Overview

Brief Summary

Biology

The Tana River mangabey is a diurnal species that primarily feeds on seeds, leaves and fruit (4) (6). This monkey occupies multimale-multifemale groups (5) that range from 10 to 36 individuals (8). Mating behaviour is not fully understood, but a single offspring is known to be usual (6), after a gestation period of around 170 to 180 days (2) (8). Life-expectancy is thought to be between 19 and 21 years (9), but little else is known about the life history of this species.
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Description

The Tana River mangabey is a medium-sized, long-tailed monkey with a yellowish-brown coat, and a centre parting on the crown with very long, darker fur diverging from it on either side (2) (4). Like all Cercocebus, this species possesses white eyelids that contrast with the dark colour of the face, a feature thought to aid visual communication through facial expression (5). The molars of this species are long and the incisors are very large, allowing this mangabey to exploit hard seeds in its diet (4) (6).
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Distribution

Range Description

This species is restricted to 27 patches of gallery forests along the lower part of the River Tana in Kenya from 20-40 m asl. It has an extent of occurrence of 60 km along the riverside, from Nkanjonja to Hewani. The area of occupancy is considerably smaller (Butynski and Mwangi 1994). Broadly sympatric with Procolobus rufomitratus rufomitratus and Cercopithecus mitis albotorquatus; narrowly sympatric on the forest edges with Papio cynocephalus ibeanus and Cercopithecus pygerythrus (T. Butynski and Y. de Jong pers. comm.).
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Historic Range:
Kenya

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Geographic Range

Tana river mangabeys, Cercocebus galeritus, are endemic to a fragmented forest mosaic along 60 km of the lower Tana River in southeast Kenya between Kanjonja to the north and Garsa to the south (Medley 1993). Their entire population is confined to roughly 34 of the 60 riverine forests supported by the river. These 34 inhabited forests cover approximately 26 sq km (Butynski and Mwangi, 1994).

Biogeographic Regions: ethiopian (Native )

  • Butynski, T., G. Mwangi. 1994. Conservation Status and Distribution of the Tana River Red Colobus and Crested Mangabey. Report for Zoo Atlanta , Kenya Wildlife Service, National Museums of Kenya, Institute of Primate Research, East African Wildlife Society: 1-58. Accessed May 07, 2011 at http://coastalforests.tfcg.org/pubs/Tana_Colobus_Mangabey.pdf.
  • Medley, K. 1993. Primate Conservation along the Tana River, Kenya: An Examination of the Forest Habitat. Conservation Biology, 7: 109-121.
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Range

Endemic to Kenya. Restricted to the lower Tana River region between Garsen and Wenje (7).
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Physical Description

Morphology

Physical Description

Tana rirver mangabeys are medium-sized mangabeys of the genus Cercocebus. They exhibit a pale-grey/brown coloration, and have a conspicuous crest on their crown and white eyelids (Medley 1993). Their body is covered in wavy hair with inconspicuous dark bands, and their forearms and hands are darker in color than their tail and upper limbs (Groves 1978). Their face is jet black with strongly contrasting white eyebrows, distinguishing it from C. torquatus and C. agilis.

Males and females are similiar in color though different in size. The tail is approximately 33% longer in males (Groves 1978). Males average 9.46 kg in mass with a head-and-body length from 49 to 63 cm and a tail length averaging 68 cm. Females weigh an average of 5.4 kg, with a head-and-body length from 44 to 53 cm and a tail length averaging 50 cm ("Tana River Mangabey (Cercocebus galeritus)" 2010).

Males have the smallest skulls in the genus Cercocebus (Groves 1978). A distinguishing crest on their crown is made up of long (10 cm) darkish brown/grey hairs, parted down the middle. Infants have pink faces, ears, and limbs, and lack the crown (Wieczkowski and Butynski 2007).

The dentition of Tana river mangabeys is uniquely adapted to a hard-item diet. Their thick molar enamel is able to withstand crushing forces, their large maxillary and mandibular fourth premolars provides increased seed-crushing surface area, and their shortened snout allows for a more powerful bite (Wieczkowski 2009).

Average mass: Males 9.46 kg; Females 5.4 kg.

Range length: 44 to 63 cm.

