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Zanzibar red colobuses do not currently have any non-human predators, but the now-extinct Zanzibar leopard (Panthera pardus adersi) was historically a predator (Nowak et al. 2008). Though Zanzibar leopards were officially declared extinct in 2012, it has most likely been extinct since the 1990s (Goldman and Walsh 2002). It is possible that young animals are taken by large snakes and raptors.
Known Predators:
Like other red colobus species, P. kirkii is a medium-sized monkey with a distinct build. It has a small head on a long-backed, pot-bellied body and very long limbs - with the hind limbs being slightly longer than the forelimbs (Kingdon 1997). All colobine monkeys share several features, including a greatly reduced thumb, a long tail, and elongated hindfeet (Struhsaker 2010). Red colobus species (Piliocolobus) differ from black-and-white colobus species (Colobus) in having a much smaller larynx and no subhyoid sac. Other defining features are the separated ischial callosities of males and the presence of perineal organs in males and females (Kingdon 1997). Adult and subadult females have true perineal swellings that vary in size over the estrus period but are consistently smaller in P. kirkii than in other red colobus species (Struhsaker and Leland 1980; Struhsaker 2010). Young males also have a perineal organ - a small protuberance around the anus that superficially resembles a small swelling – that is retained in adult males, though in a reduced form (Struhsaker and Leland 1980). Zanzibar red colobuses are the smallest Piliocolobus species (Struhsaker 2010).
Zanzibar red colobuses have distinctive pelage with red, black, and white regions (Kingdon 1997). The upper back and shoulders are black and the middle and lower back varies from orange to red-brown. There is pronounced individual variation in the extent of black and red-brown on the nape, shoulders, and upper back. The anterior edge of the shoulders, the ventral area, and the medial surface of the arms and legs are white to grey. The ventral surface of the tail is white or grey mixed with blonde hairs, the dorsal surface is red-brown with the distal half sometimes blending into blonde. The legs are grey, except for a black stripe on the lateral thigh. The lateral surface of the forearms is mostly black but varies in the amount of additional white or grey. The dorsal surfaces of the hands and feet are black (Struhsaker and Leland 1980; Kingdon 1997; Struhsaker 2010).
The black face is framed by a fringe of long white hair that extends to the red-brown crown of the head. The lips and noses of infants are pink, but vary significantly between pink and black in adults within the same social groups (Struhsaker 2010). The natal coat color of infants is black and white. The characteristic red and brown colors do not appear in infants until they are 3 to 5 months old and full adult coloration is achieved between 6 and 11 months of age (Nowak and Lee 2011a).
There is less sexual dimorphism in body size in P. kirkii than in other Piliocolobus species, with an average body weight of 5.8 kg for males and 5.5 kg for females (Struhsaker 2010). Sexual dimorphism is pronounced in cranial dimensions and canine length, however. Adult males have much longer canines, a more robust skull, and a well-developed nuchal and sagittal crests. The tail of males is generally thicker and more heavily furred than those of females. In contrast to other Piliocolobus species, adult females have significantly longer bodies and tails than dp adult males (Struhsaker 2010).
Average mass: 5.5 (females) - 5.8 (males) kg.
Range length: 45 to 70 cm.
Average length: 55.4 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; sexes shaped differently
The longevity of Zanzibar red colobuses is not known. Ugandan red colobuses (Piliocolobus tephrosceles) may live up to 21.2 years for females and 15.5 years for males in the wild. The mean lifespan for P. tephrosceles in the wild is 13.7 years for females and 10.5 years for males (Struhsaker 2010). Two other Piliocolobus species, Temminck’s red colobuses (Piliocolobus temminckii) and the Tana River Red Colobus (Piliocolobus rufomitratus), are known to live at least seven to eight years (Struhsaker 2010).
The Zanzibar Red Colobus has never been held successfully in captivity. An animal held at Antwerp Zoo in Belgium in 1964-1965 survived in captivity the longest, but this was not more than seven months (Gijzen et al. 1966).
Zanzibar red colobuses inhabit coral-rag scrub forest and mangrove swamps. In Jozani National Park, several populations also inhabit bordering farmland - known as “shamba” in Kiswahili - that is characterized by a mixture of perennial agriculture, exotic trees, and scrub forest (Siex and Struhsaker 1999b; Struhsaker 2010). On Uzi Island, disturbance of the coral-rag forest has led to compression of tred colobus populations in mangrove forest refugia. Though some groups on Uzi Island spend upwards of 85% of their time in mangrove habitat, it is unlikely that the mangrove refugia alone – without access to adjacent coral-rag thicket – would support viable populations of these monkeys (Nowak 2008). Mangroves are used as a refuge from human disturbance and as a reliable source of shelter, but it is thought that the mangrove diet may not be sufficient to sustain these monkeys, as more time is spent feeding on preferred food sources in coral-rag forest (Nowak 2008).
