The Conservation Biology of the Leopard Panthera Pardus in Gabon: Status, Threats and Strategies for Conservation
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The conservation biology of the leopard Panthera pardus in Gabon: Status, threats and strategies for conservation Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultäten der Georg-August-Universität zu Göttingen vorgelegt von Philipp Henschel aus Lich Göttingen, den 8. Dezember 2008 D 7 Referent: Prof. Dr. Michael Mühlenberg Korreferent: Prof. Dr. Stefan Scheu Tag der mündlichen Prüfung: In loving memory of Marion Andresen Abstract The leopard (Panthera pardus) has the greatest geographic distribution of the wild cats, and is the most abundant large felid in Africa. Tropical rainforests comprise a large part of the leopard’s range in Africa, and the forests of the Congo Basin in particular have long been considered an important stronghold for the species. While known leopard prey ranges in size from arthropods to the largest ungulates, recent studies suggest that leopards preferentially prey upon species within a weight range of 10-40 kg. In the rainforests of the Congo Basin, species within this weight range are also strongly preferred by bushmeat hunters, creating the possibility that leopards and humans are in direct competition for the same prey. However, baseline knowledge of leopard ecology and responses to human disturbance in African rainforests remain largely unknown. In the present study I investigate how leopard populations respond to competition for prey with hunters. My two principal hypotheses are that (1) leopards exhibit a functional response at hunted sites and switch to smaller, less preferred prey where larger prey species have been depleted; (2) leopards exhibit a numerical response at hunted sites and occur at lower population densities where larger prey species have been depleted. To test this, I collected leopard scats and camera trap data in four rainforest sites in central Gabon exposed to varying levels of anthropogenic disturbance. Hunting intensity is generally highest in the vicinity of settlements, and my four study sites were therefore situated at varying distances from settlements. I analysed camera trap data using capture-recapture models to estimate leopard densities, and employed occupancy modelling to investigate the factors affecting leopard distribution. Mean leopard prey weight and leopard population density were positively correlated to distance from settlements. Occupancy modelling revealed that leopard use of an area increased with prey abundance and distance from settlements. The results of this study imply that leopards in the African rainforest exhibit a strong functional and numerical response to competition with hunters for prey, and that leopards are absent in the direct vicinity of settlements where hunting is most intense. I present a simple geographic leopard population model to identify priority areas for leopard conservation in the Congo Basin. i ii Acknowledgements Acknowledgements This study would not have been possible without the help of a multitude of different individuals, whose help along various stages of this study I want to acknowledge here. First of all I would like to thanks my parents, for instilling a profound love for nature in me at a very early stage, and for their distinct interest in my work and their continued support for it, despite the fact that it resulted in long periods of separation from them. Furthermore, I am grateful to Günther Merz for inspiring my interest in working in Gabon, and Pauwel de Wachter for giving me my first job in this extraordinary country. My PhD supervisor, Michael Mühlenberg, became an immediate supporter when I told him about my plans to study leopards in Gabon for my degree, and I greatly appreciate all his help, his amicable supervision and strong interest in my study. In Gabon, Kate Abernethy, my field supervisor, and Lee White were equally enthusiastic to kick-start this study on leopards, and I am deeply grateful for their friendship and their permanent support during my years in Gabon. Stays at the Station d'Etudes des Gorilles et Chimpanzés (SEGC) in Lopé and all the long discussions we had there were extremely inspiring and motivating, and I am very grateful that I had this opportunity. Lee, as the director of the Wildlife Conservation Society (WCS) Gabon Program, also invited me into the WCS-Gabon family (when it still was one), which guaranteed me the vital logistical support so dearly needed for the functioning of this study. For the permission to work in Gabon and its spectacular national parks I want to express my gratitude to Gabon’s Ministry of Forestry, Water and Fishing, and in particular to Adrien Noungou, Director of Wildlife and Hunting, as well as to the country’s National Parks Board, and in particular its then permanent secretary, René Hilaire Adiahéno. In Ivindo NP, Nigel and Isabelle Orbell