i was at the zoo because i was having some sort of awful day, and i think i was recovering from some illness or injury, and my girlfriend at the time was trying to cheer me up; it's a nice zoo with well-treated and well-housed animals (they even take various exotic rescues), so it's a happy place. i don't remember what i was depressed about, only that i was beginning to feel better and cheer up, and we walked by the gorilla pavilion. i was talking to her and in the course of conversation, mimed a gorilla chest-pound, and one of the males saw me and was highly offended. he stood up and postured at me, and dared me to come across the wall-and-moat thing they had for the outdoor section of the gorilla pavilion. we walked on, to keep him from getting more upset, although it was kind of funny, since we were safe. he followed, grunting and gesturing for me to come back and fight. it is unsettling to be looked in the eye with that much intelligence, and malevolence.
as we walked down the sidewalk to the primate house, i could see him following us. the last thing i saw till the wall put me out of sight was his angry head glaring at me from over the wall, where he had climbed up on a rock to watch us go. he must have contacted the baboons, because as soon as you walk in the primate house, there is a large glass wall with the baboon house on the other side. the largest male caught one sight of me, puffed up, gave a mighty leap to a small ledge by the glass, and started pounding the glass to get to me, screaming for my blood. as we walked by, he followed, pissed as hell and banging on the glass whenever he could get up to it (their house had kind of a moat to it as well). the other baboons didn't take notice, but the alpha was clearly upset with me being there.
i asked an animal tender what might have happened; the gorilla was obvious, i'd been stupid and made a gesture that he took offense to, and rightly so. he had little ones and females to defend, he didn't know what i was about. interestingly, though the handler said of course they get that all the time from guys playing as they go by the gorillas and he (the gorilla) never seemed to react or took it seriously. and, he said, baboons are just crazy, so it was coincidental.
most of the smaller monkeys hid from us, even though they had been playing with people. however, on that same visit, a tree sloth hugged me.