Animal Diversity Web

Ge­o­graphic Range

Pil­io­colobus ru­fomi­tra­tus is lim­ited to a small range of for­est along the lower Tana River in East­ern Kenya. The Tana River runs from the east­ern Kenyan High­lands into the In­dian Ocean. Its range in­cludes the Tana River Na­tional Pri­mate Re­serve out­side the city of Wenje. (Med­ley, 1993)

• Biogeographic Regions
• ethiopian
  • native

Habi­tat

Pil­io­colobus ru­fomi­tra­tus, or Tana River red colobus mon­key, in­hab­its patches of ever­green river­ine for­est that un­dergo pe­ri­odic flood­ing from the Tana River. These iso­lated clumps of for­est are under the in­flu­ence of ground­wa­ter fluc­tu­a­tion, river course changes and human dis­tur­bance which re­sult in a very frag­mented and un­sta­ble habi­tat only fur­ther en­dan­gered by human en­croach­ment (Decker & Kin­naird, 1992). This river­ine for­est habi­tat ex­pe­ri­ences an av­er­age an­nual pre­cip­i­ta­tion of 470 mm and tem­per­a­tures rang­ing be­tween 21.4°C and 33°C (Med­ley, 1993). In con­trast to the habi­tat of the other red colobus species across East and Cen­tral Africa, this habi­tat is more arid and has a lower den­sity and di­ver­sity of tree flora (Marsh, 1981a). In gen­eral, the canopy of the Tana River for­est is more open than the habi­tat at other red colobus sites (Oates, 1994). (Decker and Kin­naird, 1992; Marsh, 1981a; Med­ley, 1993; Oates, 1994)

• Habitat Regions
• tropical
• terrestrial

• Terrestrial Biomes
• forest

• Other Habitat Features
• riparian

Phys­i­cal De­scrip­tion

The pelage of P. ru­fomi­tra­tus is ruddy black on the dor­sal side and red with brown on the chest, inner por­tions of the limbs and head (Nowak, 1999). Head and body length ranges be­tween 450 and 670 mm. The tail is gray and fairly long, mea­sur­ing 520 mm to 800 mm. This species ex­hibits sev­eral traits that may be adap­ta­tions to an ar­bo­real lifestyle, in­clud­ing long, slen­der dig­its and the loss of the thumb tu­ber­cle, com­mon in all colobine mon­keys. The hind limbs are well de­vel­oped for leap­ing across the canopy and may be par­tic­u­larly long. Though no de­fin­i­tive study on mass has been com­pleted, weights may range be­tween 5.1 and 11.3 kg like other red colobus species. A closer es­ti­mate may put their mean weight at 5.8 kg, near that of the more iso­lated West African species of the Pro­colobus kirki (Oates, 1994). (Nowak, 1999; Oates, 1994)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike

• Range mass

  5.1 to 11.3 kg

  11.23 to 24.89 lb

• Average mass

  5.8 kg

  12.78 lb

• Range length

  450 to 670 mm

  17.72 to 26.38 in

Re­pro­duc­tion

The mat­ing sys­tem in this species is gen­er­ally polyg­y­nous, es­pe­cially when only one male is pre­sent. Often the dom­i­nance hi­er­ar­chy de­ter­mines who is al­lowed mat­ing ac­cess, and in the pe­cu­liar case of Tana River red colobus mon­keys, there is fre­quently a sin­gle male or a small group of males that pro­hibits ex­tra-group males from mat­ing or even en­ter­ing the group. (New­ton and Dun­bar, 1994; Marsh, 1979) (Marsh, 1979; New­ton and Dun­bar, 1994)

• Mating System
• polygynous

Very lit­tle is known about the re­pro­duc­tive cycle of these pri­mates in the wild. They are dif­fi­cult to find and track due to their con­stant mi­gra­tion.

Un­like most colobine mon­keys, red colobus fe­males ex­hibit pe­ri­odic swelling of per­ineal tis­sue through­out the year (Nowak, 1999; Oates, 1994). These swellings often co­in­cide with an in­crease in cop­u­la­tion, so it is as­sumed that they mark the time of ovu­la­tion, though false swellings (those not cor­re­lated with ovu­la­tion) have been seen in other pri­mates and may serve as a pos­si­ble de­fense against in­fan­ti­cide. There ap­pears to be no dis­tinct birthing sea­son though stud­ies to de­ter­mine rel­a­tive birth spac­ing are lack­ing (Marsh, 1979).

