Animal Diversity Web

Ge­o­graphic Range

Pro­boscis mon­keys are con­fined to the is­land of Bor­neo; they pre­fer coastal re­gions to in­land areas. (Med­way, 1977)

• Biogeographic Regions
• oriental

• Other Geographic Terms
• island endemic

Habi­tat

Pro­boscis mon­keys in­habit man­grove for­est along rivers and es­tu­ar­ies, swamp-land, and low­land rain­for­est. (Kawabe and Mano, 1972; Kern, 1964)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• rainforest

• Wetlands
• swamp

Phys­i­cal De­scrip­tion

Pro­boscis mon­keys are sex­u­ally di­mor­phic. The males have a length of 70 cm and weight of be­tween 16 and 22 kg. Fe­males mea­sure 60 cm and weigh be­tween 7 and 12 kg.

Males have a large pro­trud­ing nose, which en­hances vo­cal­iza­tions through res­o­nance. The nose of the fe­male is smaller.

The fur of the adult pro­boscis mon­key is pink and brown with red around the head and shoul­ders. The arms, legs, and tail are gray. Males have a black scro­tum and a red penis. In­fants are born with a blue col­ored face that at 2.5 months dark­ens to gray. By 8.5 months of age, the face has be­come cream col­ored as in the adults.

There is web­bing be­tween the dig­its to allow for swim­ming. (Kern, 1964; Wolfheim, 1983; Yea­ger, 1992)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently
• male more colorful
• ornamentation

• Range mass

  7 to 22 kg

  15.42 to 48.46 lb

• Range length

  60 to 70 cm

  23.62 to 27.56 in

Re­pro­duc­tion

The basic so­cial unit in pro­boscis mon­keys is a sin­gle adult male with from 2 to 7 adult fe­males. The males mate with fe­males in their so­cial group. (Ben­nett and Se­bas­t­ian, 1988)

• Mating System
• polygynous

Pro­boscis mon­keys give birth to a sin­gle off­spring after a ges­ta­tion of 166 days. Births usu­ally occur at night. The fe­male sits on a tree branch dur­ing the birth. After the in­fant is born, the mother con­sumes the pla­centa.

The breed­ing sea­son is from Feb­ru­ary until No­vem­ber. Cop­u­la­tion is ini­ti­ated by the fe­male through purs­ing of the lips, shak­ing of the head from side to side, and pre­sen­ta­tion of the hindquar­ters to the male. Fe­males will con­tinue to ini­ti­ate cop­u­la­tions even after they have con­ceived.

In­fants stay close to their moth­ers for about one year. Males reach ma­tu­rity at about 7 years. (Hayssen, et al., 1993; Wolfheim, 1983; Yea­ger, 1990)

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

• Breeding interval

  Females can produce offspring each year.

• Breeding season

  Proboscis monkeys breed from February until November

• Average number of offspring

  1

• Average number of offspring

  1.25

  AnAge

• Average gestation period

  166 days

• Average gestation period

  166 days

  AnAge

• Range weaning age

  7 (high) months

• Average time to independence

  12 months

• Average age at sexual or reproductive maturity (female)
  Sex: female

  1460 days

  AnAge

• Average age at sexual or reproductive maturity (male)

  7 years

As is the case for most pri­mates, new­born pro­boscis mon­keys are fairly help­less. They must be car­ried by their mother until they are able to walk on their own. Moth­ers pro­vide their off­spring with milk, nurs­ing them until they are about 7 months old. They also keep their in­fants clean through groom­ing. In­fants stay close to their moth­ers for about one year. (Yea­ger, 1990)

The role of the male in parental care is less di­rect. Al­though males do not care for in­fants the way fe­males do, it can be ar­gued that they pro­vide im­por­tant pro­tec­tion for the young by ex­clud­ing po­ten­tially in­fan­ti­ci­dal rival males from the group.

