Predictors Of Mammal Distribution And Abundance In Udzungwa

226 Pages·2014·5.65 MB·English

ANGLIA RUSKIN UNIVERSITY

PREDICTORS OF MAMMAL DISTRIBUTION AND ABUNDANCE IN
AFROMONTANE FORESTS OF THE UDZUNGWA MOUNTAINS, TANZANIA

TREVOR JONES

A Thesis in partial fulfillment of the requirements of
Anglia Ruskin University for the degree of Doctor of Philosophy

Submitted: August 2013
"This unique locality preserves multiple histories of living, evolving
communities of animals and plants. Systematic study of the
Udzungwa Mountains has scarcely begun, but for knowledge to
continue and grow as it should, the area and its natural communities
must survive and must be conserved even more vigorously than they
are at present. The conservation of the Udzungwa forests and all
their inhabitants is therefore an imperative, not only for Tanzania
but also for the world."

Jonathan Kingdon, in litt.
(from unpublished essay for forthcoming book on Udzungwa)

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Acknowledgements

I could not have wished for a better PhD supervisor. Over six years, Dawn Hawkins
tolerated my unpredictable travels and regular absences, supported me whenever I
dumped the PhD to go off working on elephants, monkeys or skuas elsewhere, and still
managed to guide me through the statistical jungle and keep me on track with writing up.
Your advice, comments, patience and general positivity were invaluable to getting over
the finishing line.
Thanks to the rest of my supervisory team at ARU, who have also been excellent: Nancy
Harrison for ordination and other statistical guidance, and Guy Norton for his generous
and often brilliant advice and insights on scientific rigour, ecology of African mammals,
and life in general. I am grateful to many other colleagues and friends at ARU, including
Franc Hughes for her general support, Nick McWilliam for his cartographic expertise and
kind assistance, and Nicola Rodgers for helping me to submit when I was far from
Cambridge.
In Tanzania, I am lucky to work with a wonderful field team, on whom I was (and remain)
utterly reliant to help me do this work in the tough terrain of Udzungwa. Ninashukuru
sana Wote, hasa Athumani Mndeme, Richard Laizzer, Paolo Mndeme na Joseph Kidibule.
Thanks to Katarzyna Nowak for help in the field, and many improving comments on the
thesis; to Andy Bowkett, fundi wa duikers, for a really fun and fruitful collaboration
centred around antelope dung, and some comments on chapter 6; to Francesco Rovero
for comments on parts of the thesis, and countless discussions of Udzungwa and its
mammal fauna (we have come a long way, Mzee!); to Andy Marshall for training and
advice on GLMs; to Phil Platt of York University for helping with climate variables; and to
Len Thomas and Stephen Buckland at St. Andrews for helping me with DISTANCE, and
other study design and analytical advice.
I am thankful to Tim Davenport and Wildlife Conservation Society's Tanzania Program for
support and funding. I was also funded by the Zoological Society of London's Erasmus
Darwin Barlow Award and Anglia Ruskin University. TAWIRI, COSTECH and TANAPA issued
multiple permits over the years to grant me the privilege of working in the Udzungwas,
and I am particularly grateful to Simon Mduma, Dennis Ikanda, Ponjoli Joram and Paul
Banga for their help and collaboration.
For general and vital moral support, I am ineffably indebted to my beautiful friends in
Leeds, Tre-r-ddol, London, Cambridge, Iringa and Dar, and to my small family, especially
my amazing mother who doesn't care what I do as long as I am happy. And especially to
Kasia, with whom I have shared many "high highs and low lows" over the last five years.
Thank you for inspiring me, for all the high highs, especially in wild and beautiful places,
and most of all, for putting up with me (for the most part!).

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Around the time I began this work in 2007, the banal yet horrific killing of elephants for
their teeth began to take off in Tanzania, and the years that followed have become the
darkest, most tragic period in the history of these awe-inspiring animals - across their
entire range. Even in Udzungwa, a mountainous refuge area, they are being slaughtered,
and their faces hacked off, in increasing numbers; nowhere are they safe anymore.
Elephants are not only socially complex, emotional and intelligent individuals, they are
also a true umbrella species for African biodiversity, and saving them represents an
urgent and historic moral test for humanity. I cannot consider a world where elephants
are not living in freedom, and believe we must all do whatever we can to help make this a
reality again. I dedicate this thesis, for what it's worth, to the hope of peace and security,
some day soon, for all Tanzania's elephants.

