George Schaller: I find a group.  I recognize all of them individually, in the area where I worked, about 200 or so.  Their faces, particularly the nose area, is very distinctive.  So I’d check out who’s there.  And the wonderful thing, in Rwanda, is you go out with the guides there now. The guides now know all the gorillas and can check and see what’s happening.  But so I’d go, “How far have they gone?  What is their main food that day?  Are they meeting somebody?  And what happens when they meet?”  Usually, there’s aggression when two gorillas’ groups meet.  Sometimes they mix and you don’t know — you want to know who is aggressive.  Do you know their history?  And so forth.