Voles get a brain boost from eating their own poo - how can we gain the same benefits without the gross factor?

Eating poop boosts the generation of feel-good dopamine in voles and helps them pass cognitive tests, observed Chinese scientists in an animal experiment.

Brandt's vole is a mouse-like rodent living in the grasslands of Mongolia, Russia and China, feeding on plants and storing a large amount of food in underground tunnels. When it eats, the vole has a habit of turning around for stool still fresh and warm on the floor.

On average, about one in every five droppings is eaten by the animal, but its motivation for this behaviour remains unclear.

To find the answer, Professor Wang Dehua and colleagues at the Institute of Zoology at the Chinese Academy of Sciences in Beijing put the vole in a cage with a mesh floor where the faeces would fall through the screen.

Each vole wore a collar around its neck, so it could not reach back to catch the droppings directly from its anus.

In comparison to the voles living in normal cages, some of which also had a collar to control for the potentially stressful effect, the poop-denied voles had a greater food intake (a third more) but ended up weighing less (20 per cent less), suggesting a negative effect on metabolism.

There was also an almost across-the-board reduction in chemicals that stimulated the transmission of neurological signals. Dopamine, a main chemical of pleasure, for instance, dropped nearly half, according to their peer-reviewed study published this month in The ISME Journal, the official publication of the International Society for Microbial Ecology.

"I am not saying people should try this," Wang told the South China Morning Post on Monday. He said that was because neurological reward was a complex issue with many factors involved, and the result did not necessarily replicate in other mammals.

"But coprophagy [the behaviour of eating poo] is very popular in the animal kingdom. More popular than most people think. Pigs and dogs do it. The idea is recycling," Wang said.

Hamsters, rabbits, dogs and pigs are among the many animals that eat their own faeces. Photo: Shutterstock alt=Hamsters, rabbits, dogs and pigs are among the many animals that eat their own faeces. Photo: Shutterstock

The poop not only made the vole feel good, but also helped keep their minds sharp.

Wang and his collaborators challenged the animals with various cognitive tests, including a maze. Those eating faeces scored significantly higher when measuring memory, learning and object identification.

In the wild, the improved cognitive function leads to more food and a faster escape from predators, according to the researchers.

The secret of how coprophagy helps the vole may come from the bacteria in its waste. Genetic sequencing by Wang's team showed that poo-eating voles had a different composition of microorganism colonies in their intestines.

These gut bacteria in faeces not only provided the voles with extra nutrition through an extended period of fermentation but also prompted the production of critical brain-stimulating chemicals, according to the study.

In humans, there could be up to 2kg (4.4 pounds) of microorganisms in the body, according to one estimate. They affect almost every aspect of our life, but many details of the process remained poorly understood.

"We are strangers in this brand new world," Wang said.

Some ancient cultures used animal or human stool as a medicine and physicians tasted faeces to help diagnose an illness.

In recent years some hospitals have made pills with stool from healthy donors to cure some stomach disorders. Not all patients find this therapy acceptable but there could be a different approach, according to Wang's study.

The researchers fed the voles acetate, a key product of the natural fermenting process in the gut, and found the animals returned largely to their normal, healthy conditions even after they had stopped eating their own waste.

"Supplementation with acetate rescued microbiome structure, brain neurochemistry and cognitive performance," they said in the paper.

This article originally appeared in the South China Morning Post (SCMP), the most authoritative voice reporting on China and Asia for more than a century. For more SCMP stories, please explore the SCMP app or visit the SCMP's Facebook and Twitter pages. Copyright © 2020 South China Morning Post Publishers Ltd. All rights reserved.

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