C 2005) International Journal of Primatology, Vol. 26, No. 3, June 2005 ( DOI: 10.1007/s10764-005-4371-1
Comprehensive Conservation Profile of Tana Mangabeys Julie Wieczkowski Received August 21, 2003; revision February 21, 2004; 2nd revision June 1, 2004; accepted August 1, 2004
Forests along 60 kilometers of the lower Tana River, Kenya, provide habitat for one of the world’s top 25 most endangered primates, the Tana mangabey (Cercocebus galeritus). There is no current accurate estimate of the mangabey population, but a 1994 census estimated the population at 1,000–1,200. Their habitat has been severely degraded since then: visual estimates indicated that 30% of the forest area has been cleared and product use has increased in >80% of forests surveyed. As the mean number of mangabey groups per forest is positively correlated with forest area and density of trees, this loss is damaging to the mangabey population. There has also been an increase in mangabey-human conflict, e.g., crop raiding, set traps, mangabeys chased by dogs. Mangabeys exhibit ecological flexibility, but behavioral data come from only a few mangabey groups. A new conservation approach is needed because past approaches, particularly the Tana River Primate National Reserve and a World Bank/Global Environment Facility Project, failed to protect the forests. The failure was mainly due to a disregard of the land-tenure issue within the Reserve, exclusion of local people from decision-making, and neglect of forests outside the reserve. Future actions must include community conservation programs and forest and corridor restoration. Research should focus on traditional management, status of primate groups in severely degraded forests, ecology of additional groups, and a population estimate to inform management as they implement more specific conservation strategies for the species. KEY WORDS: Cercocebus galeritus; Tana mangabey; Kenya; management; habitat loss.
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whom correspondence should be addressed at Department of Anthropology, 332 Pafford University of West Georgia, Carrollton, GA 30118; e-mail:
[email protected]. 651 C 2005 Springer Science+Business Media, Inc. 0164-0291/05/0600-0651/0
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INTRODUCTION The forests of the lower Tana River in southeastern Kenya (1◦ 40 to 2 15 S, 40◦ 07 E, the 60-km distribution of the Tana mangabey; Fig. 1) are the most important primate conservation area in Kenya (Kenya Section of the IUCN/SSC Primate Specialist Group and the Kenya Primate Conservation Group, 2000). The forests are designated thus because they are habitat for 2 endemic and critically endangered primate species (Butynski et al., 2000a, 2000b): Cercocebus galeritus (Tana mangabey) and Procolobus rufomitratus (Tana River red colobus). The mangabey is also on the 2002 list of the top 25 most endangered primate species (Mittermeier and Konstant, 2002). The most recent census (1994) estimated the mangabey population as 1,000–1,200 individuals in 48 groups (Butynski and Mwangi, 1995). I summarize what we know to date about the conservation status, ecology, and management of Tana mangabeys. Data on threats against them are from published and unpublished work and includes quantitative (forest loss) and qualitative (forest product use, human-mangabey conflict) measures. Information on mangabey ecology are from studies undertaken by Katherine Homewood in 1973–74, Margaret Kinnaird in 1987–89, and Julie Wieczkowski in 1998–2001. For information on past conservation action, I relied on Clive Marsh’s 1976 management plan for the Tana River Primate National Reserve (TRPNR; Fig. 1) and the World Bank’s Tana GEF project document. The information is supplemented with personal observations and published accounts of dialogue with the local communities. Finally, suggestions for future action are based on information presented and on my experience in Tana River. ◦
THREATS TO TANA MANGABEYS The classification of Cercocebus galeritus as one of the world’s most endangered primates is based on their limited distribution, and recent extreme anthropogenic loss and degradation of their forest habitat (Wieczkowski and Mbora, 1999–2000). Forest in the lower Tana River occurs in ca. 62 forest fragments, measuring from 1 to 408 ha and covering 2,616 ha in total (Butynski and Mwangi, 1994; Fig. 1). Forest loss results from forest clearance for farmland. Forests are established on the most productive soils; therefore, forest land is also the most valuable for farmland. Much of the recent forest clearance, however, has been a response by the local people to conservation activities. Forest degradation results from forest product use by the local people. The most destructive activities are the felling of canopy trees to
Fig. 1. A map of forest fragments along the 60-km distribution of Tana mangabeys (Cercocebus galeritus), lower Tana River, Kenya. Adapted from Mbora and Meikle (2004).
