The red-handed howler (Alouatta belzebul) is a vulnerable species of howler monkey, a type of New World monkey. It is endemic to Brazil, found in the southeastern Amazon and disjunctly in the Atlantic Forest between Rio Grande do Norte and Sergipe. Taxonomy Considerable taxonomic confusion has surrounded this species. Until 2001, most authorities included the Amazon black howler as a subspecies (or simply a taxonomically insignificant variation) of the red-handed howler, though its distinction had already been pointed out much earlier. The red-handed howler remained variable in ecology, colour and pattern of the fur, shape of the cranium, and shape of the hyoid bone (of great importance in the voice of the howler monkeys; a likely isolating mechanism between the species), but a geographical pattern was not clear, resulting in it being treated as a monotypic species. In 2006, a major review of the Brazilian members of the genus Alouatta was able to match some of the variations to geography (though further study was recommended), resulting in the recognition of the Spix's red-handed howler and Maranhão red-handed howler as species separate from the red-handed howler. Even with these as separate species, the colour and pattern of the fur of the red-handed howler remains variable. Most adults are black with reddish-brown hands, feet and distal part of their tails, but some are entirely black (resembling the Amazon black howler), reddish (resembling the red howlers) or somewhere in between. Distribution and life history It lives in the biomes of Amazonian and Atlantic forests which consist of dense forest separated by drier areas. These animals can live up to 20 years, and do not mature until later in their lives. They have a long gestation period, and generally reproduce more slowly than similar-sized mammals of other species. From the births that have been recorded, red-handed howlers have quick, quiet births during the day when they are normally active. Once born, if the mother is experienced, she will carry her young ventrally for three weeks and then switch to dorsally once the offspring is slightly more developed. Behavior and diet When not foraging, red-handed howlers rest in the canopy of mature trees from the forest floor. They also live in social groups of seven to 12 members, with one or two mature males, females, juveniles, and infants. Threats Threats to this species are numerous. First, they are a large-bodied mammal hunted for food. Females