Average length: Males 56 cm; Females 48.5 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

  • 2010. "Tana River Mangabey (Cercocebus galeritus)" (On-line). ArKive. Accessed April 22, 2011 at http://www.arkive.org/tana-river-mangabey/cercocebus-galeritus/#text=Facts.
  • Groves, C. 1978. Phylogenetic and Population Systematics of the Mangabeys. Primates, 19: 1-34.
  • Wieczkowski, J., T. Butynski. 2007. Cercocebus galeritus. T Butynski, J Kingdon, J Kalina, eds. Mammals of Africa.
  • Wieczkowski, J. 2009. Brief Communication: Puncture and Crushing Resistance Scores of Tana River Mangabey (Cercocebus galeritus) Diet Items. American Journal of Physical Anthropology, 140: 572-577.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Wahungu et al. (2005) found that the abundance of the mangabey was highly correlated with the spatial characteristics of the forests. This species is restricted to riverine gallery forests and adjacent patches of bush (the 1974 census found animals in 27 of the forest patches (50%)). It is a semi-terrestrial species that may be found in groups of 13 to 36 individuals, sometimes combining to form aggregations of 50 to 60 animals. In 1974, 86 groups were recorded (Butynski and Mwangi 1994).

Systems
  • Terrestrial
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Tana river mangabeys are largely terrestrial and live in floodplain forests along the lower Tana river. These forests are dependent on the height of the groundwater table and the Tana river's processes of flooding, erosion, and nutrient recharge. Tana river mangabeys inhabit 27 of the 60 riparian forests along the river, inhabiting a total area of only 26 sq km. These forests are naturally fragmented due to the meandering course of the river (Wieczkowski and Kinnaird 2008).

Abundance of Tana river mangabeys is correlated with forest fragment area as well as density of trees (Weiczkowski 2004). Tana river mangabeys, though semi-terrestrial, are forest-dependent, as much of their diet is composed of plant material from the canopy or sub-canopy. On average Tana river mangabeys spend 56% of their time on the ground, 32% in vegetation up to 10 m, and 12% of their time above 10 m. Because of recent habitat fragmentation, Tana river mangabeys have been observed traveling through non-forest matrix in search of food (Weiczkowski 2010). This demonstrates their flexibility in ranging behavior, specifically their ability to increase home range size.

Four tree species account for approximately half of all trees found in this low elevation area: Phoenix reclinata, Polysphaeria multiflora, Garcinia livingstonei, and Sorindea madagascarienses. In general, however, the Tana River floodplain supports many endemic plant and animal populations with small distributions, and the area thus has high biodiversity (Butynski and Mwangi 1994).

The Tana river is a highly seasonal environment, with the most rainfall occurring from March to June and November to December. The hottest months in this region are between October and June (Medley 1993).

Tana river mangabeys tend to choose tall trees with full crowns and poor accessibility to non-arboreal species for sleeping sites. Predator avoidance, afternoon feeding area, and group ranging patterns also influences sleeping site choice. Tana river mangabeys prefer to sleep in the forks of branches near the main trunk of the tree.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: forest

Other Habitat Features: riparian

  • Wahunga, G. 2001. Common use of sleeping sites by two primate species in Tana River, Kenya. African Journal of Ecology, 39: 18-23.
  • Wieczkowski, J. 2004. Ecological Correlates of Abundance in the Tana Mangabey (Cercocebus galeritus). Journal of Primatology, 63: 125-138.
  • Wieczkowski, J. 2010. Tana River Mangabey Use of Nonforest Areas: Functional Connectivity in a Fragmented Landscape in Kenya. Biotropica, 42: 598-604.
  • Wieczkowski, J., M. Kinnaird. 2008. Shifting Forest Composition and Primate Diets: A 13-Year Comparison of the Tana River Mangabey and its Habitat. American Journal of Primatology, 70: 339-348.
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Found in dry gallery forests and Acacia woodland along the floodplain of the Tana River (2) (7). This species is largely terrestrial (4).
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Trophic Strategy

Food Habits

Tana river mangabeys feed primarily on fruits and seeds. Contrary to early descriptions of the species, they do not specialize on ripe fruits, but rather exhibit considerable flexibility in their dietary selection, both spatially and temporally (Wieczkowski 2005; Homewood 1978). This flexibility has allowed them to best exploit their fragmented riparian habitat at all times of the year and has aided their response to anthropogenic habitat change.

Tana river mangabeys increase their home range in times of food scarcity, often shuttling between forest patches through grassy matrix (Wieczkoski 2010). On average, they spend 58% of their waking hours foraging and feeding (Wieczkowski and Butynski 2007).

