Animal Diversity Web

Ge­o­graphic Range

Woolly spi­der mon­keys, or muriquis, are found scat­tered through­out the south­east of Brazil, rang­ing from Bahia in the north to Sao Palo in the south. They make their home in the lonely rem­nants of their coastal At­lantic for­est habi­tat. (Mas­si­cot, 2001; Strier, 1992; Moyni­han, 1976)

• Biogeographic Regions
• neotropical
  • native

Habi­tat

The pre­ferred habi­tat of Brachyte­les arach­noides is the ma­ture ever­green and de­cid­u­ous low­lands of the costal At­lantic forests in Brazil. B. arach­noides is ar­bo­real and spends most of its time in the canopy. How­ever, muriquis are quite re­silient de­spite their en­dan­gered sta­tus. Troops will uti­lized both pri­mary and sec­ondary growth in pris­tine as well as dis­turbed areas. Al­though they are highly ar­bo­real, they will cross open ground when there are gaps within the canopy. (Strier, 1992; Mas­si­cot, 2001)

• Habitat Regions
• tropical

• Terrestrial Biomes
• rainforest

Phys­i­cal De­scrip­tion

The muriqui is the largest South Amer­i­can pri­mate, with males weigh­ing about 15 kg, and fe­males about 12 kg. The head and body length has been re­ported as 780 mm, and the tail is about the same length. When they are seen hang­ing by their arms, they mea­sure about 1.5 me­ters tall.

Muriquis have very long pre­hen­sile tails, which aid them in their ar­bo­real ex­is­tence. Be­cause of the swing­ing na­ture of their move­ments, their thumbs have be­come re­duced in size and are con­sid­ered ves­ti­gial. Both sexes have promi­nent pot bel­lies. The coat is gray­ish-golden ex­cept for the face, which looks as if its been cov­ered with soot, and the area sur­round­ing the gen­i­tals, which tends to be much red­der in color than the rest of the body. The gen­i­tals in this species are fairly con­spic­u­ous. The male has a large os penis, and the fe­male cli­toris is very long and tipped with red­dish hair.

(Napier and Napier, 1985; Strier, 1992; Mas­si­cot, 2001; Moni­han, 1976)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger

• Average mass

  12-15 kg

  lb

• Average mass

  11170 g

  393.66 oz

  AnAge

• Average length

  780 mm

  30.71 in

Re­pro­duc­tion

There does not ap­pear to be much com­pe­ti­tion be­tween males for mat­ing opor­tu­ni­ties. Often, males will wait in line for their chance to mate with a re­cep­tive fe­male. Both males and fe­males have mul­ti­ple mat­ing part­ners. Fe­males are able to exert more choice in mates than in many pri­mate species, be­cause of the min­i­mal sex­ual di­mor­phism in this species. Fe­males also exert some mate choice when they de­cide what group of males to join when they dis­perse from their natal group at ado­les­cence.

(Strier, 1992; Mas­si­cot, 2001)

• Mating System
• polygynandrous (promiscuous)

The age of sex­ual ma­tu­rity has been recorded as ap­prox­i­mately 11 years for a fe­male and 5.5 years for a male. Their courtship is ex­tremely pas­sive. There is very lit­tle agres­sion be­tween males, and they seem ex­tremely tol­er­ant of each other. The males some­times wait in line for their op­por­tu­nity to mate with a re­cep­tive fe­male.

When it comes to choos­ing a mate, fe­males are very much in charge, which is un­usual for pri­mates. Since both sexes are ap­prox­i­mately the same size, the males can­not bully the fe­males into giv­ing in. After mat­ing, ges­ta­tion lasts 7-8.5 months, when the fe­male gives birth to a sin­gle young in the dry sea­son (May though Sep­tem­ber). A baby muriqui is born 7-8 ½ months after it is con­ceived.

(Strier, 1992; Mas­si­cot, 2001)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• viviparous

• Breeding season

  Most births occur during the dry season, from May to September.

