Southern muriqui (Brachyteles arachnoides)

Also known as: southern woolly spider monkey, woolly spider monkey
French: Atèle Arachnoïde, Eroïde, Singe-araignée Laineux
Spanish: Mono Carvoeiro, Mono Grande, Muriki
GenusBrachyteles (1)
SizeMale head-body length: 55 – 78 cm (2)
Female head-body length: 46 – 63 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 Endangered (EN) on the IUCN Red List (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 southern (Brachyteles arachnoides) and northern muriqui (B. hypoxanthus) respectively (4). One of the differences between these species is the presence of a small thumb in the northern variety (2), which is lacking in the southern species. 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; males may have a more yellow tinge (6) and they have particularly large testicles, which may be related to sperm competition (5).

Found in south-eastern Brazil, in the states of Rio de Janeiro and Sao Paulo (2).

Inhabit primary and secondary Atlantic coastal forest that comprises Brazil’s Atlantic Forest Region (4), and 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 that may number between 5 and 25 individuals (5). Groups are not territorial; there is little aggression between members and related males often cooperate with each other (5). There is no evidence of social grooming between group members but embracing is thought to help maintain bonds (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 but once they have reached adolescence at 5 – 7 years old, female offspring will disperse to join other groups (7).

Young leaves and fruits constitute a large component of the muriqui diet; individuals often feed by hanging from the branches of a tree with their prehensile tail (5). Fruits and seeds are also eaten during the more abundant rainy season (7).

The muriqui was once widespread in the Atlantic Forest Region, but today the southern species is thought to number just under 1,000 individuals (4). This region of Brazil has been devastated by habitat destruction as it is the most populated and industrialised region of the country (4). Vast tracts of forest have been lost. 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). Conservation efforts are still imperative and “Programme Muriqui” will continue to undertake 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).

Authenticated (13/02/2006) by Matt Richardson, independent primatologist and writer.

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