Giant pandas have been seen smearing themselves with horse manure in the wild, and the sweet smell of scat isn’t the only reason – it appears the manure helps them tolerate low temperatures, according to a study.
Unlike insects that make a beeline for faeces, digging for olfactory cues to locate food, attraction to excrement across mammal species is rare. But researchers from the Chinese Academy of Sciences observed that a giant panda subspecies in China’s Qinling Mountains tended to seek out and sniff fresh horse manure and then roll over it.
The researchers set up infrared cameras in the wild between July 2016 to June 2017 and captured 38 events of this rolling behaviour, which mostly occurred when the ambient temperature was less than 15C (59F).
The behaviour also appeared to be linked to droppings that were less than 10 days old. When the scientists compared fresh manure to older excrement, they found that the fresh faeces was rich in two compounds: beta-caryophyllene and caryophyllene oxide.
Owing to the apparent temperature correlation, the scientists wondered whether the two compounds were somehow implicated in the thermal sensation of mammals, so they conducted another experiment. They treated one group of mice with the two compounds and another group with saline, finding that the compound-treated mice tolerated cold temperatures better.
The researchers then found that at a molecular level the two compounds interact with a thermosensitive pathway in pandas, inhibiting cold activation, they said in a paper published in the journal Proceedings of the National Academy of Sciences.
Dr Claudia Wascher, a behavioural ecologist from Anglia Ruskin University who was not involved in the study, said: “Generally, many species avoid faeces and show disgust towards faeces, which can be explained as an evolved strategy to avoid parasites and infections. I have not heard about pandas rolling in horse manure, but I am familiar with other species rolling in faeces of other species, for example dogs. I would not be surprised if more species show similar behaviour.
“This reminds me a bit about self-medication in some species: for example, primates are known to self-medicate, so eat specific types of plant when they feel sick.”
Dr Simon Girling, the head vet at Edinburgh zoo, which houses the UK’s only two giant pandas, said the study was insightful given that most research papers focus heavily on olfaction and pheromones in faeces.
“We have always understood that olfaction is a very important sense for this particular species,” he said. “When people say splitting the genome of this, that and the other – what’s the point? Well, here’s a very interesting example, it starts to unlock our understanding of the biology of this particular species and how it how it can adapt.”
Would Edinburgh’s two pandas – Tian Tian and Yang Guang – be given some fresh horse manure to anoint themselves in the winter? “It’s certainly a possibility,” Girling said.
He cautioned that horse faeces could carry salmonella bacteria. “But potentially if it was possible to isolate these compounds in a safe way, that may well be something that could be used as an enrichment tool.”