Typ­i­cally the dom­i­nant male mates with the fe­males in his so­cial group. Cop­u­la­tions are ini­ti­ated by fe­males who per­form courtship dis­plays and pre­sent them­selves to the male. Be­fore mat­ing, there are fre­quent cop­u­la­tion calls serv­ing to draw males into the area. Dur­ing mat­ing, the fe­males may give other calls that con­tinue to at­tract males (Struh­saker, 1975; Oates, 1994). Ha­rass­ment dur­ing cop­u­la­tion by non-mat­ing males was fre­quent in the rain-for­est species (Struh­saker, 1975); how­ever, there are sig­nif­i­cantly fewer males in Tana River red colobus groups (often only one or two males) so the im­pact of this ha­rass­ment is prob­a­bly neg­li­gi­ble (Marsh, 1979). There has not been a de­fin­i­tive study on the im­pact of the smaller group size, lower male num­bers and re­duced habi­tat on the re­pro­duc­tion of Tana River red colobus mon­keys, and this could be an in­ter­est­ing re­search op­por­tu­nity. (Marsh, 1979; Nowak, 1999; Oates, 1994; Struh­saker, 1975)

In gen­eral, red colobus mon­keys breed through­out the year. Es­ti­mated ges­ta­tion is 4.5 to 5.5 months, with an es­ti­mated in­ter­birth in­ter­val of 26 months. The exact pe­riod of nurs­ing has not been re­ported for these an­i­mals, how­ever, we may infer that wean­ing prob­a­bly oc­curs be­fore the in­fant is 20 months old, as con­tin­ued nurs­ing might in­hibit con­cep­tion of an­other off­spring. (Nowak, 1999; Nowak, 1999)

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

• Breeding interval

  Females are capable of producing an offspring roughly every 2 years.

• Breeding season

  Breeding is not seasonal.

• Average number of offspring

  1

• Range gestation period

  4.5 to 5.5 months

At birth the in­fant’s pelage is silky black on the back with a gray un­der­belly, help­ing to dis­tin­guish in­fants from older mon­keys. Pink flesh is ex­posed on the muz­zles, ears, palms and soles for 3 to 4 weeks (Oates, 1994). The fur re­mains gray until 2 to 2.5 months of age, when the head be­gins to turn red­dish on the crown.

After birth, in­fants cling to their moth­ers' un­der­belly and re­main de­pen­dent on her. In gen­eral in­fants stay very close to the mother until 2 to 3.5 months of age, trav­el­ing only about 1 meter from her dur­ing this this time. By 3.5 to 5.5 months they typ­i­cally en­gage in play with other mon­keys (Marsh, 1979). NAround 18 months of age, young fe­males of the group em­i­grate to an­other group and may con­tinue to move from group to group through­out their life­time, as fe­male mem­ber­ship is very fluid. Some males may leave the group dur­ing ado­les­cence but it is dif­fi­cult to be­come ac­cepted into an­other group in this pa­tri­lin­eal so­cial struc­ture (Struh­saker, 1975).

Often only the mother grooms and car­ries the in­fant and in­fant han­dling, al­lo­moth­er­ing or aunt­ing (han­dling/care of the in­fants by non-moth­ers) are not com­mon be­hav­iors. This is most likely be­cause the pa­tri­lin­eal dis­tri­b­u­tion pat­tern in which fe­males em­i­grate from their natal group re­sults in low lev­els of re­lat­ed­ness be­tween fe­males in the same group. Un­re­lated fe­males are much less likely to allow their in­fants to be han­dled by other fe­males. This is un­like the pat­tern seen in ba­boons, in which the fe­males are more closely re­lated to one an­other (New­ton and Dun­bar, 1994).

