Zebra Stripes
9780226411019
9780226411156
Zebra Stripes
From eminent biologists like Alfred Russel Wallace and Charles Darwin to famous authors such as Rudyard Kipling in his Just So Stories, many people have asked, “Why do zebras have stripes?” There are many explanations, but until now hardly any have been seriously addressed or even tested. In Zebra Stripes, Tim Caro takes readers through a decade of painstaking fieldwork examining the significance of black-and-white striping and, after systematically dismissing every hypothesis for these markings with new data, he arrives at a surprising conclusion: zebra markings are nature’s defense against biting fly annoyance.
Popular explanations for stripes range from camouflage to confusion of predators, social facilitation, and even temperature regulation. It is a serious challenge to test these proposals on large animals living in the wild, but using a combination of careful observations, simple field experiments, comparative information, and logic, Caro is able to weigh up the pros and cons of each idea. Eventually—driven by experiments showing that biting flies avoid landing on striped surfaces, observations that striping is most intense where biting flies are abundant, and knowledge of zebras’ susceptibility to biting flies and vulnerability to the diseases that flies carry—Caro concludes that black-and-white stripes are an adaptation to thwart biting fly attack. Not just a tale of one scientist’s quest to solve a classic mystery of biology, Zebra Stripes is also a testament to the tremendous value of longitudinal research in behavioral ecology, demonstrating how observation, experiment, and comparative research can together reshape our understanding of the natural world.
Popular explanations for stripes range from camouflage to confusion of predators, social facilitation, and even temperature regulation. It is a serious challenge to test these proposals on large animals living in the wild, but using a combination of careful observations, simple field experiments, comparative information, and logic, Caro is able to weigh up the pros and cons of each idea. Eventually—driven by experiments showing that biting flies avoid landing on striped surfaces, observations that striping is most intense where biting flies are abundant, and knowledge of zebras’ susceptibility to biting flies and vulnerability to the diseases that flies carry—Caro concludes that black-and-white stripes are an adaptation to thwart biting fly attack. Not just a tale of one scientist’s quest to solve a classic mystery of biology, Zebra Stripes is also a testament to the tremendous value of longitudinal research in behavioral ecology, demonstrating how observation, experiment, and comparative research can together reshape our understanding of the natural world.
320 pages | 33 color plates, 28 halftones, 55 tables | 6 x 9 | © 2016
Biological Sciences: Behavioral Biology, Biology--Systematics, Ecology, Evolutionary Biology
Reviews
Table of Contents
Preface and acknowledgments
Chapter 1. Stripes and equids
1.1. The question of stripes
1.2. Hypotheses for striping in equids
1.2.a. Antipredator hypotheses
1.2.b. Antiparasite hypotheses
1.2.c. Communication hypotheses
1.2.d. Thermoregulation hypothesis
1.3. Equid evolution
1.3.a. Plains zebra
1.3.b. Mountain zebra
1.3.c. Grevy’s zebra
1.3.d. African wild ass
1.3.e. Asiatic wild ass
1.3.f. Kiang
1.3.g. Przewalski’s horse
1.3.h. Other equids
1.4. Zebra hair
1.5. Conclusion
Chapter 2. Predation and crypsis
2.1. Background matching
2.1.a. Initial discomfort with the idea
2.1.b. Detecting zebras
2.2. Disruptive coloration
2.2.a. Predictions
2.2.b. Sightings at dusk and dawn
2.3. Countershading
2.4. Zebras as seen by nonhumans
2.5. Conclusions
Chapter 3. Predation and aposematism
3.1. Aposematism in mammals
3.2. Signaling component of aposematism
3.2.a. Visibility
3.2.b. Noisy behavior
3.3. Defense component of aposematism
3.3.a. Response to predators
3.4. Conclusion
Chapter 4. Predation and confusion
4.1. Confusion
4.2. Miscounting numbers of prey individuals
4.3. Striping obscuring outlines of fleeing prey
4.3.a. Lines of stripes shown to humans
4.3.b. Lines of stripes in dangerous situations
4.4. Striping preventing a single prey individual being followed
4.5. Dazzle effect
4.6. Motion dazzle
4.7. Misjudging the size of prey
4.7.a. Subjective and estimated heights and girths
4.7.b. Subjective heights and girths and degree of striping
4.8. Quality advertisement
4.9. Conclusion
4.10. Difficulties with the predation hypothesis
Chapter 5. Ectoparasites
5.1. Biting flies
5.2. Behavioral indices of fly infestation in Katavi
5.3. Behavioral indices of fly infestation in Berlin
5.4. Tsetse fly traps
5.4.a. Biconical traps
5.4.b. Cloth traps
5.5. Tabanid traps
5.5.a. Canopy traps
5.5.b. Pelt canopy traps
5.6. Moving objects
5.6.a. Walking in suits
5.6.b. Walking in pelts
5.6.c. Driving with pelts
5.7. Conclusions
5.8. Polarized light
5.8.a. Reflected light
5.8.b. Horvath’s work
5.8.c. Polarization signatures of wild zebras
Chapter 6. Intraspecific communication
6.1. Intraspecific signaling
