RESUMO
The San Martin titi monkey (Plecturocebus oenanthe) is endemic to a small area of northern Peru and is considered Critically Endangered on the IUCN due to massive habitat loss. Between 1994 and 2005 small scale reforestation efforts in the 23.5 ha area of Pucunucho have led to the recuperation of habitat from an area of pasture and crop lands. The first record of P. oenanthe re-establishment in the area is from 2010, although re-establishment probably began earlier. We carried out short population surveys using triangulation to monitor densities of P. oenanthe in Pucunucho in 2011, 2012 and 2016. We estimate the current population of P. oenanthe in this area at 27 individuals, giving population densities of 35 groups/km2 and 124 individuals/km2. The successful regeneration of habitat and natural re-population of the area by this Critically Endangered species provides evidence of successful reforestation based conservation activities for this and potentially other primate species. Although now protected as a Private Conservation Area, Pucunucho remains threatened.