[3][4] The black howler is distributed in areas of South America such as Paraguay, southern Brazil, eastern Bolivia, northern Argentina, and Uruguay.

[6] The IUCN Red List has classed the black howler as Near Threatened as a result of a recent population reduction due to a variety of human-caused factors.

[7][2] They have prehensile tails with a bare patch of skin on the underside, making them versatile climbers and allowing them to comfortably stay around in the canopy of trees.

[5] Although the diet of the black howler is largely folivorous, it does not prevents the digestion of fruits, figs, mosses, bark, seeds, and flowers.

[10] Group composition has a large varied range in population density and social organization when focusing on black howler monkeys.

Due to minimal human influence along the Paraná River in Brazil, for example, the woods remain well conserved, which results in larger densities of black howlers.

[13] In a 2009 study by Lucas M. Aguiar, Gabriela Ludwig, and Fernando C. Passos, in the Upper Paraná River of southern Brazil, the black and gold howler groups size was around 6 to 18 individuals.

A study by Martin M. Kawoleski and Paul A. Garber[14] in 2010 examined the promiscuity of black howler females along the Paraná River in Argentina using a scan sampling technique.

[14] The black howler is distributed in areas of Central and South America such as Paraguay, southern Brazil, eastern Bolivia, northern Argentina, and occasionally, Uruguay.

[5] Anthropogenic disturbances are the top common reasons for the slow decrease of the black howler population; jeopardizing and degrading their ecosystems for residential and commercial development as well as agriculture.

[2] The interaction between people and black and gold howlers was also a topic of the research conducted by Marco Alesci et al. in 2020 in the city of Pilar, Paraguay.

[5] As a result, domestic dogs attacking black howlers in urban areas, electrocution on uninsulated power lines, and people killing the monkeys were all recognized as threats.