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construct canoes and to collect wild honey, harvesting of palm fronds to make thatching and mats, cutting of subcanopy trees to use as housing poles, and topping of Phoenix reclinata to collect palm wine. Butynski and Mwangi (1994) had visually estimated forest area during their primate census by measuring width between survey transects and estimating length of the transects. In 1999–2000, Wieczkowski and Mbora (1999–2000) collected data similarly during primate surveys and found a drastic loss of forest area since 1994. Eight forests that suffered the most clearance lost 769 ha, or 54% of the 1994 forest area, which represents 30% of the total forest cover in 1994. If the forest loss is measured in reference to the TRPNR, there was a 20% loss of forest inside and a 41% loss outside. In an assessment of forest loss between 1992 and 2000 via Landsat images, Tabor et al. (unpub. data) found a 9.9% decline in forest cover within the TRPNR and an 11.7% loss of forest cover in the lower Tana River. Their analysis extended 23 km north of the primates’ distribution. Because much of the forest destruction was a reaction to conservation activities, the inclusion of nonprimate habitat may underestimate forest loss within the area of conservation concern. Wieczkowski and Mbora (1999–2000) also compared changes in the level of forest product use in 12 forests between 1994 (Butynski and Mwangi, 1994) and 1999–2000. In both studies, forest product use was subjectively classified as light, moderate, heavy, very heavy, or extreme. In 1994, 10 of the forests suffered from light or moderate human activity. In 1999–2000, the level of human activity had increased in the 10 forests and all 12 forests suffered from heavy, very heavy, or extreme forest product use. Eleven of the 12 forests are within the TRPNR. As many of the tree species used heavily by the mangabey as food resources (Homewood, 1978; Kinnaird, 1990) are also used most by the local people (Medley, 1993), forest product use directly affects the resources available to the mangabeys. With forest loss and degradation comes another potential threat, mangabey-human conflict. I observed a mangabey group raiding crops, traps set by farmers to catch crop raiders, and mangabeys being chased by dogs (Wieczkowski and Mbora, 1999–2000). Because there is no mention of similar observations in the literature or from previous researchers, mangabey-human conflict appears to be on the increase.
MANGABEY ECOLOGY Behavioral and ecological research on Tana mangabeys showed that they exhibit a great deal of flexibility, which may allow them to adapt to habitat change (Homewood, 1976; Kinnaird, 1990; Wieczkowski, 2003). It
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may also be the likely reason why there has been no decrease in mean group size as occurred among Tana River red colobus (Wieczkowski and Mbora, 1999–2000). Mean mangabey group size has increased from 20.5 (Kinnaird and O’Brien, 1991; n = 7) to 30.4 (Wieczkowski and Mbora, 2002; n = 17). Although restricted to floodplain forest, the mangabeys appear to have general habitat needs. Of 10 forest attributes investigated, variation in the mean number of mangabey groups per forest is explained primarily by forest area and secondarily by density of trees ≥10 cm diameter at breast height (Wieczkowski, 2004). Other forest structural measures, i.e., mean tree height, basal area of trees, area of canopy cover, or basal area of harvested trees, and measures of food abundance, i.e., basal area of the top 15 food species, Phoenix reclinata, Ficus sycomorus, or harvested P. reclinata, did not influence mangabey abundance. Flexibility in ranging behavior also occurs. The mangabeys can compensate for a lower per capita density of food trees by increasing their home range, specifically by including additional forests (Wieczkowski, 2003). Although the flexibility in home range size was studied in the context of a group that had increased in size, it may also serve the mangabeys in situations when there are natural or anthropogenic declines in food abundance. Homewood (1976) observed mangabeys changing their ranging patterns to take advantage of fruit production by a dietary species, viz., temporarily moving to another