The Ecology and Behaviour of Giraffe in Northern Botswana

Home , Angolan giraffe, Capra (genus), Geophagia, Masai giraffe, Mikumi National Park, Moremi Game Reserve

Kylie N. McQualter Centre for Ecosystem Science School of Biological, Earth and Environmental Sciences University of New South Wales Australia

A Thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy within the University of New South Wales

January 2018 THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: McQualter First name: Kylie Other name/s Nicole Abbreviation for degree as given in the University calendar: PhD School: School of Biological, Earth and Environmental Faculty: Science Sciences Title: The Ecology and Behavior of Giraffe in Northern Botswana

Abstract

Northern Botswana is one of the giraffe strongholds across its geographic range in the absence of, or with low impact from, the major anthropological threats faced elsewhere. Yet despite its conservation significance, until now, no giraffe- specific ecological or behavioural studies have been undertaken. Moreover, Africa’s giraffe population has been significantly reduced over the last two decades, and the pressure on giraffe habitats and populations is likely to increase as the human population continues to expand, and the effects of climate change take their toll. As such, it is important to establish an ecological and behavioural baseline for giraffe in the unique ecosystems. This study provides baseline data on the behaviour and ecology of giraffe in the dry savannah and woodlands of the northern Chobe region and the wetland system of the Okavango Delta (NG26) in northern Botswana. The study first examines the home ranges, seasonal ranges and daily movements of giraffe in the two study areas. Next, the focus is on giraffe behaviours and activity budgets, and the effect of site, sex, season and time of day on behaviour. Lastly, the study describes the giraffe social grouping patterns in Chobe and examines non-random associations and spatial overlap as possible factors driving the population’s underlying fission-fusion system. Ecological and behavioural similarities were observed between the study areas, but also vast differences reflecting the adaptations made by giraffe in response to the unique set of environmental factors they face. Home ranges and daily movements were larger in Chobe where forage is more limited and patchily distributed, and ranges were larger during the dry season. Habitat, season, and sex were all found to be influential factors contributing to the observed variation in giraffe activity budgets. Social analyses revealed a complex social organisation whereby non-random associations and spatial overlap are drivers of a structured social network found within a fluid fission-fusion social system. Variation in pairwise association strengths and ranging patterns between the sexes suggest that males and females socialise differently. Association strength was generally greater for females than males though both sexes appeared to have preferred and avoided associates, indicating non-random groupings of individuals. Pairwise association strengths appear to be influenced more by social preferences and avoidances than spatial overlap, and shared space use has a greater influence over female social groupings.

Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation.

I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only).

……………………………………… ………………………………………. ………………………………………… Signature Witness Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award

i ORIGINALITY STATEMENT

‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’

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Date …..………………

‘I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstract International (this is applicable to doctoral theses only). I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.'

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‘I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.’

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I dedicate this thesis to my parents, Dawn and Peter, who have done so much for me throughout my life and have never stopped believing in me.

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ACKNOWLEDGEMENTS

I would first like to express my sincerest gratitude to my supervisor, Dr. Keith Leggett, for his continuous advice, support and encouragement throughout the years; for his patience when my chapter drafts were slow coming and communication occasionally lacking; for always having time for me; and for saying the right things when I was at risk of becoming completely overwhelmed.

Thanks go to my co-supervisor, Dr. Julian Fennessy for setting me up with a giraffe project in the first place; for all his thorough editing and advice, and for letting me take part in genetic sampling field trips which were not only important for giraffe conservation, but were super fun too.

I would like to give a huge thank you to Dr. Mike Chase and Kelly Landen from Elephants Without Borders who welcomed me into the team. They sorted out all the logistics for me to study giraffe in Botswana, obtained funding for various aspects of my research, shared their data with me, and let me stay in their beautiful research camp in the Okavango Delta, all for which I am eternally grateful. They also gave me incredible opportunities to participate in various field projects from wildlife collaring to aerial surveys which made my time in Botswana all the more memorable.

Thank you to the Paul G. Allen Family Foundation, Harry and Colleen Ferguson, and Cornelia Bargmann for their financial support, and to the Botswana Government, Department of Wildlife and National Parks, University of New South Wales and Giraffe Conservation Foundation for their general support throughout the project.

Thanks also goes to all those involved in the collaring exercises, Larry Patterson for his veterinary expertise; Andrew Baker, Peter Perlstein and Mike Holding for piloting the helicopters and light-weight plane; all

iv those in the ground capture teams; and Africa Wildlife Tracking for supplying the collars.

A special thank you to Tempe Adams who joined me on this great African adventure to study Botswana’s elephants. Always cheerful and always there for support.

To Rodney Massey, Stephanie Fennessy and Leanne Van der Weyde who didn’t mind watching giraffe for hours on end while I recorded giraffe behaviour, thank you for your company and help in photographing giraffe. Thanks also to Lyn Francey and Mark Vandewalle for your friendship and help with plant identification. A special thank you to Andy Tutchings whose friendship and support meant so much, and whose promotion of the project was greatly appreciated.

To the ever so clever Kim Young, Kerryn Carter, Neil Jordon, Clare Runge and Steve McLeod, who were ever so helpful and patient in getting me through my statistical analyses, thank you so much, I would never have got there without you!

To my new found Kasane friends who were always ready for a drink (or ten!) at The Old House or Thebe, a scrumptious feast at Pizza Plus Coffee and Curry, or sundowners on the river, thanks for all the stories, laughs, and good times. Thanks also to the Abu and Seba managers in NG26 who occasionally spoiled me with their chef-prepared, leftover food, when tinned food had lost its appeal.

Last but not least, thanks to my long-time friends who are forever supportive; and to my parents, Dawn and Peter, for their continued love, support and encouragement throughout my academic life, and life in general, even when my obsession with Africa and its wildlife takes me to the other side of the world for extended periods.

ABSTRACT

This study provides baseline data on the behaviour and ecology of giraffe in the dry savannah and woodlands of the northern Chobe region and the wetland system of the Okavango Delta (NG26) in northern Botswana. The study first examines the home ranges, seasonal ranges and daily movements of giraffe in the two study areas. Next, the focus is on giraffe behaviours and activity budgets, and how site, sex, season and time of day affect behaviour. Lastly, the study describes the giraffe social grouping patterns in Chobe and examines non-random associations and spatial overlap as possible factors driving the population’s underlying fission-fusion system.

Ecological and behavioural similarities were observed between the study areas, but also vast differences reflecting the adaptations made by giraffe in response to the unique set of environmental factors they face. Home ranges and daily movements were larger in Chobe where forage is more limited and patchily distributed, and ranges were larger during the dry season. Habitat, season, and sex were all found to be influential factors contributing to the observed variation in giraffe activity budgets.

Social analyses revealed a complex social organisation whereby non- random associations and spatial overlap are drivers of a structured vi social network found within a fluid fission-fusion social system. Variation in pairwise association strengths and ranging patterns between the sexes suggest that males and females socialise differently. Association strength was generally greater for females than males though both sexes appeared to have preferred and avoided associates, indicating non-random groupings of individuals. Pairwise association strengths appear to be influenced more by social preferences and avoidances than spatial overlap, and shared space use has a greater influence over female social groupings.

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TABLE OF CONTENTS

Dedication……………………………………………………………………… iii Acknowledgements………………………………………………………….. iv Abstract ……………………………………………………………………….. vi Table of Contents…………………………………………………………….. viii List of Tables………………………………………………………………….. x List of Figures………………………………………………………………… xi List of Appendices…………………………………………………………… xii

CHAPTER 1: General Introduction…………………………………… 1

1.1 Taxonomy, distribution and conservation status of giraffe across Africa………………………………………… 1 1.2 Taxonomy of giraffe in Botswana……………………….. 6 1.3 History of Botswana in relation to giraffes, their distribution and abundance……………………………… 7 1.4 Recent and current conservation status of giraffe in Botswana……………………………………………………… 11 1.5 Botswana……………………………………………………… 15 1.6 Northern Botswana………………………………………… 18 1.7 Study areas………………………………………………….. 19 1.8 Climate………………………………………………………… 23 1.9 Data collection………………………………………………. 25 1.10 Dissertation overview……………………………………… 26

CHAPTER 2: Home ranges, seasonal ranges and daily movements of female giraffe (Giraffa camelopardalis giraffa) in northern Botswana……………………………………………………. 28 2.1 Introduction…………………………………………………………….. 28 2.2 Methods………………………………………………………………….. 29

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2.3 Results……………………………………………………………………… 32 2.4 Discussion…………………………………………………………………. 38 2.5 Conclusion…………………………………………………………………. 39

CHAPTER 3: Giraffe behaviour and activity budgets…………….. 41 3.1 Introduction……………………………………………………………….. 41 3.2 Methods…………………………………………………………………….. 44 3.3 Results……………………………………………………………………… 48 3.4 Discussion…………………………………………………………………. 58

CHAPTER 4: Giraffe social networks and space use in Chobe National Park, Botswana…………………………………………………… 76 4.1 Introduction……………………………………………………………….. 76 4.2 Methods…………………………………………………………………….. 80 4.3 Results……………………………………………………………………… 86 4.4 Discussion…………………………………………………………………. 92 4.5 Conclusion…………………………………………………………………. 96

CHAPTER 5: General conclusions and discussion…………………. 99 5.1 Major findings and discussion..………………………………………...99 5.2 Study limitations and possibilities for future research…………..105 5.3 The future of giraffe in northern Botswana…………………………107

REFERENCES…………………………………………………………….……111

APPENDIX I……………………………………………………………….……144 APPENDIX II……………………………………………………………….…..145

LIST OF TABLES

Table 1.1 Giraffe subspecies, estimated population sizes and distribution……………………………………………………………………… 4

Table 1.2 Estimates of giraffe numbers from DWNP and EWB aerial surveys flown over Chobe District, Chobe National Park, Ngamiland District, Moremi Game Reserve, and Makgadikgadi Pans and Nxai Pan National Parks, Central Kalahari Game Reserve and Khutse Game Reserve, Botswana, from 1993 to 2014…………. 13

Table 1.3 Dates for data collection in the Chobe and NG26 study areas……………………………………………………………………………… 25

Table 2.1 Home range and seasonal home range estimates of four GPS satellite collared giraffe as determined by MCP and FKDE analysis, Chobe and NG26, Botswana……………………………………. 33

Table 2.2 Daily seasonal linear movements of four GPS satellite collared adult female giraffe in Chobe and NG26, Botswana………. 37

Table 3.1 Seasonal and combined wet and dry season diurnal activities observed for male and female giraffe in Chobe National Park and NG26, Botswana………………………………………………….. 49

Table 3.2 Negative binomial regression models examining the effect of Activity, Site and Sex (Set 1), and Activity, Sex and Season (Set 2) on the frequency of giraffe activities in Chobe National Park and NG26, Botswana…………………………………………………………. 51

Table 3.3 Wet and dry season diurnal activity budgets of giraffe in Chobe National Park and NG26, Botswana, divided into three time periods: 0700–1100, 1100-1500 and 1500-1900hrs…………………. 53

Table 3.4 Frequency of browsing events on different plant species by giraffe in the NG26, Botswana during the 2013 dry season (Feb- Apr, Sep-Nov)…………………………………………………………………… 55

Table 3.5 Mean and median foraging heights for giraffe in Chobe National Park and NG26, Botswana………………………………………. 57

Table 4.1 The mean (± SD) and range for the nodal degree and geodesic distances for giraffe observed in Chobe National Park, Botswana………………………………………………………………………… 88

LIST OF FIGURES

Figure 1.1 Distribution of the nine currently recognised subspecies……………………………………………………………………….. 5

Figure 1.2 The distribution of Botswana’s two giraffe subspecies... 7

Figure 1.3 Land use zones in Botswana…………………………………. 17

Figure 1.4 Study areas in NG26 and Chobe National Park, Botswana………………………………………………………………………. 20

Figure 1.5 Mean monthly minimum and maximum temperatures and rainfall for Kasane and Maun, Botswana, from 2001 to 2012… 24

Figure 2.1 GPS satellite unit attached with head-harness in Chobe National Park, Botswana……………………………………...... 31

Figure 2.2 Home ranges and seasonal ranges of four GPS satellite collared female giraffe as determined by MCP and FKDE analysis, Chobe National Park and NG26, Botswana……………………………… 35

Figure 3.1 Proportion of giraffe feeding time allocated to different height classes in Chobe National Park and NG26, Botswana……….. 57

Figure 4.1 Observed herd sizes in Chobe National Park, Botswana. 87

Figure 4.2 Sightings of individual giraffe by herd type in Chobe National Park, Botswana…………………………………………………….. 88

Figure 4.3 Social networks and maps of social group spatial use of giraffe observed on five or more occasions in Chobe National Park... 91

APPENDICES

APPENDIX I Female giraffe home range estimates from studies across Africa listed from north to south………………………………….. 144

APPENDIX II Giraffe identification………………………………………… 145

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CHAPTER 1

General Introduction

1.1 Taxonomy, distribution and conservation status of giraffe across Africa

The giraffe, Giraffa camelopardalis Linnaeus 1758 (Order Artiodactyla, Suborder Ruminantia), together with the Okapi, Okapia johnstoni Sclater 1901 of the lowland forests of the Democratic Republic of Congo, are the two extant species comprising the family Giraffidae. Since the giraffe was first taxonomically classified by Linnaeus (1758) as Cervus camelopardalis, numerous revisions to its classification have been proposed and made, including amendment of its generic name to Giraffa (Brisson, 1762) as it is known today, and the division of the species into subspecies, and genus into multiple species (e.g. Lydekker, 1904; Krumbiegel, 1939; Ansell, 1968, 1971; Dagg, 1971; Kingdon, 1997; East, 1999; Seymour, 2012; Brown, 2007; Mitchell, 2009; Groves and Grubb, 2011).

Initial subspecies classifications were founded primarily on pelage patterns, ossicone characteristics and geographic distribution (e.g. Lydekker, 1904; Krumbeigel, 1939), however, variation in pelage patterns of individuals from the same population (Dagg, 1962a; Dagg and Foster, 1982), and uncertainty surrounding the geographic distribution of described subspecies (Fennessy and Brown, 2010) confused taxonomical assignments. More recent studies using molecular genetic analyses (e.g. Brown et al., 2007; Hassanin et al., 2007; Brenneman et al., 2009; Fennessy et al., 2013; Bock et al., 2014; Fennessy et al., 2016) have helped resolve some of the confusion, though some aspects still remain unresolved (Fennessy et al., 2013).

Currently, it is generally accepted that all extant giraffe represent one species (Giraffa campelopardalis) classified into nine subspecies: G. c. peralta (West African giraffe), G. c. antiquorum (Kordofan giraffe), G. c. camelopardalis (Nubian giraffe), G. c. rothschildi (Rothschild's giraffe), G. c. reticulata (Reticulated giraffe), G. c. tippelskirchi (Masai giraffe), G. c. thornicrofti (Thornicroft's giraffe), G. c. angolensis (Angolan giraffe) and G. c. giraffa (South African or Cape giraffe), though the possibility of multiple species is again under debate.

Brown et al. (2007), who examined the genetic variation in mitochondrial DNA from free ranging giraffe representing six of the currently recognised subspecies, suggest that due to their findings of significant differentiation between subspecies, and almost complete lack of gene flow between populations, giraffe might represent multiple species rather than just the one. Fennessy et al. (2016) have gone one step further and conducted genetic analysis on biparentally inherited sequence data from all nine nominate giraffe subspecies. Their analyses suggest that the Rothschild’s giraffe should be subsumed into the Nubian giraffe and the Thornicroft’s giraffe into the Masai giraffe. Moreover, they identify at least four separate clades which, under the genetic isolation criterion, would be recognised as four distinct species.

Not all people (e.g. Mitchell, 2009; Bercovitch et al., 2017) consider the separation of giraffe into multiple species using the ‘genetic species concept’ appropriate, however, as it does not factor in morphology, population distributions, ecology and behaviour (Bercovitch et al., 2017); and ignores the fact that hybridization between subspecies occurs in the wild and in captivity, though infrequently (Mitchell, 2009). Furthermore, there are discrepancies between results from genetic studies which have used different analyses (e.g. Bock et al., 2014; Brown et al., 2007; Fennessy et al., 2013, 2016).

Historically, giraffe occurred throughout most of Africa (Skinner and Smithers, 1990). Desertification of the Sahara pushed their geographical range south to what is now sub-Saharan Africa where 2 their range has been further reduced by human induced habitat loss, degradation and fragmentation through increased agricultural practices and expansion of the human population and settlements; as well as hunting and illegal poaching (Dagg and Foster, 1976; East, 1999; Fennessy and Brown, 2010; Bock et al., 2014).

In West Africa, giraffe occupied areas from Senegal to Lake Chad but today the only viable population is a small population in southwestern Niger (East, 1999) (Table 1.1; Figure 1.1) representing the last remaining West African giraffe. Kordofan giraffe are found in larger numbers in Central Africa (Southern Chad, Central African Republic, northern Cameroon, northern Democratic Republic of Congo and probably South Sudan), though few populations are considered secure (East, 1999). The Nubian giraffe is represented by relatively low numbers in western Ethiopia and probably South Sudan. Three subspecies are found in East Africa, the reticulated giraffe (north eastern Kenya, southern Somalia and possibly southern Ethiopia), the Rothschild’s giraffe (northern Uganda and west-central Kenya), and the Masai giraffe (central and southern Kenya, and Tanzania). The Masai giraffe is the most populous of all giraffe subspecies and the reticulated giraffe is also found in large numbers, albeit numbers have decreased significantly (Tutchings et al., 2013). Population size estimates for the Rothschild’s giraffe are low. Thornicroft’s giraffe are found only in Zambia’s South Luangwa Valley. The population is relatively small, though apparently stable (Tutchings et al., 2013). Southern Africa is occupied by the Angolan giraffe (Namibia and central Botswana) and the South African giraffe (northern South Africa, northern and southern Botswana, and southern Zimbabwe, and extralimital populations across South Africa, Angola, Senegal, Zambia and Zimbabwe). Both subspecies occur in relatively large numbers (East, 1999).

Table 1.1 Giraffe subspecies, estimated population sizes and distribution.

Estimated Subspecies Common name Distribution population size G. c. peralta West African giraffe 400 Niger G. c. antiquorum Kordofan giraffe 2,000 Chad Central African Republic Cameroon Democratic Republic Congo South Sudan G. c. camelopardalis Nubian giraffe 650 Ethiopia South Sudan G. c. reticulata Reticulated giraffe 8,660 Kenya Somalia Ethiopia (?) G. c. rothschildi Rothschild's giraffe 1,500 Uganda Kenya G. c. tippelskirchi Masai giraffe 32,000 Kenya Tanzania G. c. thornicrofti Thornicroft's giraffe 550 Zambia G. c. angolensis Angolan giraffe 13,000 Angola Namibia Botswana G. c. giraffa South African giraffe 31,500 Botswana South Africa Zambia Zimbabwe Mozambique Subspecies are listed in order of their approximate distribution from north to south. Data obtained from GCF, 2016; http://giraffeconservation.org. NB- Results from the most recent genetic analyses propose that the Rothschild’s giraffe be subsumed into the Nubian giraffe, and the Thornicroft’s giraffe into the Masai giraffe.

Figure 1.1 Distribution of the nine currently recognised subspecies. NB – The most recent genetic analyses suggests the Rothschild giraffe should be subsumed into the Nubian giraffe, and the Thornicroft’s giraffe into the Masai giraffe. Sourced from Giraffe Conservation Foundation.

In 1998, it was estimated that there were in excess of 140,000 giraffe across Africa (East, 1999). More recent estimates by the Giraffe Conservation Foundation put the total population at fewer than 90,000 animals (GCF, 2016). As a species, giraffe are currently listed as ‘Vulnerable’ on the International Union for Conservation of Nature (IUCN) Red List (Muller et al., 2016). On a subspecies level, both the West African giraffe and the Rothschild’s giraffe are classified as

Endangered and of high conservation importance on the IUCN Red List on account of their low numbers.

1.2 Taxonomy of giraffe in Botswana

As with other giraffe subspecies in the more northern parts of their range, confusion has surrounded the geographical limits of southern Africa’s two subspecies (Fennessy, 2008). Botswana’s giraffe have been categorised as either G. c. giraffa (synonymous with G. c. capensis, and G. c. wardi) (e.g. Krumbeigel, 1939) or G. c. angolensis (synonymous with G. c. infumata) (e.g. Dagg, 1962b; Dagg, 1971; Fennessy, 2008). Results from a recent study using mitochondrial DNA analysis by Bock et al. (2014), however, revealed the occurrence of both subspecies in adjacent populations. Giraffe in the Central Kalahari Game Reserve were found to be Angolan giraffe, whilst those further north in the Chobe and Nxai Pans National Parks and the Okavango Delta are South African giraffe (Figure 1.2). Their divergence has been dated back to the early Pleistocene (Bock et al., 2014). Despite no obvious geographical barrier between the two populations today, a “cryptic” rift valley running northeast to southwest across Botswana during the Pleistocene may have caused the split in giraffe matrilines (Bock et al., 2014).

