Captive pandas suffer gastrointestinal disorders. Now new research suggests they may put a freeze on baby-making time too. JEFF J MITCHELL / GETTY IMAGES

Like some humans, giant pandas struggle with digestion due to changes in diet – an affliction that could be interrupting their reproduction, according to a new study.

Like other bears, giant pandas (Ailuropoda melanoleuca) are technically carnivores, but their diet is largely herbivorous – wild and captive pandas eat around a third of their body weight in bamboo every day.

Perhaps because of this, pandas struggle with tummy aches, and their faeces occasionally contains gelatinous membranes, which are painful and distressing to pass and interrupt the panda’s feeding habits.

Zookeepers at the Memphis Zoo noticed significant shifts in the diets of giant pandas, from bamboo stalks to bamboo leaves, depending on the season.

A team of researchers led by University of Wisconsin-Madison bacteriologist Garret Suen set out to find links between the panda’s painful pooping, digestion of different plant parts and possibly the panda’s notoriously low reproduction rates.

“Gastrointestinal diseases are a major cause of mortality in wild and captive pandas but scientists understand very little about their digestive process,” explains Ashli Brown Johnson, a biochemist at Mississippi State University and co-author of the study.

“By studying the microbial community in the panda’s gastrointestinal tract, we gain a better understanding of panda nutrition, which could help improve the health and reproduction of the endangered species.”

Data recorded at the Memphis Zoo revealed their pair of captive pandas spent 1% of their time eating leaves in winter and spring, compared with 60% during warmer months.

This increase in leaf-eating coincided with the production of the painful, membrane-heavy stools, along with symptoms of fatigue, discomfort and less eating in general.

Interestingly, the warmer part of the year also produces the highest pregnancy rates among female pandas, which led the researchers to draw a possible link between digestive trouble and reproduction.

“We think they are sloughing off the internal mucous membrane of their gastrointestinal tract and because of this, they get really sick, which coincides with gestation,” says Suen.

A faecal sample from a giant panda, showing a mix of bamboo stalks and leaves. Bamboo is tough and fibrous and panda digestive systems are not well-designed to break down this material, though it is their primary source of nutrition. CANDACE WILLIAMS

The researchers studied Memphis Zoo’s pandas’ faeces, taking note of the microbiome in the stools with and without membranes.

They found a higher diversity of gut bacteria in the stools containing membranes, including bacteria usually found in the gut lining. They also found bacteria associated with digestive problems in humans.

“What we think might be happening is that their diet is causing a strong internal reaction, leading to an inflammatory response,” says Suen.

“Pandas are basically shedding their gastrointestinal lining to allow for the replacement of those microbes. It’s kind of like resetting the microbiome.”

This process causes inflammation, and by all accounts, isn’t much fun for pandas. Problem poos can also be transferred to offspring if pandas reproduce during this period.

The paper suggests investigating treatments such as dietary supplements to keep pandas healthy and well-nourished during problem periods.

The significance of gut microbiome for humans is becoming increasingly apparent, and animals are no different, according to co-author Candace Williams, a biologist at Mississippi State University.

“Until recently, the gut microbiome hasn’t really played a role in the management of animals,” explains Williams.

“Having a balanced gut is important, and it’s also important that we know these things, especially about such unique animals. I strive to let people know how important the gut microbiome really is and the impact it has on reproduction, health and even immune function.”

The researchers acknowledge more research is needed to fully understand the phenomenon, but pandas are notoriously difficult to study.

Suen, who has previously studied the microbiomes of cows and sloths, hopes further research could help scientists understand more about human gut troubles.

The findings were published in Frontiers in Microbiology.