Shortly after dawn two mountain gorillas swing gracefully over the shoulder-high stone wall that borders Volcanoes National Park in northwestern Rwanda. Landing lightly on cropped grass, the silverbacks stroll downhill through cultivated fields—knuckle-walking at first, then upright on two legs. The adult males belly up to eucalyptus trees and score the bark with their incisors. Then, joined by females and juveniles from their group, which researchers call Titus, they advance on a spindly stand of bamboo.
Later that morning Veronica Vecellio, the gorilla program manager for the Dian Fossey Gorilla Fund International, settles onto a log inside the park, high on a thickly forested, mist-shrouded slope of the Virunga Mountains, and turns her attention to a silverback known as Urwibutso. A frequent wall hopper, Urwibutso is carefully folding thistle leaves before placing them in his mouth. When he turns toward Vecellio, an ebullient woman who studies gorilla group dynamics, she snaps a picture, then zooms in on a wound on his nose.
“He fought with another silverback from Titus this morning,” she whispers intently. (Silverbacks get their name from the white hairs that blanket males, saddlelike, when they reach maturity.)