forest fragment where the species was locally abundant. The ability of mangabeys to move through nonforest habitat to reach a neighboring forest (Kinnaird, 1992b; Wieczkowski, 2003) may also be critical in their response to habitat loss and degradation. The mangabeys also exhibit flexibility/lack of specificity in dietary species and item choice on both spatial and temporal scales (Homewood, 1978; Kinnaird, 1990; Wieczkowski, 2003). In addition, contrary to existing characterizations, the mangabeys are not ripe fruit specialists. Instead, for several important dietary species, they consume ripe fruit, ripe seeds, unripe fruit, and/or unripe seed in positive correlation with availability (Wieczkowski, 2003). In view of the seasonality of overall fruit production and the various fruiting schedules of individual dietary species (Homewood, 1976; Kinnaird, 1992a), the flexibility in dietary species and item may allow them to consume adequate resources throughout the year. It may also allow them to better respond to anthropogenic habitat changes. Tana mangabeys are not unique among primates in their ability to adapt to habitat change. They are similar to other African forest species that have exhibited persistence in changed or fragmented habitats in generality and flexibility in diet, e.g., Cercopithecus mitis labiatus (Lawes, 2002);
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´ various other Cercopithecus spp. (Ukizintambara and Thebaud, 2002), or in ability to change home range size or travel through the matrix (Cercopithecus ascanius: Chapman and Onderdonk, 1998; C. cephus and C. nictitans: Tutin et al., 1997; Lophocebus albigena johnstoni: Olupot et al., 1994).
PAST CONSERVATION ACTION In 1976, the Kenya government gazetted 169 km2 as the Tana River Primate National Reserve (TRPNR) to protect Tana River red colobus, Tana mangabeys, and their forest habitat (Marsh, 1976; Fig. 1). Although the TRPNR is officially a County Council Reserve and falls under the management of the Tana River County Council (TRCC), the TRCC has given management authority of the reserve to the national wildlife management organization, Kenya Wildlife Service. As per its designation as a reserve (and not a national park), human activity is allowed within the TRPNR’s borders (Government of Kenya, 1976, 1989). The main management concern for the TRPNR at the time of gazettement was the presence of people living and farming within its borders (Marsh, 1976). Although this problem was recognized by the TRCC in a resolution that would have compensated people for moving from the TRPNR, very few people left the TRPNR and those who did received no compensation. Subsequently, in 1991, a population and habitat viability assessment (PHVA) (Seal et al., 1991) concluded that in order to protect the lower Tana River in the long-term, the people living and farming within the TRPNR would have to be relocated (World Bank, 1996). The 1991 PHVA was the first step of a World Bank-funded US$6.2 million Tana Global Environment Facility (GEF) Project (World Bank, 1996). The project ran from 1996–2001 and included 3 components: Reserve Management, Research and Monitoring, and Community Conservation and Development. The objective of the GEF Project was conservation of the biodiversity of the lower Tana via improved management. As per the recommendations of the PHVA, one of the project’s exercises was the voluntary relocation of families within the TRPNR to land outside the area of conservation concern. The relocation exercise became the focus of the entire GEF Project, and ultimately its demise due to delayed implementation of and lack of resources for the Reserve Management and Research and Monitoring components; neglect of enforcement patrols, ecological monitoring, and dialogue with the community; mistrust and misunderstanding on the part of the local people (both those involved with and outside the Project); and the severe escalation in forest clearance between 1994 and 1999–2000 (Mbora, 2000a,
