(Un)sustainable use of frogs in West Africa and resulting consequences for the ecosystem [Elektronische Ressource] / Meike Mohneke. Gutachter: Mark-Oliver Rödel ; K. Eduard Linsenmair ; Rolf Schneider

Meike Mohneke

Description

(Un)sustainable use of frogs in West Africa and resulting consequences for the ecosystem DISSERTATION zur Erlangung des akademischen Grades doctor rerum naturalium (Dr. rer. nat.) im Fach Biologie eingereicht an der Mathematisch-Naturwissenschaftlichen Fakultät Ι der Humboldt-Universität zu Berlin Von Dipl.-Biol. Meike Mohneke Präsident der Humboldt-Universität zu Berlin Prof. Dr. Dr. C. Markschies Dekan der Mathematisch-Naturwissenschaftlichen Fakultät Ι Prof. Dr. A. Herrmann Gutachter: 1. PD. Dr. Mark-Oliver Rödel 2. Prof. em. Dr. K. Eduard Linsenmair 3. PD Dr. Rolf Schneider Tag der mündlichen Prüfung: 31.01.2011 (Un)sustainable use of frogs in West Africa and resulting consequences for the ecosystem Frog Recipe Catch a frog INGERIENTS 6 Frog Legs 2 Eggs 1 Lemon Juice 2 Parsley Sticks Dried Bread Crumps Oil Step 1: Preheat oven at 275F. Step 2: Remove frog leg skins. Flush and drain. Step 3: Add lemon juice, salt and pepper. Step 4: Beat eggs in a bowl, add chopped parsley. Step 5: Soak frog legs in the eggs. Step 6: Crush bread into tiny crumps Step 7: Roll frog legs into crumps. Step 8: Add oil in a pan: Fry frog legs in the Leptodactylus rugosus oven for 3 to 4 minutes Optionally BON APPETIT Hoplobatrachus occipitallis ÿ99ÿÿÿÿ Table of Contents Table of Contents 1. Summary 1.1 Zusammenfassung 1.

Sujets

• Biologie

Informations

• Publié par: humboldt-universitat_zu_berlin
• Publié le: 01 janvier 2011
• Nombre de lectures: 5
• Langue: English
• Poids de l'ouvrage: 13 Mo

Extrait

(Un)sustainable use of frogs in West Africa and resulting
consequences for the ecosystem


DISSERTATION

zur Erlangung des akademischen Grades
doctor rerum naturalium
(Dr. rer. nat.)
im Fach Biologie


eingereicht an der

Mathematisch-Naturwissenschaftlichen Fakultät Ι
der Humboldt-Universität zu Berlin


Von

Dipl.-Biol. Meike Mohneke


Präsident der Humboldt-Universität zu Berlin
Prof. Dr. Dr. C. Markschies

Dekan der Mathematisch-Naturwissenschaftlichen Fakultät Ι
Prof. Dr. A. Herrmann



Gutachter: 1. PD. Dr. Mark-Oliver Rödel
2. Prof. em. Dr. K. Eduard Linsenmair
3. PD Dr. Rolf Schneider



Tag der mündlichen Prüfung: 31.01.2011 (Un)sustainable use of frogs in West
Africa and resulting consequences for the
ecosystem










Frog Recipe

Catch a frog

INGERIENTS

6 Frog Legs
2 Eggs
1 Lemon Juice
2 Parsley Sticks
Dried Bread Crumps
Oil

Step 1: Preheat oven at 275F.
Step 2: Remove frog leg skins. Flush and
drain.
Step 3: Add lemon juice, salt and pepper.
Step 4: Beat eggs in a bowl, add chopped
parsley.
Step 5: Soak frog legs in the eggs.
Step 6: Crush bread into tiny crumps
Step 7: Roll frog legs into crumps.
Step 8: Add oil in a pan: Fry frog legs in the
Leptodactylus rugosus oven for 3 to 4 minutes
Optionally
BON APPETIT Hoplobatrachus occipitallis






Table of Contents

Table of Contents

1. Summary
1.1 Zusammenfassung
1.2 Resumé

1 2. Background – Introduction into the topic

2.1 Global exploitation of frogs with a focus on West Africa 1
2.1.1 Unsustainable use of amphibians 2
2.1.2 Economic consequences of over-exploited frog populations 10
2.2 Declining amphibian populations and the consequences for the ecosystem 11
2.2.1 Ecological Consequences... 12
2.2.1.1…on water quality 12
2.2.1.2…on algal vegetation 13
2.2.1.3…on other grazing species 14
2.2.2 Human health consequences declining frog populations 15

3. Dried or fried - dimension and evaluation of the use and trade of amphibians
17
in West Africa

3.1 Introduction 17
3.2 Methods 18
3.3 Results 20
3.3.1 Traded species 20
3.3.2 Collecting seasons, sites and methods 20
3.3.3 Dimensions of frog trade 22
3.3.4 Declining frog populations 31
3.4 Discussion 31