• Parental Investment
• no parental involvement
• altricial
• pre-fertilization
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • male
    • female
• extended period of juvenile learning

Lifes­pan/Longevity

Only the lifes­pan in cap­tiv­ity is known; in most an­i­mals it is at least 23 years. (Wolfheim, 1983)

• Range lifespan
  Status: captivity

  23 (high) years

• Average lifespan
  Sex: female
  Status: captivity

  20.0 years

  Max Planck Institute for Demographic Research

• Average lifespan
  Sex: male
  Status: captivity

  21.0 years

  Max Planck Institute for Demographic Research

• Average lifespan
  Status: captivity

  13.6 years

  Max Planck Institute for Demographic Research

Be­hav­ior

Pro­boscis mon­keys are di­ur­nal, pre­fer­ring to be ac­tive from late af­ter­noon until dark. They are pri­mar­ily ar­bo­real al­though they are never more than 600 m from a river. When mov­ing through the trees, they are quadrupedal. These mon­keys are good swim­mers and will leap out of the trees into the water. They are ca­pa­ble of swim­ming 20 m un­der­wa­ter. They may cross rivers by swim­ming if alone or they may cross by jump­ing from a tree on one bank to one on the other side at nar­row points if in a group.

There are two types of groups within the pro­boscis mon­key so­ci­ety: uni­male and all-male. These groups num­ber 3 to 32 in­di­vid­u­als. Sev­eral of the groups will come to­gether in the evening to sleep. These multi­group gath­er­ings are called bands. Pro­boscis mon­keys sleep 0 to 15 m from the river's edge. They do not sleep in the same place on con­sec­u­tive nights. The same groups as­so­ci­ate reg­u­larly and there is lit­tle ag­gres­sion be­tween males in uni­male groups.

Adult males co­or­di­nate the group's move­ments and lead the group. Fe­males do not leave their natal group. Males dis­perse at 18 months of age. (Yea­ger, 1990; Yea­ger, 1991; Yea­ger, 1992)

• Key Behaviors
• arboreal
• diurnal
• motile
• sedentary
• social
• dominance hierarchies

Home Range

The home range size for these mon­keys has not been re­ported.

Com­mu­ni­ca­tion and Per­cep­tion

The pro­boscis mon­key has sev­eral sounds for com­mu­ni­ca­tion. Growls are made by males and are used to calm the group mem­bers. Honks are made by males as a threat or to warn of preda­tors. Shrieks are made by fe­males and both sexes of ju­ve­niles to show ag­gi­ta­tion or ex­cite­ment, and screams are given dur­ing ag­o­nis­tic en­coun­ters. So­cial groom­ing is per­formed, usu­ally be­tween fe­males. The groom­ing usu­ally last 1 to 5 min­utes and is per­formed by both in­di­vid­u­als. (Kawabe and Mano, 1972; Kern, 1964; Yea­ger, 1992)

• Communication Channels
• visual
• tactile
• acoustic

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Pro­boscis mon­keys are fo­li­vores and fru­gi­vores. They pre­fer fruits, seeds, young leaves, and shoots of man­grove. They may also eat some in­ver­te­brates such as cater­pil­lars and lar­vae. They are more fru­giv­o­rous from Jan­u­ary through May and more fo­liv­o­rous from June through De­cem­ber. (Yea­ger, 1990; Kern, 1964; Wolfheim, 1983)

• Primary Diet
• herbivore
  • folivore
  • frugivore

• Animal Foods
• insects

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

Pre­da­tion

The anti-preda­tor be­hav­ior of these mon­keys has not been de­scribed in de­tail. Leop­ards are known to prey upon them, as are croc­o­diles. Adult males some­times vo­cal­ize, ap­par­ently to scare off po­ten­tial preda­tors.

• Known Predators

  • leopards (Panthera pardus)
  • crocodiles (Crocodylus)

Ecosys­tem Roles

The role of N. lar­va­tus in the ecosys­tem is not well un­der­stood. As her­bi­vores, they prob­a­bly have some af­fect on plant pop­u­la­tions. To the ex­tent that preda­tors rely on these an­i­mals for food, pro­boscis mon­key pop­u­la­tions may af­fect preda­tors.