Average elevation: 2 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: forest ; scrub forest
Other Habitat Features: agricultural ; riparian ; estuarine
Piliocolobus kirkii was named a species by Gray in 1868. It was named after Sir John Kirk, the Governor General of Zanzibar, who was the first to raise awareness about the species. Kiswahili names for Zanzibar red colobuses are "punju" and "kima mweupe," meaning “poison” and “white colobus,” respectively.
Piliocolobus monkeys are distributed across equatorial Africa from Gambia to Zanzibar in a fragmented manner (Struhsaker 2010). The classification of the 18 different ‘forms’ of Piliocolobus was one of longest standing unresolved issues in African primate taxonomy. Phylogenies were constructed using morphology, pelage, and vocalizations, but the first molecular phylogeny for the African colobines was only produced in 2008 (Ting 2008). As colobines that are morphologically similar to extant forms do not appear in the fossil record until the early Pleistocene, it was thought that extant African colobines had recent origins and diverged only after the extinction of the diverse Plio-Pleistocene colobines (Struhsaker 2010). Ting’s (2008) molecular phylogeny showed that the three modern colobine genera (Colobus, Procolobus, and Piliocolobus) diverged from one another by the late Miocene. Colobus (black-and-white colobuses) seems to have split from the other genera by 7.5 million years ago (mya) Piliocolobus (red colobuses) and Procolobus (olive colobuses) share a sister taxon relationship and also diverged from one another by the late Miocene, around 6.4 mya The three major clades in Piliocolobus seem to have separated by 3.0 mya Piliocolobus kirkii is within a clade containing Piliocolobus oustaleti (Central African red colobus), Piliocolobus rufomitratus (Tana River red colobus), and Piliocolobus tephrosceles (Ugandan red colobus), and their split occurred by 1.4 mya. Within this clade is the sister taxon relationship between P. kirkii and Piliocolobus gordonorum (Udzungwa red colobus), the split between these two sister taxa occurred 0.6 mya (Ting 2008).
Morphometric studies of P. kirkii show that the species has experienced accelerated morphological evolution of size, probably as a result of insularity. Piliocolobus kirkii is the smallest of the red colobus species, both in body size and cranium size. This observation is consistent with the island rule, which is the expectation that large mammals may become smaller on islands. There also appears to have been a concomitant decrease in body size sexual dimorphism in accordance with Rensch’s rule - the tendency for sexual dimorphism to reduce as body size decreases (Nowak et al. 2008).
Zanzibar red colobus vocalizations and visual displays are designed for communication within large groups and for interactions at close range with neighboring troops (Estes 1991). As in other Piliocolobus species, adult male P. kirkii are the primary vocalizers and use three different distress, warning, and threat calls: bark, chist, and wheet (Struhsaker and Leland 1980; Struhsaker 1981). Adult male P. kirkii also give a complex long call that is unique among the Red Colobus monkeys. These long call bouts begin with one or more yelps, followed by a series of warbles and shrill squeals. The long call is expressed in dominance displays, indicating sexual interest in females, and initiating and coordinating group movements (Struhsaker 1981; Struhsaker 2010).
Adult females and juveniles also give various screams related to distress. Adult female P. kirkii appear to be more vocal when living under high population density conditions, and this is likely related to the greater degree of intra- and inter-group aggressive encounters in high density versus lower density populations (Struhsaker 2010).
Visual communication is also important in Red Colobus monkeys, and they are thought to have distinct facial features, hair color, postures, and movements for this purpose (Estes 1991).
