The dusky titi lives in dense, wet forested areas in South America. It is a quick monkey but is not always on the move and will stick to its home zone or within a short distance if there is no need to do much more. It is commonly found in a crouched position gazing out into the forest during the daytime or else looking for food. It feeds by foraging for fruits and plant matter or else hunting insects and spiders, and occasionally eats small birds and the eggs of birds.

Males and females remain together in pairs or bigger family groups and they communicate with each other through a variety of chirps, squeaks and other vocalizations. Sometimes they sing to each other. They have round heads, little ears and thick fur so that if they are sitting still they can appear to be fur balls on the tree limbs except for their tails hanging down. Some have lighter red to orange fur on their undersides.