Baffled scientists reveal why pandas have been caught smearing themselves with horse manure

Motion sensitive cameras reveal widespread inclination to roll in dung among wild giant pandas

It is a question which has baffled scientists for years – why do giant pandas like to rub horse dung all over themselves?

Though domesticated dogs indulge in this pastime, among wild animals, rolling or attempting to coat themselves in other species’ excrement is a rare behaviour trait.

But in China, the pandas’ predilection for smearing horse manure all over themselves has apparently been well documented – though only in recent years.

Around 12 years ago, students of Fuwen Wei, an ecologist at the Chinese Academy of Sciences in Beijing, observed pandas in the Qinling mountains of central China seeking out horse manure, and then rubbing it into their necks and faces and rolling around in it in order to cover their entire bodies.

In the animal world droppings routinely play an important role, acting as a calling card, or a warning for others. Dung can reveal the sex and mating status of some species, while others indicate the presence of possible predators.

But none of the usual theories applied to pandas, leaving scientists scratching their heads.

After a long investigation into the intriguing behaviour, a theory to explain this unlikely scenario has emerged.

Apparently the chemical make-up of the horse manure means it has warming properties which could help the animals during the colder winter months.

In order to study the behaviour in more detail, the team needed more documentary evidence of the rarely-seen behaviour.

They set up several motion-sensitive cameras along a road in the Foping National Nature Reserve.

The cameras caught an astonishing 38 incidents of pandas marinating themselves in manure between June 2016 to June 2017.

This confirmed the students’ initial observations hadn’t been the result of one especially scatological panda.

Importantly, the apparatus also recorded the time and air temperature for each panda-poo interaction, which revealed a clear pattern.

The pandas only sought out the manure on particularly cold days. Most of the incidents were filmed when temperatures were between -5C and 5C.

The research team also noted that the pandas were only interested in fresh manure and older stuff was ignored.

The faeces contains natural compounds, called beta-caryophyllene (BCP) and beta-caryophyllene oxide (BCPO), however, these chemicals become scarce in older dung, the scientists said, according to ScienceMag.org.

There are strict laws governing any testing of pandas in China, which are highly revered, so the research team turned to mice.

They found that coating mice in a diluted BCP-BCPO solution boosted the animals’ cold tolerance, the authors said.

“Therefore, horse manure containing BCP/BCPO likely bestows the wild giant pandas with cold tolerance at low ambient temperatures,” the authors said.

Though only recently observed and detailed, the behaviour could have been occurring for thousands of years, the researchers said.

The Qinling Mountains are crisscrossed by ancient trade routes well-trodden by horses over millennia, so the researchers say horse manure has been common in the region for a long time.

Pandas’ low-calorie diet of bamboo and frequently inadequate fat reserves which provide minimal insulation means surviving cold winter temperatures can be difficult for the species.

Isaac Chiu, a neuroscientist at Harvard University who wasn’t involved in the study, told the New York Times there are also other compounds present in the dung, which have anti-inflammatory properties, which could ease pain.

“Maybe it’s like Vicks VapoRub, or maybe like Tiger Balm,” he said, describing the cool tingly sensation they cause on the skin.

“I don’t know, though,” he said. “I’ve never rolled in horse manure.”

The research is published in the Proceedings of the National Academy of Sciences