6.2. Species recognition
6.3. Stripes as a facilitator of mutual grooming and social bonding
6.3.a. Allogrooming
6.3.b. Social bonding
6.4. Stripes as a means of individual recognition
6.5. Stripes as an indicator of quality
6.6. Conclusion
Chapter 7. Temperature regulation
7.1. Black and white surfaces
7.2. Heat measurements in the field
7.3. Heat management
7.4. Conclusions
Chapter 8. Multifactorial analyses
8.1. Comparing hypotheses simultaneously
8.2. The interspecific comparison
8.2.a. Comparative methodology
8.2.b. Overall striping
8.2.c. Striping on different parts of the body
8.2.d. Evaluating the hypotheses
8.3. Conclusions
8.4. The intraspecific comparison
8.5. Concordance on multifactorial analyses
Chapter 9. The case for biting flies
9.1. Last man standing
9.2. Host choice
9.3. Ectoparasite population sizes
9.4. Host seeking
9.5. Parasites and diseases transmitted by bloodsucking diptera
9.6. Mechanistic studies
9.7. Further outstanding issues
9.7.a. Multiple functions
9.7.b. Loose ends
9.8. Conclusion
Appendix 1. Scientific names of vertebrates mentioned in the text
Appendix 2. Nature of wounding seen in African ungulates in Katavi National Park
Appendix 3. Families of insects identified in each type of biconical trap color
Appendix 4. Families of insects identified in each type of cloth trap color
Appendix 5. Photographic sources for comparative analyses
Appendix 6. Derivation of zebra phylogenies
Appendix 7. Phylogenetic analyses
References
Index
Chapter 1. Stripes and equids
1.1. The question of stripes
1.2. Hypotheses for striping in equids
1.2.a. Antipredator hypotheses
1.2.b. Antiparasite hypotheses
1.2.c. Communication hypotheses
1.2.d. Thermoregulation hypothesis
1.3. Equid evolution
1.3.a. Plains zebra
1.3.b. Mountain zebra
1.3.c. Grevy’s zebra
1.3.d. African wild ass
1.3.e. Asiatic wild ass
1.3.f. Kiang
1.3.g. Przewalski’s horse
1.3.h. Other equids
1.4. Zebra hair
1.5. Conclusion
Chapter 2. Predation and crypsis
2.1. Background matching
2.1.a. Initial discomfort with the idea
2.1.b. Detecting zebras
2.2. Disruptive coloration
2.2.a. Predictions
2.2.b. Sightings at dusk and dawn
2.3. Countershading
2.4. Zebras as seen by nonhumans
2.5. Conclusions
Chapter 3. Predation and aposematism
3.1. Aposematism in mammals
3.2. Signaling component of aposematism
3.2.a. Visibility
3.2.b. Noisy behavior
3.3. Defense component of aposematism
3.3.a. Response to predators
3.4. Conclusion
Chapter 4. Predation and confusion
4.1. Confusion
4.2. Miscounting numbers of prey individuals
4.3. Striping obscuring outlines of fleeing prey
4.3.a. Lines of stripes shown to humans
4.3.b. Lines of stripes in dangerous situations
4.4. Striping preventing a single prey individual being followed
4.5. Dazzle effect
4.6. Motion dazzle
4.7. Misjudging the size of prey
4.7.a. Subjective and estimated heights and girths
4.7.b. Subjective heights and girths and degree of striping
4.8. Quality advertisement
4.9. Conclusion
4.10. Difficulties with the predation hypothesis
Chapter 5. Ectoparasites
5.1. Biting flies
5.2. Behavioral indices of fly infestation in Katavi
5.3. Behavioral indices of fly infestation in Berlin
5.4. Tsetse fly traps
5.4.a. Biconical traps
5.4.b. Cloth traps
5.5. Tabanid traps
5.5.a. Canopy traps
5.5.b. Pelt canopy traps
5.6. Moving objects
5.6.a. Walking in suits
5.6.b. Walking in pelts
5.6.c. Driving with pelts
5.7. Conclusions
5.8. Polarized light
5.8.a. Reflected light
5.8.b. Horvath’s work
5.8.c. Polarization signatures of wild zebras
Chapter 6. Intraspecific communication
6.1. Intraspecific signaling
6.2. Species recognition
6.3. Stripes as a facilitator of mutual grooming and social bonding
6.3.a. Allogrooming
6.3.b. Social bonding
6.4. Stripes as a means of individual recognition
6.5. Stripes as an indicator of quality
6.6. Conclusion
Chapter 7. Temperature regulation
7.1. Black and white surfaces
7.2. Heat measurements in the field
7.3. Heat management
7.4. Conclusions
Chapter 8. Multifactorial analyses
8.1. Comparing hypotheses simultaneously
8.2. The interspecific comparison
8.2.a. Comparative methodology
8.2.b. Overall striping
8.2.c. Striping on different parts of the body
8.2.d. Evaluating the hypotheses
8.3. Conclusions
8.4. The intraspecific comparison
8.5. Concordance on multifactorial analyses
Chapter 9. The case for biting flies
9.1. Last man standing
9.2. Host choice
9.3. Ectoparasite population sizes
9.4. Host seeking
9.5. Parasites and diseases transmitted by bloodsucking diptera
9.6. Mechanistic studies
9.7. Further outstanding issues
9.7.a. Multiple functions
9.7.b. Loose ends
9.8. Conclusion
Appendix 1. Scientific names of vertebrates mentioned in the text
Appendix 2. Nature of wounding seen in African ungulates in Katavi National Park
Appendix 3. Families of insects identified in each type of biconical trap color
Appendix 4. Families of insects identified in each type of cloth trap color
Appendix 5. Photographic sources for comparative analyses
Appendix 6. Derivation of zebra phylogenies
Appendix 7. Phylogenetic analyses
References
Index
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