4. Amphibians as food and medicine in West Africa – ethnozoological approach 35

4.1 Introduction 35
4.2 Methods 36
4.3 Results 37
4.3.1 Methods of collecting frogs 37
4.3.2 Different species – different values 39
4.3.3 Frog meals 42
?9????9Table of Contents
4.3.4 Frogs as medicine 44
4.3.5 Who is collecting, trading and eating frogs? 46
4.4 Discussion 47

5. Tadpole communities of ephemeral savanna ponds in different disturbance
51
regimes in Burkina Faso, West Africa

5.1 Introduction 51
5.2 Material and Methods 53
5.2.1 Study sites 53
5.2.2 Data collection 54
5.2.3 Statistical analyses 56
5.3 Results 59
5.3.1 Tadpole species composition concerning disturbance regime and study 60
site
5.3.2 Tadpole species composition in relation to habitat factors 62
5.3.2.1 Tadpole species composition in relation to habitat factors and to 62
geographical distances between ponds
5.3.2.2 Tadpole species composition in relation to mosquito genera 62
composition
5.3.2.3 Comparison between tadpole species composition and ponds 63
environmental parameters and surrounding vegetation
5.3.2.4 Comparison of mosquito genera composition and tadpole 65
species composition
5.3.3 Frequencies of tadpole species and habitat factors in different 66
disturbance regimes
5.3.3.1 Differences between disturbed and undisturbed sites concerning 66
the tadpole composition
5.3.3.2 Differences of habitat factors between different disturbance sites 69
5.3.3.3 Differences between disturbance regimes concerning mosquito 71
assemblages
5.3.4 Tadpole species compositions correlating with habitat factors 72
5.3.4.1 Mosquito composition in relation to tadpole composition 74
5.4 Discussion 76
5.4.1 Tadpole species composition in relation to disturbance regime and 76
respective habitat factors
5.4.2 Tadpole species composition in relation to mosquito species composition 80 Table of Contents

5.4.3 Factors besides habitat factors affecting tadpole assemblage 82
composition

6. Ecological role of tadpoles – species exclusion experiments in artificial
87
ponds

6.1 Introduction 87
6.2 Materials and Methods 89
6.2.1 Species exclusion experiments 90
6.2.2 Collecting and raising study species 90
6.2.3 Experimental tadpole communities 91
6.2.4 Effects of species exclusion on tadpoles’ survival, growth and 93
development
6.2.5 Influence of tadpoles on parameters of water quality 93
6.2.6 Mosquito larvae composition and densities 93
6.2.7 Trophic position of tadpoles 94
6.2.8 Statistical analyses 95
6.3 Results 95
6.3.1 Effects of species exclusion on tadpoles’ survival, growth and 95
development
6.3.1.1 Survival rate 95
6.3.1.2 Growth 97
6.3.1.3 Development 99
6.3.2 Changes in trophic position through species exclusion 100
6.3.3 Influence of tadpoles on water chemistry and transparency 108
6.3.4 Mosquito assemblages and densities 105
6.4 Discussion 106
6.4.1 Tadpoles’ effect on water transparency and water chemistry 110
6.4.2 Mosquito densities and species assemblages in respect to tadpole 110
species exclusion

113 7. Final Conclusion

References 121
Appendix 1 139
Appendix 2 157
Appendix 3 164
Appendix 4 165 Table of Contents
Abbreviations 167
Acknowledgements 169
Publication list 193
Statement 194
Chapter 1 Summary
1 Summary
Amphibian populations are declining world wide. One of the main reasons for this decline is
overexploitation. All over the world many frog species are caught from the wild, mainly for
food, but also for medicinal purposes or pet trade. Herein I report first investigations from
West Africa. Whereas particular West African tribes have always used frogs as food,
medicine or for cultural reasons, a current increase in frog hunting seems to be new. With a
continuously growing human population and a simultaneous decline of protein resources
such as fish the exploitation of amphibians is likewise increasing. Consequently, amphibian
declines are likely and may result in measurable changes of aquatic and riparian
ecosystems. In the beginning of my thesis, I will provide an overview on exploitation and
trade of amphibian species in different regions of the world, with a main emphasis on West
Africa, and on possible resulting consequences for the ecosystem.
In Africa the use, mainly consumption, of different frog species has not been in the focus of
scientific research yet. By carrying out interviews with frog-collectors, market-women and
consumers in Burkina Faso, Benin and Nigeria I was able to quantify and evaluate the use
and trade of frogs in these countries. In Burkina Faso the frog trade mainly took place on a
local scale, whereas in northern Benin and Nigeria, I detected an intensive cross-border
trade of amphibians. Frogs, predominantly the African Tiger Frog, Hoplobatrachus occipitalis,
was collected in the North of Nigeria and neighbouring countries, and were subsequently
traded into the cities of southern Nigeria. It is likely that the amount of traded frogs is not
sustainable in some areas, partly already resulting in declining frog populations.
As part of my investigation ethnozoological data on the use of frogs by local ethnic groups
(Mossi, Gourmanché, Yoruba and Hausa) were additio