Demographic Structure of Zanzibar Red Colobus Populations in Unprotected Coral Rag and Mangrove Forests
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More than half of the global population of the endangered Zanzibar red colobus (Procolobus kirkii) live outside the single major protected area on Zanzibar Island. We present data on the 2 largest, discrete subpopulations living in unprotected areas at extremes of the species’ range. We compare the size and structure of 11 groups, specifically 6 core groups inhabiting interior, mature forest with 5 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 and 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 SD (the smallest reported for this species) in edge coral rag to 31.2 + 1.9 SD 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.
KeywordsHabitat fragmentation Local extinction risk Mangrove Procolobus Refuge
We thank the Department of Commercial Crops, Fruits and Forestry (DCCFF) in Zanzibar and its Director, Dr. Bakari Asseid, for support of and permission to conduct this study. For assistance in the field, we thank Aliy Abdul Rahman, Duncan Gillespie, Kirstin Siex, Mtumwa Simai, Iss-haka Hussein Abdulla, and Mwinyi Khamis Mwinyi. We thank the editors Joanna Setchell and Oliver Schülke and 2 anonymous reviewers for helpful comments on our manuscript. Thank you to Joanna Nowak for help with the study site map. K. Nowak’s fieldwork was supported by the Wildlife Conservation Society, Leakey Foundation, Primate Conservation, Inc., American Society of Primatologists, and the Leakey Trust. The monitoring of the groups in this study has continued since 2005 as part of the WCS-Zanzibar Program.
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