• Average number of offspring

  1

• Average number of offspring

  1

  AnAge

• Range gestation period

  7 to 8.5 months

• Range weaning age

  18 to 30 months

• Range age at sexual or reproductive maturity (female)

  6 to 11 years

• Range age at sexual or reproductive maturity (male)

  6 to 11 years

Parental care is prinic­pally the busi­ness of fe­males. Young are quite help­less when born, al­though able to cling to their mother's fur. For the first few weeks of life, the in­fant clings to its mother's side, under her arm and near the nip­ple. By 6 months of age, the baby rides "jockey style" on its mother's back as she goes off to for­age. After 6 months, an in­fant muriqui will begin to as­sert some in­de­pen­dence, ex­plor­ing the sur­round­ing world but never leav­ing its Mom’s side by more than a few feet.

After the tod­dler has reached a year, it will wan­der off for longer pe­ri­ods and in­ter­act with other tod­dlers. At times its mother will leave it while she goes to for­age. The mother will call her baby back when she is done. By this time the tod­dler is start­ing to eat some on its own. This idyl­lic ex­is­tence be­tween mother and baby ends abruptly when wean­ing oc­curs and the mother chases off her child. Wean­ing time varies, from 18 to 30 months of age, av­er­ag­ing 24 months. Often wean­ing in­volves peck­ing and nip­ping by the mother, with loud cries from the con­fused baby, who may go on scream­ing for 15 min­utes or more. The baby will often find com­fort with other con­fused wean­lings who are going through a sim­i­lar ex­pe­ri­ence.

In ado­les­cence (4-6 years) the young­sters will start to move their own sep­a­rate ways. The young males will at­tempt to make stronger bonds with the other males in the group and the young fe­males will begin to dis­tance them­selves as they pre­pare to leave and join an­other troop.

The male role in parental care in this species has not been re­ported.

(Strier, 1992; Mas­si­cot, 2001)

• Parental Investment
• altricial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • protecting
    • female
• post-independence association with parents
• extended period of juvenile learning

Lifes­pan/Longevity

The av­er­age life ex­pectancy of this species is un­known.

(Strier, 1992; Moyni­han,1976)

Be­hav­ior

Muriquis are nearly com­pletely ar­bo­real. They are ac­tive dur­ing the day.

Muriquis are well adapted to life in trees. Their long arms and ves­ti­gial thumbs make it easy for them to hurl them­selves from one branch to the next. When mov­ing from one for­ag­ing area to an­other, a troop will often travel in line, with one mon­key fol­low­ing an­other through the for­est. This al­lows them to avoid se­ri­ous falls be­cause all ex­cept the first muriqui in line is uti­liz­ing well used and tested branches.

Un­like many other pri­mate species, muriqui fe­males exert a great deal of con­trol in so­cial in­ter­ac­tions. In this species, the males and the fe­males are very nearly the same size. Be­cause of this, the males can­not bully the fe­males into sub­mis­sion.

This is one of a few groups of pri­mates where the males stay with their natal group and the fe­males are the ones to leave to join other troops. Troops main­tain a home range in which they for­age, and are no­madic within that home range, going from one food source to an­other.

Mem­bers of a troop are not very ag­gres­sive to­wards each other, which is said to be un­usual for pri­mates. This be­hav­ior prob­a­bly de­rived from the fact that they are so ar­bo­real. If they do fight, there is a great risk of falling out of the tree.

(Strier, 1992; Mas­si­cot, 2001)

• Key Behaviors
• motile
• nomadic
• social
• dominance hierarchies

Com­mu­ni­ca­tion and Per­cep­tion

• Perception Channels
• tactile
• chemical

Food Habits

Muriquis eat mostly fruit, leaves, flow­ers, and a few species of seeds. Fruit seems to be the choic­est item in their diet. Due to their large size and the large num­ber of in­di­vid­u­als in their so­cial groups, they can eas­ily lo­cate a fruit source and chase off other mon­keys that are al­ready ex­ploit­ing it. Once they find a good for­ag­ing area, muriquis will often camp out, wait­ing for days eat­ing leaves until the fruit is ripened.

Foods eaten in­clude: ripened fruit, leaves, flow­ers, seeds of Sa­pu­cainha, seeds of Amexia-bicha, seeds of Inga, seeds of Bicuiba and seeds of Ja­toba.

