What is "sooty mangabey"

The sooty mangabey (Cercocebus atys) is an Old World monkey found in forests from Senegal in a margin along the coast down to Ghana. While overall rated as Near Threatened, the eastern race lunulatus, also known as the white-crowned, white-naped or white-collared mangabey (leading to confusion with the collared mangabey), is considered Endangered by the IUCN. The White-collared mangabey was declared its own species by the IUCN in 2016, but it retains the endangered conservation status.