Figure 1.2 The approximate distribution of Botswana’s two giraffe subspecies.

1.3 History of Botswana in relation to giraffes, their distribution and abundance

Prior to the 1600’s, the eastern side of Botswana was inhabited by rudimentary cultivators (Campbell and Child, 1971; Cooke, 1985), whilst the west of the country around Ghanzi and along the Nosob River was occupied by nomadic groups of people with small herds of livestock (Campbell and Child, 1971). The rest of the country, however, was

7 inhabited only by nomadic bands of bushmen or San (Campbell, 1973). These hunter gatherers harvested wild foods, snared small game and hunted larger mammals, including giraffe, with bow and poison arrow, pitfall and assegai (Campbell, 1973; Bryden, 1897), with no perceptible reduction in wildlife numbers (Bryden, 1897; Butynski and von Richter, 1975).

More settlers arrived in sizeable numbers during the 1700’s, some bringing large herds of cattle and more advanced systems for agriculture (Campbell and Child, 1971). However, the instability of Botswana’s social, political and economic situation throughout the 1700’s and early 1800’s, together with invading armies in the 1820’s (Campbell, 1973), meant that most settlements were relatively temporary until the country regained some political stability around 1870, enabling communities to settle more permanently and spread (Campbell and Child, 1971). Both human and cattle numbers have continued to increase since this time, as has the intensity of agriculture (Campbell and Child, 1971; Cooke, 1985).

Until the mid-1800’s, giraffe were found across most, if not all of the country (Bryden, 1893; Schapera and Comaroff, 1991). Since then, their range in the south has been significantly reduced (e.g. Bryden, 1891; Nicholls and Eglington, 1892; Bryden, 1897; von Richter, 1970; Campbell, 1973, 1981; Campbell and Main, 2006) which can be largely attributed to intensive hunting pressure (Bryden, 1897).

During the late 1800’s, when rhinoceros were all but exterminated and hippopotamus had become scarce, the giraffe hide was much sought after, selling for five pounds or more (Bryden, 1893). Both the native and Dutch hunters flocked into the Kalahari, decimating the giraffe population (Bryden, 1893, 1897). With the introduction of the hunting horse, breech-loader gun and percussion rifle, the once subsistence native hunters had switched to commercial hunting and were said to spare no game, old or young (Nicholls and Eglington, 1892). Around 1892, it was reported that in Ngami country alone, nearly 300 giraffe 8 were slaughtered for their hides by the native hunters over just two seasons (Nicholls and Eglington, 1892; Bryden, 1897). Around this time, English hunter and naturalist, Henry Bryden (1891), predicted that very few giraffe would be left in Botswana’s southern region by 1910.

Giraffe in the north of the country were less persecuted than those in the south, particularly where the native tribes were not in possession of firearms and hunting horses (Nicholls and Eglington, 1892). Fear of trouble from the invading Matabele from the east also limited the number of native hunting expeditions to the Botletle, Mababe and Chobe districts during the late 1890’s (Bryden, 1893) which enabled giraffe to persist in considerable numbers (Bryden, 1891). Furthermore, giraffe and other wildlife were protected from the Boer hunters in the area designated as Khama’s country where they were forbidden to hunt (Bryden, 1893).

Realising the imminent threat of the giraffes’ demise in Botswana (Statistics Botswana, 1992), when laws pertaining to the preservation of game were amended in 1925, giraffe were given ‘Royal Game’ status, meaning they could no longer be legally hunted unless a special licence was issued by the Resident Commissioner (Bechuanaland Protectorate, 1926). The prohibition of trade in giraffe hides or tails was also imposed. Consequently, viable populations can still be found in protected areas today despite their extermination in other areas prior to the passing of the new laws (von Richter, 1970; Campbell, 1981).

The expansion of human settlements, agricultural land and cattle posts, and the subsequent detrimental impacts on the environment, have been blamed for the reduction or loss of wildlife in the drier parts of the Kalahari (Child, 1971; Campbell, 1973; Cooke, 1985; Dougill et al., 2016). Such human expansion has been made possible since the late 1950’s by the drilling of deep boreholes in areas which, in the past were virtually inaccessible to man due to the difficulty of obtaining water (Campbell, 1973, 1981; Cooke, 1985). Northern Botswana, on the other 9 hand, was somewhat safeguarded from the incursion of man and his livestock in any great number owing to the presence of the tsetse fly across the better watered areas (Campbell, 1973) and wildlife numbers have remained relatively high (e.g. Chase et al., 2015).

Despite lower human and cattle occupancy in the north of the country, wildlife there, as throughout the country, has still been affected by the development of Botswana’s commercial livestock industry through the erection of a vast network of veterinary cordon fences beginning in the 1950’s (Gibson/EIA, 2004; Mbaiwa and Mbaiwa, 2006; Albertson, 2010). The fences were put in place to separate wildlife from cattle in order to prevent the transmission of infectious diseases, and to satisfy the European Union beef export requirements (Mbaiwa and Mbaiwa, 2006; Gibson, 2010). However, the fences block important migration routes between rangelands and water sources (Williamson and Williamson, 1984; Mbaiwa and Mbaiwa, 2006; Gibson, 2010), and prevent access to alternate forage areas during times of reduced forage quality and abundance, as well as key resource sites such as mineral licks (Albertson, 2010). Such movement restrictions, in combination with severe drought, have been responsible for enormous wildlife mortalities, particularly of migratory wildlife species, including wildebeest, hartebeest and zebra (Williamson and Williamson, 1984; Albertson, 2010). Although giraffe may have suffered less than some other species from the prevention of access to other areas or water sources, numerous giraffe deaths have occurred from entanglement resulting from attempts to cross over or pass through the fences (Mbaiwa and Mbaiwa, 2006; Albertson, 2010).

Prior to the discovery of diamonds in the late 1960’s, the commercial livestock sector was Botswana’s largest sector, contributing to 39% of the GDP at Independence in 1966 (Lewin, 2011). Furthermore, the sector was, and still is, of great importance due to its contribution to the livelihoods of a large number of livestock farmers (Lo Moro et al., 2014). Around the same time, the Government had fully realised the

10 aesthetic and economic value of wildlife and was trying to encourage tourism (Munger, 1965). Since then, the Government has had to deal with the two opposing interests.

In the early 1930’s the Gemsbok Game Reserve was established at the request of South Africa (Campbell, 2004), but it wasn’t until the 1960’s that the Botswana Government secured more land for new game reserves and later, national parks, in accordance with its promotion of tourism (Campbell, 1973). Additional land was set aside in 1986 in the form of Wildlife Management Areas (WMAs) for the dual purpose of wildlife conservation and community development (Twyman, 2001).

1.4 Recent and current conservation status of giraffe in Botswana

A study examining the distribution of giraffe across Africa by giraffe researcher, Anne Dagg, in 1962 reported that giraffe in Botswana (then Bechuanaland) were numerous in the Northern Crown Lands and in the Southern Crown Lands, northwest of Lephephe on the Bamangwato Reserve border and northwards to the Botletle River. They were also said to be numerous on the southeast border of Batawana Reserve (southeast of the Khewebe Hills), the Mababe depression, in the central area, and along the eastern border adjoining Zimbabwe’s Wankie Game Reserve. North of Maun in the Kanga and further north near Kwaai, they were described as ‘plentiful’. Few were reported to reside south of the Sashi River, along the western border of Batawana Reserve, and at the pans west of Táu. Towards the Chobe River, giraffe were reported as decreasing (Dagg, 1962b).

A few years later in 1965 it was reported that giraffe were plentiful in both the Ngamiland and Chobe Districts, though their number appeared to be declining, and few were said to inhabit the western and eastern parts of the Bamangwato Native Reserve, south of Lake Makarikari, and south of the Sashi River (Sidney, 1965). In the Kalahari, having disappeared from much of their former range, by 1970 11 they could only be found in reasonable numbers in the Central Kalahari Game Reserve (von Richter, 1970), and in 1981 were largely confined to the area north of the Okwa River (Campbell, 1981).

In 1975, a report on the conservation status of the larger mammals of southern Africa, classified giraffe in Botswana as “apparently safe”, considered safe from extinction due to conservation measures and population status (Bothma, 1975).

The first quantitative assessment of large game carried out in the form of aerial surveys was conducted in the Kalahari from 1978-1979. The Kalahari giraffe population was estimated at approximately 3,400 individuals, found in two consistent groups, one in the north and the other around Metseamonong (DHV, 1980).

Following this initial Kalahari survey, a series of aerial wildlife surveys have been conducted by the Department of Wildlife and National Parks (DWNP) (ten surveys) and Elephants Without Borders (EWB) (three surveys) since 1993, covering either much of northern Botswana or the whole country. Survey results have shown large fluctuations in giraffe population estimates in the various areas (Table 1.2).

Region 1993 1994 1996 1999 2001 2002 2003 2004 2006 2010 2011 2012 2014

Chobe District − − 1236 1262 978 835 1528 1885 1379 1245 1483 1071 1427 Chobe NP 364 1107 666 850 692 540 999 1044 793 770 777 545 849 Ngamiland District − − 10608 9578 7577 6985 5517 6566 6763 3676 − 5041 6532 Moremi GR 1309 1334 1691 1370 1777 1233 958 1101 1088 1075 − 1047 1353 Makgadikgadi & Nxai Pan 214 390 475 200 206 524 327 867 129 227 − − 562 NPs Central Kalahari GR − − 893 2661 1416 1253 703 1148 − − − 923 − Khutse GR − − 53 0 317 0 0 154 − − − − −

The most recent population estimate for northern Botswana, calculated from EWB’s 2014 aerial survey, is 9,409 giraffe (Chase et al., 2015). This is substantially higher than EWB’s 2010 estimate of 5,537, though slightly more area was covered in the 2014 survey. Giraffe were observed throughout the region but densities were highest in Moremi Game Reserve and the adjacent WMA’s in the latest survey.

Population trend analysis based on DWNP and EWB aerial survey results suggested a severe decline in giraffe numbers (and that of 10 other large mammal species) in the Okavango Delta between 1993 and 2010, with an 8% annual rate of decline. During this same time period, populations appeared to be increasing in Chobe National Park and stable in the Chobe District, and Makgadikgadi and Nxai Pan National Parks (Chase, 2011). The wildlife declines in the Okavango Delta coincided with a 20 year drought, with annual rainfall and water flow records for the Okavango River the lowest ever to be recorded, which may have affected wildlife numbers (Chase, 2011).

Four years on, population trends between 1993 and 2014 indicated the giraffe populations in Moremi Game Reserve had become stable after an increase in numbers between 2010 and 2014, but a declining trend persisted in Ngamiland despite a continual increase in numbers since 2010. Giraffe populations in Chobe District, Chobe National Park, and Makgadikgadi and Nxai Pan National Parks are currently stable (Chase et al., 2015).

The most recent country-wide survey was conducted in 2012 which estimated a population of 8,976 giraffe (DWNP, 2012). Given the higher estimate for northern Botswana in 2014 (Chase et al., 2015), the population likely now exceeds the country-wide 2012 estimate. In any case, Botswana boasts one of the largest giraffe populations across their geographic range (Fennessy, 2008).

1.5 Botswana

Botswana is a landlocked country in southern Africa bordered by Namibia, Zambia, Zimbabwe and South Africa, and covering an area of approximately 582,000 km2. The land surface consists predominantly of a gently undulating plateau with an average altitude of 1000 m. The 2011 total human population estimate was 2,024,904, with an annual growth rate of 1.9% (Statistics Botswana, 2014a).

Approximately 82% of the country is covered by the Kalahari Desert (Winterbach et al., 2015). The vegetation changes on a gradient of increasing rainfall from the southwest to northeast (Burgess, 2006). In the southwest, bare sand dunes occur in the climatic deserts, and grasslands transition into open (low) shrub savannah. To the north, savannahs with thorn shrubs and trees dominate, and in the most northern region, Miombo woodlands with mainly deciduous species infiltrate from Zambia and Zimbabwe (Bekker and de Wit, 1991; Burgess, 2006).

The country encompasses four major ecological regions: the Kalahari sandveld, the hardveld, the alluvial plains of the Okavango-Chobe system, and the plains of the Makgadikgadi pan complex (Darkoh, 1999). The sandveld, with its nutrient-poor sandy soils, covers most of the Kalahari Desert and encompasses the grasslands, shrub savannah and woodlands described above. The hardveld, found in the east of the country, consists of hills and rocky outcrops, savannah grasslands, savannah woodlands and some forest (Winterbach et al., 2014), and is characterised by loamy soils more nutrient rich than soils of the sandveld to the west (Ringrose et al., 2002). The Okavango-Chobe system in the north of the country is a complex ecosystem with swamp, island and floodplain vegetation associations, whilst the Makgadikgadi pan complex is a lacustrine system predominantly covered by grasslands with halophytic species (Bekker and de Wit, 1991).

As a consequence of Botswana’s predominantly dry conditions, most of the country’s streams and rivers are ephemeral, resulting in valleys which are typically dry until the rains (SCC, 2012). The two remaining perennial rivers, the Okavango and Cuando-Linyanti-Chobe system, have their sources in the Angolan highlands.

Over one third (38%) of Botswana’s total land area has been gazetted for wildlife conservation, comprising national parks and game reserves (17%), WMAs (20%) and forest reserves (1%) (Honde et al., 2015). The other main management zone is the agricultural zone consisting of communal grazing land, farms (mainly for livestock production and limited crop production), game ranches, mining and residential areas (Figure 1.3) (Winterbach et al., 2014).

Figure 1.3 Land use zones in Botswana. Conservation zones, including National Parks, Game Reserves, Wildlife Management Areas and Forest Reserves are depicted in shades of green, whilst Agricultural Zones, including communal grazing land, farms, game ranches and mining are depicted in shades of brown. Sourced from Winterbach et al., 2014.

Environmental management is one of Botswana’s highest priorities due to its significant support of the economy through tourism (8.5% of the Gross Domestic Product (GDP) in 2014; WTTC, 2015) and for the role it plays in supporting the rural poor (SCC, 2012). Only the mining sector succeeds tourism in terms of contribution to the GDP, which as of 2013, was 24.5% (Honde and Abraha, 2015).

The peak tourism season runs from July to September, coinciding with the large dry season concentrations of wildlife along the Chobe and Linyanti River systems and the Okavango Delta when water sources have dried up elsewhere (Winterbach et al., 2015). Sport hunting was previously offered in many of the WMAs, but a ban on all hunting was imposed in 2014. Today, the safari industry is focused on photographic tourism (Winterbach et al., 2015). In 2014, the number of people entering Botswana for the purpose of holidaying was 274,701 (Statistics Botswana, 2014b).

1.6 Northern Botswana

Northern Botswana includes the Chobe and Ngamiland Districts and is home to Botswana’s two top tourist destination, Chobe National Park and the Okavango Delta. It forms part of the Zambezian centre of plant endemism (Skarpe and Ringrose, 2014), which is characterised by numerous and widespread grass species and tree species predominated by members of the family Fabaceae (Werger, 1978; White, 1983).

Within northern Botswana lies one of Africa’s last few remaining functional ecosystems, the Northern Conservation Zone (Brooks and Bradley, 2010). The area includes Chobe, Nxai Pan and Makgadikgadi Pans National Parks, Moremi Game Reserve, forest reserves and WMAs, and stretches over a vast, continuous area of 78,911 km2. This area is part of an even larger conservation zone, the Kavango-Zambezi Transfrotier Conservation Area (KAZA TFCA) (Winterbach et al., 2015), which covers an area of around 520,000 km2, and spans across four other Southern Africa countries: Angola, Namibia, Zambia and Zimbabwe (KAZA, 2016).

With its extensive wilderness areas, northern Botswana supports high densities of mammals (Botswana Government, 2009; Chase et al., 2015) and plays a vital role in the conservation of a number of globally threatened species including the African lion (Panthera leo), African wild 18 dog (Lycaon pictus) and African elephant (Loxodonta africana) (Botswana Government, 2009; Winterbach et al., 2014). The area is particularly well known for its elephants. Northern Botswana supports the largest number of elephants across its geographic range, with an estimated population of around 130,000 (Chase et al., 2016). Their impact on the vegetation is substantial and has raised concern (Child, 1968; Skarpe et al., 2004).

1.7 Study areas

The study was conducted in two locations within northern Botswana, the Chobe area and WMA NG26 (Figure 1.4).

Figure 1.4 Study areas in NG26 and Chobe National Park, northern Botswana. 20

1.7.1 Chobe

The Chobe study area covers approximately 1,650 km2 and encompasses the most northern section of the Chobe National Park, the Kasane Forest Reserve, and marginally, the Chobe Forest Reserve (all protected areas), as well as Zimbabwe’s Matetsi Safari Area (protected hunting area). The Chobe River marks the northern boundary.

Along the Chobe River lies the seasonally inundated floodplain which forms an open grassland dominated by Cyndon dactylon on fine sodic alluvium (Skarpe and Ringrose, 2014). Adjacent to the river, raised fossil alluvium supports Capparis tomentosa-Flueggea virosa shrubland and in some sections, a thin strip of riparian forest (Fullman, 2009; Mosugelo et al., 2002). Further back from the river, in the narrow ecocline between the alluvial soils and the Kalahari sand, dense woody vegetation dominated by Combretum mossambicense and Croton megalobotrys occur (Fullman, 2009; Mosugelo et al., 2002; Skarpe et al., 2004; Skarpe and Ringrose, 2014). In the deep Kalahari sand, woodland dominated by Baikiaea plurijuga and including Baphia massaiensis, Burkea africana, Combretum elaeagnoides, Croton gratissimus and Terminalia sericea (Mosugelo et al., 2002) transitions into Baikiaea woodland further south (Mosugelo et al., 2002; Skarpe et al., 2004).

Water availability for wildlife during the dry season is limited to the Chobe River and a number of artificial waterholes dispersed south of the river. Water becomes abundant during the wet season when ephemeral pans fill across the area.

1.7.2 NG26

The second study area lies within WMA NG26, on the Okavango Delta’s western side. The Okavango Delta is a wetland system fed by seasonal waters from the Angolan highlands through the Cubango-Okavango

River system. The Okavango River flows continually, but the degree of flooding is dependent on the intensity of rain in the highlands (Magole et al., 2009). Floodwater can spread over areas sometimes in excess of 12,000 km2 (McCarthy and Ellery, 1998). The differences in time of local rains and flooding are an important hydrological feature. The flood expands several months after the rain has ceased which almost makes water available year round (Wolski et al., 2005). Furthermore, the flooding in the seasonal swamps produces a flush of new plant growth (McCarthy and Ellery, 1998) when other areas are typically dry. The Okavango Delta was declared a Ramsar site (wetland of international importance) in 1997 due to the unique features of the area (Magole et al., 2009).

The Okavango Delta is comprised of contrasting habitats with swamp, island and floodplain associations (Burgess, 2006). The swamps and seasonal swamps support hydrophytic grasses such as Cyperus papyrus, sedges such as Phragmites australis, and various aquatic species (Burgess, 2006). The Islands support a range of vegetation types including grassland, savannah, tree savannah, mixed woodland, mopane woodland and forest (Burgess, 2006; Evans and Harris, 2008). On the larger islands, the island fringes are typically more densely vegetated, whilst the inner areas are more covered with a savanna and woodland mosaic which forms part of a Colophospermum mopane - Terminalia sericea - Lonchocarpus nelsii association. The smaller islands found in the floodplains form a Hyphaene petersiana - Garcinia livingstonei - Lonchocarpus capassa - Acacia nigrescens association. Whilst in the riverine woodlands, the predominant species are Ficus sycomorus, Garcinia livingstonei, Diospyros mespiliformis, Acacia erioloba, Combretum imberbe and Colophospermum mopane (Burgess, 2006).

NG26 covers an area of about 1,850 km2, though the study area was limited to approximately 320 km2 in the northern region of the management area. NG26 is bordered by several WMAs (NG25, NG27A, 22 and NG29) and a small section of Moremi Game Reserve. The Southern Buffalo Fence runs along the western boundary, separating NG26 from arable and pastoral agricultural zone, NG8. NG26 was a hunting concession in the past, but hunting was stopped in 2008 in favour of photographic tourism and horseback safaris (McNutt, 2012). There are three luxury tourist camps in the area. Permanent swamps provide a year-round source of water to wildlife, and during the flood season water is plentiful across the study area. Annual floods occur from April to September.