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Zanzibar red colobuses are endangered not only because of the low number of individuals, but also because of its limited and highly fragmented distribution. Various estimates of the total P. kirkii population in all its localities indicate that in 2007 its numbers were 2,000 to 2,500 individuals (Struhsaker and Siex 1998; Struhsaker 2005). The only significant populations are restricted to small, isolated pockets of forests on Unguja Island. Though they have been legally protected since 1919, less than 2% of Unguja Island is set aside for the conservation of indigenous flora and fauna (Siex and Struhsaker 1999a). The largest and only officially protected population of P. kirkii occurs in Jozani‐Chwaka Bay National Park. Approximately half of the population on Unguja reside permanently outside protected areas, many within agricultural areas. The greatest threat to populations outside protected areas is habitat loss caused by expanding agriculture and increasing demands for firewood, charcoal, and timber (Struhsaker 2005). This habitat loss has resulted in population compression of P. kirkii at Jozani with negative impacts on some of their food species (Siex 2003). Zanzibar red colobuses are occasionally killed as perceived agricultural pests. Conservation of this species is thus strongly dependent on the development of effective management plans that address the potential human-wildlife conflicts in these agricultural areas (Siex and Struhsaker 1999a).
Uzi and Vundwe Islands also contain a behaviorally and ecologically unique population of P. kirkii. The conservation status of the Zanzibar Red Colobus and its habitat on these islands is critical, as farmers were reported in 2009 to have killed at least 50 monkeys by poisoning and netting because they are perceived as crop raiders ("Update on habitat loss, conservation status of the endangered Zanzibar Red Colobus on Uzi, and Vundwe Islands" 2009). The destruction of coral-rag forest habitat is also an extensive and continuing threat. Recommendations for conservation of the Red Colobus on these islands include the gazetting of southern Uzi and Vundwe Islands as forest reserves, and the establishment of a community-based forest conservation project involving tourism (Struhsaker 2005; Nowak and Lee 2011a).
US Federal List: no special status
CITES: appendix i
State of Michigan List: no special status
In the past, farmers living near Jozani National Park have complained about crop raiding by Zanzibar red colobuses, but the evidence for this behavior is controversial. In the late 1990s, farmers claimed that they were consuming coconuts in agricultural areas and requested compensation and removal of the Zanzibar red colobuses (Siex and Struhsaker 1999a). Scientific investigation of the problem found that Zanzibar red colobus consumption of coconuts was positively correlated with harvest, maybe due to a pruning effect (Siex and Struhsaker 1999a). This example illustrates the importance of scientifically quantifying perceived human-wildlife conflicts so that appropriate measures can be taken (Struhsaker 2005). There have also been reports of crop damage to mangoes and breadfruit by P. kirkii. However, it is possible that most (if not all) damage is caused by Sykes monkeys and blamed incorrectly on Zanzibar red colobuses, as the more secretive and inconspicuous Sykes monkeys often associate with groups of Zanzibar red colobuses (Siex and Struhsaker 1999a).
Zanzibar red colobuses play an important role in tourism, which is one of Zanzibar's most important economic sectors (Siex and Struhsaker 1999a; Struhsaker 2005). By 2000, many thousands of tourists were visiting Jozani National Park to see these primates, generating at least $100,000 in park fees annually (Siex 2003). This income not only supports Jozani National Park, but also benefits the government and the local community. Tourists also spend much more throughout the island on transport, food, and lodging, thereby providing increased employment opportunities (Siex and Struhsaker 1999a).
Zanzibar red colobuses have also been the subject of 19 years of intermittent research beginning in the 1980s in Jozani National Park (Struhsaker 2010). Research on the populations in Kiwengwa and on the Uzi and Vundwe Islands was begun more recently in 2003 (Nowak 2008).
Positive Impacts: ecotourism ; research and education
Zanzibar red colobuses are one of Zanzibar’s five primate species, along with lesser bushbabies (Galago senegalensis zanzibaricus), greater bushbabies (Otolemur garnetti garnetti), vervet monkeys (Cercopithecus aethiops nesiotes), and Sykes monkeys (Cercopithecus albogularis) (Pakenham 1984). Zanzibar red colobuses are one of the main folivores and frugivores in the coral-rag forest ecosystem, and may, like other colobines, play a role in seed dispersal (though no official study has been conducted on this subject).
While mainland Piliocolobus species are commonly observed to form interspecific associations, P. kirkii has not been found to associate extensively with other species, with one possible exception. Sykes monkeys (Cercopithecus albogularis) appear to use P. kirkii as a distracting shield against harassment and hunting by humans in agricultural areas. Sykes monkeys are harassed and sometimes killed by humans because of their crop raiding, whereas P. kirkii are not because they rarely feed on crops. It has thus been suggested that Sykes monkeys associate with Zanzibar red colobuses in shamba farmland areas because the larger and noisier red colobus groups serve as a distraction against human detection (Siex and Struhsaker 1999a; Struhsaker 2010). There have also been surprising reports of Jozani populations of P. kirkii grooming cattle in shamba farmland areas (Ho 2011), but it is unclear how common this behavior is.
