The brown howler (Alouatta guariba), also known as brown howler monkey, is a species of howler monkey, a type of New World monkey that lives in forests in southeastern Brazil and far northeastern Argentina (Misiones). It lives in groups of two to 11 individuals. Despite the name "brown howler", it is notably variable in colour, with some individuals appearing largely reddish-orange or black. The two subspecies are: Northern brown howler (A. g. guariba), listed as critically endangered Southern brown howler (A. g. clamitans) Geographic distribution The brown howler lives in the Atlantic forest in South America. The region spreads through the Brazilian states of Bahia and Espírito Santo through Rio Grande do Sul, and Misiones in Argentina. Diet Brown howler monkeys are folivores and frugivorous. The diet of the brown howler monkey consists primarily of leaves and trees. Of the food sources it seems that the genera Ficus, Zanthoxylum, and Eugenia are the most significant types consumed. Brown howler monkeys that live in higher latitudes tend to eat a lower percentage of leaves in their diet. Mature leaves are less nutritious and are more fibrous, than the preferred young leaves. A typical brown howler diet will also include mature fruit, wild figs, petioles, buds, flowers, seeds, moss, stems, and twigs The Atlantic forest, where brown howlers tend to live, has an increasing forest fragmentation. Forest fragmentation means that there would be a decrease in potential food supplies. The brown howler’s feeding ecology, however, does not seem to be affected by the loss in habitat. Behavior Howling Brown howler monkeys are part of the group of monkeys known for their howls/roars. Howlers are able to create such loud and specific sounds by specific body shape and structures. The larynx is enlarged and they have an enlarged open chest that creates a resonating chamber to increase the sound produced. The howlers also have specialized vocal chords to produce the specific sound. The most frequent reason for the howling is for mate defense. Howling occurs most when there are both female and male howlers present. The males are the dominant group as they begin all cases of howling. Females participate in howling much less than males. Howling can also occur in groups during the dry season. It is believed that this is due to food scarcity. The brown howlers use their sounds to show ownership over certain food or territory. Anti-predator behavior The