Tana river mangabeys eat plant materials that are most abundant, including ripe fruit, ripe seeds, unripe fruit, and unripe seeds (Wieczkowski 2005). Their average annual diet is composed of 44% fruit and 32% seeds, with stems, leaves, insects, and fungi making up the remaining 24% (Kinnaird 1990). Food availability is highest from November to April.

Members of this species have been observed feeding on 96 different species of plants, though eight of these comprise over 80% of their diet: Aporrhiza paniculata, Acacia robusta, Diospyros mespiliformes, Ficus sycamorus, Hyphaenae compressa, Pachystela msolo, Pachystela reclinata, and Saba comorensis (Homewood 1978; Wieczkowski 2004).

Tana river mangabeys have unique dental adaptations specialized for accessing unripe fruit and hard nuts and seeds. Their large incisors delay wear from gouging fruits. They also have thick molar enamel, able to withstand crushing forces, and enlarged fourth mandibular and maxillary premolars, providing increased surface area for crushing seeds (Wieczkowski 2009).

Animal Foods: insects

Plant Foods: wood, bark, or stems; seeds, grains, and nuts; fruit

Other Foods: fungus

Primary Diet: herbivore (Frugivore , Granivore )

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Associations

Ecosystem Roles

Tana river mangabeys play an important role in seed distribution, as roughly one-third of their diet is comprised of nuts and seeds. They also serve as host for a variety of gastrointestinal parasites. Ten species of nematodes (including Ascaridia galli, Synodontis fuelleborni, and Trichuris trichiura) and three species of protozoans (Escherichia coli, Entamoeba histolytica, Entamoeba hartmanni) have been found in fecal samples (Mbora and Munene 2006). Tana river mangabeys display a high diversity of gastrointestinal parasites because of the fragmentation and diversity of their habitat combined with their large home ranges (Mbora and Munene 2006). Further study is necessary to determine the effects of this parasite load, as parasites and their associated infectious diseases are a major threat to the conservation of endangered species (Mbora and Munene 2006).

Ecosystem Impact: disperses seeds

Commensal/Parasitic Species:

  • Mbora, D., E. Munene. 2006. Gastrointestinal Parasite of Critically Endangered Primates Endemic to Tana River, Kenya: Tana River Red Colobus (Procolobuc rufomitratus) and Crested Mangabey (Cercocebus galeritus). Journal of Parasitology, 92/5: 928-932.
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Predation

Tana river mangabeys are commonly preyed upon by African rock pythons. Other predators may include African crowned eagles, martial eagles, and Nile crocodiles (Wieczkowski and Butynski 2007). Tana river mangabeys use group signaling to alert other members of the group to predators.

Known Predators:

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Life History and Behavior

Behavior

Communication and Perception

Communication among Tana river mangabeys is complex and crucial for establishing dominance and maintaining group cohesion. Visual communication predominates, and mating and competitive displays are common. Females display their receptivity to mates with large, monthly estrous swellings (Wieczkowski and Butynski 2007). They also exhibit a post-conception swelling that lasts 8 to 9 days after 2 months of pregnancy (Kinnaird 1990). Unlike other species of mangabeys, males do not head bob, swagger, or tongue-flick while courting or at other times (Wieczkowski and Butynski 2007).

Vocalizations are also common among Tana river mangabeys. Females tend to vocalize shortly following copulation (Gust 1994). Males often emit a loud "whoop-gobble," which is audible over 1 km away and lasts over 90 seconds on average. This generally is emitted in the morning hours and is used to assert dominance and to aid in intergroup spacing. This auditory communication between groups minimizes aggressive intergroup competition (Gust 1994).

During a male-male confrontation, agonistic behaviors include lunges, chases, and branch shaking. They also flash their eyelids to assert dominance, which is notable given the impressive contrast between their white eyelids and black face (Wieczkowski and Butynski 2007).

As with most other primates, the importance of olfaction has been reduced in this species.

Communication Channels: visual ; acoustic

Perception Channels: visual ; acoustic

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Life Expectancy

Lifespan/Longevity

Little information is available regarding the lifespan of Tana river mangabeys, as few are raised in captivity and few long-term field studies have been carried out on large populations, which are limited by the small total population size of this species. Nonetheless, given what is known of other members of this genus and extrapolations from field observations, longevity has been estimated at 19 years (Wieczkowski and Butynski 2007).

Average lifespan

Status: wild:
19 years.