Zoonotic diseases have not been studied in P. kirkii, but Uganda red colobuses (Piliocolobus tephrosceles) host a variety of diseases, including simian immunodeficiency virus (SIV), simian T-cell lymphotrophic virus (STLV), and simian foamy virus (SFV). African colobines are generally undersampled as potential hosts of primate retroviruses, and future studies may reveal greater importance of the colobines as hosts for zoonotic diseases (Goldberg et al. 2009).
Zanzibar red colobuses are primarily folivorous. Young leaves are consumed most often, constituting 31.1 to 60.7% of the diet in forest and shamba populations, respectively. Fruit with seeds constitutes 10 to 31.7% of the diet. The remainder of the diet consists of mature leaves, petioles, flowers, and flower buds (Struhsaker 2010). Zanzibar red colobuses feed almost exclusively on unripe fruit, in which seeds are softer and more digestible, suggesting that seeds also constitute an important part of the diet. The unripe-fruit-with-seed diet includes a wide range of plant families, but is dominated by the sycamore fig (Ficus sycomoros) in Jozani forest populations and by coconuts (Cocos nucifera) in shamba farmland populations (Struhsaker 2010). Other species commonly consumed by Jozani populations of P. kirkii include Eugenia malaccensis, Turea floribunda, Brideria micrantha, Albizia sp., and Fluergia sp. (Walz 2006). Zanzibar red colobus populations inhabiting mangrove forests on Uzi and Vundwe Islands most commonly feed on mangrove species such as Sonneratia alba, Avicennia marina, Rhizophora mucronata, Bruguiera gymnorhiza, and Ceriops tagal (Nowak 2008).
Like other colobines, P. kirkii is a foregut fermenter with a complex four-chambered stomach (Estes 1991). The stomach is divided into chambers wherein vegetation undergoes fermentation and predigestion by gut microflora before passage into the small intestine. The stomach is also enlarged, allowing for the accumulation and slow passage of food necessary for fermentation. Foregut fermentation by bacteria allows for more complete digestion of plant structural carbohydrates, but also aids in detoxification of tannins and other plant secondary compounds (Estes 1991).
Zanzibar red colobuses derive most of their water from their leaf diet, but water drinking is seen in some populations. Most notable is the discovery of frequent water drinking in populations of P. kirkii inhabiting mangrove swamps on Uzi island (Nowak 2008). Frequent water drinking emerged during confinement of these populations in mangrove refugia following displacement from their previous coral-rag forest habitat, and it is thought to be an adaptive response to the high salt intake that comes with feeding on mangrove species. Water was obtained in a number of ways, including licking rain off leaves, drinking from coral rock crevices, licking dew, and drinking from tree holes. The strategies for obtaining water were group-specific and are likely the result of learning (Nowak 2008).
Zanzibar red colobuses are the only non-human primates known to consume charcoal (Struhsaker et al. 1997). Charcoal is eaten from a variety of sources, including tree stumps, logs, and branches charred from fires associated with local swidden agriculture, as well as from kilns used by humans to burn charcoal. At least four populations in Jozani National Park and neighboring shambas consume charcoal, but not all populations eat charcoal, possibly because charcoal is not readily available in all habitats. The extent of charcoal consumption also appears to be related to diet differences among P. kirkii populations, as shamba populations have diets containing three times more phenolics than those of forest populations, primarily because of their exploitation of exotic food plants. An estimated 0.25 to 2.5 g of charcoal/kg of body weight is ingested daily (Struhsaker et al. 1997). Individuals of both sexes and all age classes have been observed to eat charcoal, and the behavior is thought to be socially transmitted by learning.
Charcoal consumption may be functionally analogous to geophagy observed in other colobines because charcoal serves as an adsorbent of potential toxins and antifeedants that may interfere with digestion (Cooney and Struhsaker 1997). Laboratory studies have shown that the charcoals eaten by P. kirkii adsorb potentially toxic materials such as phenolics and are 11 to 39% as effective as commercially manufactured activated charcoal for human consumption (Cooney and Struhsaker 1997). Charcoal consumption has allowed P. kirkii populations to exploit exotic food sources, such as Indian almond (Terminalia catappa), mango, and cassava leaves (Manihot esculenta), which, although high in toxins and antifeedants, are also of high nutritional value, being relatively high in protein and easily digestible (Struhsaker et al. 1997). Charcoal consumption is also thought to play a role in another unique feeding habit of P. kirkii, for this species is the only colobus monkey known to feed on cycads (Encephalartos hildebrandtii) (Nowak and Lee 2011b). Cycads contain carcinogenic and neurotoxic compounds such as cycasin and macrozamin, and ingested charcoal is most likely important in the immobilization of these harmful compounds (Nowak and Lee 2011b).