(Strier, 1992)

• Primary Diet
• herbivore
  • folivore
  • frugivore

• Plant Foods
• leaves
• seeds, grains, and nuts
• fruit
• flowers

Pre­da­tion

The major pre­da­tion threat to muriquis is from in­dige­nous hu­mans. These mon­keys have been hunted for food be­cause their meat is con­sid­ered a del­i­cacy in the areas where they are found. Al­though some troops of muriqui may be an im­por­tant food source for large preda­tors such as jaguars, ocelots, and harpy ea­gles, there are not many con­firmed cases of this type of pre­da­tion. One troop that was ob­served for a decade lost only five mem­bers in that time, and only two of those five dis­ap­peared mys­te­ri­ously.

(Strier, 1992)

• Known Predators

  • humans (Homo sapiens)
  • jaguars (Panthera onca)
  • Ocelots (Leopardus pardalis)
  • harpy eagles (Harpia harpyja)

Ecosys­tem Roles

Muriquis serve an im­por­tant ecosys­tem role in dis­pers­ing seeds through­out the for­est. One study showed that seeds col­lected from muriqui feces and then planted al­most al­ways ger­mi­nated. In some cases, the seeds ger­mi­nated faster than those that never passed through a muriqui di­ges­tive sys­tem.

B. arach­noides may also have some im­pact on preda­tor pop­u­la­tions, but be­cause of its own low pop­u­la­tion size, it is un­likely that any preda­tors rely very heav­ily on this species as a food source.

(Strier, 1992)

• Ecosystem Impact
• disperses seeds

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Since the early 1990’s, muriquis have been tar­geted by eco-tourists. The pop­u­lar­ity of South Amer­ica's largest pri­mate, par­tic­u­larly on the Fazenda Montes Claros Plan­ta­tion, has been in­creas­ing through­out the years. Tourists bring in dol­lars for both the local peo­ple and the gov­ern­ment.

This species has also been hunted by in­dige­nous peo­ple. Its meat is con­sid­ered a del­i­cacy.

(Strier, 1992)

• Positive Impacts
• food
• ecotourism

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Muriquis are not abun­dant enough to have neg­a­tive eco­nomic im­pacts, though they are pri­mates and are suc­cept­able to many of the same dis­eases hu­mans are. Being an en­dan­gered species in a de­graded sit­u­a­tion, dis­ease is more likely to spread.

(Strier, 1992)

Con­ser­va­tion Sta­tus

Muriqui pop­u­la­tions are es­ti­mated to have been in the hun­dreds of thou­sands prior to the Eu­ro­pean col­o­niza­tion of South Amer­ica. Pop­u­la­tions of these pri­mates are thought to have been spread through­out the con­ti­nent. Today, there are fewer than 500 in­di­vid­u­als known to per­sist in the scat­tered frag­mented forests of coastal Brazil. The species is listed on the IUCN Red List of threat­ened species and has been con­sid­ered crit­i­cally en­dan­gered since the year 2000. CITES lists these an­i­mals as Ap­pen­dix I, the most en­dan­gered sta­tus they have. Muriquis are also listed as en­dan­ged by the United States Fish and Wildlife Ser­vice. Ef­forts are being made to study this species in the at­tempt to de­velop a man­age­ment plan. With­out a man­age­ment plan, ex­tinc­tion is im­mi­nent.

(Strier, 1992; Mas­si­cot, 2001)

• IUCN Red List

  Endangered
  More information

• IUCN Red List

  Endangered
  More information

• US Federal List

  Endangered

• CITES

  Appendix I

Con­trib­u­tors

Anni Bladh (au­thor), Hum­boldt State Uni­ver­sity, Brian Ar­bo­gast (ed­i­tor), Hum­boldt State Uni­ver­sity.

Ref­er­ences

Mas­si­cot, P. Au­gust, 19, 2001. "An­i­mal Info - Muriqui" (On-line). Ac­cessed Oc­to­ber 25, 2001 at http://​www.​animalinfo.​org/​species/​primate/​bracarac.​htm.

Moyni­han, M. 1976. The New World Pri­mates. Prince­ton, New Jer­sey: Prince­ton Uni­ver­sity Press.

Napier, J., P. Napier. 1985. The nat­ural his­tory of the pri­mates. Cam­bridge, Mass­a­chu­setts: The MIT Press.

Strier, K. 1992. Faces in the For­est. New York, New York: Ox­ford Uni­ver­sity Press.