Not my experience. The big Silverback that stood right next to me didn't smell at all--or perhaps I was just so exhilarated that I never noticed. I don't recall smelling anything, perhaps because we were in the big, open outdoors and not a smelly, enclosed zoo...?

The second day, the gorilla juveniles and mothers farted quite a bit--the videos are hilarious. But we didn't smell anything--fortunately.