No mingling among 'damn dirty apes'
Here's a fascinating story from the filming of the 1968 science fiction film Planet of the Apes, from Neatorama.com.
In that movie, there are three ape species: chimpanzees, gorillas and orang-utans. When the actors for the ape characters put on their makeup and costumes, they segregated themselves by species: During the filming of Planet of the Apes in 1967, Charlton Heston noted "an instinctive segregation on the set. Not only would the apes eat together, but the chimpanzees ate with the chimpanzees, the gorillas ate with the gorillas, the orang-utans ate with the orang-utans, and the humans would eat off by themselves. It was quite spooky."
James Franciscus noticed the same thing filming Beneath the Planet of the Apes in 1969. "During lunch I looked up and realised, 'My God, here is the universe,' because at one table were all the orang-utans eating, at another table were the apes, and at another table were the humans."