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ANGLIA RUSKIN UNIVERSITY
ABSTRACT
FACULTY OF SCIENCE AND TECHNOLOGY
DOCTOR OF PHILOSOPHY

PREDICTORS OF MAMMAL DISTRIBUTION AND ABUNDANCE IN
AFROMONTANE FORESTS OF THE UDZUNGWA MOUNTAINS, TANZANIA
By Trevor Jones
August 2013

Large mammals are a species group known to be at high risk of extinction globally. This study is
the first to identify and explore factors affecting large mammal distribution, abundance and
species richness in Afromontane forests. I sampled a range of large mammals (over 2 kg) at 22
sites in ten forests of the exceptionally biodiverse Udzungwa Mountains in southern Tanzania,
using transects and camera traps. I also collected habitat and disturbance data, and tested thirty
anthropogenic and environmental variables against mammal species occurrence, richness, and
relative density within and between forests.
All variables, including altitude, forest size, protective status, and anthropogenic disturbance
varied across forests and study sites. For 27 mammal species detectable on surveys, protective
status, proximity to a ranger post, distance to the nearest village, canopy cover and stem density
all predicted species richness; size of forest patch did not. A possible mid-domain effect is
revealed with greater mammal species richness found at intermediate altitude, in submontane
forest. National park and nature reserve sites are significantly species-richer than forest reserve
sites, although the majority of Udzungwa forest reserves still contain low density populations of
important, threatened species such as Udzungwa red colobus and Abbott's duiker.
For each of the species and guilds assessed (including elephant, leopard, bushpig, forest antelopes
and porcupine), either occupancy or density were strongly predicted by anthropogenic factors
including protective status and distance to nearest ranger post, and one or two habitat variables,
especially canopy cover or canopy height. The only species showing a relationship with forest size
was the aardvark. Smaller mammals such as tree hyrax are affected by human disturbance in
terms of density but still persist at most sites, while the megaherbivores and large predators have
been largely extirpated from the forest reserves, due to hunting and reduction of prey base.
My findings confirm the richness and uniqueness of the Udzungwa mammal community, and
enable me to evaluate threats to species and forests across the mountain range, and to identify
sites in need of priority conservation attention.

Key words: Udzungwa, mammals, Afromontane forest, predictors, richness
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TABLE OF CONTENTS

Acknowledgements .......................................................................................................... iii
ABSTRACT .......................................................................................................................... v
TABLE OF CONTENTS......................................................................................................... vi
List of Tables ..................................................................................................................... xi
List of Figures .................................................................................................................. xiii

Chapter 1 Introduction .................................................................................................... 1
1.1 Introduction ................................................................................................................. 1
1.1.1 Central Research Question .................................................................................... 1
1.1.2 Study Aims ............................................................................................................. 3
1.2 Background .................................................................................................................. 4
1.2.1 Heightened Extinction Risk in Large Mammals ....................................................... 4
1.2.2 Mammals in Tropical Forests: Importance and Status ............................................ 5
1.2.3 Factors Affecting Large Mammal Distribution and Abundance in Tropical Forests . 6
1.2.3.1 Environmental Factors .................................................................................... 7
1.2.3.2 Anthropogenic Factors .................................................................................... 7
1.2.3.3 Studies of Predictors of Mammals in African Forests ....................................... 9
1.3 The Biogeographical Context ...................................................................................... 10
1.3.1 Eastern Afromontane Forests .............................................................................. 10
1.3.2 Udzungwa Mountains: An Exceptional Natural Laboratory for Mammal Studies .. 12
1.4 Structure of Thesis ..................................................................................................... 14