Males con­tribute very lit­tle to the off­spring other than prox­i­mal pro­tec­tion from pre­da­tion and re­source al­lo­ca­tion. There doesn’t seem to be any re­la­tion­ship be­tween the dom­i­nance hi­er­ar­chy of males and the in­fants pre­sent in the group. How­ever, there are re­ports of higher death rates of in­fants fol­low­ing a change in the male mem­ber­ship of the group. It is pro­posed that this is a re­sult of in­fan­ti­cide by the in­com­ing male to clear out un­re­lated males and bring fe­males into es­trus sooner (Marsh, 1979). Though in­fan­ti­cide has been ob­served in the Tana River red colobus mon­keys and other pri­mate species, the causal re­la­tion­ship of in­fan­ti­cide and its re­la­tion­ship to re­pro­duc­tion and ge­neal­ogy have yet to be fully de­ter­mined. (Marsh, 1979; New­ton and Dun­bar, 1994; Oates, 1994; Struh­saker, 1975)

• Parental Investment
• altricial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female
  • protecting
    • female
• extended period of juvenile learning
• inherits maternal/paternal territory

Lifes­pan/Longevity

Lifes­pan is dif­fi­cult to es­ti­mate be­cause very few stud­ies of these pri­mates have ever lasted more than one year, let alone for an en­tire life­time of one of these pri­mates. Fre­quently only in­fant mor­tal­ity is as­sessed. In one long term study the av­er­age in­fant/small ju­ve­nile mor­tal­ity was, on av­er­age 0.064 deaths per in­fant per month. In­fant mor­tal­ity within the first year was as high as 55% for the pop­u­la­tion sam­pled. This same study found a higher mor­tal­ity for males in the group than fe­males, pos­si­bly from vi­o­lent con­flicts be­tween group males and ex­tra-group males for mat­ing ac­cess and re­sources. (Marsh, 1979)

Other colobine mon­keys rarely live longer than 30 years in cap­tiv­ity. It is likely that P. ru­fomi­tra­tus is like other mem­bers of the fam­ily Colobi­nae in this re­spect. Lifes­pans are likely to be even shorter in the wild. (Nowak, 1999)

Be­hav­ior

Like most pri­mates, P. ru­fomi­tra­tus is a noisy, so­cial an­i­mal that lives in het­ero­sex­ual groups. Typ­i­cally, red colobus mon­keys live in groups with be­tween 30 to 50 mem­bers, in­clud­ing mul­ti­ple males and fe­males (Oates, 1994). How­ever, in the re­duced and frag­mented habi­tat of the Tana River, the num­ber of in­di­vid­u­als in each group is much smaller, rang­ing from 12 to 30 (Marsh, 1979). In stark con­trast to the rain for­est species, Tana River red colobus often have only one or two males in the group. These de­mo­graph­ics may give males greater ac­cess to mates and also in­di­rectly re­duc­ing the stress on the lim­ited re­sources of their frag­mented habi­tat. The causes and im­pli­ca­tions of the small and frag­mented Tana River habi­tat on be­hav­ior are still being in­ves­ti­gated, but the dif­fer­ences be­tween P. ru­fomi­tra­tus at Tana (small group size, low # of males) and the rain for­est species are quite stark and fas­ci­nat­ing.

The daily time bud­get of red colobus mon­keys at Tana River dif­fers sig­nif­i­cantly from the rain-for­est species. They spend on av­er­age, the ma­jor­ity of their day rest­ing (47.8%) or feed­ing (30.0%), and the rest of the time mov­ing (7.2%), groom­ing (4.1%), or at play (3.4%). Feed­ing usu­ally oc­curs dur­ing the early morn­ing or late af­ter­noon. This is typ­i­cally fol­lowed by in­ac­tiv­ity dur­ing the mid­dle of the day and late evening. Though P.​rufomi­tra­tus is mostly ac­tive dur­ing the day, ob­ser­va­tions of other red colobus species have in­di­cated that some call­ing and sex­ual ac­tiv­ity occur at night.

Like many pri­mates, P. ru­fomi­tra­tus often en­gages in so­cial be­hav­iors such as play, ag­gres­sion, and groom­ing (Struh­saker, 1975). Play can en­tail any­thing from chas­ing and wrestling to bounc­ing off of branches. Ag­o­nis­tic be­hav­iors may be minor,such as a gri­mace, touch, or sup­plan­ta­tion. These are often as­so­ci­ated with a va­ri­ety of body and limb pos­tur­ing. Major ag­o­nis­tic be­hav­iors often in­clude stares and gapes usu­ally with lung­ing, slap­ping or branch shak­ing, and in ex­treme cases, phys­i­cal vi­o­lence. These ag­o­nis­tic be­hav­iors often occur be­tween males in re­la­tion­ship to dom­i­nance and group sta­tus. In gen­eral, males groom each other more often than fe­males, though the full ef­fects of this be­hav­ior have not been ex­am­ined for the small num­ber of males in the Tana River red colobus species (Struh­saker and Le­land, 1987). This pat­tern of male groom­ing is thought to arise be­cause of the pa­tri­lin­eal or­ga­ni­za­tion. (Marsh, 1979; Oates, 1994; Struh­saker and Le­land, 1987; Struh­saker, 1975)