Plant Foods: leaves; seeds, grains, and nuts; fruit; flowers
Primary Diet: herbivore (Folivore )
Piliocolobus kirkii, the Zanzibar red colobus, is endemic to the Unguja, Uzi, and Vundwe Islands of the Zanzibar archipelago off the coast of mainland Tanzania. Unguja island is home to the largest population of P. kirkii, but the species has a highly fragmented distribution and is limited to remnant pockets of forest in the east, south-central, and southeast portions of the island, including Jozani Chwaka Bay National Park, Makunduchi, Muongoni, Kiwengwa, and Popakani (Silkiluwasha 1981; Struhsaker 2010). A small population of 14 individuals was reintroduced into Ngezi forest on Pemba Island in 1974, where some red colobus monkeys may still persist, but the size and viability of the current population is unknown (Struhsaker and Siex 1998; Campero Ciani et al. 2001).
Biogeographic Regions: ethiopian (Native )
Other Geographic Terms: island endemic
Zanzibar red colobuses are promiscuous and copulation is initiated by both sexes. Females often copulate with more than one male during a given estrous period (Struhsaker 2010). In a long-term study of P. kirkii in Jozani forest, all copulations observed were between members of the same social group (Siex 2003; Struhsaker 2010). Zanzibar red colobuses are multiple mounters, meaning that one or more incomplete mounts precede the mount during which ejaculation occurs. During a mount, the male delivers pelvic thrusts and then pauses when ejaculation occurs. In contrast to most cercopithecids - in which the male’s hindfeet grip the female’s calves during copulation - in P. kirkii, the male’s hindfeet remain on the substrate. Females have sometimes been seen to shudder and vocalize during or following copulation. Copulating pairs are harassed by other group members - usually adult males and juveniles. Harassment of the copulating pair occurs in a variety of ways, including leaping around the pair; grabbing, slapping, and twisting of the male’s head; and climbing onto the male. Harassment by adult males is likely a form of intrasexual competition, whereas harassment instigated by juveniles may represent parent-offspring conflict (Struhsaker 2010).
Mating System: polygynandrous (promiscuous)
Both sexes disperse from natal groups before any sexual activity occurs - often at an age of 37 to 52 months. Juveniles integrate into new groups before reproductive activity is initiated (Siex 2003). The age for the onset of reproductive activity has not been described in P. kirkii, but is 53 to 59 months in Piliocolobus tephrosceles and full reproductive maturity is reached after 60 months in Piliocolobus tephrosceles . In P. kirkii, females reach sexual maturity somewhat earlier than males and full reproductive maturity is attained at an estimated 4 to 5 years for females and 5 years for males (Struhsaker 2010). Zanzibar red colobuses do not have a distinct breeding season and copulations and births occur throughout the year – though births peak in distinct seasonal periods that vary somewhat between sites. In Uzi and Vundwe, most births occur during the wet season (October-December), whereas in Kiwengwa, births peak during the dry season (January-February) (Nowak and Lee 2011a). Females typically give birth to one young, though occasional twin births have been reported (Struhsaker 2010). Based on extrapolation from other Piliocolobus species, one estimate of the typical length of interbirth intervals in P. kirkii is 24 to 30 months. Another estimate based on studies of the Uzi, Vundwe, and Kiwengwa populations of the Zanzibar Red Colobus places the interbirth interval length at 28 to 36 months (Nowak and Lee 2011a).
There is evidence for paternity confusion strategies in females of Piliocolobus tephrosceles. In P. tephrosceles, female swellings are highly variable, last for long periods of time, and occur during pregnancy as well as in regular estrus cycles. Consequently, swelling size is an unreliable indicator of female sexual receptivity, and may thus hold great potential for paternity deception. Reports of infanticide by male P. kirkii has led some to speculate that Zanzibar red colobuses may employ similar paternity deception strategies (Struhsaker 2010).
Breeding interval: Breeding occurs throughout the year, but estimates of interbirth interval length range from 24 to 36 months.
Breeding season: Zanzibar red colobuses have no distinct breeding season.
Average number of offspring: 1.
Average gestation period: 5-6 months.
Range weaning age: 12 to 36 months.
