
Certain animals have evolved specific sensory abilities much wider than our own...
A well trained human—a perfumer, for example—can identify at best a few thousand smells, while dogs can apparently distinguish any number of individual humans by scent alone. Bloodhounds perform this feat with no more odor than passes through the soles of a person’s soles.
Gould, James L. and Gould, Carol Grant (1994) The Animal Mind. Scientific American Library, New York.