestive system, including Streptococcus, Escherichia, and Shigella, is similar to those found in carnivorous bears. Researchers also discovered giant pandas lack bacteria needed to properly digest cellulose.

Giant pandas (Ailuropoda melanoleuca) are an endangered species, native to China. Biologists believe they were once omnivores who started to eat bamboo roughly 7 million years ago, which then became their primary food source between 2.4 and 2 million years before our time. Eventually, the creatures evolved a pseudothumb and powerful jaws to harvest the tough plant. However, the animals lack enzymes to assist in the digestion of vegetative material, and they still posses short digestive tracks typical of meat-eating species.

"It is really interesting when you have a lineage that does something really differently from its relatives in terms of its food and what happens with the microbiome in relation to that change," said Jonathan Eisen from the University of California, Davis.

Biologists are uncertain exactly why giant pandas changed their diet millions of years ago. However, genetic evidence suggests the animals also lost their taste of umami around the same time. This is the flavor we associate with meatiness, and other savory flavors.

This study only examined the identity of the bacteria found to be living in the guts of pandas, but did not examine the function those bacteria play within their digestive track. Some biologists believe the microorganisms may have evolved to carry out some functions, such as the production of enzymes to increase the efficiency of cellulose digestion.

A study released in 2011 provided evidence that Clostridium bacteria within the digestive system of pandas could provide enzymes capable of converting cellulose into a variety of simple sugars. Future research could examine if the microbiome of bacteria within pandas are still capable of adequately digesting cellulose.

Examination of the digestive system of pandas and their carnivorous-like digestive systems was detailed in mBio, published by the American Society for Microbiology.

Photo: Gill Penney | Flickr

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