Gorillas are highly social, living in groups averaging about nine individuals. A hierarchy relating to sex, age, and dominance organizes gorilla groups. Each group is led by a silverback male, whose maturity is identifiable by a patch of silver fur on his back. Other members include blackback males, females, and infant or juvenile gorillas. Change from within or outside may sometimes dissolve groups entirely. Behavioral researchers name both groups and individuals. Learning individual personalities improves accuracy when monitoring and recording behavior within and between groups. Habituated groups are trained to accept human presence, including tourists. Conservation programs strictly regulate contact, balancing tourism revenue with gorilla well-being. Research groups are approached only for scientific purposes, while wild gorilla groups are free from human contact. Research and habituated groups are monitored closely, often accompanied by a researcher or tracker from morning until night.