Why do giant pandas (Ailuropoda melanoleuca; Carnivora: Ursidae) rub and roll in heterospecific scents?

Abstract

Free-ranging giant pandas (Ailuropoda melanoleuca) in China recently were reported to rub and roll in horse manure, a behavior that was observed frequently at low ambient temperatures. Two sesquiterpenes, β-caryophyllene (BCP) and caryophyllene oxide (BCPO), that are abundant in fresh horse manure elicited rolling in captive giant pandas. Mice and rats treated with BCP/BCPO exhibited enhanced cold tolerance in behavioral assays, and BCP/BCPO inhibited cold-activated ion channels of mammals expressed in human kidney cells; these laboratory results were cited in support of the contention that giant pandas tolerate low ambient temperatures by applying horse manure to their integument. The demonstrated biocidal activities of BCP and BCPO against insects and ticks, and the reported elicitation of anointing in giant pandas with materials other than horse manure, including substances or constituents thereof known to act as arthropod biocides, are consistent with an anti-consumer function of anointing by giant pandas. Anointing with the scents of heterospecifics as a defense against nuisance arthropods constitutes a viable hypothesis for the rubbing and rolling behaviors of giant pandas and other ursids.