Given such a strong freshness dependence, these results encouraged us to identify the crucial compounds that induce HMR behavior by comparing the volatiles in fresh ( n = 5) and aged ( n = 5) horse manure samples. Indeed, fresh horse manure (exposure time <10 d) exhibited a strong attraction for pandas (χ 2 = 30.81, df = 1, P < 0.001), evoking HMR behavior in nearly all of the approached individuals ( Fig. 2 A, almost all of the HMR behaviors were recorded when the exposure time of horse manure was less than 10 d. We found that the freshness of horse manure significantly affected HMR behavior. Beta-Caryophyllene/Caryophyllene Oxide Serves as the Key Compound for HMR Behavior. Kruskal–Wallis rank sum test with post hoc Dunn test was used for pairwise comparison, * P < 0.001.

HMR behavior exhibited by Ginny is indicated by red arrow. ( F) Time spent of panda visiting events in front of each hay. ( E) The number of panda visiting events in front of each hay. Chemical compounds contained in different types of hay are shown. ( D) A sketch indicating the experimental design method for animal behavior observation done in Beijing Zoo. ( C) Relative abundance of BCP/BCPO in fresh (in yellow) and aged (in gray) horse manure. Chemical structures of BCP and BCPO are indicated side-by-side with their peaks (shown in red and highlighted in yellow). ( B) Representative gas chromatography-mass spectrometer (GC-MS) analysis of the fresh ( Upper) and aged ( Lower) horse manure. Durations of HMR behaviors were obtained from infrared camera-trap images. ( A) Relationship between HMR behavior and exposure time of horse manure. Results Horse Manure Rolling Behavior of Wild QIN Pandas.įig. 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. S1 A) 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 QIN pandas ( SI Appendix, Fig. Interestingly, the ancient trade routes ( 13, 14) connecting Shu kingdom and Chang’an (referred to as Xi'an, the former capital city in Chinese history, SI Appendix, Fig. Our 10-y field observations of Qinling giant pandas (also named QIN pandas) indicated that fresh horse manure sometimes exhibits a strong attraction for pandas and leads them to roll in such dunghills. To our knowledge, although some casual cases of attraction to the fecal matter of heterospecifics have been recorded ( 11, 12), the biological significance is unclear, let alone the related molecular mechanisms. Together, our study described an unusual behavior, identified BCP/BCPO as chemical inhibitors of TRPM8 ion channel, and provided a plausible chemistry-auxiliary mechanism, in which animals might actively seek and utilize potential chemical resources from their habitat for temperature acclimatization. Therefore, horse manure containing BCP/BCPO likely bestows the wild giant pandas with cold tolerance at low ambient temperatures. BCP/BCPO (beta-caryophyllene/caryophyllene oxide) in fresh horse manure was found to drive HMR behavior and attenuated the cold sensitivity of mice by directly targeting and inhibiting transient receptor potential melastatin 8 (TRPM8), an archetypical cold-activated ion channel of mammals. The frequency of HMR events was highly correlated with an ambient temperature lower than 15 ☌.

Pandas not only frequently sniffed and wallowed in fresh horse manure, but also actively rubbed the fecal matter all over their bodies. Here we introduce the horse manure rolling (HMR) behavior of wild giant pandas ( Ailuropoda melanoleuca). Attraction to feces in wild mammalian species is extremely rare.

Giant panda