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Lifespan, longevity, and ageing

Observations: Little is known about the longevity of these animals. One wild born specimen of the *chrysogaster* subspecies was about 24 years old when it died in captivity (Richard Weigl 2005).
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Reproduction

Tana river mangabeys live in multi-female social groups averaging 27 animals. Groups are generally composed of 2 adult males, 7 adult females, 2 subadult males, 2 subadult females, 10 juveniles, and 4 infants (Wieczkowski and Butynski 2007). The species exhibits a polygynous mating system; the dominant male mates with many estrous females (Kinnaird 1990).

Agonistic behaviors demonstrated in competing males include eyelid flashes, lunges, chases, grabs, bites, branch shaking, and vocalizations (Gust 1994). Males also emit a loud "whoop-gooble" call that can be heard for nearly a kilometer, which in part is used to assert and maintain dominance (Wieczkowski and Butynski 2007). Mean duration of the gobble is 90.5 seconds, with most calls occurring in the morning hours between 0630 and 1100 h.

Females exhibit large, monthly estrous swellings that last 4 to 5 days and signal receptivity to copulation (Wieczkowski and Butynski 2007). Amicable behavior demonstrated between courting couples includes stylized presentations, grooming, and play (Gust 1994). Males exhibit a unique pattern of mounting during copulatory behavior. The male grasps the female's ankles with his feet and places his hands on her hips. After copulation, the female darts away from the male (Gust 1994).

Mating System: polygynous

Female Tana river mangabeys exhibit large, monthly estrous swellings that last 4 to 5 days and signal receptiveness to copulation (Wieczkowski and Butynski 2007). After a gestation period of 180 days, females give birth to a single offspring (Kinnaird 1990). Twins have never been observed in the wild (Kinnaird 1990). During parturition, other individuals in the group do not stand within 5 m of the birthing female. Females in the group may approach the female and her newborn approximately 20 min after birth (Kinnaird 1990).

Copulation and births are largely timed to coincide with greatest food availability. Thus, births tend to peak between August and April, a time of high food availability. Female Tana river mangabeys give birth once every 18 to 24 months, and about 63% of females in a group give birth during a given year (Kinnaird 1990).

Growth is likely similiar to that of other species in the genus Cercocebus. Females likely reach sexual maturity at 3 years of age and breed for the first time at 6.5 years of age. Males reach sexual maturity slightly later, at around 5 years of age, and successful males breed soon thereafter, often by the age of 7 (Wieczkowski and Butynski 2007).

Breeding interval: Female Tana river mangabeys give birth to a single offspring once every 18 to 24 months.

Breeding season: Based on birthing peaks, mating of Tana river mangabeys likely peaks between February and October.

Average number of offspring: 1.

Average gestation period: 180 days.

Average age at sexual or reproductive maturity (female): 3.5 years.

Average age at sexual or reproductive maturity (male): 5 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Female Tana river mangabeys exhibit post-conception swellings 2 months after fertilization (Kinnaird 1990). This has also also been observed in chimpanzees, gorillas, red colobus, and rhesus macaques, and likely functions to confuse paternity, thereby encouraging male investment in the young.

With dominance reversal among males, or when a new male enters and takes over a group, the newly dominant male may practice infanticide (Kinnaird 1990). Females protect their infants from the new alpha male during dominance changes (Gust 1994).

Not much is known about provisioning post-weaning, though females likely provide the most care (Gust 1994). Although both males and females display interest in newborn infants, only juvenile and adult females demonstrate sustained interest, suggesting further maternal behavior (Kinnaird 1990).

Parental Investment: female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

  • Gust, D. 1994. Brief Report on the Social Behavior of the Crested Mangabey (Cercocebus galeritus galeritus) with a Comparison to the Sooty Mangabey. Primates, 35: 375-383.
  • Kinnaird, M. 1990. Pregnancy, Gestation, and Parturition in Free-Ranging Tana River Crested Mangabeys (Cercocebus galeritus galeritus). American Journal of Primatology, 22: 285-289.
  • Wieczkowski, J., T. Butynski. 2007. Cercocebus galeritus. T Butynski, J Kingdon, J Kalina, eds. Mammals of Africa.
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
C2a(ii)

Version
3.1

Year Assessed
2008

Assessor/s
Butynski, T.M., Struhsaker, T., Kingdon, J. & De Jong, Y.