Range time to independence: 37 to 52 months.
Average age at sexual or reproductive maturity (female): 4-5 years.
Average age at sexual or reproductive maturity (male): 5 years.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Young are altricial and weaning may not be complete until two years of age. Infants are carried, clinging to the belly of the mother, for 6 months. After that, infants can locomote independently but may continue to be carried by the mother for more than a year. Juveniles become relatively independent at the age of 24 to 36 months, when they are mainly self-sufficient and feed entirely on adult foods. Complete independence is achieved with dispersal from the natal group, which usually occurs at an age of 37 to 52 months (Nowak and Lee 2011a). Grooming of infants by non-mother females and allomothering (handling and carrying infants of other females) has only been reported in P. kirkii - not in any other Piliocolobus species. The degree and frequency of allomothering in P. kirkii is, however, much less than that seen in other Cercopithecidae species (Siex 2003; Struhsaker 2010). There is some evidence for differential investment by mothers in sons compared to daughters, as sons are often suckled longer than daughters. Adult males have also been observed to suckle. In other Piliocolobus species, mothers groom their sons more than their daughters and develop longer-term affiliative relationships with sons. It is suggested that mothers invest more in sons than daughters in order to increase their inclusive fitness (Struhsaker 2010).
Parental Investment: altricial ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); post-independence association with parents
The Zanzibar red colobus (Piliocolobus kirkii) is a species of red colobus monkey endemic to Unguja, the main island of the Zanzibar Archipelago, off the coast of Tanzania. It is also known as Kirk's red colobus after Sir John Kirk, the British Resident of Zanzibar who first brought it to the attention of zoological science. It is now classified as an endangered species and in the mid-1990s was adopted as the flagship species for conservation in Zanzibar. The population is still decreasing, and conservationists are attempting to work with the local government to devise a proper, effective strategy to protect the population and habitat. Challenges include the species' habitat, which is limited to the archipelago. The species has been reclassified three times; it was previously in the genus Colobus, then in the genus Procolobus, and later in the genus Piliocolobus.
The Zanzibar red colobus, Piliocolobus kirkii, population on Zanzibar, represents a population of red colobus that is believed to have been isolated on the island after sea levels rose toward the end of the Pleistocene epoch. Furthermore, it is suggested through mitochondrial analysis, that phylogenetic groups within the red colobus have been genetically isolated from another since the Pliocene.[4]
Examining cranial morphology has shown that P. kirkii has diverged from mainland Piliocolobus to its own species. It has experienced an acceleration in morphological evolution of size which is suggested to be the result of insularity on the island and environmental pressures such as competition, habitat, predation and/or resource availability. There has been no evidence for population bottlenecks in the species.[5]
The smaller cranium of P. kirkii in contrast to the mainland colobus monkey, is consistent with Foster's rule (also known as the island rule) in which the original (larger) animal becomes smaller over time when there are limited resources.[5][6] Males tend to have pedomorphic traits which include a shorter face, large orbits and an enlarged neurocranium. It is not certain how long ago and where this evolutionary change occurred.
Through molecular analyses, it is indicated that P. kirkii is more closely related to the Udzungwa red colobus (P. gordonorum) compared to other red colobus species.[7] This analysis has also placed the divergence of P. kirkii from its sister species P. godronorum at about 600,000 years ago,[8] which actually allows for an older evolutionary age compared to the previous assumption that it had become its own species around the last glacial period. The species has been reclassified twice; it was previously in the genus Colobus, and more recently in the genus Procolobus and then the genus Piliocolobus.[1][9]
An alternative common name is Kirk's red colobus after Sir John Kirk (1832–1922), the British Resident of Zanzibar who first brought it to the attention of zoological science.[10]
This Old World monkey's coat ranges from dark red to black, accented with a black stripe along the shoulders and arms, and a pale underside. Its black face is crowned with long, white hair, and features a distinguishing pink mark on its lips and nose. Also, the Zanzibar red colobus has a long tail used only for balancing—it is not prehensile.[11] Sexual dimorphism is generally decreased in the species, meaning the females have little difference in their body size and colour from their male counterparts.[5] Females usually outnumber the males in their groups. The species has a notably small cranium and rotund body shape, with males potentially reaching over 12 kg (26 lb) and females, 10 kg (22 lb).[12] In adults, highly differentiated facial features help them to distinguish each other in a group.[11]
The word "colobus" comes from Greek ekolobóse, meaning "he cut short", and is so named because of the significant reduction in size, or complete lack of an opposable thumb in comparison to other primates.[13] To make up for this, they have four long digits that align to form a strong hook, allowing them to easily grasp branches and climb.[11]
Locals on the island have called the Zanzibar red colobus kima punju which means "poison monkey" in Swahili because of their strong smell unlike other monkeys. This has caused people to hold negative views of the monkey and even to say it has an evil influence on trees on which they feed, ultimately killing the trees.[14]
The Zanzibar red colobus is found in three forests of the Zanzibar archipelago.[15] It displays a wide habit tolerance, but it is mainly an arboreal species and prefers drier areas over wet ones. Its habitats include coastal thickets and coastal rag scrub, but it can also be found in agricultural areas and in mangrove swamps; the latter provides food year-round.[15][16] When found in agricultural areas, the monkey is more used to humans and comes closer to the ground.