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2000b). The only conservation goal of the Project that was achieved was the production of a 5-year management plan. Not a single person relocated. Conservation of the forests and primates of the lower Tana River has not been very successful, as evidenced by the recent forest destruction, especially within the protected TRPNR (Wieczkowski and Mbora, 1999– 2000), which can be attributed to the failure to properly address the issue of people living and farming within the TRPNR since its gazettement, the exclusion of the local people from management decision-making and dialogue/information about the Tana GEF Project, and lack of research and management in forests outside the TRPNR. The last is a detrimental oversight in such a small ecosystem as the lower Tana River. The fate of Nkanjonja Forest illustrates what can happen when the focus is on one management issue (relocation of the human population) within the TRPNR, when information is not disseminated, and when an ecosystem approach is not taken. The 500-ha Nkanjonja Forest, just north of the TRPNR on the east bank, was habitat for 8% of the mangabey population (Butynski and Mwangi, 1994). The people living in the neighboring village were not included in the relocation exercise (they do not depend directly on the resources of the TRPNR), but the fear of being relocated did not escape them. Consequently, they cut down the entire forest (Wieczkowski and Mbora, 1999–2000; Mbora, 2000a). The people reasoned that if there was no forest, there would be no monkeys, and the World Bank would not want to relocate them. Although the people of Nkanjonja were not included in the relocation exercise, they and the forest were included in the GEF Project area (World Bank, 1996). The destruction of the Nkanjonja Forest during the Tana GEF Project should never have occurred.
SUGGESTED CONSERVATION AND RESEARCH ACTION In view of recent forest destruction and findings that mangabey abundance is associated with forest area and density of trees, habitat protection must be top priority. The national moratorium on cutting indigenous forest must be enforced both inside the TRPNR and in forests outside. Forest product use must be managed within the TRPNR. In addition, management and local communities should undertake forest restoration activities to enlarge forest fragments, provide additional food resources, and connect isolated fragments. Conservation in the lower Tana River must include forests outside the TRPNR. Forty-four percent of the mangabey groups and 66% of the red colobus groups are in forests outside the TRPNR (Butynski and Mwangi,
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1994). Furthermore, Wieczkowski (2004) and Mbora and Meikle (2004) found that forests outside are larger or comparable in certain habitat attributes, e.g., density of trees, basal area of trees, basal area of mangabey food trees, basal area of colobus food trees, to forests inside. Although protected areas are successful in biodiversity protection (Bruner et al., 2001), the recent forest destruction in Nkanjonja and elsewhere (Mbora, 2000a, 2000b) and threats by the local people to cut down the forest or kill the primates if research resulted in extension of reserve boundaries (D. Mbora, pers. comm.; pers. obs.) call for an alternative to strict protection (gazettement) outside the TRPNR borders. Research on the human population is needed, with the aim of understanding the socioeconomic context of resource use (Cowlishaw and Dunbar, 2000), assessing the potential success or failure of community-based conservation and education programs following the criteria of Becker and Ostrom (1995) and Salafsky et al. (2001), and reviving traditional forms of management. Knowledge of mangabey ecological flexibility is critical to their conservation because this flexibility may allow them to withstand habitat change. Three studies of Tana mangabeys show a large amount of flexibility; however, they were undertaken on only 3 groups in relatively undisturbed forests. Forests of the lower Tana River are extremely variable in specific composition, forest structure, and level of human impact (Hughes, 1990; Medley, 1992). Behavioral and ecological research on mangabeys should expand into more forests in order to increase the habitat diversity in which we observe the full range and limitations of their behavior and ecology and to more fully understand their responses to anthropogenic habitat change. In addition, the status of mangabey groups in severely degraded forests must be