Reviewer/s
Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)

Contributor/s

Justification
Listed as Endangered given the small population size (ca. 1,200 individuals) and the fact that all the animals occur in a single subpopulation. This taxon needs to be closely monitored given the insecurity of the area and potential future threats which could very quickly move it into the Critically Endangered category.

History
  • 2000
    Critically Endangered
  • 1996
    Endangered
  • 1994
    Endangered
    (Groombridge 1994)
  • 1990
    Endangered
    (IUCN 1990)
  • 1988
    Endangered
    (IUCN Conservation Monitoring Centre 1988)
  • 1986
    Endangered
    (IUCN Conservation Monitoring Centre 1986)
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Current Listing Status Summary

Status: Endangered
Date Listed: 06/02/1970
Lead Region: Foreign (Region 10) 
Where Listed: Entire


Population detail:

Population location: Entire
Listing status: E

For most current information and documents related to the conservation status and management of Cercocebus galeritus, see its USFWS Species Profile

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Tana river mangabeys are endangered and, with only 1,000 to 1,200 individuals remaining in the wild, they are ranked as one of the world's 25 most threatened primates in 2002 (Wieczkowski and Butyski 2007). Their numbers continue to decrease.

The greatest threat to Tana river mangabeys is habitat degradation through unsustainable forest clearing and resource extraction (Butynski and Mwangi 1994). Between 1994 and 2000, approximately 30% of the forest within their range was cleared for agriculture (Wieczkowski 2005). Decimation of the favored food source of Tana river mangabeys, the palm species Phoenix reclinata, has only exacerbated the general habitat degradation.

The Tana River Primate National Reserve, created in 1976, has helped stem the habitat degradation, however only 56% of mangabey groups are located in this preserve. Additionally, the preserve was degazzetted in 2007, and currently none of the habitat of Tana river mangabeys is legally protected (Wieczkowski and Butynski 2007).

The lower Tana River contains an abundant wealth of biodiversity, and its conservation is seen as one of East Africa's most serious and challenging biodiversity conservation problems (Butynski and Mwangi 1994). Tana river red colobus (Colobus badius *rufomitratus), are also endemic to the lower Tana River and are endangered (Butynski and Mwangi 1994).

US Federal List: endangered

CITES: appendix i

IUCN Red List of Threatened Species: endangered

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Status

Classified as Endangered (EN) on the IUCN Red List and listed on Appendix I of CITES (3).
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Population

Population
This species is common within its small range. In 1994, the global population was estimated to number 1,000 to 1,200 individuals. The population appears to be somewhat below the 1975 estimate of 1,200 to 1,600 individuals. The population has declined by roughly 10-30% since 1975 (Butynski and Mwangi 1994).

Population Trend
Decreasing
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Threats

Major Threats
This species is threatened by deforestation for agricultural land and timber, burning of adjacent grasslands preventing forest regeneration, overgrazing of forest understory by livestock, and changes to the flow of the Tana River and water table by damming and irrigation projects. Wahungu et al. (2005) estimates 35% of forests within the colobus’ geographical range was lost between 1979 and 2000. Animals may be persecuted for crop-raiding. There is no evidence of hunting for meat. There is a proposal to plant oil palm plantations, but it is not clear where as yet. The proposed Tana Integrated Sugar Project in Tana River and Lamu Districts threatens more than 200 km² of semi-natural habitat in the area.
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The Tana River mangabey has a restricted range of just 60 km of the Tana River (10), and a highly fragmented population that is in continuing decline due to rapid habitat destruction (1). Without urgent action, there is a high probability of this mangabey becoming extinct over the next 50 - 100 years (11). In 1994 it was estimated that just 1,000 to 1,200 individuals remained (1). The population is possibly much lower today, since their habitat has been severely degraded since then, with an approximate 30 % loss of original vegetation (10) (12). In addition, local communities continue to degrade the remaining forest for products used in the construction of homes and canoes, the collection of wild honey and the topping of date palms to make palm wine (12). As the average number of mangabey groups has been found to correlate with forest area and density of trees, the loss and degradation of forest is a major cause for concern. Mangabey-human conflict has also increased in recent years due to crop-raiding, resulting in traps being set (1).
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Management

Conservation Actions

Conservation Actions
This species is listed on Appendix I of CITES and on Class A of the African Convention on the Conservation of Nature and Natural Resources. The Tana River Primate National Reserve (TRPN) holds about 56% of the mangabey groups. Of the 48% of mangabey groups outside of TRPN 10% of the groups live in forests under the management of the Tana Delta Irrigation Project while the remainder are on Trust/Government land.

