The angle of the lower jaw and the hyoid bone are both greatly enlarged, making it possible for the animal to produce such a remarkable voice. The lower jaw and neck are quite large, which, with other characteristics such as the low facial angle, gives the animals a forbidding expression. The strongly prehensile tail is naked on the underside for the terminal third. The tail is so powerful that the animal sometimes jumps from a limb but does not release its tail hold, and so checks its flight. Also, when a monkey falls, if its tail can catch a limb, it keeps the animal from hitting the ground.
Howlers are arboreal, mainly diurnal forest dwellers.
Four groups moved an average of 340-445 meters per day and slept in the tallest available trees at night. Territoriality was not evident, with ranges overlapping by 32-63 percent. Young of both sexes dispersed from their natal groups. In another investigation of A. palliata, Neville et al. He also observed that group size averaged 5.4 and that there appeared to be 1 dominant male in the group.