About 1,600 to 3,000 individuals remain,[17] and currently, 50% of the monkeys found on the islands live outside protected zones.[15][18] The largest and most significant area of protection and habitat for the monkey is in Jozani National Park, which provides 25 km2 (9.7 sq mi) of land reserve.[19] It is located on the main island and the populations here have been greatly studied in regards to both their ecology and behavior. Even so, many groups have been found in shambas (Swahili for "farmland") in close proximity to the park.[20] In these shambas adjacent to the park, higher densities of the red colobus have been reported living here in more cohesive groups, compared to inside the park reserve.[20] The incidence of some of these monkeys living permanently outside the zone of the protected park reserve can increase the endangerment of the groups.
The groups consist of up to four adult males and many adult females; typically yielding a 1:2 ratio of males to females.[15] Young of varying ages are also incorporated in the group. The number of monkeys in a group can range from 30 to 50 individuals. The species is a very social animal, and can often be observed playing and grooming during the rest periods between meals. Unlike females, in a group, males actually maintain close bonds, acting together in defense of their group and even in grooming each other.[11]
Feeding is also a group activity. It begins to feed in the morning, and is more active during the cooler parts of the day. Loud calls from males indicate the group is ready to move to another tree to feed. This monkey is mainly a foliovore, and on average, half of the leaves consumed are young leaves.[17] They also eat leaf shoots, seeds, flowers, and unripe fruit. It has also been found eating bark, dead wood, and soil.[17] It is one of the few species that do not eat ripe fruits; it has a sacculated stomach with four chambers specific for breaking down plant materials, however it cannot digest the sugars contained in mature fruits.[21] Because the monkey feeds on young leaves (though not limited to them), there are instances where it consumes charcoal, which is believed to aid their digestion of the toxins (possibly phenolic compounds) found in the young leaves of the Indian almond tree and mango tree.[17] The habit of consuming charcoal is thought to be a learned behavior presumably passed on from the mother to her offspring.[17] The presence of charcoal deposits were shown to result in these monkeys being more likely to inhabit areas that had trees as a food source that were rich in phenolics.[22] It has been noted, however, that not all populations on the islands carry out the behavior, but that it is rather mostly done by those who consume more perennial and exotic foliage.[17]
Since some populations use mangroves as a source of food, it is natural for the monkey to consume more sodium chloride (NaCl). Because of this, those populations have been observed to drink water directly from tree-holes, or licking water off of leaves. This innovative behavior shows the adaptation of the monkey to novel ecological and environmental circumstances.[16]
In the dry season, one of the staple foods, Indian almond tree, as previously mentioned, drops its leaves and can cause the monkey to go beyond park boundaries in order to extend its feeding range. This puts the already endangered colobine at more risk.[17]
Males usually reach sexual maturity at about 3–3.5 years old, while females attain it at about two years old.[11] Females approaching estrous can be easily identified because of the swelling and bright red coloration of the genital area. This signals to males that the given female is ready for mating.[11] Moreover, just prior to mating, males will use their fingers to probe the female's birth canal. This is immediately followed by sniffing the area because estrogen and progesterone can be detected by this method, further helping the male conclude if the female is indeed ready to breed.[11]
Gestation is about 6 months for colobus monkeys and one female has about 1–2 new-born every two years. Parental care is intense and often, the role is shared by multiple females of the group. It is observed that about 76% of offspring are born between September and December.[17] Infanticide has also been noted on occasion when a new male joins a given group that has infants.[15]
Research has suggested that the ability for dietary expansion, which consuming charcoal partly allows, explains the higher birth rates and densities due to resource availability.[17] Birth rates for those living in mangroves are higher than colobus monkeys living in coral rag forests.[23]
There are higher birthing rates between October–December for colobines on Uzi Island and then January–February for those in Kiwengwa, located on the eastern side of the main island.[17] Infant mortality can be significantly high with half of the infants born not reaching more than six months of age.[24] The birth rates themselves, however, are actually decreased in comparison to mainland colobus monkeys and interbirth intervals are longer as well.[20] Research has suggested that this is a consequence of disturbed habitats in which mainland colobi are not so affected.