1.8 Climate

Botswana’s climate is semi-arid. Rainfall is low and temperatures high. Annual rainfall is highly variable and drought is a reoccurring event due to the country’s location within the sub-tropical high pressure belt of the southern hemisphere and distance from oceanic influences (SCC, 2012). Rain generally falls between November and April (Burgess, 2006). Average annual rainfall in Kasane and Maun (2001-2013, excl. 2010 for Maun), the nearest towns to Chobe and NG26 respectively, were 593 mm and 427 mm (Department of Meteorological Services, Botswana 2013) (Figure 1.5). However, in Chobe, 2012 was a drier year (440 mm) and 2013 a wetter year (675 mm); and in Maun, both years had below average annual rainfalls (250 mm and 392 mm respectively) (Department of Meteorological Services, 2013). Average maximum temperatures (2001-2012) for both towns in the hottest and coldest months (October and July respectively) were 35˚C and 26˚C (Department of Meteorological Services, Botswana, 2013).

A . 40 160 35 140

30 120 (mm) Rainfall ˚C) 25 100 20 80 15 60

10 40 Temperature ( 5 20 0 0 J F M A M J J A S O N D B . 40 120 35 100

30 (mm) Rainfall ˚C) 25 80 20 60 15 40 Rainfall

10 Max Temp Temperature ( ( Temperature 5 20 Min Temp 0 0 J F M A M J J A S O N D

Figure 1.5 Mean monthly minimum and maximum temperatures and rainfall for (A) Kasane and (B) Maun, Botswana, from 2001 to 2012.

As rainfall varied between the two study sites, for the purpose of this research, the wet season was defined as the first day of rainfall ≥ 10 mm to the day after the last rains in each site (19 November 2012 - 8 February 2013 in NG26, and 24 November 2012 - 19 March 2013 and 28 October 2013 - 11 April 2014 in Chobe). All other days fell within the dry seasons.

Some studies divide the dry season into the cold/early dry season and the hot/late dry season on account of typical maximum daily temperatures or resource availability (e.g. Leuthold and Leuthold, 1978; Fennessy, 2004). However, insufficient data were obtained in this study during the dry season to do this. Furthermore, the flush of new

24 vegetative growth promoted by flooding in the Okavango Delta during the dry season (McCarthy and Ellery, 1998) further complicates division of the dry season if the two study areas are to be compared. So whilst analyses were based on only two seasons, wet and dry, it should be noted that early in the dry season, temperatures are cooler and vegetation is still in abundance, whereas in the late dry season, temperatures are very high and vegetation is scarce. These conditions likely have different effects on the giraffes’ ecology and behaviour.

1.9 Data collection

Observational data were collected between September 2012 and May 2014 (Table 1.3). Observations were made during daylight hours between 7am and 7pm. All observations were made from a vehicle, and were largely restricted to areas visible from the road network. Viewing distances varied from 10 m to around 300 m, but always from a distance which did not interfere with giraffe behaviour. When required, observations were made through a pair of 10 X 32 binoculars.

Table 1.3 Date range and number of days for observational data collection in the Chobe and NG26 study areas.

Study area Date range No. days

2 September 2012 – 17 February 2013 38 Chobe 25 April 2013 – 12 September 2013 18 7 November 2013 – 14 May 2014 30 16 February 2013 – 24 April 2013 36 NG26 13 September – 6 November 2013 40

As all observational data collection took place during the dry season in NG26, only dry season data were used in behavioural comparisons between the two study sites. 25

1.10 Dissertation overview

The overall objective of this study was to examine the behaviour and ecology of giraffe in two unique ecosystems in northern Botswana, and to provide the first baseline data on these populations.

Chapter 2 examines the home ranges, seasonal ranges and daily movements of four female giraffe, calculated from spatial data obtained from GPS satellite collars. Ranges and daily movements are described and compared between the two study areas and those reported for giraffe in other ecosystems.

In Chapter 3, the focus lies on giraffe behaviour and activity budgets. Activity budgets of male and female giraffe in the two study areas are presented, and the effects of site, sex and season assessed and discussed. Whether behaviour changes with time of day is also examined. It was hypothesised that activity budgets of giraffe would vary with site, sex, season and time of day. It was predicted that females would allocate more time to feeding, and walking due to their increased nutritional demands resulting from their smaller size and/or reproductive status. It was also predicted that more time would be devoted to feeding and walking during the dry season because of the limited food resources. Additionally, due to the high temperatures often reached in Botswana and the potential for thermal stress in giraffe, it was expected that giraffe would be less active during the heat of the day, particularly during the warm summer months. Natural history observations are also provided, giving more insight into giraffe behaviour

Chapter 4 investigates the giraffe social system in Chobe. Firstly, common measures of sociality, such as group size and herd composition, as well as the level of interconnectivity between individuals and how they differ between the sexes, are presented and comparisons are made with other populations. Then, herd membership was used to quantify pairwise association strengths and test for non-random

26 associations and individual association patterns and determine the social structure of the giraffe population. Next, the possibility of giraffe having community structures is examined, followed by how much influence spatial overlap has on association strengths and social groupings. The aims of the study were to describe the grouping patterns of the Chobe population using common measures of sociality, and make comparisons with other populations; to test for sex differences in non- random associations with other individuals; to investigate the influence of space use on pairwise associations and social groupings; and lastly, to look for evidence of a multi-tiered social structure. It was hypothesised that males and females would show different patterns of sociality, and that spatial overlap would have some effect on the level of association between individuals or groups.

CHAPTER 2

Home ranges, seasonal ranges and daily movements of female giraffe (Giraffa camelopardalis giraffa) in northern Botswana

A revised version of this chapter was published in African Journal of Ecology:

McQualter, K. N., Chase, M. J., Fennessy, J. T., McLeod, S. R. and Leggett, K. E. A. 2015. Home ranges, seasonal ranges and daily movements of giraffe (Giraffa camelopardalis giraffa) in northern Botswana. African Journal of Ecology 54, 99-102.

2.1 INTRODUCTION

Animal movements across the landscape are rarely random but instead are focused within well traversed areas or home ranges (Burt, 1943). Following foraging theory, movement patterns are considered to be largely driven by the distribution of food resources (Anderson et al., 2005; Owen-Smith et al., 2010), with ranges generally expanding when food resources are scarce, patchily distributed and/or of reduced quality (Owen-Smith and Cain, 2007). However, other factors including water availability, habitat structure, topography, sex of the individual, population structure and density, energetic requirements and predation risk can also be influential (Fennessy, 2009; Owen-Smith and Cain, 2007; van Beest et al., 2011).

Movement studies have been conducted on various giraffe subspecies across different ecological and management environments in Africa. However, prior to recent advancements in GPS satellite technology, studies were limited to identification methods relying on chance encounters of individuals (e.g. Berry, 1978; Foster, 1966; Le Pendu and Ciofolo, 1999) and then VHF radio-tracking (e.g. Dagg and Foster, 1982; 28

Langman, 1973), both of which can underestimate movements (Fennessy, 2009). Now, GPS satellite units enable remote monitoring of movements with the increased ability to collect more accurate and copious data sets (e.g. Fennessy, 2009; Suraud, 2011).

This study used GPS satellite collar technology to determine home ranges, seasonal ranges and daily movements of giraffe (G. c. giraffa) (Bock et al., 2014) in two vastly different environments of northern Botswana, the dry savannahs and woodlands of the Chobe region and the wetland system of the Okavango Delta.

2.2 METHODS

2.2.1 Study area

The study area includes two sites in northern Botswana. The Chobe study area covers approximately 1,650 km2 and encompasses the northern region of Chobe National Park, the Kasane Forest Reserve and small sections of the Chobe Forest Reserve and the Matetsi Safari Area (Zimbabwe). To the far north of the area lies the Chobe River, marking the northern boundary. The seasonally inundated flood plain lining the river forms open grassland. On the edge of the grassland lies Capparis tomentosa – Fleuggea virosa shrubland (Skarpe and Ringrose, 2014). Further south, the vegetation is dominated by Combretum mossambicense and Croton megalobotrys dense shrubland (Skarpe and Ringrose, 2014). Further south still, the vegetation transitions into mixed, then Baikiaea woodland (Mosugelo et al., 2002). A more detailed description is provided in Chapter 1, section 1.7.1.

The second study area lies within Wildlife Management Area (WMA), NG26 on the western side of the Okavango Delta. The WMA covers an approximate area of 1,850 km2, though the study area covers approximately 320 km2. The area includes contrasting habitats with swamp, seasonal swamp and island vegetation. The Islands support a

29 variety of vegetation types including forest, woodlands, tree savanna, savanna and grasslands (Burgess, 2006; Evans & Harris, 2008). A more detailed description of the Okavango Delta environment is available in Chapter 1, section 1.7.2.

Botswana’s climate is semi-arid. The wet season was defined as the first day of rainfall ≥ 10 mm to the day after the last rains, which occurred between 19 November 2012 to 8 February 2013 in NG26 and 24 November 2012 to 19 March 2013 in Chobe. Further details on the climate in the study area are provided in Chapter 1, section 1.8.

2.2.2 GPS satellite collaring

Three adult female giraffe (F0018CH, F0174CH and F0311CH) in Chobe and one (F0001ABU) in NG26 were fitted with GPS satellite units supplied by Africa Wildlife Tracking, South Africa. Individuals were selected by the veterinarian from a Robinson 44 helicopter based on their physical condition and likelihood of being in the early to mid-years of adulthood. Giraffe were darted from the helicopter with immobilisation drug, Thianil, and once the drug had taken effect, the ground team brought the giraffe to the ground. Once restrained, the reversal drug, Naltrexone, was injected and the collar fitted.

The GPS units sat upon the head in front of the ossicones and were attached with a harness fastening behind the ossicones and under the chin (Figure 2.1). Units were programmed to transmit coordinates at four hourly intervals and location data were accessed through an online application via a standard internet browser. Collar function and longevity varied over the study period (see Table 2.1).

Figure 2.1 GPS satellite unit attached with head-harness in Chobe National Park, Botswana.

The study period was from July 2012 to May 2013, though collars operated variably over the period (Table 2.1). Ranges presented were calculated from all GPS collar data available and should be viewed as minimum ranges and not the annual or complete seasonal ranges.

2.2.3 Data analysis

Home and seasonal range size estimates were calculated from GPS satellite collar data using the minimum convex polygon (MCP) and fixed kernel density estimator (FKDE) (Worton, 1989). Home and seasonal ranges were defined as the 95% FKDE probability isopleths, and core areas were defined as the 25% FKDE probability isopleths (after Leggett, 2006). Estimates were calculated with the spatial analysis software, Geospatial Modelling Environment (Beyer, 2012) which utilises the software R (R Core Team, 2013) as the statistical engine to drive the FKDE analysis tool and ArcGIS (Version 10.0) (ESRI, 2010).

Factors influencing the range sizes (MCP; FKDE 95% and 25%) of the giraffe were examined using linear mixed-effects models. Season, number of GPS readings and site were included as fixed effects, and individual giraffe were included as random variables. Fixed effects were added sequentially to the null model, and the statistical significance of the additional variable was determined using the likelihood ratio test (alpha level = 0.05). Analyses were performed using R (R Core Team, 2015) and the lme4 package (Bates et al., 2014).

Daily movements were determined by adding linear distances between consecutive four-hourly location fixes. Days with only a full set of fixes were included. Linear mixed-effects models and likelihood ratio tests were again used to test for impacts of season and site on daily movements.

2.3 RESULTS

The GPS units were expected to last approximately two years, but three of the four harnesses were observed to be chafing behind the ossicones and were removed prematurely. The fourth giraffe is believed to have died of natural causes, however, no autopsy was carried out as the carcass was too decomposed when found.

2.3.1 Home ranges

Home ranges ranged from 67.5 to 623.4 km2 (MCP) and 47.1 to 536.5 km2 (FKDE 95%) (Table 2.1). The combined average home range of all giraffe was 259.1 (MCP) and 205.7 km2 (FKDE 95%). Average home range of the Chobe giraffe only was 323.0 (MCP) and 258.6 km2 (FKDE 95%), five-fold estimates for F0001ABU. However, the combined and Chobe home range averages were skewed by F0016CH’s much larger home range.

Table 2.1 Home range and seasonal home range estimates of four GPS satellite collared giraffe as determined by MCP and FKDE analysis, Chobe and NG26, Botswana. Core areas are represented by the 25% FKDE estimates.

Period of collar Home range size Giraffe ID No. of readings Seasonal range estimates (km2) function estimates (km2) MCP FKDE MCP FKDE 95% 25% 95% 25% Total Dry Wet Dry Wet Dry Wet Dry Wet NG26 F0001ABU 28/6/2012 - 8/3/2013 1479 986 493 67.5 47.1 3.9 63.1 31.2 50.4 18.9 4.5 0.7 Chobe F0016CH 9/10/2012 - 10/2/2013 708 257 451 623.4 536.5 44.1 434.7 406.2 390 336.5 15.4 26.4 F0174CH 8/10/2012 - 10/2/2013 668 263 405 207.4 144.6 8.7 171 74.6 169.2 62.5 12 3.5 F0311CH 8/10/2012 - 30/5/2013 597 300 297 138.3 94.5 5.9 118.8 25.1 98.5 23.1 8.2 2 Mean Chobe 323.0 258.6 19.6 241.5 168.6 219.2 140.7 11.8 10.6 Mean all 259.1 205.7 15.7 196.9 134.3 177.0 110.2 10.0 8.1

F0016CH’s home range extended across Chobe National Park (CNP) and Kasane Forest Reserve and showed transboundary movements between Botswana and Zimbabwe’s Matetsi Safari Area (Figure 2.2). F0174CH’s movements extended from CNP and marginally into Chobe Forest Reserve, whilst F0311CH’s home range was confined within CNP. F0001ABU ranged across the islands and floodplains in the far north, central section of NG26.

Core areas followed the general home range trends. They averaged 15.7 km2 for all giraffe, though this figure was again skewed by F0016CH’s larger core area (44.1 km2). The other giraffe had core areas covering less than 9 km2.

Figure 2.2 Home ranges and seasonal ranges of four GPS satellite collared female giraffe as determined by MCP and FKDE analysis, Chobe and NG26, Botswana.

2.3.2 Seasonal ranges

No giraffe had mutually exclusive wet and dry season ranges, with seasonal ranges overlapping markedly for F0001ABU (46.2% of home range), F0016CH (38.5%) and F0174CH (26.81%); and marginally for F0311CH (9.5%) (Figure 2.2). There was no overlap in seasonal core areas. Only the models for MCP and 95% FKDE range sizes incorporating season were an improvement over the null models and the likelihood ratio tests indicated significantly different range sizes for wet and dry seasons (MCP: χ2 = 6.209, df = 1, P = 0.013; FKDE 95%: χ2 = 7.652, df = 1, P = 0.006). Dry season ranges were larger than wet season ranges for F0001ABU, F0174CH and F0311CH (Figure 2.2; Table 2.1). Although slightly larger for F0016CH, the difference between seasonal home range sizes was less marked. The average dry season range was 1.4 times larger than the wet season range.

2.3.3 Daily Movements

There was large variation in daily distances travelled (Table 2.2). Giraffe in Chobe moved over a range of 1.03 – 22.04 km depending on the season, whilst F0001ABU’s daily movements ranged from 0.71 to 11.73 km. Neither season nor site had a significant impact on distances (all P values > 0.05).

Table 2.2 Daily seasonal linear movements (mean ± SD, median, and ranges) of four GPS satellite collared adult female giraffe in Chobe and NG26, Botswana.

Giraffe ID Wet Season Dry Season Mean Median Mean Median n Range (km) n Range (km) (km + SD) (km) (km + SD) (km) NG26 F0001ABU 78 2.81 ± 1.17 2.66 0.71 - 7.06 129 3.18 ± 1.24 3.03 0.90 - 11.73 Chobe F0016CH 50 7.74 ± 4.10 6.87 2.47 - 18.97 30 7.73 ± 5.23 5.53 2.36 - 22.04 F0174CH 34 3.70 ± 1.77 3.49 1.62 - 11.36 28 4.00 ± 2.90 3.36 1.71 - 16.97 F0311CH 12 7.49 ± 6.12 5.14 1.03 - 21.04 Mean Chobe 6.10 ± 3.89 4.88 6.20 ± 4.91 4.24 Mean All 4.52 ± 3.34 3.49 4.24 ± 3.38 3.31

2.4 DISCUSSION

2.4.1 Home ranges

Giraffe home ranges have shown a tendency to be larger in areas with reduced forage availability, such as Niger (Le Pendu and Ciofolo, 1999), the northern Namib Desert (Fennessy, 2009), the Kalahari (Flanagan, 2014) and Tsavo East National Park (Leuthold and Leuthold, 1978); and smaller where forage density is higher, such as Lake Manyara National Park (van der Jeugd and Prins, 2000), and Luangwa Valley (Berry, 1978) (Appendix I). Home range sizes of the Botswana giraffe also appear to follow this trend. In NG26 where forage is more abundant throughout the year, F0001ABU’s home range was similar in size to those observed in Luangwa Valley (Berry, 1978), whereas in Chobe, where forage is more limited and patchily distributed, ranges were significantly larger and more closely resembled those in the northern Namib Dessert (Fennessy, 2009) and Niger (Le Pendu and Ciofolo, 1999).

The larger dry season ranges observed in this study contrast with the larger wet season ranges more typically seen for large African browsers including black rhinoceros, Diceros bicornis (Goddard, 1967), elephant, Loxondonta africana (Lindeque and Lindeque, 1991; Thouless, 1995; Leggett, 2006; Chase, 2007; Young et al., 2009), eland, Taurotragus oryx (Hillman, 1998) and kudu, Tragelaphus strepsiceros (Owen-Smith, 2008), though this is likely linked to the giraffe’s ability to be away from surface water for extended periods (Berry, 1973; Fennessy, 2004, 2009).

Giraffe have, however, shown differing seasonal movement patterns across their range. Similar to findings of this study, larger dry season ranges and seasonal shifts in core areas were observed for giraffe in Niger (Le Pendu and Ciofolo, 1999), whereas larger wet season ranges were observed in Tsavo National Park (Leuthold and Leuthold, 1978) where giraffe congregate in smaller areas near rivers with permanent food supplies during the dry season, and disperse away from the river

38 into the deciduous woodlands during the rainy season. Conversely, movements of giraffe in Namibia (Fennessy, 2009) and Zambia (Berry, 1978) were largely restricted to areas within proximity to watercourses where the only palatable and available forage was distributed throughout the year, resulting in limited seasonal movements or seasonal range partitioning.

Seasonal shifts in range are likely linked to changes in the phenology and productivity of forage species with giraffe continually modifying their diet, feeding on plant species with the highest quantity of new leaves, shoots, flowers or pods, which provide high levels of energy and protein (Pellew 1984a; Fennessy, 2004).

2.4.2 Daily Movements

Mean daily movements of the giraffe were larger than those reported in Namibia: 1.87 km (Fennessy, 2009), South Africa: 2.9 km (Langman, 1973), and Zambia: <2.3 km (Berry, 1978), although it is unknown whether this is due to greater measurement accuracy with new technology or actual movement.

Daily wildlife movements are often longer during the dry season given the need to travel between foraging patches more frequently due to the reduction in forage biomass, and/or the need to move to and from surface-water (e.g. Owen-Smith, 2013). However, length of daily movements showed no seasonal differences in Chobe contrary to seasonal range shifts and differences in seasonal range sizes.

2.5 Conclusion

This study, together with others, highlights the variation in giraffe movement patterns across Africa which is likely a reflection of the spatio-temporal availability of the most nutritious forage resources within the different environments. Giraffe ranges in the Chobe area 39 were seen to extend outside the national park, suggesting resources within the park might be insufficient to support the giraffe population exclusively. These findings emphasise the importance of adjacent forest reserves, protected areas and community land to wildlife; and the significance of cross-border conservation cooperatives in this unique Kavango-Zambezi Tranfrontier landscape.

CHAPTER 3

Giraffe behaviour and activity budgets

3.1 INTRODUCTION

Activity patterns are shaped by an individual’s need to carry out fundamental activities necessary to maximise their biological fitness, and the need to minimise the costs and risks of partaking in those activities (Lima and Dill, 1990; Owen-Smith and Goodall, 2014). As time is limited and activities are often mutually exclusive, animals are faced with daily compromises as to how much time they allocate to each activity (Sih, 1980; Hamel and Côté, 2008; Owen-Smith and Goodall, 2014). Such decisions are influenced by, and change in response to any combination of intrinsic characteristics such as sex, age class (e.g. Prates and Bicca-Marques, 2008), and reproductive status (e.g. Neuhaus and Ruckstuhl, 2002; Hamel and Côté, 2008); and extrinsic factors such as habitat type (e.g. Young and Isbell, 1991; Tadesse and Kotler, 2014), season (e.g. Doran, 1997; Tadesse and Kotler, 2014), weather conditions (e.g. Leuthold, 1977; Owen-Smith, 1998), food quality and availability (e.g. Jarman and Jarman, 1973; Pellew, 1984a), perceived or actual predation risk (Hunter and Skinner, 1998; Lima, 1998), and group size and composition (e.g. Caraco, 1979; Fritz and de Garine-Wichatitsky, 1996; Fischer and Linsenmair, 2006).