investigated. A complete population estimate must also be made. ACKNOWLEDGMENTS My primary research was made possible through research permission from the Government of Kenya (permit OP/13/001/27C 90), and research affiliation from Kenya Wildlife Service. The research was funded by The Wildlife Conservation Society, Margot Marsh Biodiversity Fund, Conservation International’s Primate Action Fund, and Primate Conservation, Inc. The research would not have been possible without the support of the people of Tana, especially the field assistants who contributed to data collection: Abio Gafo, Hassan Jillo, Michael Moroa, John Kokani, Galana Galole, Galana Jumaa, Komora Phanuel, and Zakaria Maro. My work and this manuscript have benefited greatly through discussions with Dr. David Mbora. Three anonymous reviewers commented on a draft of this
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manuscript. Finally, I thank Dr. Mary Glenn and Lindsay Magnuson for organizing the Conservation of African Monkeys symposium at the 2003 American Society of Primatologists meeting, for which this manuscript was written. REFERENCES Becker, C. D., and Ostrom, E. (1995). Human ecology and resource sustainability: The importance of instituitional diversity. Ann. Rev. Ecol. Syst. 26: 113–133. Bruner, A. G., Gullison, R. E., Rice, R. E., and da Fonseca, G. A. B. (2001). Effectiveness of parks in protecting tropical biodiversity. Science 291: 125–128. Butynski, T., and Members of the Primate Specialist Group. (2000a). Cercocebus galeritus ssp. galeritus. In: IUCN. (2003). 2003 IUCN Red List of Threatened Species. www.redlist.org. Downloaded on 17 February 2004. Butynski, T., and Members of the Primate Specialist Group. (2000b). Procolobus rufomitratus. In: IUCN. (2003). 2003 IUCN Red List of Threatened Species. www.redlist.org. Downloaded on 17 February 2004. Butynski, T. M., and Mwangi, G. (1994). Conservation Status and Distribution of the Tana River Red Colobus and Crested Mangabey. Unpublished report for Zoo Atlanta, Kenya Wildlife Service, National Museums of Kenya, Institute of Primate Research, and East African Wildlife Society. Butynski, T. M., and Mwangi, G. (1995). Census of Kenya’s endangered red colobus and crested mangabey. Afr. Primates 1: 8–10. Chapman, C. A., and Onderdonk, D. A. (1998). Forests without primates: primate/plant codependency. Am. J. Primatol. 45: 127–141. Cowlishaw, G., and Dunbar, R. (2000). Primate conservation biology, The University of Chicago Press, Chicago. Government of Kenya. (1976). The Wildlife (Conservation and Management) Act, 1976, Kenya Gazette Supplement, Nairobi. Government of Kenya. (1989). The Wildlife (Conservation and Management) Act, 1989, Kenya Gazette Supplement, Nairobi. Homewood, K. M. (1976). Ecology and Behaviour of the Tana Mangabey (Cercocebus galeritus galeritus), Ph.D. Dissertation, University College, London, London. Homewood, K. M. (1978). Feeding strategy of the Tana mangabey (Cercocebus galeritus galeritus) (Mammalia: Primates). J. Zool. Lond. 186: 375–391. Hughes, F. M. R. (1990). The influence of flooding regimes on forest distribution and composition in the Tana River floodplain, Kenya. J. Appl. Ecol. 27: 475–491. Kenya Section of the IUCN/SSC Primate Specialist Group and Kenya Primate Conservation Group. (2000). Joint recommendations of the Kenya Section of the IUCN/SSC Primate Specialist Group and of the Kenya Primate Conservation Working Group for emergency action to conserve the forests, primates, and biodiversity of the lower Tana River, Kenya. Unpublished report to World Bank and Kenya Wildlife Service. Kinnaird, M. F. (1990). Behavioral and Demographic Responses to Habitat Change by the Tana River Crested Mangabey (Cercocebus galeritus galeritus), Ph.D. Dissertation, University of Florida, Gainesville, FL. Kinnaird, M. F. (1992a). Phenology of flowering and fruiting of an East African riverine forest ecosystem. Biotropica 24: 187–194. Kinnaird, M. F. (1992b). Variable resource defense by the Tana River crested mangabey. Behav. Ecol. Sociobiol. 31: 115–122. Kinnaird, M. F., and O’Brien, T. G. (1991). Viable populations for an endangered forest primate, the Tana River crested mangabey (Cercocebus galeritus galeritus). Conserv. Biol. 5: 203–213.
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