Our new paper is out in the Proceedings of the National Academy of Sciences
Abstract: All animals harbor beneficial microbes. One way these microbes can benefit their animal hosts is by increasing the diversity and efficacy of communication signals available to the hosts. The fermentation hypothesis for mammalian chemical communication posits that bacteria in the scent glands of mammals generate odorous metabolites used by their hosts for communication and that variation in host chemical signals is a product of underlying variation in the bacterial communities inhabiting the scent glands. An effective test of this hypothesis would require accurate surveys of the bacterial communities in mammals’ scent glands and complementary data on the odorant profiles of scent secretions—both of which have been historically lacking. Here we use next-generation sequencing to survey deeply the bacterial communities in the scent glands of wild spotted and striped hyenas. We show that these communities are dominated by fermentative bacteria and that the structures of these communities covary with the volatile fatty acid profiles of scent secretions in both hyena species. The bacterial and volatile fatty acid profiles of secretions differ between spotted and striped hyenas, and both profiles vary with sex and reproductive state among spotted hyenas within a single social group. Our results strongly support the fermentation hypothesis for chemical communication, suggesting that symbiotic bacteria underlie species-specific odors in both spotted and striped hyenas and further underlie sex and reproductive state-specific odors among spotted hyenas. We anticipate that the fermentation hypothesis for chemical communication will prove broadly applicable among scent-marking mammals as others use the technical and analytical approaches used here.
Original papers proposing the fermentation hypothesis for mammalian chemical communication
Gorman, M. L. 1976. A mechanism for individual recognition by odour in Herpestes auropunctatus, doi:10.1016/S0003-3472(76)80107-8
Albone, E. S., Eglinton, G., Walker, J. M. & Ware, G. C. 1974. The anal sac secretion of the red fox (Vulpes vulpes); its chemistry and microbiology. A comparison with the anal sac secretion of the lion (Panthera leo), doi:10.1016/0024-3205(74)90069-1
Review papers discussing a more general symbiotic hypothesis for animal chemical communication
Archie, E. A. & Theis, K. R. 2011. Animal behaviour meets microbial ecology, doi:10.1016/j.anbehav.2011.05.029
Davis, T., Crippen, T., Hofstetter, R. & Tomberlin, J. 2013. Microbial volatile emissions as insect semiochemicals, doi:10.1007/s10886-013-0306-z