Board Thread:Speculation House/@comment-112.198.159.92-20130927053820/@comment-16502426-20131001014718

Teravor wrote: Maybe Faunus just smell subtly different from humans?

If they have enhanced animal senses, it's almost a guarantee they will have an enhanced sense of smell, so if they smell different from humans most Faunus would pick up on it quickly. My guess is either that, or the same reason that aura lets you sense someone without knowing they are there.