The giant panda Ailuropoda melanoleuca belongs to the family of Ursidae; however, it is not carnivorous, feeding almost exclusively on bamboo. Being equipped with a typical carnivorous digestive apparatus, the giant panda cannot get enough energy for an active life and spends most of its time digesting food or sleeping. Feeding and mating are both regulated by odors and pheromones; therefore, a better knowledge of olfaction at the molecular level can help in designing strategies for the conservation of this species. In this context, we have identified the odorant-binding protein (OBP) repertoire of the giant panda and mapped the protein expression in nasal mucus and saliva through proteomics. Four OBPs have been identified in nasal mucus, while the other two were not detected in the samples examined. In particular, AimelOBP3 is similar to a subset of OBPs reported as pheromone carriers in the urine of rodents, saliva of the boar, and seminal fluid of the rabbit. We expressed this protein, mapped its binding specificity, and determined its crystal structure. Structural data guided the design and preparation of three protein mutants bearing single-amino acid replacements in the ligand-binding pocket, for which the corresponding binding affinity spectra were measured. We also expressed AimelOBP5, which is markedly different from AimelOBP3 and complementary in its binding spectrum. By comparing our binding data with the structures of bamboo volatiles and those of typical mammalian pheromones, we formulate hypotheses on which may be the most relevant semiochemicals for the giant panda.

Anogenital gland secretions play a major role in chemical communication by giant pandas, Ailuropoda melanoleuca (David, 1869). We analyzed 45 samples of anogenital gland secretions collected from 24 captive pandas (5 male adults, 6 female adults, 6 male subadults, and 7 female subadults) by gas chromatography and mass spectrometry. The secretions contained over 95 compounds. Based on 56 common compounds (relative abundances >0.1%) shared by more than three individuals, we identified steroids, long-chain fatty acids, fatty-acid esters, aldehydes, alkanes, alkenes, amines, terpenes, and furans. The chemical composition of each secretion was individual-specific. Although none of these individual compounds was age- or sex-specific, the relative abundances of several compounds differed between males and females and between adults and subadults. This result shows that information about sex and age could be coded in analog form. Information about age but not gender could also be digitally coded by the presence or absence of some of the 56 compounds, in addition to the analog coding.