Chlorocebus monkeys were treated as a single species for a very long time, so many are actual hybrids and a lot of zoos do not know what their green guenons actually are. I am almost sure the two (1.1) siblings I saw in Volta Redonda were pure vervets solely because of their appearance, although I could be wrong, and they are actually hybrids between green monkeys and grivets, both formerly in Rio, where they came from.
I was told by one of the head keepers a few years ago either one or both are castrated, so no prospects of breeding anytime soon. I am skeptical the male off-display in Rio would help save this species in Brazil by any means, because they three are likely related.
