Population Ecology of guenons with particular reference to six species common in Nigeria, the Mona Monkey (Cercopithecus mona); the Sclater Monkey (Cercopithecus scateri); the Putty-nosed Monkey (Cercopithecus nictitans ludio); the Nigerian White-throated Monkey (Cercopithecus erythrogaster pococki); the Red-eared Monkey (Cercopithecus erythrotis) and the Preuss's Monkey (Allochrocebus preussi preussi) was carried out in Afi Mountain Wildlife Sanctuary (AMWS) Boki local Government Area, Cross River State, using invasive and non invasive methods.