Northern muriqui (Brachyteles hypoxanthus)

Also known as: northern woolly spider monkey
Spanish: Muriqui
GenusBrachyteles (1)
SizeMale head-body length: 55 – 78 cm (2)
Female head-body length: 50 – 65 cm (2)
Male tail length: 74 – 80 cm (2)
Female tail length: 65 – 74 cm (2)
Male weight: 12 – 15 kg (2)
Female weight: 9.5 – 11 kg (2)

Classified as Critically Endangered (CR B1ab(i,ii,iii,iv,v) +2ab (i,ii,iii,iv,v)) on the IUCN Red List 2003 (1), and listed on Appendix I of CITES (3).

The muriqui, or woolly spider monkey, is the largest New World primate, and in the late 1980s was recognised as two distinct species: the northern muriqui (Brachyteles hypoxanthus) and the southern muriqui (B. arachnoides) (4). The main difference between the northern and the southern muriqui is the presence of a small thumb in the northern variety (2). Otherwise, however, they are almost identical in appearance. Muriquis have long limbs and a long prehensile tail, allowing them to be particularly agile amongst the trees (5). The thick coat is greyish-brown in colour and males may have a more yellow tinge (5) (6).

Endemic to the Atlantic Forest Region of eastern Brazil, the northern form is found in the states of Minas Gerais, Espirito Santo, Rio de Janeiro, and, at least formerly, Bahia. The southern muriqui is found in the states of São Paulo and Parana (7).

Inhabits subtropical, tropical and moist lowland rainforest in Brazil’s Atlantic Forest Region (4), and is found at altitudes from sea level to 1,000 metres (6).

Muriquis are arboreal and active during the day (7). They live in multimale-multifemale groups (5) that may number between 8 and 80 individuals (2). Groups are not territorial; there is little aggression between members and related males often cooperate with each other (5). Social grooming between group members appears to be rare but embracing is thought to help maintain bonds (2) (5). Females tend to give birth to a single offspring in the dry season that runs between May and September (7). Males remain with their natal group, while female offspring disperse to join other groups once they have reached adolescence at 5 – 7 years old (7).

Young leaves and fruit constitute a large component of the muriqui diet; individuals often feed by hanging from the branches of a tree with their prehensile tail (2) (5). Seeds, bark, flowers and some insects are also eaten during the more abundant rainy season (7).

The northern muriqui was once widespread in the Atlantic Forest region, but today there are only a handful of sub-populations in nine or more protected areas, including Rio Doce State Park, Caparaó National Park, Serra do Brigadeiro State Park, and Augusto Ruschi Biological Reserve (1) (2) (4). The total known population is very low, at only 300 to 400 individuals (2), and the largest sub-population recorded has only 157 individuals, which severely limits the group’s breeding potential (1). This species is threatened by habitat destruction as it occurs in one of the most populated and industrious region of Brazil (4). Vast tracts of forest have been lost, and the remaining healthy forests are fragmented and at risk of being destroyed in the future. In addition, these large primates were an important food source for people in the region and have been widely hunted (4).

The muriqui has been a flagship species for the conservation of Brazil’s fragile Atlantic Forest region (8). However, information on these critically endangered primates is still lacking and data on population distribution and status is urgently required. Programme Muriqui has been undertaking research on populations within the Serra dos Organos National Park; the possibility of reintroductions is being investigated and an ongoing education programme has been established (9).

For more information on the muriqui and other mammals see:

Authenticated (24/04/2006) by Matt Richardson, independent primatologist and writer.

  1. IUCN Red List (December, 2003)
  2. Richardson, M. (2006) Pers. comm.
  3. CITES (December, 2003)
  4. Mittermeier, R.A., Myers, N. and Mittermeier, C. (1999) Hotspots: Earth’s biologically richest and most endangered terrestrial ecoregions. Cemex, Mexico City.
  5. Primate Info Net (December, 2003)
  6. Macdonald, D. (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.
  7. Animal Info (December, 2003)
  8. Conservation Breeding Specialist Group (December, 2003)
  9. Programme Muriqui (in Portuguese) (December, 2003)