berengi - mountain, grauri - eastern lowlands, gorilla - western lowlands male-female relationship basis of cohesion of group - half of their day is spent feeding males don't participate in raising children - eat leaves, stems, bamboo, bark - females more arboreal (smaller) - build nests, use them for one night only - chest beating is adult intimidation - adult male may take baby if mother dies - walk on knuckles - lots of time sitting upright - extensive overlap in ranges - get water from plants - females leave group often when just presexual