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

Home Range

Pil­io­colobus ru­fomi­tra­tus ex­hibits smaller home ranges than other red colobus mon­keys (Marsh, 1979). The av­er­age an­nual home range of P. ru­fomi­tra­tus is near 9 ha com­pared to that of 34 to 114 ha for their coun­ter­parts. The av­er­age day range is 603 me­ters.

Com­mu­ni­ca­tion and Per­cep­tion

Like many pri­mates, P. ru­fomi­tra­tus often en­gages in so­cial be­hav­iors such as play, ag­gres­sion, and groom­ing (Struh­saker, 1975). Play can en­tail any­thing from chas­ing and wrestling to bounc­ing off of branches. Ag­o­nis­tic be­hav­iors may be minor, such as a gri­mace, touch, or sup­plan­ta­tion. These are often as­so­ci­ated with a va­ri­ety of body and limb pos­tur­ing. Major ag­o­nis­tic be­hav­iors often in­clude stares and gapes usu­ally with lung­ing, slap­ping or branch shak­ing, and in ex­treme cases, phys­i­cal vi­o­lence. These ag­o­nis­tic be­hav­iors often occur be­tween males in re­la­tion­ship to dom­i­nance and group sta­tus. In gen­eral, males groom each other more often than fe­males, though the full ef­fects of this be­hav­ior have not been ex­am­ined for the small num­ber of males in the Tana River red colobus species (Struh­saker and Le­land, 1987). This pat­tern of male groom­ing is thought to arise be­cause of the pa­tri­lin­eal or­ga­ni­za­tion. (Nowak, 1999; Struh­saker and Le­land, 1987)

• Communication Channels
• visual
• tactile
• acoustic
• chemical

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

Pil­io­colobus ru­fomi­tra­tus is pri­mar­ily a fo­li­vore, and this is re­lated to a com­ple­ment of mor­pho­log­i­cal adap­ta­tions to this kind of diet. All colobine mon­keys are dis­tin­guished from other old world pri­mates in that they posses a ru­mi­nant-like stom­ach rather than a sim­ple stom­ach. This stom­ach con­sists of a large sac­cu­lated cham­ber with a forestom­ach al­ka­line/acid sys­tem de­signed to di­gest plant mat­ter using bac­te­r­ial fer­men­ta­tion (Chivers, 1994). These pri­mates also have high cusped, ridged mo­lars de­signed to shear and fold leaves and seeds. This helps break down cell walls and ex­tract the nu­tri­ents con­tained within (Teaford and Lucas, 1994).

Pil­io­colobus ru­fomi­tra­tus is pri­mar­ily a fo­li­vore, though it feeds on a va­ri­ety of other plant mat­ter in­clud­ing fruits and flow­ers. In a study of diet choice, Tana River red colobus fed not only on young leaves (36%), but fruit and seeds (25%, mostly large and un­ripe), leaf buds (16.4%), ma­ture leaves (11.5%) and flow­ers (6.2%). The top three plant species eaten were Ficus syco­morus (29.4%), Sorindeia ob­tusi­fo­li­o­lata (19.6%) and Aca­cia ro­busta (15.0%). These species con­tribute the ma­jor­ity of the diet of Tana River red colobus mon­keys (Marsh, 1981a; Marsh, 1981c).

