Panda bamboo digestion
Le Le, the male panda in the zoo, eats bamboo stalksCandace Williams

Analysing panda poop may provide an explanation as to why the endangered mammal struggles to reproduce in captivity, scientists have said. During mating season and gestation, the animals often appear to suffer from debilitating gastrointestinal problems.

The study, published in the journal Frontier in Microbiology, focuses on two captive giant pandas, a male called Le Le and a female called Ya Ya, who live at Memphis zoo in the US.

The scientists looked at data about their feeding behaviours collected since 2003, as well as faeces samples.

Spring time is usually when the animals are usually able to reproduce, but researchers have detected that this time of year also coincides with dietary shifts. This then led to significant digestive complaints in the months to follow, when the panda should have been mating or when females should be in gestation.

Bamboo leaves or stalks

Looking at Ya Ya and Le Le, the team measured how much time the two pandas spent eating bamboo leaves or stalks. They discovered that this varied with seasons. During winter and spring months, most of their nutrition was based on bamboo stalks. However, at the end of spring, the pandas went through a transition, switching to leaves. By August, 60% of their feeding time was spent eating leaves.

Late spring and summer were also the time faeces resembling strange gelatinous masses and known as "mucoids" began to appear. When pandas passed such mucoids, they became more lethargic, stopped eating and appeared to be suffering a great deal.

In this context, pandas may not be able to engage in reproductive behaviours and females may go through a complicated gestation in the summer.

Spike in bacteria

In total, the team analysed normal faeces samples dating from February 2013 and mucoids dating from June-August 2014.

Panda bamboo digestion
Dietary changes could lead to 'mucoids' which cause great pain for pandas.Candace Williams

Compared to other herbivores, "normal" panda poop has a low bacterial diversity. However, the number of bacteria present spiked in mucoids.

The scientists discovered bacteria typically found in the gut lining, in these samples. Thus, they believe pandas are sloughing off the internal mucous membrane of their gastrointestinal tract, driven by changes in their diet.

"What we think might be happening is that their diet is causing a strong internal reaction, leading to an inflammatory response," says lead author Garret Suen. "Pandas are basically shedding their gastrointestinal lining to allow for the replacement of those microbes. It's kind of like resetting the microbiome."

Improving health overall

Understanding how the microbiome and digestive system of the animals function can also be crucial to reduce the incidence of other diseases and mortality in this rare species.

"Gastrointestinal diseases are a major cause of mortality in wild and captive pandas but scientists understand very little about their digestive process," concludes co-author Ashli Brown Johnson. "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."