The Rio Mayo titi (Callicebus oenanthe) is a species of titi, a type of New World monkey, endemic to Peru.The Rio Mayo titi, though previously believed to have a small range of origin in the Alto Mayo valley, research has proven that the range extends southward and reaches the Huayamba River, as well as Bajo Mayo. It has been classified as vulnerable but due to major habitat loss and restricted living space, it is better classified as Critically Endangered. In October 2012, it was included in The World's 25 Most Endangered Primates list. An increase in deforestation is leading to the decrease in available living space for the Titi monkey, forcing it to live in sympatry with another species of Callicebus. Yet in some areas, such drastic deforestation has resulted in extremely high populatio