The red colobus species have a smaller larynx compared to other members of the Colobinae subfamily. The male's call is more of an alto or soprano in contrast to the low bass of a male's in black-and-white colobus species. The Zanzibar red colobus is non-territorial in nature and as so does not typically make loud, territorial threat calls. Zanzibar red colobus distress and warning calls are the "bark", "chist", or "wheet". One of the loudest calls from the monkey is heard when he expresses his dominance over the group and when checking the sexual status of his females.[11]
The call heard most often by people in or near Jozani Forest is the 'alerting signal'. This is an attention-getting call that is derived from the progression call. Chirps and grunts are made when there are changes in the surrounding environment such as changes in weather or animal movement in proximity to the group. With most arboreal animals, there are two different alerting calls, one for when a predator is on land, and another when there is an aerial predator. However, because of the lack of larger birds of prey in Zanzibar, such calls are not often witnessed. The young, on the other hand, because of their smaller size and vulnerability, do at times make such calls when they see shadows.[11]
Because the Zanzibar red colobus is extremely social, it has a specific call for when it is alone for a certain amount of time upon which it feels vulnerable or threatened. The young are typically the ones to make such a call that sounds like a loud scream, but adults are occasionally likely (when deemed necessary) to make some variation of the call as well.[11]
A number of factors have contributed to the monkey's endangered status. First, an increase in deforestation has resulted in a significant reduction in resources and habitat; second, it is hunted for meat and pet markets. To counteract the decline in population, various attempts have been made to protect the species. In 1974, specimens were moved to Ngezi Forest on Pemba Island to try to re-establish the monkey's population.[15] It had been found, however, that 20 years after the translocation to the island only one group of Zanzibar red colobus was found and with few sightings and interviews with locals, the population was estimated to be between 15 and 30 individuals. Researchers concluded that the group had certainly survived but did not increase in number possibly due to adverse relations with humans. Some locals in Pemba hold superstitions against the monkey because of the idea that it brings bad luck upon farmers.[15] This may explain the reason that they have not significantly grown in population size.
On Uzi and Vundwe Islands, the Zanzibar red colobus is subject to extensive habitat destruction, particularly with coral rag forests. There is also reported poisoning, netting, and disappearance of monkeys as well as other with animals.[23]
Various attempts have been made for conservation of the species. One project was with the World Wildlife Fund, specifically in Menai Bay which is located just west of Uzi Island.[23] Another funded by the Wildlife Conservation Society designated the Zanzibar red colobus as the flagship species in a long-term study on population, human influence, and behaviour.[25][26]
The African Convention has played a role in the conservation of the animal by categorizing it as 'Class A.'[27] According to the document African Convention on the Conservation of Nature and Natural Resources, 'Class A' is described as:
species in Class A shall be totally protected throughout the entire territory of the Contracting States; the hunting, killing, capture or collection of specimens shall be permitted only on the authorization in each case of the highest competent authority and only if required in the national interest or for scientific purposes.[27]
It has been suggested that an important way to promote conservation of the monkey is to simply spread awareness about it – that it is not a harmful animal and that it can actually be good for the region's economy because it draws tourism. This has been the case on the island of Unguja (Zanzibar).[15] Furthermore, it would be necessary to establish and designate protected zones.
Wikimedia Commons has media related to Piliocolobus kirkii. The Zanzibar red colobus (Piliocolobus kirkii) is a species of red colobus monkey endemic to Unguja, the main island of the Zanzibar Archipelago, off the coast of Tanzania. It is also known as Kirk's red colobus after Sir John Kirk, the British Resident of Zanzibar who first brought it to the attention of zoological science. It is now classified as an endangered species and in the mid-1990s was adopted as the flagship species for conservation in Zanzibar. The population is still decreasing, and conservationists are attempting to work with the local government to devise a proper, effective strategy to protect the population and habitat. Challenges include the species' habitat, which is limited to the archipelago. The species has been reclassified three times; it was previously in the genus Colobus, then in the genus Procolobus, and later in the genus Piliocolobus.
