Geographical variation of chemical signals and odor discrimination in a wild mammal

Background Signal divergence and sensory preferences may cause reproductive isolation and eventually speciation between animal populations. These patterns are particularly well known in systems with acoustic or visual signals. However, relatively few studies have quantified the patterns, causes and consequences of geographical variation of chemical signals, especially in mammalian populations. Results We examined Hipposideros armiger (the great Himalayan leaf-nosed bat) and collected secretions from the forehead glands of males. We selected nine colonies across a large geographic scale and investigated both the potential causes and patterns of variation in chemical signals from that gland across geography. We also examined whether or not males could tell the difference between gland scents from a foreign colony and their colony using habituation–discrimination tests. To determine whether females preferred the scent of foreign versus local males, we performed two-choice tests. Overall, we found significant colony-level differences in the concentrations of compounds and in general compound categories. We show that symbiotic microbes inhabiting odor glands may explain the observed chemical variation between colonies. Moreover, behavioral studies indicated that males were able to discriminate between gland scents from their own colony and those from a distant colony. Finally, females were more attracted to scents of local males from their own colony compared to scents from foreign colonies. Conclusions Microbe-mediated chemical divergence may potentially drive scent discrimination and mating preference in H. armiger . This study expands our limited knowledge of geographical variation of mammalian chemical signals and highlights the importance of bacterial communities in shaping chemical divergence.