Giraffe behaviour has been studied in a number of habitats across their geographic range. A number of these studies have focused on a particular aspect of behaviour such as feeding (e.g. Pellew, 1984a and b; Ginnett and Demment, 1997; Ciofolo and Le Pendu, 2002); social interactions (Leuthold, 1979); and movement (e.g. Berry, 1978; Fennessy, 2009; McQualter et al., 2015), whilst others have been less

41 specific, detailing several or numerous components of behaviour (e.g. Innis, 1958; Pratt and Anderson, 1982). Studies on the giraffes’ daily activity patterns have, so far, been somewhat limited. Fennessy (2004) reported on the activity budgets for giraffe in the arid northern Namib Desert, Namibia, Leuthold and Leuthold (1978) examined activity budgets for twelve giraffe over sixteen days in the wooded grasslands of Tsavo East National Park, Kenya, and du Toit and Yetman (2005) examined only female giraffe in Kruger National Park, South Africa. This chapter examines the activity budgets of giraffe in two vastly different habitats of northern Botswana, with a focus on variation between sites, sexes, seasons and time of day.

Various studies have documented how activity budgets of the same species differ between sites or habitats, with ecological variation given as the reason for behavioural differences. For example, the quality and distribution of food resources in an area has been found to impact the amount of time an herbivore spends feeding or moving between foraging patches (e.g. Wauters et al., 1992); whilst the amount of cover offered by vegetation has been shown to influence the amount of time an individual devotes to vigilance (e.g. Tchabovsky et al., 2001; Tadesse and Kotler, 2014), as does carnivore density (e.g. Hunter and Skinner, 1998).

Linked to physiological differences, sexual variation in activity budgets is common in ruminants that are sexually dimorphic in body size (e.g. giraffe (Ginnett and Demment, 1997; Fennessy, 2004), waterbuck, Kobus ellipsiprymnus (Spinage, 1968), Nubian ibex, Capra nubiana (Gross et al., 1995)), with differences in time devoted to feeding and rumination often particularly notable (e.g. Ginnett and Demment, 1997; Pellew 1984a). Digestive capacity, total metabolic requirements and basal metabolic rate have been found to increase with body size (Kleiber, 1947; Demment and Van Soest, 1985), whilst mass-specific metabolic rate decreases with body size (Kleiber, 1947). Consequently,

42 larger herbivores must eat more (Bell, 1971), but as they are able to process food more efficiently, can tolerate food with a higher fibre content (Cumming, 1982; Illius and Gordon, 1992). Smaller animals, however, require a more high-protein diet which digests more quickly to compensate for their higher metabolic rate and energy demands (Bell, 1971). Another cause of sexual differences in feeding times is thought to be the additional nutritional requirements of females during periods of gestation and lactation (e.g. Norton, 1981; Neuhaus and Ruckstuhl, 2002).

Seasonal variation in behaviour has been demonstrated across various wildlife studies and often relates to the response of individuals to changes in environmental conditions (e.g. Owen-Smith, 1994; Morris et al., 2009; Owen-Smith and Goodall, 2014; Tadesse and Kotler, 2014). Seasonal differences in the phenology of vegetation and the consequent availability of nutritious food, for example, can affect movement patterns and feeding duration (e.g. Norton, 1981; Owen-Smith, 1994; Owen-Smith and Cain, 2007; Tadesse and Kotler, 2014), whilst the changes in vegetation cover can impact perceived or actual predation risk, and in turn, the amount of time individuals spend being vigilant (e.g. Tadesse and Kotler, 2014). Vigilance has also been found to increase during breeding seasons when predation risk is often higher (e.g. Childress and Lung, 2003; Tadesse and Kotler, 2014). Yet another example is the seasonal differences in the average daily ambient temperature which, due to thermal stress, can influence the proportion of time an individual is active (Belovsky and Slade, 1986; Owen-Smith, 1998).

In addition to affecting seasonal behaviours, it has been suggested that ambient temperature also influences an animal’s daily activity schedule (Belovsky and Slade, 1986; Owen-Smith and Goodall, 2014). In order to conserve energy and reduce water loss, some animals living in areas marked by high daily temperatures minimise the time they engage in 43 the more energy expending activities (e.g. feeding and walking) during the hottest period of the day in order to manage their heat load. This has been observed for black rhinoceros (Diceros bicornis; Goddard, 1967), white rhinoceros (Ceratotherium simum; Owen-Smith, 1974), buffalo (Owen-Smith and Goodall, 2014), elephant (Leggett, 2009; Shannon et al., 2008), lesser kudu, Tragelaphus imberbis (Mitchell, 1977), and impala, Aepyceros melampus (Jarman and Jarman, 1973).

The overall aim of the study was to document the behaviour and activity budgets of giraffe in areas where they have not previously been studied. In line with findings from other studies it was hypothesised that activity budgets of giraffe would vary with site, sex, season and time of day. It was predicted that females would spend more time feeding, and walking due to their increased nutritional demands resulting from their smaller size and/or reproductive status. It was also predicted that giraffe would spend more time feeding and walking during the dry season because of the limited food resources. Furthermore, given how high temperatures can reach in Botswana, and the potential for thermal stress in giraffe, it was expected that giraffe would be less active during the heat of the day, particularly during the warm summer months.

3.2 METHODS 3.2.1 Study areas

The study was conducted in two areas of northern Botswana, the Chobe Riverfront area situated in the extreme north of Chobe National Park, and in the northern region of Wildlife Management Area, NG26, on the western side of the Okavango Delta. In the Chobe site, habitats graduate from grassy floodplains lining the Chobe River in the north, to a thin strip of riparian forest, shrubland, mixed woodland, then Baikiaea woodland in the south. In contrast, the NG26 site comprises a mosaic of habitats including swamps, floodplains, woodlands, and

44 island vegetation. A more detailed description of the two study areas is provided in section Chapter 1, Section 1.7.

3.2.2 Data collection

Behavioural data were collected from a vehicle by direct observations in Chobe National Park from September 2012 to February 2013, May to September 2013, and November 2013 to May 2014; and in NG26 from February to April and September to November 2013 (see Chapter 1, Table 1.3 for more precise dates). Observations were made between 7am and 7pm although giraffe in Chobe were typically hard to locate and observe in the early mornings, and the seasonal light availability and closing hours of the Park restricted the number of observations which could be made after 6pm. There were a total of 617.5 observation hours in NG26 and 549.5 in Chobe.

Activities were recorded on a datasheet at two minute intervals using the scan method (Altman, 1974) for as long as individuals were in view. Whilst many studies have used five minute scan sampling (e.g. Innis, 1958; Leuthold and Leuthold, 1978; Pellew, 1984a), giraffe behaviour has been found to change more frequently than every five minutes (Fennessy, 2004) and as such, two minute interval scans were used.

Depending on the habitat type and the ease at which individuals could be monitored, behavioural data were collected on as many as eight individuals at a time but typically less. Individuals were randomly selected from any of the 604 individuals (adults and sub-adults) identified in Chobe and 139 individuals in NG26, though their identification was not recorded in relation to their behaviour.

Individuals were classified into juveniles (<1 year, estimated height: <2.5m), sub-adults (1-5 years, estimated height: 2.5-4 m), and adults (5+ years, estimated height: >4 m; van der Jeugd and Prins, 2000). Males and females were differentiated by ossicone characteristics (size, 45 shape, hair), presence/absence of testes and penis sheath, and/or general size.

Following Fennessy (2004), each activity was categorised under one of the following activities:

 Feeding - including browsing, grazing, chewing or swallowing, but not ruminating  Walking (or running) - travelling between foraging sources or within the study areas (not ruminating)  Ruminating – when either standing, sitting/lying or walking  Resting - either standing up or lying down  Vigilant - other activities cease as an individual scans surroundings or is fixated on an external stimuli  Drinking  Grooming - scratching, rubbing itself, or nibbling/licking body parts  Excreting - defecating or urinating  Social - including necking, rubbing against or chesting another individual, suckling; nuzzling, sniffing (but not flehmen)  Sexual activity - including flehmen, courtship and mounting

Where possible, feeding height, plant part consumed and in NG26, plant species, were recorded on the data sheet when feeding activity was recorded. Dietary species were not identified in Chobe due to the difficulty in identifying many of the plant species, particularly those which were heavily browsed. Following Wyatt (1969), feeding heights were visually estimated using the typical heights and measurements of male and female adult giraffe as a guide. Males and females were considered to be 1.2 and 1 m at the knee, 2.2 m and 1.7 m at the elbow, 2.6 and 2.2 m mid chest, 3 and 2.5 m at the shoulder and 5.5 and 4.5 m at the top of the head respectively (following Young and Isbell, 1991 and based on own observations). Feeding height estimates were checked 46 regularly in the field with a measuring stick. Whilst some studies have used neck angles to examine behavioural foraging differences (e.g. Du Toit, 1990; O’Conner et al., 2015), this study only examined foraging heights.

Additional information on the number and timing of drinking bouts was also recorded when possible. Drinking time was recorded using a stopwatch.

Activity data were pooled together for each sex at the two sites, but divided into time periods (0700 – 1100, 1100-1500 and 1500-1900hrs) representing the morning, the middle of the day when ambient temperatures are typically at their highest, and the late afternoon/evening period, following Leggett (2009) and Rose and Robert (2013). These time periods allow for variation in daylight length throughout the year and differences in behaviour that may result from variation in ambient temperatures. Data were additionally split into wet or dry season for Chobe. The wet season fell between 24 November 2012 - 19 March 2013 and 28 October 2013 - 11 April 2014 as described in Chapter 1, Section 1.8. All other days fell within the dry seasons.

3.2.3 Data analysis

Due to the variation in number of behavioural records for the different time periods, results are presented as a percentage of the total records for each period. To identify whether site, sex and season affected behaviour, data were fitted to a series of negative binomial regression models, a common method for dealing with overdispersed data (Ver Hoff and Boveng, 2007). Models were fitted in R using a maximum likelihood estimator (R Development Core Team, 2008). As behavioural data were only collected during the dry season in NG26, two sets of models were constructed. For the first set, models were fitted with the entire dataset, with the frequency of a given activity as the response variable and sex, site and activity as the explanatory variables. An additional offset 47 variable, was also included to correct for differences in sampling efforts between sampling times and sites, whereby offset = log(sampling hours). The dataset was simplified using activity categories of ‘Feeding’, ‘Walking’, ‘Resting’, ‘Ruminating’ and ‘Other’. The ‘Other’ class represented those activities which did not occur frequently enough to produce usable percentages in the computer analyses, including drinking, urinating, defecating, grooming, interaction, and sexual and social behaviours. The second set of models were fitted using only the Chobe data to assess whether adding season as an explanatory variable improved the fit of the data to the model. Models from the two model sets were compared using Akaike’s information criterion (AIC; Akaike, 1973, 1974), with the best supported model indicated by the lowest AICc value.

3.3 RESULTS

3.3.1 Activity budgets

Feeding, ruminating, resting and walking made up the bulk of the diurnal activity budgets for both sexes, constituting 84.3% and 89.9% of the budgets for males and females respectively in Chobe and 93.7% and 95.77% for males and females in NG26 (Table 3.1).

Table 3.1 Seasonal and combined wet and dry season diurnal activities observed for male and female giraffe in Chobe National Park and NG26, Botswana. Data are expressed as percentages of observations.

Chobe NG26 Dry Wet Annual Dry

Male Female Male Female Male Female Male Female Activity n = 3820 n = 3094 n = 5475 n = 3260 n = 9295 n = 6354 n = 7388 n = 13105 Feeding 43.38 47.87 40.82 45.71 41.57 47.07 60.57 66.54 Ruminating 15.76 10.21 14.23 13.31 14.91 11.79 9.94 9.58 Resting 10.18 10.63 9.39 11.53 9.93 10.76 7.44 4.19 Walking 16.05 18.91 19.29 21.66 17.94 20.42 15.78 15.47 Vigilance 6.31 9.63 3.82 5.74 4.85 7.65 2.64 2.8 Drinking 1.13 1.68 0.55 0.55 0.77 1.1 0.24 0.4 Grooming 0.73 0.58 0.82 0.89 0.79 0.66 0.93 0.56 Excretion 0.10 0.19 0.07 0.09 0.11 0.14 0.07 0.19 Social 5.24 0.29 10.34 0.52 8.27 0.41 1.49 0.26 Sexual 1.13 0.00 0.68 0.00 0.86 0 0.89 0.02

Comparison of the negative binomial regression models in Set 1 (Table 3.2) showed support for only two models (∆AICc < 3), both of which include the Activity – Site interaction, and the best fitting model containing no other explanatory variables. The evidence ratio indicates that evidence for the best model is 3.6 times stronger than the second best fitting model which contained the additional variable of Sex. Thus the models show that the frequency of activities differed between the two sites, though the effect of Site differed depending on the activity. There is also support that Sex has some effect on the frequency of behaviours. When Site was removed and Season included as a response variable in Set 2, the model with the most support contained only the

Activity response variable, though with a relatively low weight (wi = 0.529), there is some model selection uncertainty. The evidence ratios indicate that the best model is only 2.8 times more likely to be the best model compared to the next best model with variables Activity and Season, and 3.1 times more likely compared to the third most supported model with variables Activity and Sex. This shows that the frequency of each activity differs and that sex and season have some effect, albeit their influence is not all that strong.

log- Model AICc K ∆ AICc wi ER likelihood

Set 1 (Chobe & NG26)

Activity : Site -592.303 1209.390 10 0.0 0.781 1.000 Sex + Site : Activity -592.276 1211.936 11 2.5 0.219 3.566 Activity : Sex : Site -586.259 1226.691 20 17.3 <0.001 >1000 Activity + Site -606.138 1227.288 6 17.9 <0.001 >1000 Activity -607.819 1228.353 5 19.0 <0.001 >1000 Activity + Sex + Site -606.113 1229.592 7 20.2 <0.001 >1000 Activity + Sex -607.806 1230.625 6 21.2 <0.001 >1000 Activity + Sex : Site -605.48 1230.737 8 21.3 <0.001 >1000 Site + Sex : Activity -602.583 1232.55 11 23.1 <0.001 >1000 Activity : Sex -604.333 1233.451 10 24.1 <0.001 >1000 Null -667.44 1338.925 1 129.5 <0.001 >1000

Set 2 (Chobe only) Activity -382.861 778.833 5 0.0 0.529 1.000 Activity + Season -382.656 780.896 6 2.1 0.188 2.813 Activity + Sex -382.746 781.077 6 2.2 0.172 3.076 Activity + Sex + Season -382.539 783.232 7 4.4 0.059 8.970 Activity : Sex -379.191 784.872 10 6.0 0.026 20.346 Activity + Sex : Season -382.516 785.855 8 7.0 0.016 33.062 Season + Sex : Activity -379.031 787.561 11 8.7 0.007 75.571 Activity : Season -381.391 789.272 10 10.4 0.003 176.300 Sex + Season : Activity -381.234 791.968 11 13.1 0.001 529.000 Activity : Sex : Season -376.456 816.450 20 37.6 <0.001 >1000 Null -415.750 835.569 1 56.7 <0.001 >1000

The best fitting model has the lowest corrected Akaike's information criterion (AICc) value. K: number of parameters,

ΔAICc: difference of AICc value from the best fitting model, wi: AICc weight, ER: evidence ratio.

Females were found to spend slightly more time feeding than males at both sites (Table 3.1). Males spent more time than females ruminating in Chobe, but there was little difference between the sexes in NG26. In Chobe, females spent more time walking, but in NG26, there was little difference between the sexes. Males rested more than females in NG26 but males and females spent similar times resting in Chobe. Males interacted with other individuals more than females at both sites; and females were more vigilant than males in Chobe. Only very minor differences were noted between the sexes and sites for the other less frequently observed activities.

In Chobe, feeding and walking activity was slightly higher during the dry season for both sexes. Females rested and ruminated more in the wet season whilst males allocated slightly more time to these activities in the dry season. Males interacted more in the wet season.

All activities were observed throughout the day but some activities were observed more during particular time periods (Table 3.3), albeit these were not always consistent between sexes, sites and seasons. There was no obvious pattern for when giraffe predominantly fed or were involved in “other” activities. Rumination was observed mostly in the mornings, except males in NG26 who ruminated more during the middle of the day and females in Chobe who ruminated similar amounts across all time periods during the dry season. Resting was observed mostly during the middle of the day with the exception of the Chobe females in the wet season who rested more in the mornings, and the NG26 females who rested similar amounts throughout the day. Most walking was observed later in the day, except for the Chobe females who spent similar amounts of time walking throughout the day.

Wet season Dry season 0700- 1100- 1500- 0700- 1100- 1500- 1100 1500 1900 1100 1500 1900 (%) (%) (%) (%) (%) (%) CHOBE Males Feeding 26.52 44.01 41.55 35.77 40.85 52.16 Ruminating 33.97 17.01 8.64 34.57 14.94 4.16 Resting 7.45 11.46 8.44 5.04 13.81 8.48 Walking 14.73 17.69 21.19 12.36 15.57 19.23 Other 17.33 9.84 20.19 12.24 14.83 15.97 Females Feeding 22.27 44.05 51.61 58.70 43.00 47.06 Ruminating 30.67 17.81 5.15 13.04 13.32 13.25 Resting 15.97 10.35 12.15 3.56 12.42 10.13 Walking 22.69 21.38 21.80 18.18 18.15 18.16 Other 8.40 6.41 9.29 6.52 13.11 11.41 NG26 Males Feeding N/A N/A N/A 62.71 55.88 63.08 Ruminating N/A N/A N/A 8.23 15.08 6.43 Resting N/A N/A N/A 6.63 8.05 7.76 Walking N/A N/A N/A 16.01 14.22 17.20 Other N/A N/A N/A 6.41 6.78 5.54 Females Feeding N/A N/A N/A 65.88 67.55 66.13 Ruminating N/A N/A N/A 11.81 9.57 6.97 Resting N/A N/A N/A 3.34 4.43 4.89 Walking N/A N/A N/A 14.68 14.47 17.54 Other N/A N/A N/A 4.28 3.97 4.46

3.3.2 Diet and feeding height

Giraffe in NG26 were observed feeding on 25 different plant species during the two dry season study periods (Table 3.4), with Acacia species, Terminalia sericea and Ziziphus mucronata forming the bulk of the diet. The proportion of observations in which a particular species was consumed varied from month to month and not all plant species were eaten each month. Various plant parts were consumed. Of the 5,625 records of parts utilised, 96% were leaves, 3.36% fruit, and less than 1% flowers, flower buds and stems combined.

Table 3.4 Frequency of browsing events on different plant species by giraffe in the NG26, Botswana, during the 2013 dry season (Feb-Apr, Sep-Nov). The values show the use of each plant species expressed as a percentage of total records for each month observations were made.

Feb Mar Apr Sep Oct Nov n=259 n=581 n=1123 n=1496 n=1960 n=133 (%) (%) (%) (%) (%) (%) Acacia erioloba 26.6 20.1 15.4 38.6 42.2 19.5 A. fleckii 11.6 18.9 16.7 0.1 5.3 A. hebeclada 5.4 4.1 5.9 32.4 10.4 6.0 A. nigrescens 5.0 22.5 6.6 0.3 11.0 A. terminalis 0.1 Colophospermum mopane 0.2 10.3 3.0 Combretum erythrophyllum 0.5 C. hereroense 0.3 0.1 3.0 5.5 C. imberbe 8.3 5.3 2.1 1.7 C. mossambicense 0.2 Dichrostachys cinerea 3.5 2.1 2.1 0.1 Diospyros lycioides 6.2 3.5 0.2 0.3 D. mespiliformis 3.4 0.6 Euclea sp. 0.4 0.2 Gymnosporia senegalensis 0.5 2.4 0.2 0.8 Jasminum fluminense 0.5 0.2 2.5 0.9 5.3 Kigelia africana 1.5 3.2 13.0 4.3 0.8 Lonchocarpus nelsii 2.3 3.6 9.7 0.1 3.0 Peltophorum africanum 0.7 Rhus tenuinervis 1.6 Sclerocarya birrea 0.8 Terminalia sericea 11.6 1.7 2.4 3.1 13.0 2.3 Unidentified climber 0.5 Zehneria marlothii 0.4 0.5 Ziziphus mucronata 32.4 8.1 14.6 5.8 57.9 NB – Not all columns add exactly to 100 due to number rounding.

