No photos, I saw three different groups of them in area, but failed to be quick enough to get any pictures of the fleeing monkeys.
I did get a decent, albeit quick, look at one. And I was also with somebody who recognized their alarm calls and knows Bioko's primates well.
The Red-eared Guenon, Red-eared Monkey, or Russet-eared Guenon (Cercopithecus erythrotis) is a species of primate in the Cercopithecidae family. It is found in Cameroon, Equatorial Guinea, and Nigeria. Its natural habitat is subtropical or tropical moist lowland forests. It is threatened by habitat loss.
