I was motivated to write this book because I realize that humans are visual predators, and that our perceptions of the world are based on this one modality. We are cognizant of how animals hide from predators that use vision to hunt them. Yet, I wanted to know how animals hide from predators that use olfaction to hunt them. My curiosity about a simple question grew into a theory that animals can and do hide from olfactory predators, and that there is a constant struggle between olfactory predators and the animals that hide from them. I called this the

olfactory concealment theory

. I realized not only that animals face risks from both their depositional odor trails and odor plumes, but also that animals can take measures to reduce the risk that each poses to them.