Foraging ecology and conservation biology of African elephants: Ecological and evolutionary perspectives on elephant-woody plant interactions in African landscapes Item Type Thesis Authors Dudley, Joseph Paine Download date 27/09/2021 15:01:40 Link to Item http://hdl.handle.net/11122/9523 INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter free, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. 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Further reproduction prohibited without permission. NOTE TO USERS The original manuscript received by UMI contains pages with indistinct print. Pages were microfilmed as received. This reproduction is the best copy available UMI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. FORAGING ECOLOGY AND CONSERVATION BIOLOGY OF AFRICAN ELEPHANTS: ECOLOGICAL AND EVOLUTIONARY PERSPECTIVES ON ELEPHANT - WOODY PLANT INTERACTIONS IN AFRICAN LANDSCAPES A THESIS Presented to the Faculty of the University of Alaska Fairbanks in partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY By Joseph Paine Dudley, M.S. Fairbanks, Alaska May 1999 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 9918836 UMI Microform 9918836 Copyright 1999, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. FORAGING ECOLOGY AND CONSERVATION BIOLOGY OF AFRICAN ELEPHANTS: ECOLOGICAL AND EVOLUTIONARY PERSPECTIVES ON ELEPHANT - WOODY PLANT INTERACTIONS IN AFRICAN LANDSCAPES By Joseph Paine Dudley RECOMMENDED: Department Head, Biology & Wildlife APPROVED: Dean, College of Science, Engineering, and Mathematics De^rfof the Graduate School Date Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT The available scientific evidence indicates that African forest elephants and bush elephants are ecologically and evoiutionarily distinct taxa. The current practice of regarding these two taxa as ecotypes of a single species, Loxodonta africana (i.e., L. a. africana Blumenbach 1797. L. a. cyclotis Matschie 1900) appears unwarranted, and obscures issues of major significance to the conservation biology of African elephants. Under a proposed taxonomic revision, the African bush elephant retains the designation Loxodonta africana Blumenbach 1797 while the African forest elephant is recognized as Loxodonta cyclotis Noack 1906. The browsing of woody plants by African bush elephants is a major factor in the structural dynamics of semi-arid woodland and scrubland habitats in Hwange National Park (HNP) and the Sengwa Wildlife Research Area (SWRA), Zimbabwe. Drought, frost and fire also influence the structure and species composition of woody vegetation within HNP. Interactions among these three abiotic factors and elephant browsing may have significant impacts on the dynamics o f semi-arid woodland and scrubland habitats of HNP. Mortality attributable to elephant damage was identified as a principal cause of death among large trees (> 5:0 m height), and a relatively minor but not insignificant cause of death for shrubs and trees in the 1.0 - 5.0 m height class. The responses ofColophospermum mopane in SWRA to fertilization treatments corresponded to those predicted by the carbon/nutrient hypothesis of plant anti-herbivore defense. Comparisons of these results with those of previous studies suggest possible changes in the ecology and population biology of elephants in HNP during the past decade. Observed differences in the age-specific mortality of elephant in HNP during die-offs in 1993-1995 and 1980-1984 provide independent evidence of changes in the ecology of elephants in HNP during the period 1983-1993. The population of L. a. africana inhabiting the Matabeleland-Ngamiland-Okavango region of southern central Africa (which includes the HNP population), is the largest extant elephant population on Earth. The magnitude of this population (110, 000 - 120,000), and the high proportion of its range currently under protection as wildlife reserves, indicate that this population may rank as the most viable and potentially sustainable elephant population on Earth. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table of Contents List of Figures .......................................................................................................................................v List of Tables ...................................................................................................................................... vii Acknowledgments ............................................................................................................................ ix Introduction ........................................................................................................................................... I Chanter 1 Ecological and evolutionary perspectives on niche segregation in African elephants ....................................................................................................... 21 Chapter 2 Browsing selectivity of African elephants among Colophospermum mopcme woodlands in the Sengwa Wildlife Research Area, Zimbabwe ..............................39 Chapter 3 Elephant-frost-fire interactions among woodland and scrubland habitats in Hwange National Park, Zimbabwe ............................................................................67 Chapter 4 Seed dispersal of Acacia erioloba by African bush elephants in Hwange National Park, Zim babw e .......................................................................................... 94 Chapter 5 Seed content and utilization of the dung of African bush elephants in Hwange National Park, Zimbabwe .......................................................................... Ill Chapter 6 Drought mortality o f African bush elephants in Hwange National Park, Zim babw e.................................................................................................................. 127 Chapter 7 Current trends in the conservation status of African and Asian elephants 147 Chapter 8 Conservation implications of evolutionary trends in insular elephant populations ................................................................................................................ 158 Synopsis and Conclusions ................................................................................................................ 179 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V List of Figures Chapter 1 Fig. 1. A cladogram of evolutionary relationships among major proboscidean and elephant lineages based on osteological and dental criteria (after Shoshani, 1996; Kalb et al. 1996) . 37 Chapter 2 Fig. I. Major topographic features and location o f the Sengwa Wildlife Research A r e a 59 Fig. 2. Blocking design and location of experimental plots ......................................................... 60 Fig. 3. Effects of distance and treatment on the nitrogen content of mature Colophospermum mopane leaves .....................................................................................................................................61 Fig 4. Effects o f distance and treatment on the nitrogen content of young Colophospermum mopane leaves .....................................................................................................................................62 Fig. 5. Effects o f distance and treatment on the diterpene content of young Colophospermum mopane leaves ...................................................................................................................................