Not all plants on which giraffe were observed feeding on in Chobe were identified, however, Capparis tomentosa made up a significant portion of the diet in both wet and dry seasons. Afrocanthium pseudorandii, Boscia albitrunca, Canthium glaucum, Combretum mossambicense, Dichrostachys cinerea, Erythroxylum zambesiacum, Flueggea virosa, Gardenia livingstonei, Lonchocarpus nelsii, Markhamia zanzibarica, and Strychnos madagascariensis were also observed being eaten. Of the records of plant parts consumed (dry season: n=2,021; wet season: n=722), 90.6% and 97.8% were of leaves in the dry and wet seasons respectively. Additional plant parts to those utilised in NG26 were consumed in Chobe, supplementing the predominantly leafy diet. In the dry season, bark made up 4.7% of records, and twigs, flowers, flower buds, dry leaves and pods made up the remaining 4.6%. In the wet season, bark, twigs, fruit and stems made up the remaining 2.2% of records. Giraffe in both study areas were further observed licking and eating soil (geophagy) and giraffe in NG26 were observed chewing bones (osteophagy).

Distinctive feeding height patterns were noted between the sexes and age classes. In NG26, adult males were most often observed feeding at heights above 4.5 m (60% of observations; Table 3.5 and Figure 3.1), whilst adult females fed predominantly between 1.5 - 4 m (77% of observations). Average feeding heights were lower for sub-adults, with heights between 1 - 3 m making up 80% of observations for females and heights between 1.5 – 3 m making up 78% of observations for males. Giraffe were found feeding at heights lower than 1.5 m in only 15% of observations.

Table 3.5 Mean and median foraging heights for giraffe in Chobe National Park and NG26, Botswana.

Chobe NG26 Mean Mean N Median n Median ± SD ± SD

Adult female 526 2.77 ± 1.00 2.5 1357 3.01 ± 1.03 3 Adult male 925 4.07 ± 1.06 4 536 4.52 ± 1.09 5 Sub-adult female 174 2.57 ± 0.71 2.5 328 2.06 ± 0.95 2 Sub-adult male 243 2.70 ± 0.89 3 297 2.51 ± 0.90 2.5

Adult Males Adult Females % % Chobe Chobe 30 NG26 30 NG26 20 20

10 10

0 0

Feeding height (m) Feeding height (m)

Sub-adult Males Sub-adult Females % Chobe % Chobe 30 NG26 30 NG26 20 20

10 10

0 0

Feeding height (m) Feeding height (m)

Figure 3.1 Proportion of giraffe feeding time allocated to different height classes in Chobe National Park and NG26, Botswana.

The mean and median foraging heights for adults in Chobe were slightly lower than in NG26, yet feeding heights still followed the same general trend with adult males feeding at greater heights than adult females. Adult males tended to feed at heights above 3 m (87% of feeding 57 observations), whilst adult females typically fed at heights between 1.5 - 4 m (80% of observations). They very rarely fed at heights above 4.5 m from where adult males fed the most. The mean and median foraging heights of the Chobe sub-adults was slightly higher than for sub-adults in NG26, albeit were still lower than adult feeding heights. The Chobe sub-adults fed predominantly at heights between 2 - 3.5 m (89% of sub- adult female observations; 85% of sub-adult male observations). Less than 6% of feeding height records for all age and sex classes were below 1.5 m.

3.4 DISCUSSION

3.4.1 Behavioural differences between sites, sexes and seasons

Site differences

The activity budgets of giraffe differed significantly between the two sites, largely due to differences in the amount of time allocated to feeding (up to 48% of activity budgets in Chobe, and as much as 67% in NG26). This variation further demonstrates the differences found for giraffe across their geographic range. In Tsavo East National Park, Kenya, feeding was found to occupy from 26.9 - 53.1% of daytime activity in a single day (Leuthold and Leuthold, 1978); in Niger, the portion of time spent feeding ranged from 45 - 80% depending on the month (Ciofolo and Le Pendu, 2002); and feeding took up to 49.3% and 59% of daytime activity in Mikumi National Park, Tanzania, and the northern Namib Desert, Namibia, respectively (Ginnett and Demment, 1997; Fennessy, 2004). Such differences might be explained by any number of factors including population density, the distribution and quality of food resources, or the chemical composition of forage across these distinct habitats (e.g. Strier, 1987). Increased feeding time for both males and females in NG26 compared to Chobe may also lie, at least in part, in differences in bite mass and/or browsing mode (e.g. leaf stripping or picking), which are influenced by foliage properties and the 58 presence or absence of thorns (Pellew, 1984a; du Toit and Yetman, 2005).

Giraffe devoted more time to resting in Chobe but as the proportion of time allocated to resting is inversely related to the proportion of time allocated to other activities, it is not surprising that giraffe in NG26 rested less given the large amount of time they allocated to feeding.

Innis (1958) noted that in areas of abundant forage, giraffe may not travel far each day. Thus, a greater proportion of time devoted to walking in Chobe compared to NG26 was probably due to more sparsely distributed food resources in Chobe or greater competition for these resources, though greater assessment of vegetation in the study areas is needed to support these inferences.

As animals allocate time to activities in a manner that maximises biological fitness whilst minimising risks (Lima and Dill, 1990; Owen- Smith and Goodall, 2014), the larger portion of time spent vigilant by both male and female giraffe in Chobe compared to NG26 is likely an indication that predation risk is higher in Chobe. Differences in vigilance behaviour between sites of varying predation risk have been demonstrated for other herbivores, including impala and wildebeest (Connochaetes taurinus) (Hunter and Skinner, 1998). Giraffe in both sites were also observed being vigilant in response to various external stimuli from predators to other herbivores to vehicles and people. Lions (Panthera leo), were found in the vicinity of giraffe on several occasions in Chobe but never in NG26. Not surprising given that the lion is the giraffes’ main predator (e.g. Kruuk and Turner, 1967; Pienaar, 1969), once noted, nearly all giraffe present watched for longer (sometimes over 30 minutes) and more intently than any other stimuli, and this likely accounts for at least some of the difference in time spent vigilant between the two study sites. Curiously, Cameron and du Toit (2005) suggested predation risk had little influence on vigilance behaviour in Kruger National Park. Similarly, Périquet et al. (2010) found no significant influence of predation risk on giraffe vigilance behaviour at a 59 waterhole in Hwange National Park, though the relationship between lion presence and the proportion of time devoted to vigilance and the frequency of vigilance bouts whilst drinking did approach statistical significance.

Whilst sampling took place across many days and months and at different times of the day at both sites, giraffe were typically easier to find and follow in NG26 than Chobe which meant that sampling effort, in terms of how many data points were collected, was substantially greater in NG26. It is possible that this difference had some impact on results, however, with over 549 hours of study at each site, we believe that the results are a true reflection of their behaviour.

Sexual differences

As hypothesised, sex was also found to have some influence over activity budgets, with the differences in time spent feeding of particular note. As predicted, females allocated more time to feeding than did males. In the Serengeti, the diet of females was found to be nutritionally richer, whilst the male diet had a significantly higher fibre and lignin content (Pellew, 1984a). If similar differences exist in Botswana, the larger portion of time spent foraging by females may be due to the increased time required for selective foraging.

Longer foraging times for females may also be related to an increase in food intake necessary to sustain the substantial metabolic demands associated with gestation and lactation (Ginnett and Demment, 1997; Oftedal, 1985). Furthermore, male giraffe have been found to have a higher food intake rate than females (Ginnett and Demment, 1997) which may facilitate shorter feeding times despite their larger food requirements. Shorter feeding times for males may also be an indication that males compromise feeding time in order to carry out other behaviours such as neck sparring (either practice sparring or to establish dominance) and sexual interactions, which are important 60 activities necessary to increase their biological fitness (Wittenberger, 1981).

The time dedicated to walking also differed slightly between the sexes in Chobe (as expected) but not in NG26. These differences are possibly linked to feeding, with increased walking time for females a consequence of being more selective, feeding for longer, and moving between more forage patches. Ginnett and Demment (1997) similarly found that females in Mikumi National Park walked more than males. Longer patch residency times by males (e.g. Ginnett and Demment, 1997) might also explain their reduced walking time. In contrast, males in the Namib Desert spent more time walking than females (Fennessy, 2004), corresponding with their longer daily, and more frequent long distance movements, attributed, at least in part, to searching for receptive females in the sparsely populated environment. The higher giraffe density and higher female to male ratio in Chobe possibly renders such large movements by males superfluous.

Similar to findings in Mikumi National Park, Tanzania (Ginnett and Demment, 1997), no sex differences in rumination time were observed in NG26. In contrast, males ruminated more in Chobe, similar to males in the northern Namib Desert (Fennessy, 2004), Tsavo National Park (Leuthold and Leuthold, 1978) and Serengeti National Park (Pellew, 1984a). The variation between the sexes might be a factor of differences in diet quality (Pellew, 1984a). Indeed a study on captive giraffe found that ruminating increased with dietary fibre content (Baxter and Plowman, 2001). Thus it is possible the increased digestibility of higher quality forage consumed by females lowered the amount of time required for rumination. Along similar lines, it is possible that in areas where no differences in rumination time were detected, the diet of both sexes is more similar. The nutritional quality of the male and female diets in Chobe and NG26 would need to be analysed to determine whether this is the case in these areas of Botswana.

Seasonal differences

Season was found to affect giraffe activity budgets, although differences in the proportion of time allocated to activities were not as marked as expected. As was the case in this study, giraffe have consistently been found to increase feeding activity during the dry season across their range (Innis, 1958; Pellew, 1984a; Ciofolo and Le Pendu, 2002; Fennessy, 2004). Omphile and Powell (2006) noted the opposite in Chobe National Park but as they only recorded behaviour during the first and last three hours of daylight, their results cannot be used to make accurate inferences about diurnal giraffe activity. The longer dry season feeding times are likely necessary to compensate for the deterioration of food quality and quantity during this time (Sinclair, 1975; Owen-Smith, 1982; Cooper et al., 1988; Leggett et al., 2003). Such seasonal patterns are also typical of other browsers and mixed feeders including kudu, impala and springbok (Owen-Smith, 1982).

Seasonal differences in the amount of time spent ruminating were inconsistent between the sexes, with males ruminating slightly more during the dry season, similar to giraffe in the northern Namib Desert (Fennessy, 2004), whilst females ruminated more in the wet season. Pellew (1984a), conversely, noted no seasonal differences in the Serengeti, Tanzania.

In many species, an increase in feeding time during the dry season is accompanied by an increase in the time spent walking (Bunnell and Gillingham, 1985), but contrary to predictions, the opposite was true for giraffe in Chobe, though differences were relatively small. Given the lack of seasonal differences in the length of daily movements for adult female giraffe in Chobe reported previously (Chapter 2; McQualter et al., 2015), these minor seasonal differences in walking time are perhaps not all that surprising. Greater dry season movements in water-dependent species have also been attributed, in part, to the frequent need to move between food and water resources (e.g. Cain et al., 2012; Jarman and Jarman 1973). However, due to the giraffes’ ability to go for extended 62 periods without drinking (Chapter 2; Berry, 1973; Fennessy, 2009), their movements are probably little affected by water demands, and are more likely driven by the distribution and quality of food.

The proportion of time dedicated to resting showed little variation between the wet and dry seasons. However, the dry season has hot and cold phases where maximum temperatures can differ by as much as ten degrees. By not considering the hot-dry and cold-dry periods separately in this study, any effects that ambient temperature might have on resting were indistinguishable. It is possible that if the dry season had been further divided into hot-dry and cold-dry seasons, resting patterns would have been similar to finding in Namibia where giraffe rested significantly less in the cold-dry season, and more during the warmer seasons (Fennessy, 2004). Du Toit and Yetman (2005) also reported on increased resting on days with high maximum temperatures for giraffe in South Africa.

3.4.2 Daily activity patterns

Despite giraffe displaying a biphasic diurnal distribution of energy consumptive activities in some areas (e.g. Pellew, 1984a; Fennessy, 2004; Dagg, 2014), only the NG26 males and Chobe females during the dry season followed this pattern. Although males in Chobe rested most during the warmer parts of the day, neither feeding nor walking were at their lowest during this time which does not follow the heat load concept (e.g. Lewis, 1975; Mitchell, 1977; Leuthold and Leuthold, 1978). Rumination time was also not at its lowest in the middle of the day.

Rumination typically predominated in the morning for both males and females and possibly indicates feeding prior to 0700 hr (see also Mitchell et al., 2015). Pellew (1984a), however, found that in the Serengeti, ruminating is the dominant nocturnal activity and feeding is

63 at a minimum in the early morning. Investigation into the nocturnal activities of the giraffe in Botswana is needed to provide further insight.

More walking was observed later in the day in both seasons and sites, except for the Chobe females for whom walking was evenly spread across the three time periods. This increase in walking during the latter part of the day did not always correspond with increased feeding, which suggests additional reasons for increased walking time. One possible reason is movement towards areas in which they spend the nocturnal hours. In Chobe, giraffe moved into the forests as the light faded. Leuthold and Leuthold (1978) reported similar evening movements into the riverine forest by giraffe in Tsavo National Park which they proposed may have been for reasons of thermoregulation, feeding, or protection from predators. There were no temporal patterns noticeable for the other activities.

Whilst there are many behavioural similarities across giraffe populations there is also much variation resulting from distinct combinations and effects of extrinsic factors. By examining the amount of time allocated to particular activities, it possible to gain insight into ecological pressures acting on a population. This study demonstrates how activity patterns are influenced by multiple factors simultaneously. Habitat, sex and season were all found to affect the amount of time giraffe allocated to the various activities, with habitat being the most influential. Behavioural activities were not evenly distributed throughout the day, albeit no common temporal behavioural pattern was found between the sites, sexes or seasons.

3.4.3 Behavioural observations

Various records of giraffe natural history observations (e.g. Innis, 1958; Coe, 1967; Western, 1971; Foster and Dagg, 1972; Berry, 1973; Mejia (see Moss, 1982); Fennessy, 2004) describe many giraffe behaviours, some of which are site specific, others which have only been observed 64 rarely. Few natural history observations have been reported for giraffe in Botswana. This section describes observed feeding behaviours (including diet and feeding heights) of giraffe in northern Botswana in addition to other observed behaviours which have either not been previously documented or have been reported elsewhere but with no or limited backup from repeat observations. These observational accounts might later inspire the development and testing of new hypotheses.

Giraffe diet and feeding heights

The diverse diet of the giraffe is well documented across its geographic range, demonstrating the giraffes’ ability to adapt to temporal changes in vegetation composition and availability (e.g. Innis, 1958; Lamprey, 1963; Leuthold and Leuthold, 1972; Lightfoot, 1978; Pellew, 1984a and b; Ciofolo and Le Pendu, 2002; Fennessy, 2004; O’Kane et al., 2011) and possibly “dilute” toxic compounds (tannins and phenolics) from particular species in nutrient-poor environments (Mramba et al. 2017; Freeland and Saladin, 1989). The highest diversity has been reported in Zimbabwe, with giraffe utilising 77 plant species (Lightfoot, 1978), whilst giraffe in the northern Namib Desert have the least diverse diet recorded from a long-term study with only 29 species (Fennessy, 2004). The actual number of dietary species in NG26 most likely exceeds the 20 identified during the limited field study. Marked seasonal differences in the diet of giraffe have been noted elsewhere (e.g. Leuthold and Leuthold, 1972), thus it is probable that during the wet season, giraffe in NG26 also utilize deciduous or semi-deciduous species which are unavailable during the dry season. Additionally, as the consumption of some plant species differs according to the plant phenology (Pellew, 1984a; Ciofolo and Le Pendu, 2002) it is possible that important growth stages (e.g. flowering or fruiting) for some plant species were missed due to the limited study period. More extensive lists of dietary species may also result from giraffe altering their ranging patterns and exploiting

65 different habitats during the different seasons (e.g. McQualter et al., 2015; Leuthold and Leuthold, 1972; Ciofolo and Le Pendu, 2002).

The bulk of the giraffe diet in both study sites consisted of leaves, but fruits and flowers were readily consumed when available. This is consistent with giraffe elsewhere (e.g. Hall-Martin, 1974; Ciofolo and Le Pendu, 2002). Ingestion of woody materials (bark and twigs) was only observed in Chobe and was greater in the dry season when green leaves were limited. Similar behaviour was noted in Timbavati Private Nature Reserve, South Africa (Hall-Martin, 1974). That it was never observed in NG26 is likely a reflection of the differences in available browse, with sufficient browse biomass in NG26 rendering the consumption of less nutritional, woody items unnecessary.

Typical adult feeding heights varied only slightly between Chobe and NG26, but differences between areas may simply be a reflection of the heights of vegetation available. Leuthold and Leuthold (1972), for example, found that much of the giraffe diet in Tsavo National Park was from low shrubs, and consequently, 50% of browsing was below 2 m. Feeding height differences between sub-adults of the two study sites are likely due to a greater number of larger sub-adults observed in Chobe than NG26.

Across Africa, male giraffe predominantly feed at heights above that of females (this study; du Toit, 1990; Young and Isbell, 1991; Ginnett and Demment, 1997; Ciofolo and Le Pendu, 2002; O’Connor et al., 2015; Mramba et al., 2017), which is not surprising given their size differences. Young and Isbell (1991) found that feeding rates for giraffe are greatest at intermediate heights of 3 m for adult males and 2.5 m for adult females. Whilst the mean and median foraging heights for females in Botswana was found to be at or around optimal foraging height, males fed much higher at sub-optimal levels. Giraffe in Kruger National Park and Niger showed similar height feeding patterns (du Toit, 1990; Ciofolo and Le Pendu, 2002). Du Toit (1990) suggests that males feed higher to access the protein-rich shoots found in the upper canopy 66 which females often cannot reach. This seems plausible as competition for such preferred food items would be reduced at these higher levels, and it may be that the benefits of feeding higher with reduced competition for favoured items outweighs any losses incurred by feeding at a reduced rate.

In addition to the shrubs and small trees giraffe predominantly feed on in Chobe and NG26, large adult males have the advantage of being able to feed on desirable mature trees (e.g. Kigelia africana and Strychnos madagascariensis) in which the browse line is beyond the reach of females and smaller males. Feeding on such trees accounted for most feeding observations at heights beyond 5.5 m.

Young and Isbell (1991) offer an alternative explanation as to why males might feed higher. They suggest dominant males may feed at greater heights as it enables them to maintain vigilance for competing males whilst feeding, and at the same time advertise their presence to these other males. This is certainly a possibility though the capacity to be vigilant may be dependent on how high the male is feeding and the corresponding angle of the head, as vigilance may be reduced when the head and neck are extended vertically (du Toit, 1990).

Consistent with other studies, average feeding heights for giraffe were above those for the smaller browsers, greater kudu (Tragelaphus strepsiceros), impala and bushbuck (T. scriptus) found in the two study areas (Woolnough and du Toit, 2001; Makhabu, 2005; O’Kane et al., 2011). This may be related to the optimal foraging heights for feeding rates mentioned above. Alternatively, it may be a function of the greater leaf mass available per browsed shoot at heights above those reachable to the smaller browsers (Woolnough and du Toit, 2001).

Grazing, geophagia and osteophagia

On two separate occasions during the dry season, giraffe were observed eating grass on the Chobe River floodplain, once by an adult male and once by an adult female. Seeber et al. (2012) have suggested that grasses might provide micronutrients when they are lacking in browse. Deliberate grazing by giraffe has been noted in several other areas (e.g. Lamprey, 1963; Pienaar, 1963; Ciofolo and Le Pendu, 2002; Fennessy, 2004; Parker and Bernard, 2005; Seeber et al., 2012), though as in Chobe, it was observed infrequently. Leuthold and Leuthold (1972) never observed grazing, whilst other studies have reported accidental consumption of grass with other food items (e.g. Field, 1976; Pellew, 1984a).

In addition to botanical items, giraffe were frequently observed licking and eating dirt (geophagia) in Chobe, and occasionally in NG26. Geophagia has been noted for giraffe previously (Langman, 1978; Ciofolo and Le Pendu, 2002; Seeber et al., 2012) and is common in other large herbivorous and omnivorous mammals (Kreulen, 1985). Contrary to Langman (1978) who found that geophagia was almost exclusive to sub-adults, giraffe of all age-sex classes were observed eating soil in Botswana. Why they eat soil is unknown, however, various explanations have been put forward for geophagia in general, including supplementation of essential mineral nutrients (Kreulen and Jager, 1984; Klaus et al., 1998; Stephenson et al., 2011), reduction of the effects of secondary plant compounds (Klaus et al., 1998), defence against acidosis (Kreulen, 1985; Klaus and Schmid, 1998), and remediation of gastrointestinal upsets such as diarrhoea (Wilson, 2003). In Chobe, giraffe were only seen licking soil on the floodplains where, presumably, the soil is richer in nutrients and clay particles than the nutrient-poor Kalahari sands further from the river (Wang et al., 2007). Similar to giraffe in Niger and Timbavati Nature Reserve (Ciofolo and Le Pendu, 2002; Langman, 1978), giraffe in NG26 licked soil from termite mounds.

