Abstract: The endangered Zanzibar red colobus Procolobus kirkii is endemic to Unguja, the southern main island of the Zanzibar archipelago. Over half of the total population inhabits unprotected areas but these are little studied. We surveyed two discrete subpopulations of P. kirkii and sympatric Sykes monkeys (Cercopithecus mitis albogularis) for 14 mo between February 2004 and September 2005 in the northernmost (Kiwengwa-Pongwe Forest) and some of the southernmost (Uzi and Vundwe Islands) parts of the species range, in unprotected areas in indigenous habitat types. Surveys totalled 365 hours and 307.8 km along >16 km of line transects, and 472 sightings of both primate species were made (n colobus = 252, n Sykes = 220). P. kirkii was found to be more abundant than previously estimated, with the southern mangrove-adjacent coral rag forest supporting a higher overall colobus density at 17.7 groups/km2 than northern coral rag thicket at 3.7 groups/km2. These two regions likely support the two largest subpopulations of red colobus and Sykes after Unguja’s single protected area, the Jozani-Chwaka Bay National Park, with which there is little evidence for gene flow, although some limited corridor potential between Uzi Island and Jozani remains and there exist plans for a Jozani-Kiwengwa Regeneration Corridor. Plant stem density but not basal area was found to be a significant predictor of monkey density. We describe the possible role of mangrove as refuge and source habitat for red colobus, and urge that mangrove habitat be considered in conservation action plans and corridor planning.
Abstract: More than half of the global population of the endangered Zanzibar red colobus Procolobus kirkii live outside the one major protected area on Zanzibar Island. We present data on the two largest, discrete subpopulations living in unprotected areas at extremes of the species’ range. We compare the size and structure of 11 groups, specifically six core groups inhabiting interior, mature forest with five peripheral groups living in disturbed / degraded edge habitats. Groups living in southern mangrove forest – a species-poor but more productive and less seasonal habitat than coral rag thicket – had larger group sizes, more heterogeneous age structure, were more stable and had higher rates of infant survival than did groups in northern coral rag. Group size ranged from 5.5 ± 1.6 S.D. (the smallest reported for this species) in edge coral rag to 31.2 + 1.9 S.D. in core mangroves. Edge groups were significantly smaller than core groups in northern coral rag while in the south, where all groups had access to mangroves, we found no significant difference in mean group size between edge and core areas. Groups using mangroves exhibited frequent social play, an indicator of habitat quality, and had a higher ratio of births per female per year. We suggest that mangroves are an important refuge and possibly source habitat for Zanzibar red colobus. We urge the conservation of mangrove and remaining coral rag in the unprotected areas described here in an effort to sustain this endemic species throughout its range.
Abstract: We investigated the role of geographical insularity in divergence and
speciation of Procolobus kirkii by examining cranial morphology. The sample (n=
369) included museum specimens of Procolobus spp. and recently deceased
individuals of P. kirkii from the main island of Zanzibar and 2 smaller islands in
the archipelago. Geometric morphometrics evinced pronounced divergence of
Procolobus kirkii from mainland Procolobus, including members of P. badius ssp.,
P. pennantii ssp., P. rufomitratus, P. gordonorum and also representatives of the
assemblage of red colobus populations from Central Equatorial Africa. Procolobus
kirkii has a small cranium, consistent with the island rule for large mammals,
reduced sexual dimorphism consistent with Rensch’s rule, and a distinct cranial
form. Analyses of phenotypic variance of Procolobus kirkii gave no evidence for
population bottlenecks in the history of the species, but there is a clear indication that
the species has experienced accelerated morphological evolution of size, probably as a
result of insularity. Their highly distinctive morphology lends weight to the argument
that they are a unique insular endemic species in need of active conservation.
