I cant remember if it was at Toronto Zoo or Chester Zoo in England but a few years ago I went into the Chimpazee house and almost all the chimps were on a big boulder in the encloser that was covered in crap. They were crappping in there hands and eating it. It was SICK!
Another time I was at Chester Zoo and I went into the monkey house. One of the male monkeys (can't remember the species, it was black and white) was playing with its self. That was sick too.
Primates are pretty dirty!
The coolest thing at Chester zoo is the bat cave where there are all these species of bats flying around (including flying foxes) and you wall through the cave and the fly around you its cool and the cave is HUGE and it also has a pond in it.