Urban Gorillas

Amy Vedder has seen it all a thousand times before. Gazing into a jungle clearing, she watches as a lumbering group of gorillas approaches. Brushing through rain-forest shrubs, knuckle-walking past a strangler fig, they push their way into the open. While the adults forage, the juveniles climb the trunk of a fallen tree and play king of the mountain. From somewhere above, hornbills and blue monkeys sound an alarm.

Familiar as the scene is, Vedder--a conservationist who began studying gorillas in Rwanda in 1978 with Dian Fossey--can't help noticing that it's also a bit surreal. For one thing, she's standing behind...