What monkey is the only truly nocturnal primate in the Americas?

The only truly nocturnal primate in the Americas is the owl monkey, also called the night monkey or douroucouli.

Owl monkeys belong to the genus Aotus, whose name means “earless” because their small ears are mostly hidden by fur. They live in forests from Panama through much of South America, including rainforests, cloud forests, and recovering secondary forests. Their enormous eyes help them see in dim light, while their monochromatic vision is well suited to nighttime activity.

Most owl monkeys live in small family groups made up of a breeding pair and their young. They eat fruit, leaves, insects, and other small animals, and often become more active when moonlight is available. A common mix-up is calling any nocturnal primate an owl monkey; the name specifically refers to Aotus. Some populations of Azara’s owl monkey are cathemeral, meaning they may be active during both day and night, but Aotus remains the only nocturnal primate genus native to the New World.