Wild Giant Pandas

Wild giant pandas (Ailuropoda melanoleuca) not only frequently sniff and wallow in fresh horse manure at low ambient temperatures, but also actively rub the fecal matter all over their bodies.

Beta-caryophyllene and caryophyllene oxide-induced horse manure rolling behavior of Ginny, the giant panda at Beijing Zoo. Image credit: Zhou et al., doi: 10.1073/pnas.2004640117.

“Attraction to feces in wild mammalian species is extremely rare,” said first author Dr. Wenliang Zhou from the Institute of Zoology at the Chinese Academy of Sciences and colleagues.

“Our 10-year field observations of Qinling giant pandas (Ailuropoda melanoleuca qinlingensis) indicated that fresh horse manure sometimes exhibits a strong attraction for pandas and leads them to roll in such dunghills.”

“Interestingly, the ancient trade routes connecting Shu kingdom and Chang’an made the captive horses for good transit into a stable member in the present panda habitat for thousands of years, thereby keeping horse dunghills and their odor familiar to the populations of the pandas,” they noted.

“Unlike any novel odor that attracts animals, this type of frequent and stable panda-dunghill interaction triggered our great interest in uncovering its underlying mechanism by combining behavioral observation, compound analysis, climate data, animal assays, molecular cloning, and functional tests to provide further perspective on this behavior.”

In the study, the researchers observed 38 horse manure rolling behaviors in Qinling giant pandas.

The frequency of the manure rolling correlated with the freshness of the manure and with the ambient air temperature, as almost all events were recorded at temperatures between minus 5 and 15 degrees Celsius.

Hypothesizing that the presence of chemical compounds beta-caryophyllene and caryophyllene oxide in fresh manure may drive the behavior, the scientists found that in winter, pandas at the Beijing Zoo preferentially sniffed, rubbed, and smeared hay treated with those compounds.

They further hypothesized that the compounds may be related to cold temperatures, and found that mice treated with the compounds exhibited increased cold tolerance.

Beta-caryophyllene and caryophyllene oxide were then found to interact with the pandas’ thermosensitive receptor pathway called transient receptor potential melastatin 8 (TRPM8) and inhibit cold activation of the pathway.

The authors think that manure rolling behavior may help the pandas acclimatize to cold temperatures.

“As seen in human history for discovering hot sensation or coolness from chili peppers or mints, more generally, we assumed that the thermal sensations induced by beta-caryophyllene and caryophyllene oxide play a role in the life history of giant pandas,” Dr. Zhou and co-authors.

“Thus far, our current understanding of horse manure rolling behavior based on the functional impact of beta-caryophyllene and caryophyllene oxide may further reveal the origin of this behavior together with other unknown factors required for future efforts.”

The study was published in the Proceedings of the National Academy of Sciences.

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Wenliang Zhou et al. Why wild giant pandas frequently roll in horse manure. PNAS, published online December 7, 2020; doi: 10.1073/pnas.2004640117