welcomed me into their home whenever I came through the park’s HQ, and their friendship and wonderful company made my stay in this fantastic park an even better one. Their door (including the one of their fridge) was always open for me after lengthy stays in one of my field camps, and I likewise want to thank their fantastic kids, Claire and Michael, for accepting me as their “foster-brother”. Nigel organized all my logistics in Ivindo, and I am extremely grateful for the incredible support he managed to provide under the very demanding logistical conditions. Also in Ivindo, Thomas Gilbert joined me as a voluntary research assistant for a couple of months, and I greatly appreciate his enthusiastic and professional help and pleasant company. iii Acknowledgements While working in my remaining study areas near the town of Koulamoutou, Lauren Coad provided me with a base and shared her room in Koulamoutou and her house in the village of Dibouka with me. Her friendship and her moral and logistical support made the often disheartening fieldwork in these heavily hunted study areas less difficult – cheers Loz! I am also grateful to the people of Dibouka, for accepting yet another weird “blanc” into their small village community, and for their warm and welcoming attitude towards me. Thanks also to Lauren’s field assistants, Wilson, Arthur and Jean-Felix, for their help in my first site there, and to Crystel, Anas, Chaud and “mon parent” Socrates for their great company. Budgetary constraints did not allow me to hire any Gabonese research assistants, camp aids or the like, and fieldwork was hence almost invariably carried out alone. But I want to use this space, freed up as I don’t have to thank any field assistants, to express my gratitude to the Gabonese people in general. So many individual Gabonese have helped me, encouraged me, entertained me and shared their thoughts with me during random encounters all across Gabon, and the exceptionally open and welcoming nature of the Gabonese is one of the reasons why I liked working in this country so much. Organizing logistics in this country can be challenging though, and for all the logistical support I’d like to thank the entire WCS Gabon crew and people from SEGC in Lopé, and especially Heaven, Olga (si tu m’entends, grande sœur), Linda, Annie, Olly and Pierre in Libreville, and Kath, Constant, Papa Jules and Malcolm in Lopé. And a special thanks to Bryan, for using his famed organizational talent on more than one occasion to my advantage, to acquire dearly needed items for my work, like a motorbike for the work outside the parks or additional funding to replace stolen camera traps. In Gabon, I would also like to thank my colleagues-turned-friends whom I did not mention earlier, as they might not have played an integral part in the accomplishment of this very study, but whom I want to thank for many great discussions and for being friends. In particular these are, by order of first appearance, Ludo, my Lopé “family”, Collette, Ed, JT and Pélagie, Natu, Miguel, Raul, the boys, Rich, Josh and JG (thanks also for your open door in LBV), Eric, Paul and Trish, Liz and Paul A., and Romain. The fieldwork on leopards was wholly financed by WCS, New York (a special thanks to donors Michael Cline and Bob Spehar for their generous contributions!), and the one person who really made this happen is Justina Ray. She fought the first battles for me in iv Acknowledgements NY to secure funding for my study, in a time where other species of big cats are more critically endangered than the leopard, and for a region where almost all conservation work has traditionally been focused of forest elephants, gorillas and chimps. Against many odds, she managed to convince people that leopards in the Congo Basin rainforest might disappear unnoticed from large tracts of forest due to uncontrolled hunting, as did tigers all across tropical Asia, and that there is a need to invest funding now to gather crucial evidence for this alarming trend. Justina also aided in the design of the study, and I am extremely grateful for all her help and support during the early stages of this study. When Justina moved to her new position with WCS in Canada, Luke Hunter “inherited” me from her, and has been an incredible help since then. Nobody has read more draft versions of my various reports, articles and thesis chapters, and I extremely grateful for all the constructive comments, and for his time and patience. Luke and Panthera, NY, also secured funding for the surveys on lions mentioned in this thesis, and I also want to thank Nicole Williams from Panthera for her help in organizing those surveys and in other issues. I am also grateful to Matt Hayward, for inviting me to present a talk at his symposium on large carnivore reintroduction at the SCB meeting in Port Elizabeth. The chapter 4 of this thesis based on this talk, and I want to thank Matt for all his comments on earlier drafts.