Stud­ies of the im­pact of plant phy­to­chem­istry on di­etary choice have found that the young leaves pre­dom­i­nately cho­sen are higher in ni­tro­gen (pro­tein) con­tent and lower in hard-to-di­gest fiber than the more abun­dant, ma­ture leaves. Thus P. ru­fomi­tra­tus re­lies mostly on sea­sonal young leaves, flow­ers and fruits when avail­able and re­verts to ma­ture leaves when nec­es­sary. Pil­io­colobus ru­fomi­tra­tus rarely eats the leaves of Diopy­ros mespili­formis de­spite that fact that this is the most com­mon tree in their habi­tat. This might be due to the sec­ondary com­pound naptho­quinone, a phe­no­lic toxin pro­duced in the leaves (Mowry et al., 1996). (Chivers, 1994; Marsh, 1981a; Marsh, 1981c; Mowry, et al., 1996; Teaford and Lucas, 1994)

• Primary Diet
• herbivore
  • folivore
  • frugivore

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

Pre­da­tion

Pil­io­colobus ru­fomi­tra­tus has very few preda­tors due to its large size and ar­bo­real lifestyle. Pre­sum­ably the pelage, dark red dor­sally and lighter ven­trally, helps to cam­ou­flage the shape of these mon­keys when viewed from above and below, blend­ing them into the for­est branches when viewed from above and the sky and canopy when viewed from below.

In the rain for­est species of red colobus, where pre­da­tion pres­sures from chim­panzee hunt­ing are sig­nif­i­cant, these an­i­mals often ex­hibit male-male bond­ing, swamp­ing and ag­gres­sion against chim­panzee hunt­ing par­ties (Struh­saker, 1975). How­ever, Tana River red colobus, which do not ex­pe­ri­ence this pres­sure, do not ex­hibit these be­hav­iors. Alarm call­ing in the form of a loud bark is a com­mon de­fense against pre­da­tion. Un­for­tu­nately they have few adap­ta­tions against their pri­mary preda­tors, hu­mans. Frag­men­ta­tion and re­duc­tion of habi­tat ex­poses Tana River red colobus to bush­meat traders (Oates, 1994). (Oates, 1994; Struh­saker and Le­land, 1987)

• Known Predators

  • humans (Homo sapiens)
  • crowned hawk-eagles (Stephaboaetus coronatus)
  • chimpanzees (Pan)

Ecosys­tem Roles

Pil­io­colobus ru­fomi­tra­tus is host to a va­ri­ety of par­a­sites, though the exact num­ber and species are not known. They also may in­flu­ence plant growth and flow­er­ing pat­terns in their food species as some plant species may bloom syn­chro­nously to limit the im­pact of P. ru­fomi­tra­tus feed­ing. (Oates, 1994)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Tana River red colobus could be used for eco­tourism. Al­though they are not as sought after by tourists as are the great apes, they are nonethe­less a very promi­nent and in­ter­est­ing species. They are also often used as a source of food for hu­mans in the bush meat trade. (Med­ley, 1993; Struh­saker, 1975)

• Positive Impacts
• food
• ecotourism
• research and education

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse ef­fects of P. ru­fomi­tra­tus on hu­mans.

Con­ser­va­tion Sta­tus

Tana River red colobus mon­keys are listed as crit­i­cally en­dan­gered by IUCN be­cause their ex­tremely frag­mented habi­tat is under the con­stant threat of human en­croach­ment (IUCN Web­site, 2001). The small tract of for­est sur­round­ing the river is pri­mar­ily ex­ploited for agri­cul­ture uses but also for canoe con­struc­tion. Cat­tle feed­ing, in­ten­tional burns to in­crease grass pro­duc­tion, and dam con­struc­tion have also detri­men­tally al­tered the habi­tat on the Tana River.

These pri­mates pre­fer in­te­rior for­est habi­tat (Med­ley, 1993). Al­ter­ations to the for­est that re­sult in frag­men­ta­tion, re­duc­tion of for­est area and in­crease pe­riph­eral ex­po­sure ad­versely af­fect pop­u­la­tions. A pop­u­la­tion cen­sus found that be­tween 1975 and 1985, pop­u­la­tions de­clined by 80% mostly due to these habi­tat loss (Decker & Kin­naird, 1992). Con­ser­va­tion ef­forts should focus on main­tain­ing the in­tegrity of the in­te­rior for­est and re­duc­ing the causal fac­tors of frag­men­ta­tion. (Decker and Kin­naird, 1992; IUCN, 2000; Med­ley, 1993)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  Appendix I

Other Com­ments

Pil­io­colobus ru­fomi­tra­tus was pre­vi­ously con­sid­ered a sub­species of a more wide­spread species of red colobus mon­key (Nowak, 1999; Oates, 1994). They were also pre­vi­ously rec­og­nized under the name Pro­colobus ru­fomi­tra­tus. (Nowak, 1999; Oates, 1994)

Con­trib­u­tors

Nancy Shef­ferly (ed­i­tor), An­i­mal Di­ver­sity Web.

