Black Howler Monkeys are a relatively large species of monkey that are named for the noises they make, though they sound gruff and loud, more like roarers than howlers. Males are mostly black and females and juveniles are a yellowish blonde colour. They are social animals, found in small to large groups that average around 8 individuals. They call to ensure that other groups of howlers know where they are and avoid them. Females may share care of the young. They are not very active, sleeping for up to 70% of their days.