Chapter 2 General Methods ........................................................................................... 16
2.1 Introduction ............................................................................................................... 16
2.1.1 Aims of Chapter ................................................................................................... 16
2.2 Udzungwa Mountains ................................................................................................ 17
2.2.1 Geography, Topography and Rivers ..................................................................... 17
2.2.2 Vegetation ........................................................................................................... 19
2.2.3 Climate ................................................................................................................ 20
2.2.4 Human Population and Ecosystem Services ......................................................... 21
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2.2.5 Protected Areas ................................................................................................... 22
2.3 Mammals of Udzungwa .............................................................................................. 24
2.3.1 Study Species, Guilds and Communities ............................................................... 26
2.4 Study design: General considerations ......................................................................... 28
2.4.1 Selection of Sites ................................................................................................. 29
2.4.2 Timeframe and Seasonality .................................................................................. 30
2.5 Data Collection ........................................................................................................... 32
2.5.1 Recce Transect Method ....................................................................................... 32
2.5.2 Verifying Dung Identification ............................................................................... 35
2.5.3 Camera Trapping ................................................................................................. 38
2.6.1 General Statistics ................................................................................................. 40
2.6.2 DISTANCE ............................................................................................................ 40
2.6.3 Spatial Analysis .................................................................................................... 40
2.6.4 Ordination ........................................................................................................... 41
2.6.5 Generalised Linear Models .................................................................................. 41
2.6.6 Figures ................................................................................................................. 42
2.7 Summary .................................................................................................................... 43

Chapter 3 Environmental and Anthropogenic Attributes of Afromontane Forest ........... 44
3.1 Introduction ............................................................................................................... 44
3.1.1 Aims of Chapter ................................................................................................... 45
3.2 Methods .................................................................................................................... 46
3.2.1 Selecting and Generating Predictor Variables ...................................................... 46
3.2.2 Data Exploration and Variable Reduction: An Ecological Approach ...................... 48
3.3 Predictor Variables ..................................................................................................... 49
3.3.1 Anthropogenic Variables...................................................................................... 49
3.3.2 Environmental Variables ...................................................................................... 53
3.3.3 Climatic Variables ................................................................................................ 60
3.3.4 Forest-level Variable ............................................................................................ 62
3.4 Relationships Between Variables ................................................................................ 63
3.4.1 Relationships Between Anthropogenic Variables ................................................. 63
3.4.2 Relationships Between Environmental Variables ................................................. 65
3.4.3 Relationships Between Climatic Variables ............................................................ 70
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3.4.4 Other Relationships Among Variables .................................................................. 71
3.4.5 Ordination of Predictor Variables......................................................................... 74
3.5 Final List of Key Variables and Hypotheses Relating to Mammals ............................... 77
3.6 Summary of Findings .................................................................................................. 78

Chapter 4 Predictors of Mammal Species Richness in Afromontane Forest .................... 79
4.1 Introduction ............................................................................................................... 79
4.1.1 Aims of Chapter ................................................................................................... 80
4.2 Methods .................................................................................................................... 81
4.2.1 Survey Methods ................................................................................................... 81
4.2.2 Communities and Guilds ...................................................................................... 81
4.2.3 Ordination ........................................................................................................... 81
4.2.4 Generalised Linear Models .................................................................................. 82
4.2.4.1 Predictors of Species Richness ....................................................................... 82
4.2.4.2 Testing for Effect of Protective Status ........................................................... 82
4.2.4.3 Examining Species-Area Relationships ........................................................... 83
4.2.5 Correlations ......................................................................................................... 83
4.3 Predictors of Species Richness.................................................................................... 84
4.3.1 Mammal Communities by Site ............................................................................. 84
4.3.2 Associations Between Species and Sites .............................................................. 86
4.3.3 Predictors of Mammal Species Richness .............................................................. 90
4.3.4 Predictors of Species Richness Within Guilds ....................................................... 93
4.3.5 Does Species Richness Correspond Between Guilds? ........................................... 97
4.4 Species-Area Relationships Among Mammals in Afromontane Forest ........................ 98
4.4.1 Mammal Communities by Forest ......................................................................... 98
4.4.2 Mammal Species Richness and Forest Size ......................................................... 100
4.4.3 Within-Guild Species Richness and Forest Size ................................................... 101
4.5 Summary of Findings ................................................................................................ 103

