10% or so of Bigfoot sightings are connected with a strong smell (John Green). On some occasions, however, the smell has been reported to be unbearable and overpowering, akin to being wrapped in "dirty diapers". There are persistent suggestions that the smell is "turned on" on demand.
An illuminating observation comes from mountain gorillas as recorded by Dian Fossey. She describes males as producing an "overpowering, gagging fear odor", either when fleeing from enemies such as poachers with dogs, or else in confrontational encounters with other males. The smell is intense at a distance of 80 feet, coincidentally accompanied by discharge of diarrheic stool, as human gorilla observers are known to have emulated when charged by a male gorilla. George Schaller describes the odor as a mixture of "sweat, manure, charred wood, and burning rubber". The origin of the odor appears to be in the axillary organ, a mass of apocrine sweat glands many layers deep in the armpit.