A priority action is the re-establishment of the Mchelelo Research Station in the Tana River Primate National Reserve.
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Conservation

The Tana River National Primate Reserve was established in 1976 to preserve the endemic and endangered Tana River mangabey and Tana River red colobus (Colobus rufomitratus) (13), but only covers part of the mangabey's range. A 5-year project with the World Bank and Global Environment Facility (GEF) was also started in 1996. Originally designed to relocate several hundred families that presently live within the reserve, financial support was ultimately withdrawn before completion of the project (12). Sadly, forests continue to decline and a new conservation approach is desperately needed to protect them, where past approaches have failed. Their failure was largely due to disregard of land-tenure issues within the Reserve, exclusion of local people from decision-making and neglect of forests outside the reserve (10). Solutions must be found for the problem of forest clearing, and the harvesting of forest products must be better managed, if there is any chance of protecting the habitat of this critically endangered primate and evading its otherwise imminent extinction.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

There are no known adverse affects of Tana river mangabeys on humans.

However, humans have attempted to utilize much of the forests surrounding the Tana River as farmland, encroaching on the little remaining habitat of this species. In this way, the conservation of Tana river mangabeys has adversely affected development and agricultural expansion in the lower Tana River region of Kenya (Wieczkowski and Butynski 2007).

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Economic Importance for Humans: Positive

Tana river mangabeys are of tremendous research and educational importance. Given their limited distribution, they are well studied, and research of their ecosystem dynamics has proven enlightening (Homewood 1978; Wieczkowski and Butynski 2007). Tana river mangabeys have also become a popular face for the conservation of the lower Tana River, which contains an astounding variety of species, many of which, including Tana river mangabeys and Tana river red colobus, are not found anywhere else in the world (Butynski and Mwangi 1994).

Positive Impacts: research and education

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Tana River mangabey

The Tana River mangabey (Cercocebus galeritus) is a highly endangered species of primate in the Cercopithecidae family. Some authorities have included the taxa agilis and sanjei as subspecies of this species,[3] while others award these full species status.[1]

It is endemic to riverine forest patches along the lower Tana River in southeastern Kenya. It is threatened by habitat loss and degradation, which has increased in recent years.[4] This species was, together with the equally endangered Tana River red colobus, the main reason for the creation of the Tana River Primate Reserve in 1978,[5] but human encroachment within this reserve continues.[6] 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.[7]

Physical description[edit source | edit]

The Tana River mangabey is a medium-sized primate with a long semi-prehensile tail, yellow-brown coat, and a center part on the crown of the head with long, dark fur. The species has white eyelids that contrast to its darker face like other Cercocebus species. This contrast in the eyelids is believed to be used as part of the species complex communication system.[8] The species also has specialized dental morphology for feeding on hard nuts, seeds, and fruits.

Behavior and ecology[edit source | edit]

The Tana River mangabey is diurnal and semi-terrestrial. It spends most of its time on the ground but is still considered arboreal due to its sleeping area. The species sleeps in trees which are approximately 27-37m in height which have a sparse canopy cover of 25-60%. The primate sleeps in the forks of the branches of these trees or near the main trunk. It is believed to sleep in trees to reduce the risk of predation and chooses this site according to its last feeding position in the area.[9]

Group size ranges from 13-36 individuals, and sometimes combining to form aggregations of 50 to 60 individuals.[10] These groups consist of multiple males and multiple females. The species have an average day-range length of 1.25 km.[11] During the dry season when food is limited groups maintain discrete territories with minimal overlapping. To maintain these territories males give spatial vocalizations and territorial displays at fixed boundaries. The males within the group may also engage in active combat with outside group leaders invading the territory. In the wet season when food is abundant boundaries are broken down. Foraging ranges for different groups extend and there is considerable overlap between the different groups. During this time groups are more tolerant of one another and meet and intermingle.[12] The Tana River mangabey has a few predators, such as Python sebae, Crowned Eagle, Martial Eagle, and Nile crocodile.

