The black titi monkey (Cheracebus lugens), is a species of titi, a type of New World monkey, from South America. It is found in Brazil, Colombia, and Venezuela. It was described in 1811 as Calicebus lugens. It is sometimes called the widow monkey. Distribution This species has the largest range of the Cheracebus species, ranging from the Branco River and Rio Negro north to the Orinoco and Caqueta river basins. The species has been observed on the left bank of the Guayabero River,, where it was collected in 1959 by Jorge Hernández Camacho, both in La Macarena National Park, and recently it was observed by the Colombian biologist Rocío Palanco north of the Guayabero above La Cordillera de los Picachos National Park. The species is found in the Vichada selva between the Vichada and Guaviare Rivers and the northernmost Colombian population extends north of the Vichada River, reaching the middle Tomo River, where it probably extends to the upper Tomo, although this needs to be confirmed. The black titi is not found on the lower Tomo or lower Tuparro River nor on the north bank of the lower Vichada River, contrary to the distribution map of Hershkovitz. This error is due to the collection of a specimen by the English ornithologist Cherrie in about 1904 from Maipures, which may have been a captive animal obtained in the village, since extensive and concerted efforts have failed to identify it for the entire area mentioned above; nor is it known by locals for this area. The nearest titi monkeys from Maipures in Colombia are found on the middle Tuparro River and south of the lower Vichada River. Description The pelage is generally blackish mixed with dark brownish and some reddish brown hairs on the back and the flanks. Hands are white or yellowish. Natural history Social groups are made up of a monogamous pair and one or two of its young. A count of ten groups in Vichada yielded an average of 3.5 per group. Occasionally groups of five are seen and unpaired individuals ("floaters") can also be detected from time to time. Second year youngsters usually leave the group, although they may make it into the third year before leaving. These young animals sometimes appear, moving peripherally to the group and then disappear again to move alone. Measured home ranges have varied from about 15–25 ha. Appropriate habitat contains 4–5 groups/km2