How did the relationship between Fossey and Digit begin?

When Digit was still quite young, several of the gorillas in his group left to go to another group. There was a clash between groups, which left Digit seriously wounded. The thing that seemed to bother Digit the most was that he was left without playmates. Digit began to spend time with Fossey. Digit seemed to have taken on some human characteristics and obviously saw Fossey as a pal.