The San Martin titi monkey, Callicebus oenanthe
Oldfield Thomas described in 1924 a new species of Peruvian titi monkey, Callicebus oenanthe. His description was based on a specimen collected near Moyobamba, northern Peru. He described the species as being “pale grey, much less rufous than other Peruvian forms. General colour above grizzled buffy greyish, not strongly rufous, paler than in any species except C. pallescens. Bases of the hairs blackish brown, then dull buffy, the ends tipped or ringed with dark brown. Hinder back and thighs warmer buffy, this colour extending down the hinder side of the legs. Under surface dull ochraceous rufous throughout, on body and inner side of limbs. A supraorbital band whitish. Crown pale buffy brownish. Hairs on ears grizzled greyish, like back. Hands and forearms pale brownish, nearly matching the crown; fingers dull whitish. Hind feet dull brownish ochraceous, the digits lighter. Tail grizzled brownish above and below, the end very slightly lighter”.
This species, also known as the Rio Mayo titi monkey or Andean titi monkey, has a restricted distribution range and is endemic to Peru. Until 2007, very little was known about the species, but this has changed since the start of a conservation programme initiated by Proyecto Mono Tocón.