Reproduction[edit source | edit]

The Tana River mangabey is a polygynous species with two or more males within each group depending on the size of the group. The average adult male weighs approximately 10.2 kg while the average adult female weighs 5.5 kg exhibiting sexual dimorphism within the species.[11]

The primate gives birth to a single offspring after a gestation period of approximately 170–180 days. During the first two months after birth, the infant is guarded by its mother and begins to develop a close bond. In the third month the infant begins socializing with other infants and adult group members but remains in close proximity to mom. The females within the group usually have lasting bonds with their mother while the males become more independent and spend more time away from the group or on the periphery. If a group loses one of its males, another male may be recruited from peripheral solitary males to maintain the structure of the group.[12]

Diet[edit source | edit]

The species is an omnivore, feeding on leaves, seeds, fruits, insects and reptile and bird eggs. It is an opportunistic feeder and is semi-terrestrial where it may rummage through the leaf litter for food. The mangabey gets most of its food from sub-canopy and canopy trees, although they spend most of their time feeding and moving on the ground. It consumes the fruit and seed from approximately fifty different tree species. Feeding is performed 48% of the day, while sleeping accounts for 15%, and resting accounts for 14% of the day.[11] The species annual diet consists of 46.5% seeds and 25.6% consists of fruit consumption.[13] Critical food resources for the species are Ficus sycomorus which fruits year round, and Phoenix reclinata which is also a primary food species and fruits when others do not.[14]

The Tana River mangabey has dental morphology well suited for the food type it consumes. The species has large incisors for the tearing of the tough skin on the fruits it eats. Large maxillary and mandibular fourth premolars which increase surface area to crush seeds, and a shortened face which increases bite force.[15]

Geographic range and habitat[edit source | edit]

The Tana River mangabey is found on the continent of Africa in the southeastern portion of Kenya along the Tana River. It is found within 27 forest fragments along a 60 km stretch of floodplain forests. The gallery forest along the Tana River is home to several primate species: the Tana River mangabey, Tana River red colobus, blue monkey, yellow baboon, vervet monkey, and two species of bush babies.[16]

This species is restricted to riverine gallery forests in this area.[17] The forests in which it is found are naturally fragmented due to the meandering of the Tana River and its fluctuating water levels. The forest is becoming even more fragmented due to habitat loss from human disturbance reducing the chance of the species survival.

Conservation[edit source | edit]

One of the greatest threats to endangered species is habitat loss. This is also the case with the Tana River mangabey. It is estimated that 50% of the original forest has been lost in the last 20 years. The Tana River area is losing its forests to agriculture.[8] Felling of canopy trees for canoe construction, wild honey collection, and Palm fronds are being used for thatching and mats. Subcanopy trees are being used for housing poles and the topping of Phoenix reclinata for palm wine collection severely impacts the resources used by the species.[18] Tana River mangabeys are also hunted and trapped in response to local crop damage. This trapping may occur and appears to be occurring at low levels within the forests.

The Tana River mangabey is listed as one of The World's 25 Most Endangered Primates. A 1994 census estimated the species population to be 1,000 to 1,200 individuals.[18] It was listed under the U.S. as being endangered in 1970. The species was also listed as endangered under the International Union for Conservation of Nature and under CITES is listed under Appendix I. This species is listed on Class A of the African Convention on the Conservation of Nature and Natural Resources.

The Tana River Primate Reserve was established in 1976 to protect the remaining forest along the Tana River and the endemic Tana River mangabey. The reserve protects an area of approximately 171 km² with 9.5 km² and 17.5 km² of that being forested area. The reserve contains about 56% of the Tana River mangabey groups, with approximately 44% living in forests outside of the reserve. 10% of the groups living in forests outside of the reserve are under the management of the Tana Delta Irrigation Project.

The objective of the Tana River Primate Reserve was to conserve the biodiversity within the Tana River area and protect the endangered Tana River mangabey. The conservation of this species is a high priority for primate conservation in Kenya. In 2007, the High Court in Kenya ruled the reserve was not abiding by the laws. This led to the forested areas which the mangabey inhabited losing their legal protection.[19] With the poor management of the Tana Delta Irrigation Project, habitat loss outside the reserve also continues. The Tana and Athi Rivers Development Authority, who is in charge of the project, are now in the process of expanding to establish a sugar cane plantation which will in turn remove more forested areas.

A five-year project in 1996 with the Kenya Wildlife Service and Kenya Forest Department was funded by the World Bank/GEF. The projects goals were to enhance conservation and protection of these primates and forests. The project was poorly managed and was terminated after two years of implementation, leaving the wildlife service with the protection of these areas.