Giraffe in NG26 were observed chewing on bones (osteophagia) on three occasions. This is a well-documented phenomenon in giraffe (Western, 1971; Wyatt, 1971; Leuthold and Leuthold, 1972; Langman, 1978; Ciofolo and Le Pendu, 2002) and other artiodactyls (Sutcliffe, 1973) and likely indicates phosphorus deficiencies (Theiler et al., 1924).

Drinking

Giraffe were always cautious before and whilst drinking, presumably because of their increased vulnerability when in the drinking position (also noted by Innis, 1958). Particularly on the Chobe River, giraffe were often seen to approach the water, splay their legs and lower their head and necks, only to whip their heads up, spring their legs back beneath them and move away from the water without drinking, often returning to the water moments later. Sometimes, this occurred as many as three or four times before the individual drank, whilst some did not end up drinking at all. The giraffe appeared especially nervous when other herbivores were in the vicinity, particularly elephants (Loxodonta africana) which were often aggressive around the water.

As recorded by Innis (1958), giraffe rarely drank in one continuous stretch. More typically they were observed drinking in short bouts lasting from a few seconds to almost a minute, resuming an upright position in-between. The most drinking bouts observed in a single drinking session was that for an adult male who bent down to drink seven times.

Grooming

Giraffe were observed rubbing their head, neck and torso against tree trunks and branches, scratching their underbellies by rocking back and forth over shrubs, scratching their legs by dragging them through the branches of shrubs, and nibbling or licking body parts that could be

69 reached. Such grooming behaviours have been noted for giraffe elsewhere (Innis, 1958; Fennessy, 2004). Presumably, such actions helps rid them of ectoparasites such as ticks, and relieve skin irritations.

Grooming was generally observed infrequently (though see below), making up less than 1% of the activity budget for both sexes and study sites. This is similar to what was found in Namibia (Fennessy, 2004). Innis (1958) on the other hand, reported that giraffe in South Africa spent “much time” grooming but was not quantified. Why giraffe in some areas allocate more time to grooming than in other areas is unclear. Fennessy (2004) proposed that giraffe in Namibia might be less affected by water-born parasites because of their limited use of free- water, however this is not an issue in either Chobe or NG26.

Though grooming was not commonly observed, a number of giraffe in NG26 whom were frequently observed together all became infected or infested by something unknown, leading to longer and more frequent bouts of grooming. Irritation was so severe that after a few weeks the giraffe had rubbed away much of the hair on their necks and sides of their heads. This demonstrated how parasite infestations or transmissible infections could easily alter grooming behaviour.

Social behaviours

As observed in other giraffe studies (e.g. Innis, 1958; Leuthold, 1979; Fennessy, 2004), behaviours such as sniffing, rubbing, neck sparring and testing for oestrus were commonplace and frequently observed. Only neck sparring between males, however, occupied significant amounts of time which explains the disparity between the sexes in time devoted to interaction in the activity budgets.

The familiarity of individual giraffe to each other and the male dominance hierarchy within populations is well documented (e.g.

Leuthold, 1979; Pratt and Anderson, 1982; Fennessy, 2004; Dagg, 2014). The established hierarchy, although not rigidly fixed (Moss, 1982), might be determined in the sub-adult and early adult years by frequent neck sparring (Leuthold, 1979), though Pratt and Anderson (1985) have suggested that the non-serious sparring is instead just play behaviour, preparing them for later in life when males compete for dominancy and the right to breed.

Numerous sparring events were observed, particularly in Chobe, involving all age group combinations as seen elsewhere (e.g. Coe, 1967; Fennessy, 2004). Coe (1967) reported that necking was only observed in all-male herds in Kenya, but in Botswana, necking was also observed in mixed herds. One sparring bout persisted for almost an hour but more typically they lasted for 20 minutes or less, though sometimes sparring only ceased momentarily whilst partners fed.

Sparring was often instigated by younger males but not always. Sparring began with the individual pushing or rubbing his neck or head on another, or gently nudging the other with their ossicones. The onset of sparring often encouraged others to either join in with those already sparring or begin sparring with another partner. On one occasion, five pairs of males from an all-male herd of fourteen individuals were observed sparring at the same time. As many as four giraffe were seen sparring together as a group, though Pratt and Anderson (1982) reported an even larger group of five sparring together.

The intensity of blows appeared dependent on the size of the opponent, such that larger males were gentler with smaller males, presumably to avoid injuring them, though all sparring, except for serious agonistic bouts between mature males, rarely involved really heavy blows.

Very occasionally, mature males were seen with bloodied ossicones and battle wounds, but only two violent sparring bouts were witnessed. Males appeared to be well aware of their placing in the hierarchy which likely reduces agonistic events (Coe, 1967; Leuthold, 1977). Several

71 scenarios were observed which demonstrated the social standing among males. These included a subordinate male approaching a herd but changing direction upon (presumably) sighting a dominant male in the herd; a subordinate male leaving a herd when a dominant male approached the herd; a mature male moving away from a herd and intercepting an approaching male where the two stood sizing each other up without physical contact, before the second male walked off; and a subordinate male being displaced from a shrub it was feeding on by a dominant male.

Observations of mounting between males, sometimes with erect penises, during or after neck sparring have been reported throughout the literature (e.g. Innis, 1958; Coe, 1967; Leuthold, 1979; Fennessy, 2004). This was seen on a few occasions in Chobe. Innis (1958) and Coe (1967) proposed that such male-male mounting behaviour had sexual significance. In contrast, Mejia (see Moss, 1982) and Leuthold (1979) perceived such behaviour as a mark of dominance, though Pratt and Anderson (1985), through intent observations and thorough recording of positions and movement, failed to find evidence of this.

Sexual behaviour was observed frequently, though occupied little of the activity budget. The nuzzling or sniffing of a female’s rump by a male was common and occurred when a male came into contact with a female during the course of his daily activities. Such behaviour was most typical of adult males and sometimes, but not always, stimulated urination by the female for flehmen. Pratt and Anderson (1985) found that older males were more successful in prompting urination by females which they attributed to the inexperience of younger males and the preference for females for mature males. Contrary to Pratt and Anderson (1985) whom never observed sub-adults assessing females for oestrus, sub-adult males were seen to nuzzle a female’s rump on several occasions in the study areas and surprisingly, on two instances this prompted the female to urinate.

Though it was usually the males who instigated the flehmen sequence, on one occasion an all-female herd was observed walking down a road when they met a male coming from the opposite direction. All individuals stopped momentarily then all but one female moved off again. The remaining female then proceeded to circle around the male before presenting her rear end for him to nuzzle. Such behaviour has not previously been reported for giraffe. Leuthold (1979) also observed females initiating the flehmen sequence but they did so by rubbing their neck on a male’s flank. Pratt and Anderson (1985) similarly recorded females rubbing on males, presumably aroused, but the males rarely reacted. Pratt and Anderson (1985) also noted that younger females occasionally urinated if a mature male passed them, even without any contact from the male.

When a female was in oestrous she was carefully guarded by a male. Several times a female was seen weaving around and circling shrubs with a male in close pursuit. When the female stopped to forage the male would press up against her from behind and then follow her when she moved on again. Such behaviour persisted for hours and even days. A number of times, a male was seen attempting to mount a female only for the female to step forward and away, but the male persisted. Successful copulation was observed only twice over the study period and as noted by Dagg (2014), lasted only a matter of seconds.

The only non-sexual interactions observed between male and females were of males sniffing females or females sniffing males; females rubbing their head or neck on males; females nudging sub-adult males to make them move out of the way; and females butting sub-adult males. Female-female interactions were rarely observed but included naso-frontal greetings (Pratt and Anderson, 1979), sniffing, rubbing and butting. Leuthold (1979) also noted very few interactions among females in Tsavo National Park, though they were found to be quite common in the Namib Desert (Fennessy, 2004) and Tarangire National Park (Pratt and Anderson, 1985).

The giraffe mother-calf relationship is curious. In some ungulate species, the young constantly follow the mothers (e.g. zebra, rhinoceros, wildebeest and elephant; Leuthold, 1977), whilst in others, the young are left on their own for long periods (e.g. Grant’s gazelle Nanger granti: Walther, 1965; Gerenuk Litocranius walleri: Leuthold, 1978). Giraffe, however, demonstrate a combination of both behaviours, though this seems somewhat site specific. In Arusha National Park, giraffe calves are rarely left unattended by their mothers (Pratt and Anderson, 1982), yet in Fleur de Lys ranch (Innis, 1958), Serengeti National Park (Pratt and Anderson, 1979) and Timbavati Private Nature Reserve (Langman, 1977), calves were often left on their own or in nursery groups for extended periods. In Chobe and NG26, calves were seen both with and without their mothers in sight. Pratt and Anderson (1982) suggested that calves may be left behind when mothers have to travel long distances to find water, though in Chobe and NG26, it seems more likely that female were travelling long distances to find preferred food. Supporting this notion, Leuthold (1979) found the distance between a calf and its mother increased during the dry season when food became sparser.

Only eight suckling events were witnessed, reinforcing previous reports of low suckling frequencies (Langman, 1977; Leuthold, 1979; Moss, 1982; Pratt and Anderson, 1982). The duration of suckling observed ranged from 5 to 65 seconds, though durations of up to 226 seconds have been recorded elsewhere (Pratt and Anderson, 1979). When calves were in the herd with the mother, it was typically the calf who initiated the suckling, mostly by first rubbing their head and neck on the mother’s rump before reaching for the teat. In some cases, the mother stepped away from the calf preventing it from suckling. Often the female would sniff the calf prior to, or during suckling. In cases where the mother returned after feeding a considerable distance away, the mother would stand looking at the calf and wait for the calf to approach and suckle. Suckling was generally terminated when the mother walked off

74 or lifted her hind leg, though on two occasions, an adult male was seen to interfere, one pushing himself between the female and her calf, and the other shepherding the female away. Innis (1958) witnessed similar interference behaviour.

The observed displacement of subordinate males by dominant males mentioned previously suggests that individuals are able to recognise others by visual cues, yet scent also seems to play a large role in individual recognition. On numerous occasions, giraffe from separate herds were observed sniffing one another upon coming together. As this did not occur every time, it is possible such behaviour is reserved for individuals that have either not previously met or have not seen each other in some time. Supporting this view is the behaviour of giraffe towards new calves and their mothers. When a female introduced her new calf to a herd, a herd approached a female and her new calf, or an individual or herd merged with another in which there was a new calf, all individuals sniffed the calf. The females, whom had likely been secluded from others for up to a few weeks post-partum (Leuthold, 1979), were also often sniffed by the other giraffe. Fennessy (2004) and Leuthold (1979) also noted the interest generated by new calves.

Only once was a female observed trying to shield her calf from others. Curiously, on one occasion a calf and a young sub-adult male who was not a sibling of the calf, were found together whilst the calf’s mother fed a hundred or so metres away. A sub-adult male and sub-adult female approached and sniffed the two. The original sub-adult male then sniffed the newly arrived sub-adult male before pushing the new arrivals away from the calf then standing between them and the calf.

CHAPTER 4

Giraffe social networks and space use in Chobe National Park, Botswana

4.1 INTRODUCTION

The social structure of a population is defined by the patterning of relationships between its members (Hinde, 1976). Social structures can influence foraging, anti-predator, dispersal and reproductive strategies (Krause et al., 2007; Krause et al., 2015). They can also influence the development and maintenance of cooperative relationships (Krause et al., 2015), gene flow (Sugg et al., 1996), diffusion of information through a population (e.g. Rendell and Whitehead, 2001), and disease transmission within and between populations (Couzin, 2006; Wey et al., 2008; Krause et al., 2015). As such, they have important implications for aspects of biology, ecology and evolution. Nonetheless, knowledge of the structure and function of social relationships in many species is lacking (Couzin, 2006).

Numerous studies have reported common measures of sociality (e.g. group size) but these measures only indirectly reflect social relationships and assume homogeneity of associations between individuals (Wey et al., 2008). However, association patterns are often non-random, with individuals having a greater affinity to associate with particular individuals more than others (e.g. Bigg et al., 1990; Holekamp et al., 1997; Archie et al., 2006). Furthermore, individual’s exhibit variation in social contact patterns, i.e. individuals have varying numbers of associates (Krause and Ruxton, 2002). The recent application of social network analysis to animal systems and the development of new quantitative methods of social analysis now provide

76 useful tools in which to measure social relationships directly and establish a deeper understanding of animal social structures (Wey et al., 2008). This has led to a growing awareness among researchers of the importance of social affiliation and bonding which have been found to influence individual fitness through improved health, longevity, reproductive success and offspring survival within social species (Feh, 1999; Weidt et al., 2008; Cameron et al., 2009; Silk et al., 2009, 2010; Schülke et al., 2010; Archie et al., 2014).

With whom individuals associate has been found to be influenced by a number of factors including kinship (e.g. elephant, Loxodonta africana: Moss and Lee, 2011; killer whales, Orcinus orca: Parsons et al., 2009; lions, Panthera leo: Bertram, 1975; baboons, Papio sp.: Silk et al., 2006), reproductive status (e.g. Bechstein's bat, Myotis bechsteinii: Kerth and König, 1999; male African elephants: Goldenberg et al., 2014; male plains zebra, Equus quagga: Fischhoff et al., 2009), social rank (e.g. spotted hyaena, Crocuta crocuta: Holekamp et al., 1997) and age (e.g. male African elephant: Lee et al., 2011). Moreover, it has been pointed out that shared space use is also likely to impact association patterns due to increased potential for animals to come across each other and interact (Lusseau et al., 2006; Wey et al., 2008; VanderWaal et al., 2014).

Social systems for many species are characterised by fission-fusion dynamics, whereby members of communities form frequently changing sub-groups in their bid to maximise fitness and reproductive success (Alexander, 1974; Lehmann and Boesch, 2004). Fission-fusion species can be further categorised as either “higher” or “lower” fission-fusion species (Aureli et al., 2008). Higher fission-fusion species, including the common chimpanzee, Pan troglodytes (Lehmann and Boesch, 2004), spider monkey, Ateles geoffroyi (Ramos-Fernández et al., 2009), spotted hyaena (Smith et al., 2008), common eland, Taurotragus oryx (Hillman, 1987) and some bottlenose dolphin populations, Tursiops sp. (Lusseau 77 et al., 2006), are characterised by social groups which vary greatly in group size and composition and show temporal variation in spatial cohesion (Aureli et al., 2008). In contrast, lower fission-fusion species exhibit greater temporal stability in group cohesion and membership (e.g. elephant family units and hamadryas baboons, Papio hamadryas (Aureli et al., 2008).

In fission-fusion species, group size and composition often change in response to fluctuations in environmental variables such as resource availability and predation risk (Altman, 1974; Wrangham et al., 1993). For example, elephant herd sizes increase with the onset of rain and gradually decline as food resources diminish through the dry season (Western and Lindsay, 1984); the size of spider monkey (Ateles paniscus chamek) foraging parties increases with feeding patch size and density and subsequent fruit abundance (McFarland Symington, 1988); and social groups of hamadryas baboons separate when food availability is reduced, but coalesce in response to perceived increases in predation risk (Schreier and Swedell, 2012).

Incompatible differences in the physiological needs or preferences and/or activity budgets of individuals can also impact associations and group formation (Rubenstein, 1986, 1994; Ruckstuhl and Kokko, 2002; Caister et al., 2003). For example, differences in the amount of time males and females spend feeding and walking have been associated with sexual segregation in many sexually dimorphic ungulate species (Ruckstuhl and Neuhaus, 2002). Similarly, differences in dietary or water needs and/or susceptibility to predation between sexes or females of varying reproductive condition (or their young) can result in segregation due to a lack of behavioural synchronisation, or occupation of different areas (Rubenstein, 1986, 1994; Mysterud, 2000; Caister et al., 2003; Alves et al., 2013; Godde et al., 2015).

Giraffe were initially considered to have little social structure on account of the changeability of herd size and composition, with herds described as ‘loose’ and 'unstable', and with individuals ‘lacking close social ties’ (Innis, 1958; Dagg and Foster, 1982; Berry, 1973; Leuthold, 1979). More recent studies, however, have recognised that giraffe are more socially complex, displaying fission-fusion dynamics and structured relationship patterns (Bercovitch and Berry, 2012; Carter et al., 2013a and b; VanderWaal et al., 2014). VanderWaal (2014) has even provided evidence of giraffe having a multi-tiered social structure similar to those documented for elephants (Moss and Poole, 1983), geladas (Dunbar, 1984), hamadryas baboons (Kummer and Kurt, 1963) and killer whales (Bigg et al., 1990).

Whilst fission-fusion social organisations are not uncommon among species, the factors driving the underlying structure of fission-fusion systems have not been widely studied. In this study, herd membership was used to quantify individual association patterns and determine the social structure of a giraffe population in Chobe National Park, Botswana. The aims of the study were (1) to describe the grouping patterns of the Chobe population using common measures of sociality, and make comparisons with other populations; (2) to test for sex differences in non-random associations (preferred or avoided relationships) with other individuals; (3) to investigate the influence of space use on pairwise associations and social groupings; and (4) to look for evidence of a multi-tiered social structure. It was hypothesised that males and females would show different patterns of sociality, and that spatial overlap would have some effect on the level of association between individuals or groups.

4.2 METHODS 4.2.1 Study Area The study was conducted in Chobe National Park’s most northern section, the Chobe Riverfront, in northern Botswana. The area is comprised of grassy floodplains, shrublands, mixed woodland and Baikiaea woodlands (Mosugelo et al., 2002; Skarpe et al., 2004). A more detailed vegetation description is provided in Chapter 1, section 1.7.1. The climate in northern Botswana is semi-arid with the wet season typically falling between November and April (Burgess, 2006). More details on the climate are given in Chapter 1, section 1.8. The giraffe density has been estimated at 0.11/km2 (CI= 98; Chase, 2011).

4.2.2 Data collection Giraffe herd composition and locations were recorded opportunistically from 2 September 2012 - 17 February 2013, 25 April – 12 September 2013, and 7 November 2013 – 14 May 2014. All observations were made from a vehicle, and were largely restricted to areas visible from the road network. Different routes covering different habitat types were traversed each day in an attempt to randomise giraffe encounters. As this study was mostly conducted concurrently with the behavioural study (Chapter 3), the distance covered per trip depended on which route was taken, where giraffe were first located, how long they stayed in view for behavioural observations and the distance to the next herd encountered. Trips ranged from around 30 – 100 km. All observations were made during daylight hours.

As giraffe can potentially maintain visual contact over large distances of 1 km or more, it can be difficult to decide which individuals comprise a single herd (Foster, 1966). The definition of a giraffe herd has, therefore, varied across studies. Backhaus (1961) described a herd as ‘any number of the same species that moves together and engages in the same activity, at any one time’. Other studies included an element of distance. For example, Foster and Dagg (1972) considered individuals to 80 be in the same herd if they were ‘less than 1 km apart and moving in the same general direction’, whilst van der Jeugd and Prins (2000) defined a herd as all individuals within 100 m of each other. Fennessy (2004) viewed the distance between individuals irrelevant and took a more social approach, considering giraffe to be in the same herd if giraffe were observed associating with one another for a period of ten minutes or more, perhaps moving in the same direction or feeding next to each other, but not when individuals coincidentally moved into or through an area without associating with individuals already there.

The definition of herd used in this study is adjusted from that used by Fennessy (2004). A herd was defined as a group of one or more individuals that moved together in the same direction and were generally, but not necessarily, engaged in the same activity. For example, a group of giraffe all feeding at the same time and moving in the same direction at a similar pace, was considered a single herd. If a number of giraffe were feeding whilst others were resting or ruminating nearby and they all moved off together, they were also considered to be in the same herd. If, however, a group of giraffes moved through an area, foraging as they went, and passed another group of giraffes standing under a tree resting or moving in another direction, the two groups were considered separate herds. Giraffe herds were usually distinct as distances between individuals within a herd were substantially smaller than distances between herds (see Carter et al. 2013b). It is possible that some giraffe within a herd remained unobserved due to think vegetation and therefore were not recorded as part of the herd and potentially impacted results of the study. However, this is improbable as a significant amount of time was spent with the herds as behavioural data were collected, and any additional giraffe would likely have come into view or been heard at some stage. Furthermore, most reported giraffe herds were observed in the more open habitats where individuals could be seen.

Although the definition of a herd used in this and all studies is human- centric, as it is impossible to know what a giraffe might constitute a herd, we can only use a definition which makes most sense and fits in with observed behaviours. The definition used in this study is well in line with the definition used by other authors for giraffe and other animals.

