Having nothing to do with BF, an article in weekend's NYT reveals that researchers who have long known that many organisms release "danger" or "alarm" or is it "fear" pheromones, but did not know for a fact if mammals actually did this or how they did it, until recently.
http://www.nytimes.com/2008/08/26/science/26obdang.html
Googling "Grueneberg ganglia" brings up a number of other similar articles.
Its relevancy to BF's natural history is to me interesting. I've read many level-headed assessments of BF's talents and abilities basically stating that there's no reason to think that they have supernatural or superhuman abilities and I, and I suspect most who see BF as an intelligent hominin existing in a natural world, would generally agree. So, how do they know how to avoid us so well?
In this article, however, there is an example of what would be an almost superhuman ability (smelling of emotional states) that we've long suspected operates in h. sapiens in a sort-of barely perceptible sub-conscious fashion. If the BF are, as they are usually described, at least partially nocturnal or crepuscular, one could suspect that their olfactory array is more accute than most modern humans' ability which has been primarily adapted for daytime activity where accute color-vision is most advantageous. Subsisting in a nocturnal world of complex chemical clues instead of visual ones, BF may have a more conscious awareness of another animal's intent, emotional state and otherwise suspicion-generating behaviors which could be integral to a strategy that puts them outside of our normal ability to detect them intentionally in a predictable way.