The Ishaqbin Conservancy is a community initiative in the Tana River Primate Reserve. Here communities are working with Kenya Wildlife Service to develop tourism side by side with conservation. Tourism development is believed to be important in that it will secure the conservation of the habitat and the species with the communities around the reserve. Tourism will benefit both the mangabey and local communities through economic development and a reduction in habitat loss. The conservancy will also help to form a buffer around the reserve which will help to reduce human impact inside the reserve.[20]

References[edit source | edit]

  1. ^ a b Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. p. 153. OCLC 62265494. ISBN 0-801-88221-4. 
  2. ^ Butynski, T. M., Struhsaker, T., Kingdon, J. & De Jong, Y. (2008). Cercocebus galeritus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 4 January 2009.
  3. ^ Grubb, P., Butynski, T. M., Oates, J. F., Bearder, S. K., Disotell, T. R., Groves, C. P., & Struhsaker, T. T. (2003). Assessment of the diversity of African primates. International Journal of Primatology 24. pp. 1301–1357. 
  4. ^ Wieczkowski, J. & Mbora, D. N. M. (2000). "Increasing threats to the conservation of endemic endangered primates and forests of the lower Tana River, Kenya". African Primates 4: 32–40. 
  5. ^ "Kenya Wildlife Service – Tana River Primate Reserve". www.kws.org. Retrieved 2009-12-30. 
  6. ^ Kenya’s rare monkey species threatened with extinction . African Conservation Foundation. Accessed 2008-07-20
  7. ^ Tana gets temporary reprieve. BirdLife International. Accessed 2008-07-20
  8. ^ a b Richardson, M. (2006-04-03). "Tana River mangabey". ARKive. Retrieved 2013-02-06. 
  9. ^ Wahungu.G.M. (2001) Common use of sleeping sites by two primate species in Tana River, Kenya. East African Wild Life Society, African Journal of Ecology, Vol. 39, pp. 18-23.
  10. ^ Butynski, T. M. and Mwangi, G. 1994. Conservation Status and Distribution of the Tana River Red Colobus and Crested Mangabey. Report for Zoo Atlanta, Kenya Wildlife Service, National Museums of Kenya, Institute of Primate Research and East African Wildlife Society. The Harvey, P.H. and Clutton-Brock, T.H. (1981) Primate Home Range Size and Metabolic Needs. Behavioral Ecology and Sociobiology, Vol. 8, No. 2. Pp.151-155.
  11. ^ a b c Harvey, P.H. and Clutton-Brock, T.H. (1981) Primate Home Range Size and Metabolic Needs. Behavioral Ecology and Sociobiology, Vol. 8, No. 2. Pp.151-155.
  12. ^ a b Homewood, K. 1974. Can the Tana Mangabey Survive? Oryx
  13. ^ Harvey, P.H. and Clutton-Brock, T.H. 1981. Primate Home Range Size and Metabolic Needs. Behavioral Ecology and Sociobiology, Vol. 8, No. 2. Pp.151-155.
  14. ^ Wieczkowski,J. 2004. Ecological Correlates of Abundance in the Tana Mangabey (Cercocebus galeritus). American Journal of Primatology. Vol. 63 pp.125-138.
  15. ^ Wieczkowski, J. (2009) Brief Communication: Puncture and Crushing Resistance Scores of Tana River Mangabey (Cercocebus galeritus) Diet Items. American Journal of Physical Anthropology, Vol. 140, pp. 572-577.
  16. ^ Wahungu, G.M. 1998. Diet and habitat overlap in two sympatric primate species, the Tana Crested mangabey Cerocebus galeritus and yellow baboon Papio cynocephalus. African Journal of Ecology. Vol. 36 pp.159-173
  17. ^ Wahungu, G. M., Muoria, P. K., Moinde, N. N., Oguge, N. O. and Kirathe, J. N. 2005. changes in forest fragments sizes and primate population trends along the river Tana floodplain, Kenya. African Journal of Ecology 443: 81-90.
  18. ^ a b Wieczkowski, J. (2005) Comprehensive Conservation of Tana Mangabeys. International Journal of Primatology, Vol.26, No. 3, pp. 651-660.
  19. ^ Mbora, D.N.M & Butynski, T.M. Tana River Red Colobus: Procolobus rufomitratus (Peters, 1879). Kenya 2008.
  20. ^ Kenya Wwildlife Reserve http://www.kws.go.ke/parks/community_wildlife_program/Conservancies/Ishaqbin.html
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