Individuals in the herd were identified by their unique coat patterns or other distinguishing characteristics such as wonky or broken ossicones, missing tail tips, birth marks and skin lesions (Appendix II). For each herd encounter, photographs of individuals were taken and compared with those in a photographic database to which previously unknown individuals were added. Photographs were compared by eye or with the pattern extraction and matching software program, Wild-ID (http://dartmouth.edu/faculty-directory/douglas-thomas-bolger), which provides the top ranking possible matches that are then compared with the focal individual by eye (Bolger et al., 2012). Each individual was allocated an identification code and categorised into one of four age class: adult (5+ years, estimated height: >4 m), sub-adult (1- 5 years, estimated height: 2.5-4 m), or juvenile (<1 year, estimated height: <2.5 m) as per van der Jeugd and Prins (2000), and sex class with males and females differentiated by their general size, the presence/absence of testes and penis sheath, and/or their ossicone characteristics (size, shape and hair).

Juveniles were excluded from the social analyses as their associations are likely similar to their mother’s (Carter et al., 2013b).

Herd size was recorded when all individuals present could be seen and therefore, counted. However, thick vegetation sometimes hindered visibility such that not all herd members could be individually identified. Giraffe were considered to be associated if they were recorded in the same herd at any time during the study period. 82

4.2.3 Data analysis Social network analysis measures

The degree, the number of individuals observed associating with any given individual, was calculated in Visone (v2.9.2; Brandes and Wagner, 2004). The mean and median degree and range were calculated from only those individuals observed at least ten times so as to ensure a high level of accuracy.

The ‘geodesic distance’ or ‘path length’, defined as the number of associations in the shortest path between two individuals in the network, was calculated in UCINET (version. 6.579; Borgatti et al., 2002). To reduce the potential for bias towards longer path lengths resulting from under representation of some individuals, but maintaining a sufficient number of individuals in the analysis, only individuals observed at least five times were used in the calculations.

Pairwise association indices

To determine the strength of associations between pairs of giraffe, association indices were calculated in SOCPROG 2.5 (Whitehead, 2009) using the half-weight index (HWI). The HWI is the most appropriate association index when individuals are sighted infrequently and the probability of sighting at least one member of any given pair is higher if the individuals are not together (Cairns and Schwager, 1987). The HWI is defined as:

HWI = x/(x + yab + 0.5 (ya + yb)),

where x = the number of sampling periods in which both giraffe ‘a’ and giraffe ‘b’ were observed in the one group; yab = the number of sampling periods in which giraffes ‘a’ and ‘b’ were observed in separate groups;

83 ya = the number of sampling periods in which only giraffe ‘a’ was observed; and yb = the number of sampling periods in which only giraffe ‘b’ was observed (Cairns and Schwager, 1987). HWI values are between zero and one, where zero indicates a pair of individuals never observed together and one indicates they were always seen together. The sampling period was defined as a single day. Giraffe herd compositions have been found to change almost daily (Moss, 1982) or more frequently (Leuthold, 1979). Therefore, a day was considered sufficient time for giraffe to change associates and thus ensure independent evidence of associations.

Preferred and avoided associations

Preferred associations and potential avoided associations were tested for in SOCPROG 2.5 (Whitehead, 2009) using a modified version of Bejder, Fletcher and Bräger’s (1998) adaptation of the Monte Carlo method (Manly, 1995; see Whitehead 2008). The test takes the observed HWI data and generates random datasets with identical features (number of individuals and groups, group size and sighting frequency) to the observed dataset. The coefficient of variation (CV) of association indices and the proportion of non-zero association indices calculated from the observed and random data sets can then be compared to test the null hypothesis of random associations. If the CV of associations from the observed dataset is significantly greater than the permuted data set, it is an indication of preferred associates. Conversely, avoided associations are indicated if the proportion of non-zero association indices from the observed data set is significantly less than that from the permuted data set (Whitehead, 2008).

To override possible biases associated with non-independence of the random data sets (a result of maintaining the features of the observed data set), sets of 1,000 random permutations were repeated ten times and sets of 5,000 and 10,000 permutations were repeated five times

84 each (following Carter et al., 2013b and as suggested by Bejder et al., 1998).

To minimise the potential for false null-associations without sacrificing too much data, tests for non-random associations were carried out on individuals sighted at least five times within herds for which at least 50% of herd members could be identified. Tests were then repeated using only adults; only individuals observed more than five times but observed in each of the three study years (to exclude individuals which may have died, immigrated or emigrated); and only individuals sighted eight or more times, to assess whether these factors had any influence over association patterns. Due to the different ranging patterns and reproductive strategies of males and females, whereby males exhibit a roaming strategy seeking sexually receptive females (Bercovitch et al., 2006) and females are thought to select habitats that will maximise their reproductive success (Ginnett and Demment 1999), the two sexes were analysed separately.

Community structure

Newman’s (2006) eigenvector based algorithm for modularity (the difference between the proportion of the total association within groups and the expected proportion if individuals are assigned at random, given the tallied associations of each individual) was used to test for, and identify social groups nested within the larger community. This method has shown to provide higher quality results than competing methods for network division (Newman, 2006). Calculations were performed in SOCPROG 2.5 (Whitehead, 2009) using only individuals observed at least five times from herds for which at least 50% of herd members could be identified. Social divisions with a modularity value of >0.3 are considered meaningful (Newman, 2004).

Spatial overlap

Spatial overlap of individuals was calculated using the adehabitatHR Package (Calenge, 2006) in R (R Development Core Team, 2015). First, the 95% probability isopleths were estimated using the Kernel Utilization Distribution function (Worton, 1989) with the amount of smoothing determined by the reference (“href”) bandwidth. Percentage overlap was then calculated for each pair of individuals by dividing the area of overlap by each individual’s total area. These methods were then repeated to examine the spatial overlap of the defined social groups, with the location data being pooled data from each of the group members.

As observations were predominantly limited to areas along the Park’s road network, utilization distributions estimated from recorded GPS locations of sighted individuals only reflect presence within these areas and not entire home ranges.

4.3 RESULTS

Eight-hundred and forty-eight (848) separate herds were encountered within the study area over the study period. At least 50% of individuals could be identified in 641 of these herds and at least 75% could be identified in 553 herds. Herd size ranged from 1 to 31 (Figure 4.1) with a mean of 5.39 (n = 601; SD = ± 4.99) and median of 4. Excluding herd sizes of one, mean herd size increased to 6.58 (n = 473; SD = ± 5.00). 49.5% of herds were of mixed sex (87% of these herds contained at least one adult male), 36.3% were all-male herds, and 14.3% all-female herds. Omitting herds of one, 63.1% of observed herds were mixed-sex herds, 15.6% were all-male herds, and 12.0% were all-female herds.

10 % of%sightings

0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 Herd size

Figure 4.1 Observed herd sizes in Chobe National Park, Botswana.

Six hundred and eighty-two (682) individuals were identified (185 adult males; 261 adult females; 81 sub-adult males; 74 sub-adult females; 60 juveniles; and 21 of unknown age/sex class). Of these, 551 were identified on more than one occasion and 291 on five or more occasions. Individual males were observed up to 26 times (n = 266; mean ± SD = 6.37 ± 0.21; median = 5) and females up to nineteen times (n= 335; mean ± SD = 4.36 ± 3.17; median = 4). Individuals were most frequently observed in herds of mixed sexes, followed by same sex herds then solitary individuals (Figure 4.2). There were 180 sightings of solitary individuals (21% of herds); of which 83% were males (77% adults) and 17% were females (16% adults).

90 Adult Males 80 Adult Females 70 Sub-adult Males 60 Sub-adult Females 50 40

%of sightings 30 20 10 0 Mixed Same-sex Solitary individuls Herd type

Figure 4.2 Sightings of individual giraffe by herd type in Chobe National Park, Botswana.

All giraffe were connected in a single network component. The average degree was greater for males than females, whether considering all individuals, or connections within same sex groups (Table 4.1).

Table 4.1 The mean (± SD) and range for the degree and geodesic distances for giraffe observed in Chobe National Park. Degree and geodesic distances are given for non-specific sex associations, male- male associations and female-female associations.

Degree Geodesic distance n Mean ± SD Median Range n Mean ± SD Range Male & female 55 73.56 ± 22.74 73 27 - 138 243 2.1 ± 0.6 1 - 4 Male - male 40 46.03 ± 13.47 46 12 - 77 131 2.1 ± 0.6 1 - 4 Female - female 15 32.07 ± 10.44 29 13 - 54 112 2.7 ± 1.2 1 - 6

Association strength and spatial overlap

The average HWI ± SD when considering individuals observed at least five times was 0.02 ± 0.07 for the 6,216 female-female pairs and 0.02 ± 0.06 for the 8,515 male-male pairs. Excluding all HWI with a zero value, the average HWI ± SD was 0.19 ± 0.03 for the 827 female-female pairs and 0.15 ± 0.03 for the 1631 male-male pairs. Average HWI ± SD increased slightly when only individuals observed on at least eight occasions were included: 0.03 ± 0.02 for females and 0.05 ± 0.02 for males, but not when HWI with a zero value were excluded, females: 0.18 ± 0.05, males: 0.13 ± 0.03. Association strength between pairs of individuals was positively correlated with their level of spatial overlap, though the correlation was weak.

Preferred and avoided associations

For both males and females, the CV of HWI were significantly higher in the observed data sets than the random data sets (males - CV of HWI: observed = 2.36, random=2.20, n=131, p=0.0000; females - CV of HWI: observed = 2.85, random=2.64, n=112, p=0.0001), indicating preferred associations. Conversely, the proportion of non-zero HWI were lower in the observed data sets than the random data sets (males – proportion of non-zero HWI: observed=0.19, random=0.21, n=131, p= 0.0000; females – proportion of non-zero HWI: observed 0.13, random=0.015, n=112, p=0.0000) which indicated avoided associations. Removing sub-adults from the analyses did not alter patterns of significance for either sex, nor did only using individuals observed during all three years in which the study was conducted, or when considering only individuals sighted more than eight times.

Population division and spatial overlap

Division of the community by the modularity algorithm resulted in five social groups for each sex. Optimal modularity values were 0.365 for males and 0.539 for females, indicating stronger social divisions for the latter. These female groupings were also typically more obvious in a sociogram (Figure 4.3). Space use of male social groups was more extensive than for female groups and all exhibited significant overlap (mean percentage overlap = 71.12%). Female groups, however, typically showed a larger degree of spatial separation, with less overlap between groups (mean percentage overlap = 33.60%) and only two of the five groups overlapping with all other groups (Figure 4.3).

When considering the results of the study, the impications of having only a limited numer of resigtings for some indivduals and having to exclude many indivduals from the analyses due to an insufficient number of resightings should be considered. Although the patterns revealed are likely sound, it is most likely that the value of the social metrics described (except for herd size) are below their true value.

A. B.

Figure 4.3 Social networks and maps of social group spatial use of giraffe observed on five or more occassions in the Chobe Riverfront, Chobe National Park for (A) females and (B) males. Each dot in the network represents one individual and the lines represent an association between individuals.

4.4 DISCUSSION

Mean herd sizes of giraffe are on average relatively small at between 3.5 - 5.5 individuals (e.g. Fennessy, 2004; VanderWaal et al., 2014; but see Le Pendu et al., 2000 for larger mean herd sizes in Niger). The mean giraffe herd size for Chobe, Botswana (5.39) (this study), fits within this range. The maximum observed herd size has varied across locations with fewer than 23 individuals reported for some areas (see Berry, 1973; Fennessy, 2004; Brand, 2007; Shorrocks and Croft, 2009), to over 100 individuals (M. Brown unpub. data) as was observed in Uganda. Other studies have reported herd sizes between 28 and 44 individuals (this study; Bercovitch and Berry, 2009; van der Jeugd and Prins, 2000; Carter et al., 2013b; VanderWaal et al., 2014). These differences may be linked to any number of factors including forage distribution and availability, predation risk, and demography (Jarman, 1974; Bercovitch and Berry, 2009). What researchers constituted a herd would also have impacted reported herd sizes. For example, a researcher who considered all giraffe within 1 km of one another to be a single herd (e.g. Foster, 1966) might have reported larger herd sizes than another researcher who only considered the giraffe moving in the same direction and whom were observed associating with one another to be in the same herd (e.g. Fennessy, 2004).

Males in Chobe were observed alone in only 13% of male sightings which seems typical given that Innis (1958), Foster (1966), and Pratt and Anderson (1982) all reported percentages around 12 -16%. In stark contrast, Bercovitch and Berry (2009) reported that adult males were alone in 67% of all male sightings.

Marked differences in grouping patterns have been observed across populations, with mixed-sex herds predominating in some areas (this study; VanderWaal et al., 2014), but single-sex herds in others (e.g. Innis, 1958; Foster, 1966; van der Jeugd and Prins, 2000). These

92 differences might be related to the presence or absence of sexual segregation resulting from sexual differences in habitat preferences. Foster (1966), who reported observing more same-sex herds in his study area, noted that males preferred denser habitats, whilst females typically opted for more open habitats (see also Pratt and Anderson, 1982). In this study, where mixed herds were observed most frequently, there was no evidence of sexual differences in habitat preferences (see also Le Pendu and Ciofolo, 1999), although temporary same-sex groups were observed within the shared habitat. Bercovitch and Berry (2014) proposed that male giraffe might benefit from all-male groups through knowledge acquisition about the habitat (including food and female distribution), protection from predators, a reduction in feeding competition, and access to sparring partners to enhance competitive skills. Some of these benefits have also been linked to formation of all- male groups (akin to bachelor groups) in other species including elephants (Chiyo et al., 2011; Evans and Harris, 2008), zebra, Equus burchelli (Rubenstein and Hack, 2004) and Soay sheep, Ovis aries (Pérez-Barbería et al., 2004). The benefits of all-female giraffe herds remains largely unexplored, but advantages may include cooperative care of offspring (Langman,1977; Leuthold, 1979; see also Whitehead et al., 1991 for sperm whales, Physeter macrocephalus), avoidance of sexual harassment from males, or the avoidance of sparring males (Wearmouth and Sims, 2008).

Similar to other giraffe populations (see Shorrocks and Croft, 2009; Carter et al., 2013a; VanderWaal et al., 2014), a high level of interconnectivity between individuals was found in Chobe. The mean degree calculated for individuals (~74) was less than that recorded by VanderWaal et al. (2014) who found the average individual had around 98 connections, but this is likely due to the lower number of sightings (average of 13) per individual in this study compared to VanderWaal et al.’s (2014), where each individual was observed more (~30 times). Shorrocks and Croft (2009) reported an average degree of five or six, but

93 the duration of their study was short and the number of sightings per individual, low (maximum four times). As such, it is unlikely a reflection of the social network over an extended period.

The average geodesic distances connecting individuals across populations, including this study, have been, on average, low (1 - 3) (e.g. Shorrocks and Croft, 2009; Carter et al., 2013a). Geodesic distances and degrees can be used as an indication of the likelihood of, and the speed at which, information or disease might spread through a population (Christley et al., 2005; Shorrocks and Croft, 2009). Thus, in complex networks with high nodal degrees and low geodesic distances, such as that characteristic of giraffe societies, the potential for disease and information transmission is high. If we consider the Chobe population as an example, information or disease would, theoretically, be able to spread through the population quite quickly as it only needs to diffuse between four giraffe to reach the most distant individual in a network (e.g. Lentz et al., 2016).

Similar to findings by Carter et al. (2013b) in Etosha National Park, the number of observed pairwise associations was low for both males and females given the number of possible associates with overlapping ranges. This may, in part, be due to the limited number of sightings for some individuals or the absence of temporal overlap, but could also be the result of avoidance behaviour (see below). Associations were also generally quite weak – shown by low mean association values (HWI), but this is not uncommon in fission-fusion species (e.g. McSweeny et al., 2009; Dungan et al., 2012; Best et al., 2013) and has been noted previously in giraffe (Carter et al., 2013b). The few high dyadic association values calculated in this and other giraffe studies (Fennessy, 2004; Bercovitch and Berry, 2012; Carter et al., 2013b) is testimony to the high degree of fission-fusion dynamics within giraffe social systems.

Male giraffe are thought to socialise differently to females (Carter et al., 2013b), and results from this study support this. In Chobe, as found in other studies (e.g. Foster and Dagg, 1972; Fennessy, 2004; Carter et al., 2013a and b; Bercovitch and Berry, 2012; VanderWaal et al., 2014), the strength of male associations, particularly those of adult males, were generally weaker than for females, though males had more associates. It is possible that males have greater opportunity to encounter and associate with different individuals given their larger, extensively overlapping ranges (this study; Berry, 1978; Leuthold and Leuthold, 1978; Le Pendu and Ciofolo, 1999; Fennessy, 2004), but given the competition between males for mating, strong bonds between males are likely rarely formed. The lack of strong bonds between males are not unusual among animals in social systems with contest polygyny (Van Hooff and Van Schaik, 1994; Chiyo et al., 2011).

Longer term studies of giraffe (Carter et al., 2013a; Bercovitch and Berry, 2014) have shown that male-male associations are less stable and do not persist over time. Though lagged association rates between individuals were not measured in this study, the decrease in mean association values between males of the same age class with increasing age are likely indicative of non-lasting associations. The weakening of social ties with maturity is consistent with a roaming, mate-searching strategy (Clutton-Brock, 1989; Dagg and Foster, 1982; Bercovitch et al., 2006). As in other areas (see Leuthold, 1979; Pratt and Anderson, 1982 and 1985; Fennessy, 2004; VanderWaal et al., 2014), males in Chobe appear to become increasingly solitary and less tolerant of other males as they reach an age when they are likely to be competing for mates. This would not only contribute to weaker association strengths between older males, but also the mean association value for males overall.

Despite overall low association strengths, there was evidence that males had preferred and avoided associations. There are inconsistencies between studies concerning the existence of non-random male

95 associations. VanderWaal et al. (2014) observed that bachelor herds in Ol Pejeta Conservancy, Kenya, appeared to consist of young males which associate often and were not just random groupings; Fennessy (2006) observed strong male-male bonds in a bull-biased area of the northern Namib Desert; and Foster (1966) reported repeated sightings of particular males together. Conversely, there was no significant evidence that males in Etosha National Park had preferred or avoided associations (Carter et al., 2013b), albeit infrequent sightings, and the consequent lower sample size, may not have provided sufficient statistical power for accurate assessment of their social relationships (Carter et al., 2013b).

Kinship was not examined in this study but others have found that strong bonds often form between mothers and offspring (Bercovitch and Berry, 2012; Carter et al., 2013b), and also sisters (Bercovitch and Berry, 2012), which could help explain the stronger female bonds observed in Chobe and evidence of preferred and avoided associations. Furthermore, Bercovitch and Berry (2013) found that female calves form strong, long-term associations with non-kin born into the same age cohort, suggesting a more complex social system than one dictated by only kinship and/or spatial overlap. Various studies have reported evidence of affiliative social behaviour between females having direct benefits and fitness consequences (e.g. feral horses: Cameron et al., 2009; baboons, Papio cynacephalus ursinus: Silk et al., 2009; Archie et al., 2014; kangaroos, Macropus giganteus: Carter et al., 2009), but what benefits stronger female-female bonds provide for giraffe are not well understood.

As has been found in other giraffe studies (Carter et al., 2013b; VanderWaal et al., 2014), association strength could not be fully explained by the level of spatial overlap. If individuals were randomly associating with others within their home range, a strong correlation should exist between range overlap and association strength, but this

96 was not the case. Though there was a weak correlation, some dyads had substantially overlapping ranges yet were never, or rarely observed together, whilst others showed limited spatial overlap but had relatively high association values. Carter et al. (2013b) suggested such results are a reflection of the social preferences and avoidances of individuals.

Network analysis of the female population showed somewhat defined social divisions, with subgroups consisting of more strongly associated individuals connected by numerous weaker ties to other subgroups with overlapping ranges. These findings are indicative of a fluid, fission- fusion system with an underlying structure driven by some degree of social preferences (see Silk et al., 2014). The social divisions (likely equivalent to the sub-communities identified in a study by VanderWaal et al. (2014), support VanderWaal et al.’s (2014) proposal of giraffe having a multi-tiered social structure.

The smaller ranging areas of female sub-groups overlapped significantly less than those of males which indicates that shared space use has greater influence over female social groupings, or alternatively, that social factors influence their ranging patterns. Male subgroups were poorly defined in the network analysis with males highly connected but with weak ties, indicating a highly-fluid fission-fusion social system which is little affected by the social preferences of individuals (see Silk et al., 2014). VanderWaal et al. (2014) found little connection between social clustering and home range overlap of males, and this is likely the case in Chobe also.

