English               -           Brown howler 

 Portuguese       -           Bugio marrom 

 Latin                  -           Alouatta guariba

Brown howlers, like other howler monkeys, are best known for their impressive howls, which can be heard more than 1.6 km away. They are found  on the eastern coast of south America, inhabiting highly seasonal subtropical and temperate forests in the Brazilian states of Bahia and Espirito Santo through to Rio Grande do Sul and the Misiones in Argentina.

Brown howlers have relatively large, stocky frames with fur that varies in colour from brown to dark red or black. The hair is lighter coloured and less coarse on the belly, and the face and ears are dark and hairless. Brown howler males weighing around 2.5 kg more than females on average. Many males have a dark-red venter, with yellowish red dorsal pelage and darker arms, legs, and tails. Adult females are covered in dark brown or reddish brown hair.  Males tend to be more red in the south and less red in the north, whereas females range from lighter brown in the south to darker brown in the north. They have prehensile-tails, with a naked patch of skin on the ventral surface of the tip of the tail..

Brown howlers are one of the largest leaf-eating primates in the South American forests but will also eat flowers, and fruit; however, their diet varies according to the season and location. Leaves make up close to a third of their diet and when available they prefer young leaves. The flowers and leaves of various types of lianas (i.e., any type of woody vine) are commonly ingested by brown howlers in south-eastern Brazil and make up approximately 27% of their diet. When available, they preferentially select fleshy fruits. Brown howlers spend more time foraging during autumn and winter as their food source is harder to find.

Brown howlers form multi-male, multi-female groups; single-male, multi-female groups; and single-male, single-female groups. The most common group composition is single-male, multi-female with up to 10 individuals. Brown howlers are year-round breeders. The female has an average of one offspring which she carries for around 6 months before giving birth and will feed the infant for around 12 months until the infant is able to feed itself. Females reach adulthood at approximately 3.6 years and males at approximately 5 years. 

Although this species as a whole is classified as “Near Threatened” overall, one of two subspecies, the northern brown howling monkey (Alouatta guariba guariba), is classified as “Critically Endangered”. The species’ populations are extremely fragmented and reduced due to habitat destruction and development in the coastal forests of south-eastern Brazil and north-eastern Argentina. Habitat destruction and development in South America does not seem to be slowing down and it is feared that this primate and many others will suffer even more in due course.

The 2 photos of the Brown howler were taken at Marechal Floriano Espirito Santo.

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