If those chemical cues reflect a trait that’s useful to know about – say, gender, strength, or fertility – the host animal might evolve scent organs to nourish and harbour those specific microbes. Eventually, the inadvertent cues turn into full-blown signals. So, by creating airborne messages, microbes could affect the behaviour of animals far outside their original hosts. And if that’s the case, it shouldn’t be surprising to learn that they can affect animal behaviour in more local ways.