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Pro­boscis mon­keys are con­sid­ered a del­i­cacy al­though they are not heav­ily hunted. They are also de­sired for zoos be­cause of their unique ap­pear­ance. (Med­way, 1977)

• Positive Impacts
• food
• research and education

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse af­fects of N. lar­va­tus on hu­mans.

Con­ser­va­tion Sta­tus

Pro­boscis mon­keys are pro­tected from hunt­ing and cap­ture in Bor­neo but the de­struc­tion of the man­grove for­est has lim­ited the pop­u­la­tion. They are listed as Ap­pen­dix I by the Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species (CITES). (Ap­pen­dix I is de­fined as a species threat­ened with ex­tinc­tion with trade al­lowed only in ex­treme cir­cum­stances.) They are listed as en­dan­gered by the In­ter­na­tional Trade in En­dan­gered Species of Wild Fauna and Flora (IUCN). ('En­dan­gered' is de­fined as an es­ti­mated 50% re­duc­tion in the pop­u­la­tion in the next 10 years.) ("Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species of Wild Flora and Fauna", 2003; "In­ter­na­tional Union for Con­ser­va­tion of Na­ture and Nat­ural Re­sources", 1997)

• IUCN Red List

  Endangered
  More information

• IUCN Red List

  Endangered
  More information

• CITES

  Appendix I

Con­trib­u­tors

Nancy Shef­ferly (ed­i­tor), An­i­mal Di­ver­sity Web.

Amy Woltan­ski (au­thor), Michi­gan State Uni­ver­sity, Bar­bara Lun­dri­gan (ed­i­tor), Michi­gan State Uni­ver­sity.

Ref­er­ences

CITES Sec­re­tariat. 2003. "Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species of Wild Flora and Fauna" (On-line ). Ac­cessed 02/02/03 at http://​www.​cites.​org.

IUCN. 1997. "In­ter­na­tional Union for Con­ser­va­tion of Na­ture and Nat­ural Re­sources" (On-line). Ac­cessed Feb­ru­ary 02, 2003 at http://​www.​redlist.​org.

Ben­nett, N., A. Se­bas­t­ian. 1988. So­cial or­ga­ni­za­tion and ecol­ogy of pro­boscis mon­keys (Nasalis lar­va­tus) in mixed coastal for­est in Sarawak. In­ter­na­tional Jour­nal of Pri­ma­tol­ogy, 9: 233-255.

Hayssen, V., A. Van Tien­hoven, A. Van Tien­hoven. 1993. As­dell's pat­terns of mam­malian re­pro­duc­tion: a com­pendium of species-spe­cific data. Ithaca, NY: Com­stock/Cor­nell Uni­ver­sity Press.

Kawabe, M., T. Mano. 1972. Ecol­ogy and Be­hav­ior of the Wild Pro­boscis Mon­key in Sabah, Malaysia. Pri­mates, 13: 213-228.

Kern, J. 1964. Ob­ser­va­tions on the Habits of the Pro­boscis Mon­key made in the Brunei Bay Area, Bor­neo. Zo­o­log­ica, 49: 183-192.

Med­way, L. 1977. Mam­mals of Bor­neo.

Wolfheim, J. 1983. Pri­mates of the World. Seat­tle and Lon­don: Uni­ver­sity of Wash­ing­ton Press.

Yea­ger, C. 1990. Pro­boscis Mon­key So­cial Or­ga­ni­za­tion: Group Struc­ture. Amer­i­can Jour­nal of Pri­ma­tol­ogy, 20: 95-106.

Yea­ger, C. 1991. Pro­boscis Mon­key So­cial Or­ga­ni­za­tion: In­ter­group Pat­terns of As­so­ci­a­tion. Amer­i­can Jour­nal of Pri­ma­tol­ogy, 23: 73-86.

Yea­ger, C. 1992. Pro­boscis Mon­key So­cial Or­ga­ni­za­tion: Na­ture and Pos­si­ble Func­tions of In­ter­group Pat­terns of As­so­ci­a­tion. Amer­i­can Jour­nal of Pri­ma­tol­ogy, 26: 133-137.