Rachel Hogan sat on the floor chomping on a banana leaf while Nkan Daniel, a baby gorilla, watched. She waited for signs that he might mimic her behavior. Sure enough, seconds later the ape grabbed some leaves of his own and began to nosh.

It was 2001, and Hogan was in Cameroon on a three-month stint volunteering with Ape Action Africa, a nonprofit primate rescue organization. Meeting Nkan Daniel (Nkan means gorilla in a local dialect) changed her life, she says. Hogan stayed on in Cameroon and in 2010 became the director of Ape Action Africa.

The baby gorilla, just two weeks old, had been found by the Cameroonian government in the home of a woman seeking to sell him as