Abstract: Isolated populations of Procolobus kirkii on Uzi Island, Zanzibar, use Rhizophora mucronata dominated mangrove forest for refuge. Three groups, observed over 14 months, spent up to 85% of total observation time in mangroves with brief excursions to adjacent upland coral rag forest, habitat degraded by human cutting. A large proportion of monkeys’ diets consisted of plant parts of five mangrove species. Water drinking was common and 326 water-drinking events were recorded at a rate of up to 0.87 drinks/hr. Groups used different strategies to obtain water including licking dew, drinking from treeholes, licking rain off leaves and tree trunks, and drinking from coral rock crevices with Cercopithecus mitis albogularis. Drinking frequency increased with time spent in and consumption of mangroves. Strategies for obtaining water were group-specific and likely the result of
learning. Drinking appeared to be an acquired behavior in movement-restricted groups living in a habitat with low plant species diversity and limited salty foods.
Abstract: Members of many Old World primate genera use swamp forest regularly, seasonally or opportunistically. With widespread deforestation in the Afrotropics, an ability to exploit swamp forests for forage and refuge may contribute to the population persistence of threatened primate taxa. Flexibility in habitat use and the capacity to introduce novel foods to the diet are hallmarks of most primates, although some groups such as the colobids, have been categorized as ‘specialists’ due to their morphology and digestive physiology which restrict their capacity to exploit specific foods. The ‘specialist’ Temminck’s red colobus monkey in Senegal uses mangroves for shelter and forage as part of its adaptive capacities. Here, we compare the density, demography, and behavioural flexibility of two Zanzibar red colobus subpopulations living in human-disturbed habitats, one with and one without access to mangrove habitat. Groups in a mangrove-coral rag matrix had a mean group size of 22 individuals, more heterogeneous age structure, were more stable and had higher rates of infant survival compared with groups in coral rag with a mean group size of 13. Red colobus density was higher at the mangrove site, at 18 groups/km2, than at the coral-rag-only site with 4 groups/km2. Near-exclusive use of mangroves by Zanzibar red colobus was associated with innovative behaviour, including frequent water-drinking, terrestrial locomotion, and retreat into mangroves during high tide when the habitat was inaccessible to humans. The species’ ability to shift habitats, diet and activity budgets to exploit mangroves in response to disturbance of upland, colobus-preferred, coral rag forest brings its classification as a specialist into question. We hope to highlight 1) the potential importance of mangrove and other swamp forests for primates where terrestrial forest fragments are heavily disturbed, and 2) the behavioural plasticity of primates traditionally considered to be specialists.
Abstract: Specialization is considered to be the major correlate of extinction risk in primates; however, rather than trying to identify the traits that predispose species to extinction, studying populations that survive episodes of chronic biological impoverishment provides a new perspective. Field studies on behavioural adaptations and learning suggest that a capacity for flexibility in local responses to disturbance could buffer some so-called specialists against that disturbance. This thesis sets out to explore specifically these issues of learning, flexibility and biological resistance in the context of disturbance in two populations of Zanzibar red colobus monkeys (Procolobus kirkii). Colobus monkeys are ideal for such study because they are considered to be rare, specialized forest-dwellers, which nevertheless occupy a wide variety of habitats in groups that range from some
of the smallest to the largest recorded for arboreal forest primates. This study documented behaviour of the Zanzibar red colobus from June 2003 to September 2005 in two ecologically distinct and geographically separate sites. In coastal thicket, the typically foliage-eating, tree-dwelling monkeys were observed to become synchronised and opportunistic feeders, occasionally descending to the ground. They shared a communal range in fission-fusion subgroups, associated with Sykes monkeys (Cercopithecus mitis albogularis) in the presence of humans, and fed on succulent leaves of primitive
plants (cycads). In mangrove forest, groups spent up to 85% of their day in the mangroves, which act as refuges where surrounding coastal thicket has become severely degraded. They formed cohesive groups in small ranges of as few as 2.55 hectares with little overlap. Near-exclusive use of mangroves by colobus required clambering over prop roots with observance of tides. Mangrove plant parts were staple foods and made frequent drinking of brackish water necessary (up to 0.87 drinking events hr-1). The development of these unusual behavioural strategies, along with other highly innovative behaviour, may aid in maintaining these marginal populations of P. kirkii. Greater survivorship of infants to juvenility and significantly larger group sizes were found in mangroves than in coastal
thicket. The mangrove site also supported a higher overall colobus density (118 individuals/km2) than the coastal thicket (24 individuals/km2), suggesting that mangroves serve as refuges and potentially as re-population centres for these as well as other colobus species (e.g. P. badius temmincki in Senegal). While there is no question that variation in plastic responses exists among species and that extinction risk is non-random, the so-called intrinsic specialization of colobus, and that of primates in general, appears to be moderated by flexible and learned behaviour and may not represent a useful species trait in comparative analyses of vulnerability to extinction. Furthermore, the use of red colobus as indicators of the health of Africa's rain forests and assumption that primates in general are reliable indicators of the effects of disturbance on communities needs to be balanced with their capacity to adjust behaviourally in both the short- and long-term to diminish the effects of environmental heterogeneity and stochasticity.
