George Schaller: Having worked in Alaska with various species, you know that nothing is wholly ferocious.  That if you do it right, if you go near them gently, if you make them realize that you mean no harm, they’re not going to be concerned.  And the same with gorillas.  Day after day, you follow them slowly, a group.  You sit near them.  Don’t stare at them.  Look away.  If they come near you, just sit quietly.  And after a few meetings, they realize you’re no problem and that you come there day after day.  You can see now that, in the tourist groups, the big problem is that the gorillas want to come and touch you.  Well, that’s not a good idea, either, because people are full of diseases which they can transmit to the gorillas.  But all these animals — lions, tigers, and so forth — they become very used to people.  You’ve got to be a little careful because you never know if a tiger has had a bad experience with people and jumps at you.  But I’ve met tigers — from me to you — and they’re both surprised and back off without any aggression on either side.