Chapter 5 Variation in Mammal Density in Afromontane Forest .................................. 105
5.1 Introduction ............................................................................................................. 105
5.1.1 Aims of Chapter ................................................................................................. 106
5.2 Methods .................................................................................................................. 107
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5.2.1 Scale and Presentation of Results ...................................................................... 107
5.2.2 Sampling of Mammals ....................................................................................... 107
5.2.3 Encounter Rates ................................................................................................ 108
5.2.4 Density Estimates .............................................................................................. 109
5.2.5 Correlations ....................................................................................................... 109
5.3 Encounter Rates ....................................................................................................... 110
5.3.1 Primary Consumers............................................................................................ 110
5.3.2 Tree hyrax.......................................................................................................... 112
5.3.3 Aardvark ............................................................................................................ 114
5.3.4 Bushpig .............................................................................................................. 116
5.3.5 Buffalo ............................................................................................................... 117
5.3.6 Monkeys ............................................................................................................ 117
5.3.6.1 Udzungwa Red Colobus ............................................................................... 121
5.4 Density Estimates ..................................................................................................... 121
5.4.1 Forest Antelopes................................................................................................ 122
5.4.2 Elephant ............................................................................................................ 126
5.5 Relationships Between Mammal Densities ............................................................... 129
5.6 Summary of Findings ................................................................................................ 131

Chapter 6 Predictors of Mammal Presence and Density in Afromontane Forest ............ 133
6.1 Introduction ............................................................................................................. 133
6.1.1 Aims of Chapter ................................................................................................. 134
6.2 Methods .................................................................................................................. 135
6.2.1 Data Collection and Processing .......................................................................... 135
6.2.2 Generalised Linear Models ................................................................................ 135
6.2.2.1 Testing for Effect of Protective Status ......................................................... 136
6.2.2.2 Testing for Effect of Forest Size ................................................................... 137
6.2.3 Correlations ....................................................................................................... 137
6.3 Predictors of Mammal Presence............................................................................... 138
6.3.1 Buffalo and Elephant ......................................................................................... 140
6.3.2 Leopard ............................................................................................................. 142
6.3.3 Aardvark ............................................................................................................ 143
6.3.4 Bushbuck and Blue Duiker ................................................................................. 146
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6.3.5 Porcupine .......................................................................................................... 147
6.3.6 Giant Pouched Rat ............................................................................................. 148
6.4 Predictors of Mammal Density ................................................................................. 149
6.4.1 Elephants ........................................................................................................... 150
6.4.2 Bushpig .............................................................................................................. 154
6.4.3 Forest Antelopes................................................................................................ 156
6.4.4 Tree Hyrax ......................................................................................................... 159
6.5 Synthesis: Patterns Among Mammal Predictors ....................................................... 162
6.5.1 Anthropogenic Factors....................................................................................... 162
6.5.2 Environmental Factors ....................................................................................... 162
6.6 Summary of Findings ................................................................................................ 164

Chapter 7 General Conclusions and Recommendations ............................................... 166
7.1 Introduction ............................................................................................................. 166
7.2 Synthesis of Findings ................................................................................................ 166
7.2.1 Predictors of Mammal Species Richness ............................................................ 166
7.2.2 Predictors of Mammal Presence ........................................................................ 168
7.2.3 Predictors of Mammal Densities ........................................................................ 170
7.3 Implications for Mammal Conservation in the Udzungwa Mountains ....................... 172
7.3.1 Protective Status and Management ................................................................... 172
7.3.2 Ecological Connectivity ...................................................................................... 174
7.3.3 Most Threatened Mammal Species.................................................................... 176
7.3.4 Most Threatened Forests ................................................................................... 178
7.4 Future Research Directions ...................................................................................... 180
7.5 Conclusion ............................................................................................................... 181

References ..................................................................................................................... 183

Appendix. Gallery of Udzungwa Mammals ................................................................... 207

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