Mandrills and Microbes: Characterising the mandrill scent-gland microbiome and its potential role in olfactory communication

Olfactory communication conveys information about an individual through the release and reception of semiochemicals. Mammals harbour a diverse array of microorganisms, many of which have co-evolved to facilitate otherwise impossible metabolic pathways for the host. For example, the fermentation hypothesis holds that microbes inhabiting scent-glands digest secretions, producing odour signals. Olfaction is integral to primate communication, impacting behaviour and reproductive success. Mandrills (Mandrillus sphinx) are one of the few African monkey species to possess scent-glands, which produce odour that differs with age, sex, male dominance rank, group membership, and possibly individual identity. We aimed to determine the composition of the mandrill scent-gland microbiome and investigate how the bacterial composition differs with individual traits and states, and with glandular activity. We collected 121 skin swab samples from the scent-glands of mandrills living in a large, semi-free ranging colony in Franceville, Gabon. We used 16S rRNA amplicon sequencing and bioinformatic analyses with the QIIME2 pipeline to determine bacterial composition and diversity measures. Analysis is ongoing, but initial results indicate that the mandrill scent-gland is dominated by four phyla: Firmicutes (47.6%), Bacteroidota (16.5%), Actinobacteriota (12.9%) and Proteobacteria (11.9%). We also identified fermentative genera previously found in other mammalian scent-glands, including Staphylococcus (9.8%), Prevotella (9.1%), Lactobacillus (3.4%), Corynebacterium (0.4%), Fusobacterium (0.3%) and Anaerococcus (0.1%). This first description of the mandrill scent-gland microbiome will test the potential for microbiota to mediate signals used in selecting mates, the capacity for hosts to control their microbiome composition, and the co-evolutionary consequences of this symbiosis for primate communication.