Abstract
Bonobos (Pan paniscus) and Chimpanzees
(Pan troglodytes) are the two closest primate
relatives to humans, sharing over 98% of our genetic blueprint and
more than 99% with one another. However, behaviorally they are
remarkably different. Chimpanzees are hierarchical, male-dominant
and use aggression to resolve conflicts. Bonobos are egalitarian,
female-biased and use a wide array of sexual behaviors to resolve
conflict. Their diverse sexual repertoires are pronounced when food
is present, suggesting that food-related pressures fostered this
notable behavioral adaptation, raising the question: Do bonobos
experience food stress, and if so, how do they respond? Popular
theories attempting to explain differences in social behaviors
between both species of Pan often include the
hypothesis that terrestrial herbaceous vegetation (THV) is a key
factor in maintaining large party sizes seen in bonobos. Although
this theory has been negated repeatedly over the years and across
sites, there are still gaps in our understanding about its role in
wild bonobo diets. Using a year's worth of behavioral
and ecological data from a community of wild bonobos and their
environment, I examined seasonal patterns in resource availability
and diet in the Iyema community, corresponding seasonal patterns in
nest party sizes and energetic hormonal profiles that accompanied
these changes to see if shifts in resource availability and
sociality were reflected in three key hormonal metabolites
associated with different kinds of stress. The Iyema forest
displayed seasonal patterns in both fruit abundance and diversity,
and both these factors proved significant in predicting nest party
sizes, using a generalized linear mixed model. THV was the third
most frequently consumed food item in the Iyema bonobo diet, but
its consumption was significantly negatively correlated with an
increase in party size. THV consumption showed distinctly seasonal
patterns, suggesting that its nutritional properties should be
reexamined on a seasonal scale. Urinary C-peptide and urinary
cortisol were predictably inversely correlated in the context of
diet, environmental diversity and shifts in party sizes, showing
that bonobos experience periods of environmentally-related
energetic stress that affect their sociality and long-term use of
non-invasively collected hormonal metabolites effectively
demonstrate complex social and energetic relationships in wild
primates.
Table of Contents
Table of Contents
CHAPTER 1 1
INTRODUCTION 1
CHAPTER 2: 8
LOMAKO FOREST AND THE IYEMA STUDY SITE 8
CHAPTER 2 ABSTRACT 9
2.1 LOMAKO FOREST 10
2.2 FOREST COMPOSITION AT IYEMA 15
2.2.1 RESOURCE DENSITY AND DISTRIBUTION 17
2.3 COMMUNITY STRUCTURE 19
CHAPTER 3: 21
SEASONALITY AND DIET OF THE IYEMA FOREST AND BONOBO COMMUNITY
21
CHAPTER 3 ABSTRACT 22
SEASONALITY AND DIET OF THE IYEMA FOREST AND BONOBO COMMUNITY
23
3.1 BACKGROUND: 23
3.1.1 ABUNDANCE AND DIVERSITY 24
3.1.2 DIFFERENCES IN PAN SOCIAL STRUCTURE 24
3.2 ORGANIZING QUESTIONS: 27
3.3 METHODS 27
3.3.1 RAINFALL AND TEMPERATURE 27
3.3.2 PHENOLOGICAL TRANSECTS 30
3.3.3 COLLECTION AND ASSESSMENT OF FECES 33
3.4 RESULTS 34
3.4.1 DOES THE IYEMA BONOBO COMMUNITY LIVE IN A SEASONAL
ENVIRONMENT? 34
3.4.2 ARE SEASONAL FLUCTUATIONS IN THE ENVIRONMENT REFLECTED IN THE
IYEMA BONOBOS' DIET? 45
3.4.2.1 DOES DIETARY DIVERSITY (MEASURED THROUGH THE NUMBER OF
SPECIES FOUND IN BONOBO FECES) REFLECT ENVIRONMENTAL DIVERSITY OF
AVAILABLE RIPE FRUIT? 45
3.5 DISCUSSION 47
CHAPTER 4: 48
TERRESTRIAL HERBACEOUS VEGETATION AND THE IYEMA BONOBO DIET
48
CHAPTER 4 ABSTRACT 49
TERRESTRIAL HERBACEOUS VEGETATION: CONSUMPTION PATTERNS BY THE
IYEMA BONOBOS AND IMPLICATIONS FOR DIET AND SOCIALITY 50
4.1 BACKGROUND/LINEAGE 50
4.1.2 THV CONSUMPTION PATTERNS ACROSS PAN 50
4.1.2 PREFERENCES FOR THV 51
4.1.3 NUTRITIONAL CONTENT OF THV 52
4.2 ORGANIZING QUESTIONS 54
4.3 METHODS 54
4.3.1 DISTRIBUTION ACROSS THE STUDY SITE 54
4.3.2 FECAL ANALYSIS 54
4.4 RESULTS 55
4.4.1 DO BONOBOS EAT MORE THV WHEN DIETARY RESOURCES ARE LOW?
56
4.4.2 IS THE CONSUMPTION OF THV CORRELATED WITH LARGER PARTY SIZES?
63
4.5 DISCUSSION 65
CHAPTER 5: 67
NEST PARTIES AND THEIR ECOLOGICAL CORRELATES AT IYEMA 67
CHAPTER 5 ABSTRACT 68
NEST PARTIES AT IYEMA: BASIC PATTERNS OF SEASONAL SOCIALITY AND
THEIR ECOLOGICAL CORRELATES 69
5.1 BACKGROUND 69
5.1.1 FACTORS THAT AFFECT PRIMATE SOCIAL DYNAMICS 69
5.1.2 FEEDING PARTIES IN BONOBOS AND CHIMPS: 72
5.2 ORGANIZING QUESTIONS 75
5.3 METHODS 75
5.3.1 NEST PARTIES 75
5.4 RESULTS 76
5.4.1 DO PARTY SIZES SHIFT SEASONALLY? 76
5.4.2 DO SEASONAL SHIFTS IN RESOURCE AVAILABILITY, MEASURED THROUGH
ABUNDANCE AND DIVERSITY AFFECT PARTY SIZE? 79
5.5 DISCUSSION 82
CHAPTER 6: 84
HORMONAL CORRELATES OF SEASONALITY, SOCIALITY AND DIET IN THE IYEMA
BONOBO COMMUNITY 84
CHAPTER 6 ABSTRACT 85
HORMONAL CORRELATES OF SEASONALITY, SOCIALITY AND DIET IN THE IYEMA
BONOBO COMMUNITY 86
6.1 INTRODUCTION: 86
6.1.1 BONOBO (AND CHIMPANZEE) BEHAVIOR, ECOLOGY, SOCIAL STRUCTURE
AND THEIR HORMONAL CORRELATES 89
6.2 RESEARCH GOALS AND ORGANIZING QUESTIONS 94
6.3 METHODS 97
6.3.1 COLLECTION 97
6.3.2 PRESERVATION AND FIELD PROCESSING 97
6.3.3 EXTRACTION 101
6.3.4 ANALYSIS AND VALIDATION 109
6.3.5 KETONES: PROBLEMS WITH COLOR AND RELIABILITY 120
6.4 RESULTS 122
6.4.1 HORMONES AND SEASONALITY 124
6.4.2 HORMONES AND TERRESTRIAL HERBACEOUS VEGETATION (THV)
143
6.4.3 HORMONES AND NEST PARTIES 148
6.5 DISCUSSION: 151
6.5.1 DISCUSSION OF METHODS: 151
6.5.2 SUMMARY OF RESULTS: 155
CHAPTER 7 CONCLUSION 158
REFERENCES 166
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