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.
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.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
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.
US Federal List: no special status
CITES: appendix i
IUCN Red List of Threatened Species: least concern
There are no known adverse effects of P. rufomitratus on humans.
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.
Positive Impacts: food ; ecotourism ; research and education
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.
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).
Plant Foods: leaves; seeds, grains, and nuts; fruit; flowers
Primary Diet: herbivore (Folivore , Frugivore )
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.
Biogeographic Regions: ethiopian (Native )
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).
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: forest
Other Habitat Features: riparian
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.
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.
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).
Range mass: 5.1 to 11.3 kg.
Average mass: 5.8 kg.
Range length: 450 to 670 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
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).
Known Predators:
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)
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.
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.
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.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
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.
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
The Tana River red colobus (Piliocolobus rufomitratus), also called the eastern red colobus, is a highly endangered species of primate in the family Cercopithecidae. It is endemic to a narrow zone of gallery forest near the Tana River in southeastern Kenya.[1][4]
As here defined, P. rufomitratus is a monotypic species restricted to Kenya, following Groves.[1] As all red colobuses, it was formerly considered a subspecies of a widespread P. badius.[4] Some recent authorities include P. tephrosceles, P. foai and P. tholloni as subspecies of P. rufomitratus instead of recognizing them as separate species.[5]
The Tana River red colobus had been considered one of The World's 25 Most Endangered Primates.[6][7] It was, together with the equally endangered Tana River mangabey, the main reason for the creation of the Tana River Primate Reserve in 1978,[8] but human encroachment within this reserve continues.[9] Recently, it has been suggested that 20,000 hectares of the Tana River Delta should be transformed into sugarcane plantations, but this has, temporarily at least, been stopped by the High Court of Kenya.[10] Contra Groves,[1] it was not recognized as a species separate from the Ugandan, Central African and Thollon's red colobus in the 2008 IUCN Red List. With these as subspecies, P. rufomitratus is considered to be of least concern in the 2008 IUCN Red List,[5] while P. (r.) rufomitratus is considered endangered.[2]
The Tana River red colobus has been under the watch of the Tana River Primate National Reserve (TRPNR). They put a large amount of research and study into the conservation of the Tana River red colobus. They found that only 37% of the red colobuses lived inside the preservation itself, which has brought the conservation strategy into question.[11]
The Tana River red colobus is located only in a very small section of the world. Its current endangerment is caused by habitat loss and persecution by humans.[5] Tropical forests are constantly being cut down, causing the destruction of habitat for the red colobus. Cultivation of the land and the creation of levees and dykes have had the most devastating impact. Both human creations involve partial or complete forest clearing, resulting in further devastation of forest patches.[12] Both the Tana River red colobus and the Tana River mangabey have been put in a dangerous situation due to deforestation and destruction created by an increasing human population. Forest is vacant primarily for agriculture; in the last 20 years approximately 50% of the unique forest has been lost.[13] A survey conducted in 1987 concluded that since 1975 there has been approximately an 80% decline in the numbers of Tana River Colobus monkeys. Habitat disturbances, changing farming practices, and the altering course of the river were found to be the main reasons for endangerment.[14]
Another developing threat to the Tana River red colobus is the introduction of parasitic diseases to their habitats. The presence of parasites in the monkeys was noticeably higher than other primates.[15]
Colobus monkeys eat mostly leaves from a limited number of tree species. They choose mature leaf species that are high in nitrogen and low in fiber.[16] They supplement this bulky cellulose diet with occasional unripe fruit, moss and seeds. Human food is of no interest to these leaf specialists. Their stomachs are large and have three chambers, and carry a specific bacterium which helps to ferment and digest the leaves. They eat about two to three kilograms of leaves a day. Sometimes they eat soil, clay and charcoal to help digest toxins and toxic leaves. Because of the poor nutritional quality of their food, they must browse intensively for many hours each day looking for food, and spend much of the remainder of the day resting to aid digestion.[17]
Tana River red colobus monkeys tend to be sedate and quiet creatures. They live together in small numbers and give out low calls when necessary.[18]
The Tana River red colobus monkey gets its name from where it resides, along forests along the floodplain in the lower Tana River in eastern Kenya, the country's longest river. The river is roughly 1,000 km long. When the river is in a flood, the floodplain measures from one to six km in width, and about 60 to 100 m in width when not in a flood. Floods occur roughly once a year, with a major flood occurring every three years. Although the floodplain is mostly grassy, there are places with bushland, woodland, and forests.
The lower Tana River is generally hot and dry, with temperatures ranging from 86 °F to 100 °F (30 °C to 38 °C). The hottest months generally occur during January and February while the coldest months are May through July. The average annual rainfall is between 500 and 600 mm, with the wettest months being March and April and the driest being November and December.
The main vegetation that appears along the lower Tana River includes grassland, wooded grassland, bushland, deciduous woodland and lowland evergreen forest. Due to human disturbances as well as floods, patchy distributions of forests have resulted.[18] A study was done in 1988 to determine what was causing the drastic decline of the crested mangabey and the Tana River red colobus. The forest was found to be regenerating and causing a new kind of vegetation to appeal to newer species. This could have been a cause of their drop of numbers.[19]
The Tana River red colobus has a polygynous mating system especially when only one male is present. The dominance hierarchy typically determines which individuals are allowed to mate. Little is known about the reproductive cycle in the wild due to this species' constant migration. The dominant male usually mates with females within the same social group. Females initiate mating through courtship displays and copulation calls. Red colobus monkeys breed throughout the year, and have a gestation period of about 4.5 to 5.5 months.
Infants cling to their mother's underbelly. Up until about 3.5 months in age infants travel only one meter away from the mother. By 3.5 to 5.5 they usually play with other monkeys. Females leave the group around 18 months of age and continue to move from group to group. Males may leave the group during adolescence but have a harder time being accepted into other social groups due to hierarchy.[20]
The Tana River red colobus (Piliocolobus rufomitratus), also called the eastern red colobus, is a highly endangered species of primate in the family Cercopithecidae. It is endemic to a narrow zone of gallery forest near the Tana River in southeastern Kenya.
