It belongs to the Mona monkey group - Cercopithecus mona/cambelli/lowei - having a shot of the entire body, or knowing where the photo was taken, would help pinpoint exactly which species it is.
The pic was taken yesterday in "Bioparc" Valencia (Spain) in the "Equatorial Africa" zone, i think like you ungulate, it is a species of the (Cercopithecus mona) group
This is definite a Lowe's Monkey (Cercopithecus lowei). Before now subspecies of Cambell's Monkey (C. campbelli lowei) or Mona Monkey (C. mona lowei) – today synonyms.
