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Reproductive Tactics of Male African Savannah Elephants (Loxodonta Africana)

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Reproductive Tactics of Male African Savannah Elephants (Loxodonta Africana) Reproductive tactics of male African savannah elephants (Loxodonta africana) Henrik Barner Rasmussen Balliol College Thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy at the University of Oxford Michaelmas Term 2005 i Abstract The present thesis investigates aspects of the reproductive strategy of male African savannah elephants (Loxodonata africana). The existence of, and differences between alternative conditional dependent reproductive tactics are evaluated using a combination of behavioural, endocrinological and GPS tracking data and the age and tactic related success is measured using genetic paternity analysis. Hidden Markov Models were used as a probabilistic framework for analysing temporal changes in reproductively active and inactive periods based on shifts in association preferences of individuals. Distinct shifts between active and inactive periods were evident well before the onset of the aggressive reproductive tactic of musth, seen in older dominant males, hence providing the first quantitative evidence for the previously suggested sexually active periods in non-musth males. The link between hormones and reproductive status and tactics were investigated using a new technique for non-invasive faecal analysis of hormones. A combined analysis of androgens (Epiandrosterone) and glucocorticoid (3a,11-oxo-CM) hormones in relation to age, reproductive state and musth signals confirmed previously reported elevated levels of androgens during periods with temporal gland secretion and urine dribbling (Musth) but further showed that this increase is indeed linked to the presence of musth signals and not to the age of the individual. Androgen levels were generally increased during sexually active periods with a two-fold increase seen in active non- musth bulls and a four to six-fold increase in musth bulls. Contrary to expectations, increased glucocorticoids outputs were not seen in musth bulls but slightly elevated outputs were seen in active non-musth bulls. Brief peaks in glucocorticoids occurred immediately after physical fights and during periods of injuries. A general elevation of glucocorticoids was seen towards the end of the long dry season, a likely effect of ecological conditions. Behavioural changes and onset of musth signals occurred after an initial change in androgen levels suggesting that sex steroids may play an activiational role of sexually active periods as well as activation of the musth tactic within sexually active periods. Some evidence was found for increased androgen levels following encounters with receptive females, suggesting that such encounters may act as a “boosters vaccine” on androgen levels and hereby prolong active periods at times with high numbers of receptive females. Both musth and sexually active non-musth (SAN) bulls reduced their foraging and walked more than sexually inactive bulls. However musth bulls had a higher time specific investment in reproduction compared to SAN bulls with musth bulls doubling their daily walking distance compared to a 50% increase in SAN bulls. The (younger) non-musth bulls spent a larger part of the year sexually active (70%) compared to musth bulls (20%) hence SAN bulls have a tactic of prolonged low investment compared to the short and high investment seen in musth bulls, emphasising the need for evaluating the duration of reproductive bouts when comparing overall investments between tactics. The youngest (non-musth) bull to sire offspring was 21 years but older musth bulls above 35 years had a much higher age specific reproductive success compared to bulls below 30 years. However on a population level, bulls less than 30 years contributed 30% of the reproduction and 20- 25% could be attributed to non-musth bulls. ii Acknowledgements This thesis would not have been written without the help an support of a great deal of people and for some of life’s strange coincidences. Iain Douglas-Hamilton and my advisor Fritz Vollrath have supported me throughout the process and deserve a special thank together with Thiemo Krink. However without a casual remark from Morten Bjerrum drawing my attention to a small hand written note saying “Do you want to work with elephants” now many years ago at University of Aarhus I may have ended up above the arctic circle rather than studying elephants near equator. Many others have helped me during the last years. The entire Save the Elephants team have provide immense help, especially Wainaina Kimani (WK), Juliet King and Njoki Kibanja for sorting out my permits and accounting mess, discussions and general help. In the field the sometime tedious hours would have been less fun without my assistant and great companion Lugard Lenaiyasa. I also owe much to George Wittemyer who has been a great friend, colleague and discussion partner in the field and during our collaborations on the genetic project. I am happy that one of my focal bulls probably saved you life when you “played” with one of the musth bull. Don’t mess with the big guys. David Daballen also provided help in the field and has become one of my closest friends and family in the process. Two non-organic but potentially sentient beings “The Beast” and “The Lunch-box” provide transport in the field, don’t know if I should thank or curse you! Several collaborations have been an integrated part of this project. The physiological studies were conducted in collaboration with Dr. Andre Ganswindt and Prof. Keith Hodges from German Primate Centre in Göttingen, Germany. Genetic analysis of paternity was carried out in collaboration with John Okello, University of Makarere, Uganda and Dr. Hans Siegismund University of Copenhagen, Denmark and is part of a larger ongoing genetic study on African elephants conducted in collaboration between Save the Elephant and the Wildlife Genetic Project. Dr. Gerton Lunter enlightened and helped me in the use of hidden Markov models. Without money this study would never have come to be. I am especially grateful for the support given by the International Elephant Foundation, by the funding provided by Iain Douglas-Hamilton’s Dawkins price for animal conservation and welfare, Balliol College and the immense support provided by Save the Elephant and it’s donors who believe that not all assets should be place on the stock exchange. However without emergency funding from my parents during the last leg of the project I would have been stranded before completion. I would also like to thank The Office of the President of the Republic of Kenya the Kenya Wildlife Service and especially Samburu and Isiolo County council for permission to conduct this research as well as the warden and rangers of Samburu, Shaba and Buffalo Springs National Reserves. Finally without David Mayntz and Cedric Dicko my time as a D.Phil. student here in Oxford would have been a great deal less joyful (although the completion of the thesis may have occurred earlier). Oxford 28 September 2005 iii Table of Contents ABSTRACT .............................................................................................................................II ACKNOWLEDGEMENTS.................................................................................................. III TABLE OF CONTENTS.......................................................................................................IV 1 INTRODUCTION AND BACKGROUND...................................................................... 1 1.1 INTRODUCTION ................................................................................................................. 2 1.1.2 REPRODUCTIVE BEHAVIOUR OF MALE AFRICAN ELEPHANTS ........................................... 5 1.2 OBJECTIVES AND AIMS ................................................................................................... 12 1.3 THESIS OUTLINE ............................................................................................................. 13 2 STUDY AREA, POPULATION AND METHODOLOGY.......................................... 14 2.1 STUDY AREA.................................................................................................................... 15 2.2 CLIMATE ......................................................................................................................... 16 2.3 STUDY POPULATION........................................................................................................ 16 2.4 DATA COLLECTION ......................................................................................................... 20 2.4.2 SPOT OBSERVATIONS OF INDIVIDUALS........................................................................... 20 2.4.3 GPS TRACKING DATA.................................................................................................... 22 2.4.4 COLLAR TYPES AND RECORDING PERIODS ..................................................................... 23 2.4.5 IMMOBILIZATIONS ......................................................................................................... 23 3 AGE ESTIMATION OF ELEPHANTS ........................................................................ 25 3.1 INTRODUCTION ............................................................................................................... 27 3.2 MATERIAL AND MOULDS:............................................................................................... 28 3.3 RESULTS.......................................................................................................................... 29
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