Abstract: Uzi and Vundwe Islands contain a significant and behaviourally and ecologically unique population of the endangered Zanzibar red colobus (Procolobus kirkii). Recent surveys found that the conservation status of this flagship species and its habitat on these islands is critical and requires immediate action. Reported poisoning and disappearance of colobus, netting of monkeys and other animals, and widespread and extensive destruction of coral rag forest are ongoing. A collective effort will be needed to protect these monkeys and their habitat, and inform and mobilize the community. Recommendations include immediate initiation of the process to gazette southern Uzi and Vundwe Islands as a Forest Reserve; support on the ground for the local forestry officer to establish a community based forest conservation project; and assistance to the community in developing primate-focused
nature tourism and other income-generating activities.
Abstract: Savanna elephants of eastern and southern Africa have been well-studied in open habitats, while their ecology in relatively closed habitats remains poorly understood. In Tanzania, savanna elephants make extensive use of forested habitats in at least three montane regions, including the species-rich Udzungwa Mountains where human-elephant conflict is escalating. Traditional elephant corridors between the Udzungwas and the surrounding Protected Areas of Selous Game Reserve and Mikumi and Ruaha National Parks are rapidly being lost to agriculture and settlements, and the perceived increase in and conflict with elephants may be an outcome of population compression. The potential consequences for biodiverse forest habitats of confining a potentially increasing population of an ecosystem engineer well known for modifying its habitat in non-forested sites, are in urgent need of investigation. We have begun the first study of this population by assessing distribution, population structure, diet and seed dispersal using counts and analysis of elephant dung (n>2000 piles) along approximately 300km of transects across the Udzungwa Mountains. Of the various techniques developed for non-invasive age estimation, the use of dung bolus diameter is arguably the most promising. Using dung bolus diameter to estimate age of individual elephants and thus population structure is simple, low-cost and has great potential for ranger-led studies of elephants in closed habitats. To date, however, this method has been used in only a small number of sites, and has only been attempted in a single central African forest site. We used over 300 measures of dung bolus diameter in the Udzungwas to predict age using a von Bertalanffy equation derived from Amboseli, Kenya, which models the growth relationship of dung diameter with known age. The results are promising, with preliminary age structure supporting the hypothesis of a growing population in the Udzungwas. This method has considerable potential as a conservation research tool for elephant populations in forest elsewhere in Tanzania, and across Africa, though its precision and accuracy require further tests. The ultimate goal of our study is to establish a long-term elephant monitoring programme in this Eastern Arc forest.
Abstract: Swamp forests may play a major role as refuges for primate and felid species where these taxa are threatened with habitat loss. Mangroves and peat are often impenetrable and wet habitats, inaccessible and uninhabitable to humans. These habitat types are neglected in field studies compared with relatively species-rich forests probably because of the difficulties associated with surveying them. As a result, maps of primate and felid distributions may overlook these habitats. Although mangrove and peat face threats from logging and land conversion, in some regions they may be the most important remaining habitats for endangered primate and felid species. Presented is a preliminary literature review of mangrove- and peat-dwelling primates and felids in Africa and Asia. Records are categorized as representing animals' 1) historical occupancy of the habitat (notably proboscis monkeys and Bengal tigers), 2) potential recent niche shifts in response to human disturbance, 3) temporary or seasonal extensions of range for feeding or shelter, 4) dispersal or movement between other habitat types and 5) exploratory behaviour. Behavioural adaptations to living in swamps are described. Significance of these habitats to primate and felid conservation is discussed.