4.5 Conclusion

Results from this study complement findings from previous studies which have shown shared patterns of giraffe sociality across their geographic range despite differences in giraffe density, habitat type and forage availability. Moreover, findings revealed the complexity of giraffe

97 sociality which feature fluid fission-fusion social systems, within which are found structured social networks (at least for females) shaped in part by preferred and avoided relationships and shared space use. This further contradicts speculations from early studies that giraffe lack social structure. Furthermore, despite males and females showing both preferred and avoided relationships and having weak pairwise associations, clear differences in social patterns and ranging behaviour were observed, supporting previous claims that males and females socialise differently. These results may have implications for other fission-fusion species by demonstrating how social preferences and shared space use can influence social systems and structures. Additionally, they may provide insight into the evolution of social behaviour.

CHAPTER 5

General conclusions and discussion

Despite the giraffe being one of Africa’s most iconic and charismatic species, and their numbers having declined by as much as an estimated 40% in the last two decades (GCF, 2016), conservation efforts have been relatively limited. With continually expanding human populations and changing climatic conditions, it seems inevitable that pressure on giraffe populations will continue to increase. If effective conservation management strategies are to be put in place to halt or reverse the giraffes’ downward population trend, a sound understanding of their ecology and behaviour is required. Whilst various studies have been undertaken, our insight into some of the complexities of giraffe ecology and behaviour is still lacking.

This study of giraffe in two distinct habitats of northern Botswana, and comparisons with other giraffe studies across Africa, has highlighted some ecological and behavioural similarities between populations. However, many differences also exist, reflecting the adaptations made by populations in response to the unique set of environmental factors in which they are faced, which emphasises the value of focused ecotype studies on species.

5.1 Major findings and discussion

Giraffe movement

The movement and ranges of various giraffe subspecies have previously been examined (e.g. Foster, 1966; Langman, 1973; Berry, 1978; Dagg and Foster, 1982; Le Pendu and Ciofolo, 1999; Fennessy, 2009; Suraud, 2011). However, most of these studies lacked the GPS

99 technology used in this study which likely resulted in underestimates of movement and ranges.

Significant variation in movement patterns were observed between the two study areas, likely reflecting the differences in forage availability and distribution. With more limited and patchily distributed forage in Chobe, home ranges and daily movements were more extensive, whilst in NG26 where forage is abundant, ranges and movements were smaller. This association between home range size and food resource availability is evident for giraffe across their range (e.g. Berry, 1978; Leuthold and Leuthold, 1978; Le Pendu and Ciofolo, 1999; van der Jeugd and Prins, 2000; Fennessy, 2009; Flanagan, 2014), and appears to exist for most animals ranging in size from herbivorous megafauna to small rodents (e.g. Douglas-Hamilton, 1971; Blake et al., 2003; Taitt and Krebs, 1981; Hubbs and Boonstra, 1998; Broughton and Dickman, 1991; Herfindal et al., 2005; Loveridge et al., 2009).

In contrast to the typical seasonal ranging behaviour of large African browsers (e.g. Goddard, 1967; Lindeque and Lindeque, 1991; Thouless, 1995; Hillman, 1998; Leggett, 2006; Young et al., 2009; Owen-Smith, 2008) the giraffe ranges in Chobe and NG26 were larger in the dry season than the wet season. However, this pattern is not consistent across giraffe populations (e.g. Berry, 1978; Leuthold and Leuthold, 1978; Le Pendu and Ciofolo, 1999; Fennessy, 2009) with the size and location of seasonal ranges likely determined by the distribution of forage. Movements of many other herbivorous species are limited by distance to water (e.g. Western, 1975; Bergström and Skarpe, 1999) but giraffe are able to go without drinking for extended periods (one giraffe went without drinking for at least 27 days in this study, but see also Berry, 1973; Fennessy, 2004), allowing them to focus their movements in areas where nutritional demands can be best met. By focusing their movements away from areas near surface water during the drier months, giraffe likely reduce their competition with other browsers, and alleviate at least some of the pressure on the already over-browsed

100 vegetation closer to water sources (see Fullman and Child, 2012). They may also reduce their risk of predation as lions often concentrate their hunting efforts near water access points (Davidson et al. 2012; Davidson et al., 2013).

The study showed that similar to other large African herbivores including elephant (e.g. Lindeque and Lindeque, 1991; Thouless, 1996; Leggett 2006) and eland (Hillman, 1998), the area required by giraffe to meet metabolic and nutritional demands can be substantial. In the Chobe area, some giraffe ranges extended beyond the boundaries of the national park suggesting resources within the park are insufficient to sustain the giraffe population exclusively. This is also likely the case for many of the other larger species. Certainly the elephants are well known for their extensive ranging patterns within and beyond the Chobe region into surrounding areas (e.g. Adams, 2015). This highlights the significance of the adjacent forest reserves, protected areas and community land. Movements of giraffe into and out of Zimbabwe were also noted, emphasising the value of cross-border conservation cooperatives.

Mean daily movements for the Chobe giraffe were longer than those so far reported elsewhere (e.g. Langman, 1973; Berry, 1978; Fennessy, 2009). Daily movements for the giraffe in NG26 were longer during the dry season, whilst in Chobe, no seasonal differences in daily movements were noted despite seasonal range shifts and larger dry season ranges. This may be an indication that the energy cost in searching for better quality food items outweighs the nutritional benefits. As daily movement patterns are an indication of habitat use (Carbone et al., 2005), it seems plausible that daily distances travelled could be used as an indicator of food deficiencies in giraffe and other species (see Owen- Smith (2013).

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From a conservation perspective, the movement study highlighted the importance of keeping extensive habitat areas free for wildlife, and considering seasonal ranging patterns when making management decisions which might impact wildlife movements, such as the erection of wildlife fences.

Giraffe behaviour

Whilst several studies have documented particular aspects of giraffe behaviour across their range (e.g. Berry, 1978; Leuthold, 1979; Pellew, 1984a and b; Ginnett and Demment, 1997; Ciofolo and Le Pendu, 2002; Fennessy, 2009; McQualter et al., 2015) studies of the giraffe’s daily activity patterns have been somewhat limited (but see Leuthold and Leuthold, 1978; Fennessy, 2004; du Toit and Yetman, 2005). This behavioural study examined and compared the activity budgets of giraffe in Chobe and NG26, and documented interesting behavioural observations. Moreover, the study examined how giraffe behaviour can be impacted by habitat, season and sex.

The results showed that despite slight variations, giraffe everywhere (see Leuthold and Leuthold, 1978; Fennessy, 2004; du Toit and Yetman, 2005) tend to follow the same general pattern of allocating much of their diurnal time to feeding, with walking, ruminating and resting also occupying significant amounts of time.

Habitat (site) had the largest effect on the diurnal behaviour of the giraffe which adds to the literature demonstrating the significant impact of environmental factors on behaviour e.g. Wauters et al., 1992; Hunter and Skinner, 1998; Tchabovsky et al., 2001; Tadesse and Kotler, 2014).

Sex was also found to have an impact on activity budgets, which is common in species that are sexually dimorphic in body size (Spinage, 1968; Gross et al., 1995). Most notable was the greater proportion of time that females spent feeding. Sexual differences in activity budgets have been used as an explanation for sexual social segregation between

102 the sexes in a number of dimorphic species (Ruckstuhl and Neuhaus, 2002), but whether it plays a role in the sexual segregation of giraffe observed in Botswana and elsewhere (e.g. Innis, 1958; Foster, 1966; van der Jeugd and Prins, 2000; VanderWaal et al., 2014) remains unknown.

Season was also found to have an effect on activity budgets, which is unsurprising given the striking differences in food availability and distribution between the wet and dry seasons, and the significant proportion of time allocated to feeding regardless of season. However, the differences were only slight and the seasonal effect for any given activity was not necessarily the same for both sexes.

Contrary to other giraffe studies which have observed reduced mobile activity during the heat of the day (e.g. Pellew, 1984a; Fennessy, 2004; Dagg, 2014), only males in NG26 followed this behavioural pattern. Behavioural activities were unevenly distributed throughout the day, though no common temporal pattern between the sites, sexes or seasons was observed.

Giraffe sociality

Early studies concluded that giraffe lack social structure and that giraffe associate randomly (Foster and Dagg, 1972; Dagg and Foster, 1976; Leuthold, 1979; Le Pendu et al. 2000), but more recent studies have found evidence of a more structured and complex social structure (Pratt and Anderson, 1982; Fennessy, 2004; Bashaw et al., 2007; Shorrocks and Croft, 2009; Bercovitch and Berry, 2012; Carter et al. 2013a and b; VanderWaal et al., 2014). This study provided even more evidence of the complexity of giraffe sociality.

Whilst common patterns of sociality exist across giraffe populations, including their high level of fission-fusion dynamics and interconnectivity between individuals (see Foster and Dagg, 1972; Dagg and Foster, 1976; Leuthold, 1979; Le Pendu et al. 2000; Pratt and

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Anderson, 1982; Fennessy, 2004; Bashaw et al., 2007; Shorrocks and Croft, 2009; Bercovitch and Berry, 2012; Carter et al., 2013a and b; VanderWaal et al., 2014), marked differences in grouping patterns have also been noted.

In Chobe, giraffe were more typically observed in mixed herds, though more single-sex herds have been observed in other studies elsewhere. Some giraffe populations have shown sexual habitat segregation (e.g. Foster 1966; Pratt and Anderson, 1982) which would lead to social segregation and more single-sex herds. However, habitat segregation was not observed in Chobe, indicating other forces behind the formation of the same-sex herds observed - possibly differences in activity budgets or social preferences for the same sex (Bon, 1991; Ruckstuhl and Neuhaus, 2000; Ruckstuhl and Neuhaus, 2002) which have been proposed for other species.

Consistent with previous findings (e.g. Foster and Dagg, 1972; Fennessy, 2004; Carter et al., 2013a and b; Bercovitch and Berry, 2012; VanderWaal et al., 2014), male and female giraffe were found to socialise differently. Whilst both males and females showed evidence of preferred and avoided associations, males had more associates but overall weaker bonds, whereas females had fewer associates but slightly stronger bonds. The lack of strong ties between males is not uncommon in social systems with contest polygyny (Van Hooff and Van Schaik, 1994; Chiyo et al., 2011), whilst strong bonds between female kin, as well as non-kin born into the same age-cohort, might help explain the overall stronger bonds amongst females (Bercovitch and Berry, 2012; Carter et al., 2013b). Association strengths were correlated (albeit weakly) with spatial overlap which demonstrates that the underlying patterns in space use can influence the social structure of fission-fusion species. Non-random associations, at least in giraffe, is another driving force.

Evidence of a structured social system within the giraffes’ flexible fission-fusion social system was provided, with defined social groupings

104 found within the female population. This supports the findings of VanderWaal et al. (2014) who were the first to find quantitative evidence of a multi-tiered social structure in giraffe. A similar pattern of fluid fission-fusion dynamics embedded in higher levels of organisation have been recognised in various other species including white-tailed deer, Odocoileus virginianus (Aycrigg and Porter, 1997); African buffalo, Syncerus caffer (Cross et al., 2005), and impala, Aepyceros melampus (Murray 1982).

5.2 Study limitations and possibilities for future research

This study provides useful baseline information on the ecology and behaviour of giraffe in two previously unstudied populations. However, although its duration was longer (particularly for Chobe), and the data collected more copious than for some other giraffe studies, it was still only a snapshot in time which does not take into account the longer- term dynamics of the ecosystems, communities and populations.

The premature removal of the GPS satellite collars meant that the home and seasonal ranges reported in this study were only minimal ranges. Furthermore, the low number of collars deployed meant that strong inferences about female giraffe movements could not be made. Some studies have also found male ranges to be substantially larger than female ranges (e.g. Fennessy, 2004). Additional movement studies spanning multiple years and including both sexes and a greater sample of individuals are, therefore, necessary for a more comprehensive understanding of the area required by giraffe in the two ecosystems, as well as their general ecology. Examination of habitat use, preferred habitat types and possible movement corridors would also be valuable in terms of management and conservation. At the time of this study, all available vegetation maps of Chobe were out dated and thus were not used. There had been talk of the development of new maps of the area

105 but this did not transpire. Vegetation maps for NG26 were in the process of being developed.

The GPS collars used in this study were unable to be programmed to transmit locations more frequently than every four hours. Future studies could examine giraffe movements on a finer scale which would allow for more accurate measurements of travel distances and ranges, and combined with vegetation data, assessments of resources accessed.

One limitation of the behavioural study was the lack of night time observations which meant it was impossible to consider the diurnal activity budget in relation to the nocturnal activity budget. Although one study has examined giraffe nocturnal behaviour (Pellew, 1984a), given the differences in diurnal activity budgets between areas, it cannot be assumed that nocturnal activity patterns are similar everywhere. Nocturnal movement was recorded by the collared giraffe which would suggest they spend some time feeding, but nocturnal observations are necessary to quantify their behaviours. Another limitation was the bias of observations towards the more open areas where visibility was better. How activity patterns differ in the more densely vegetated areas and whether this has skewed the results is unknown. With respect to the giraffe feeding behaviour, knowledge of the nutritional value of each of the plant species consumed, bite size and chewing rates would have enabled more informed inferences about the differences in feeding times.

Regarding the social network part of the study, analyses were limited by the number of times individual giraffe were resighted. Given that the population is open with individuals free to move in and out of the area, and that individuals could remain unseen in areas inaccessible to vehicles, this is not surprising. A longer-term study would have increased the chances of individuals being observed and strengthened the analyses. However, the data from this study provide a platform for future possible investigations including studies examining the duration of associations, the effect of age on an individual’s level of sociability,

106 dispersal patterns, and how association patterns change in response to changes in population density, or extrinsic factors such as food availability.

Another avenue of study is the use of genetics to further examine the influence of kinship on association strengths and overall social structure. Previous studies, have suggested the existence of a kinship- based social structure and a matrilineal-based, multi-tiered social organisation (e.g. Bercovitch and Berry, 2012; Carter et al., 2013b), but confirmation through long-term genetics studies is needed.

As little is known about the giraffe of Botswana there is enormous scope for future research. Additional studies specific to Botswana could examine:

 How the high elephant density in Chobe affects giraffe behaviour  The effect of flood levels in the Okavango Delta on the population and distribution of giraffe  The behavioural response of giraffe to ecosystem modification resulting from climate change  The impact of poaching on giraffe populations and whether there is an Allee effect  The impact of fencing on the giraffe population and their distribution

5.3 The future of giraffe in northern Botswana

Unlike many regions where giraffe are threatened by human encroachment and habitat fragmentation, northern Botswana consists of a significant and continuous area set aside for wildlife, protected from the incursion of human settlements and agricultural plots by the cordon veterinary fences bordering much of the wildlife area (Albertson, 2010; Brooks and Bradley, 2010). This is likely one of the reasons why, overall, the giraffe population is currently stable in the region. This may

107 change, however, as the effects of global warming and rapidly increasing human and livestock populations take their toll on the land, whether inside or outside protected areas.

Giraffe may be able to withstand drought periods better than many other species due to their predominantly browse diet and non- dependence on surface water. However, if extended drought periods become more frequent in Botswana as predicted (Tyson, 1991), additional browsing pressure on woody vegetation by elephants (e.g. Beer et al., 2006), giraffe, and other species may not only cause a significant reduction in browse cover, but also plant diversity, exacerbated by the restriction of movements beyond the veterinary fences (e.g. Ruess and Halter, 1990; Bond and Loffell, 2001; Loarie et al., 2009; McGahey, 2010; Cassidy et al., 2013; Straus and Packer, 2015), and this may negatively impact giraffe populations in some areas. The continued monitoring of wildlife populations and habitat changes in the region is therefore important for proper management of these wilderness areas if environmental degradation is to be limited and biodiversity maintained.

It is also possible that heavy selective browsing by giraffe and elephant might mediate a shift in plant composition towards species that are unpalatable, resulting in a decline in the quality and quantity of the giraffe’s food supply, and in turn, a reduction in the giraffe population. Strauss (2014) (see also Strauss and Packer, 2015) found evidence of such an occurrence in the Seronera area of the Serengeti, Tanzania whereby a decline in the giraffe population coincided with an increase in Acacia robusta, a species largely avoided by giraffe, and a decrease in preferred or heavily utilised species. These findings emphasise the importance of considering both food accessibility and palatability when making assessments of giraffe food supply, as measurements of woody plant density alone may be deceiving. In the Okavango Delta, abundance measurements of Acacia erioloba, A. fleckii, A. hebeclada, A. nigrescens, Terminalia sericea and Ziziphus mucronata which are

108 prevalent in the giraffe diet would provide an estimate of food availability for giraffe.

An opposing scenario for northern Botswana is the encroachment of woody species into former grassland / floodplain areas as the region becomes drier (e.g. Murray-Hudson et al., 2006). In the Okavango Delta, floodplains, where flooding has ceased for a decade or more, are often colonised by Acacia species (Murray-Hudson et al., 2006), an important food source for giraffe. Thus such vegetation succession would likely be detrimental to grazers but could facilitate an increase in giraffe numbers due to additional browse (e.g. Pellew, 1983).

Changes to the vegetation structure and composition would probably result in a number of behavioural adjustments which could be used by wildlife managers as an indicator of environmental stress (e.g. Owen- Smith and Cain, 2007; Owen-Smith, 2013). In addition to dietary changes, reduced browse cover and plant diversity would likely result in increased travelling time and daily distances travelled as giraffe search for sparse food resources. Similarly, giraffe might be required to expand their home ranges to obtain enough food. Furthermore, if they are forced to eat more food of reduced nutritional value it may be necessary for them to spend more time feeding and/or ruminating, leaving less time for other activities such as resting. In contrast, if woody species become more prevalent, particularly if they are of high nutritional value, giraffe daily movements and home ranges might decrease, as well as the amount of time they spend travelling, feeding and ruminating. Vegetation changes could also impact giraffe herd structure and social dynamics by regulating maximum herd size and altering the potential for individuals to encounter one another.

It seems probable the effects of a warmer, drier climate will have indirect detrimental impacts on humans outside the wildlife areas, with increased land degradation from overgrazing, and reduced stream flows and underground water recharge because of reduced rainfall (Dube, 2003) resulting in loss of livestock and crop yields, and consequently,

109 loss of income and food to sustain themselves. More people living near wildlife areas may subsequently turn to illegal wildlife poaching in order to generate an alternative income and/or alleviate their lack of food (e.g. Grey-Ross, 2010; Lindsey et al., 2011; Rogan et al., 2015). If this occurs, giraffe populations (and those of other desired species) may become at risk of collapse in some areas if offtake rates are unsustainable (e.g. McNutt, 2012). Whilst fewer giraffe have been poached in the past compared to some of the smaller antelope species (Central Statistics Office, 2008; Rogan et al., 2015), they may be targeted more if populations of other, less drought tolerant species, decline. Wildlife managers should take measures to address poaching before it escalates out of control by ensuring increased benefits to communities near wildlife areas, thus providing greater incentive to protect wildlife; strengthening law enforcement efforts; ensuring food security; and establishing alternative, non-wildlife consumptive sources of income.

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APPENDIX I

Female giraffe home range estimates from studies across Africa listed from north to south.

Study area Country N Mean home Range (km2) Source (Year) range (km2)

Niger Niger 5 (Non-res) 487 200 - 1307 Le Pendu & Ciofolo (1999) 14 (Res) 324 151 - 1378 El Karama Ranch Kenya 28 13 Moore-Berger (1974) Ruma NP Kenya 13 7.09 3.03 - 12.08 Anyango & Were-Kogogo (2013) Nairobi NP Kenya 10 85 Foster & Dagg (1972) Serengeti NP Tanzania 120 Pellew (1984b) Tsavo NP Kenya 50 161.8 8.8 - 438.8 Leuthold & Leuthold (1978) Lake Manyara NP Tanzania 8.6 0.5 - 27 van der Jeugd & Prins (2000) Luangwa Valley Zambia 4 68 60 - 82 Berry (1978) Namib Desert Namibia 16 199.5 (100%) 12.9 - 1098 Fennessy (2004) 100 (95%) 8.33 - 702.1 Chobe NP Botswana 3 323 (MCP) 138.3 - 623.4 This study 258.6 (95% FKDE) Okavango Delta Botswana 1 67.5 (MCP) This study 47.1 (95% FKDE) Kruger NP S. Africa 1 282 du Toit (1990) Timbavati PNR S. Africa 1 41 Langman (1977) Timbavati PNR S. Africa 24.6 Langman (1973) Non-res = Non-resident; Res = Resident All home ranges calculated with the convex polygon method except Foster & Dagg (1972) who used dot grid method and this study which used 95% FKDE where specified.

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APPENDIX II Giraffe identification

F0014CH F0027CH

F0090CH F0135CH

Sample of ID photos showing the variation in pelage pattern and colour of adult female giraffe in Chobe National Park.

Examples of distinguishing characteristics used to identify giraffe in addition to pelage pattern, including wonky or broken ossicones, missing tail tips, birth marks and skin lesions.

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