These New World monkeys from South America are best known for their impressive howls which can be heard 2 km away. Despite the name "brown howlers", these monkeys vary in color, with some individuals appearing largely reddish-orange or black. They have long and prehensile tails which don't have fur on the underside near the tip. These interesting features allow Brown howlers to hang from branches using their tails as an anchor while feeding. Males in this species are larger than the females.
Brown howlers live in the Atlantic forest in South America. The region spreads through the Brazilian states of Bahia and Espirito Santo through the Rio Grande do SUl and the Misiones in the Argentine. They inhabit lowland, submontane, montane forest and mixed broadleaf forest.
Brown howlers are social animals that live in groups of 2 to 11 individuals. They are arboreal and spend most of their time in the upper canopy. They are diurnal spending most of their day resting, usually in the mid-day when it's very hot. The rest of the day howlers spend moving around, feeding, allogrooming and rubbing for group communication. Brown howlers are known for their howls/roars. The most frequent reason for the howling is for mate defense. Howling occurs most when there are both female and male howlers present. Males are the dominant and begin all cases of howling. Females participate in howling much less than males. Howling can also occur in groups during the dry season, probably due to food scarcity. Brown howlers also use their sounds to show ownership over certain food or territory. When threatened by the areal predator Brown howlers use three ways to protects themselves. First is to alarm the group and immediately become silent. Next they descend in the understory of the trees, and finally, they will all disperse in an organized manner. When Brown howlers are threatened by terrestrial animals they will remain in the tree canopy and remain silent for 5-15 minutes.
Little information is known about the mating system in Brown howlers. They breed year-round. Females give birth to a single infant after the gestation period that lasts around 6 months. Infants start moving around independently from their mother at 5 months of age and become weaned at 1 year of age. Females in this species become reproductively mature at around 3.6 years of age and males attain maturity when they are 5 years old.
Main threats to Brown howlers include the loss of their habitat and fragmentation, hunting. Another important threat to these animals is disease epidemics. Brown howlers are highly susceptible to the yellow fever virus and have a high mortality rate when infected. When mass amounts of Brown howlers are found dead it is a good inclination that there may be a yellow fever outbreak occurring.
The IUCN Red List and other sources don’t provide the number of the Brown howler total population size. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.
Due to their frugivorous diet, Brown howlers play a very important role in dispersing the seeds. This way these animals benefit the local ecosystem.