Abstract
Anal sacs are an important odor producing organ found across the mammalian Order Carnivora. Secretions from the anal sac may be used as chemical signals by animals for behaviors ranging from defense to species recognition to signaling reproductive status. In addition, a recent study suggests that domestic cats utilize short-chain free fatty acids in anal sac secretions for individual recognition. The fermentation hypothesis is the idea that symbiotic microorganisms living in association with animals contribute to odor profiles used in chemical communication and that variation in these chemical signals reflects variation in the microbial community. Here we examine the fermentation hypothesis by characterizing volatile organic compounds (VOC) and bacteria isolated from anal sac secretions collected from a male bengal cat, a cross between a domestic cat and wild leopard cat (Felis catus × Prionailurus bengalensis).
Both left and right anal sacs of a male bengal cat were manually expressed (emptied) and collected. Half of the material was used to culture bacteria or to extract bacterial DNA and other half was used for VOC analysis. DNA was extracted from the anal sac secretions and used for a 16S rRNA gene sequence based characterization of the microbial community. Additionally, some of the material was plated out in order to isolate bacterial colonies. The same three taxa, Bacteroides fragilis, Tessaracoccus, and Finegoldia magna were abundant in the 16S rRNA gene sequence data and also isolated by culturing. Using Solid Phase Microextraction (SPME) gas chromatography-mass spectrometry (GC-MS), we tentatively identified 52 compounds from bengal cat anal sac secretions and 67 compounds from cultures of the three bacterial isolates chosen for further analysis.. Among 67 compounds tentatively identified from bacteria isolates, 52 were also found in the anal sac secretion.
We show that the bacterial community in the anal sac consists primarily of only a few abundant taxa and that isolates of these taxa produce numerous volatiles that are found in the combined anal sac volatile profile. Many of these volatiles are found in anal sac secretions from other carnivorans, and are also associated with known bacterial biosynthesis pathways. This supports the fermentation hypothesis and the idea that the anal sac is maintained at least in part to house bacteria that produce volatiles for the host.