Je­remy Jones (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, On­drej Pod­laha (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Chivers, D. 1994. Func­tional Mor­phol­ogy of the Gas­troinesti­nal Tract. Pp. 205-228 in J Oates, A Davies, eds. Colobine Mon­keys: Their Ecol­ogy, Be­hav­iour and Evo­lu­tion. Cam­bridge: Cam­bridge Uni­ver­sity Press.

Decker, B., M. Kin­naird. 1992. Tana River Red Colobus and Crested Mangabey: Re­sults of re­cent cen­suses. Amer­i­can Jour­nal of Pri­ma­tol­ogy, 26: 47-52.

IUCN, 2000. "IUCN Web­site" (On-line). Ac­cessed No­vem­ber 18, 2001 at http://​www.​redlist.​org/​search/​details.​php?​species=39993.

Karere, G., N. Oguge, J. Ki­rathe, P. Muo­ria, N. Moinde, M. Sule­man. 2004. Pop­u­la­tion Sizes and Dis­tri­b­u­tion of Pri­mates in the Lower Tana River Forests, Kenya. In­ter­na­tional Jour­nal of Pri­ma­tol­ogy, 25: 351-365. Ac­cessed Jan­u­ary 07, 2004 at http://​www.​ingentaconnect.​com/​content/​klu/​ijop/​2004/​00000025/​00000002/​00479983.

Marsh, C. 1979. Com­par­a­tive as­pects of so­cial or­ga­ni­za­tion in the Tana River red colobus. Zeitschrift fur Tierpsy­cholo­gie, 51: 337-362.

Marsh, C. 1981a. Diet choice among Red colobus (*Colobus ba­dius ru­fomi­tra­tus*) on the Tana River, Kenya. Folia Pri­ma­to­log­ica, 35: 147-178.

Marsh, C. 1981c. Rang­ing be­hav­iour and its re­la­tion to diet se­lec­tion in Tana River Red colobus. Jour­nal of Zo­ol­ogy (Lon­don), 195: 473-492.

Marsh, C. 1981b. Time bud­get of Tana River Red Colobus. Folia Pri­ma­to­log­ica, 35: 30-50.

Med­ley, K. 1993. Pri­mate con­ser­va­tion along the Tana River, Kenya: An ex­am­i­na­tion of the for­est habi­tat. Con­ser­va­tion Bi­ol­ogy, 7/1: 109-121.

Mowry, C., B. Decker, D. Shure. 1996. The role of phy­to­chem­istry in di­etary choices of the Tana River Red Colobus Mon­keys. In­ter­na­tional Jour­nal of Pri­ma­tol­ogy, 17(1): 63-81.

New­ton, P., R. Dun­bar. 1994. Colobine Mon­key So­ci­ety. Pp. 311-346 in J Oates, A Davies, eds. Colobine Mon­keys: Their Ecol­ogy, Be­hav­iour and Evo­lu­tion. Cam­bridge: Cam­bridge Uni­ver­sity Press.

Nowak, R. 1999. Walker's Pri­mates of the World. Bal­ti­more: Johns Hop­kins Uni­ver­sity Press.

Oates, J. 1994. The nat­ural his­tory of African colobines. Pp. 75-128 in J Oates, A Davies, eds. Colobine Mon­keys: Their Ecol­ogy Be­hav­iour and Evo­lu­tion. Cam­bridge: Cam­bridge Uni­ver­sity Press.

Struh­saker, T. 1975. The Red Colobus Mon­key. Chicago: Uni­ver­sity of Chicago Press.

Struh­saker, T., L. Le­land. 1987. Colobines: In­fan­ti­cide by Adult Males. Pp. 83-97 in B Smuts, D Ch­eney, R Sey­farth, R Wrang­ham, T Struh­saker, eds. Pri­mate So­ci­eties. Chicago: The Uni­ver­sity of Chicago Press.

Teaford, M., P. Lucas. 1994. Func­tional Mor­phol­ogy of colobine teeth. Pp. 173-204 in J Oates, A Davies, eds. Colobine Mon­keys: Their Ecol­ogy, Be­hav­iour and Evo­lu­tion. Cam­bridge: Cam­bridge Uni­ver­sity Press.