Today’s mountain gorilla trek typically involves two to four hours of walking through thick brush over steep, rugged terrain at elevations ranging from 7,000 to 9,000 feet —and can include exposure to stinging nettles and re ants. As overexposure to humans is harmful to mountain gorillas, contact is limited to one hour—and there is the possibility that they may become agitated and retreat back into the bush in less than our allotted time. Any travelers showing signs of obvious illness may be refused entrance by park authorities.