Avoiding Attack The Evolutionary Ecology of Crypsis, Warning Signals and Mimicry

by Ruxton, Graeme D.; Sherratt, Thomas N.; Speed, Michael P.

• ISBN13: 9780198528609
• ISBN10: 0198528604
• Format: Paperback
• Copyright: 2005-02-03
• Publisher: Oxford University Press

Summary

This book discusses the diversity of mechanisms by which prey avoid attack by predators and questions how such defensive mechanisms have evolved through natural selection. It considers how potential prey avoid detection, how they make themselves unprofitable to attack, how they signal theirunprofitability, and how other species have exploited these signals. Using carefully selected examples drawn from a wide range of species and ecosystems, the authors present a critical analysis of the most important published works in the field. Illustrative examples of camouflage, mimicry and warning signals regularly appear in undergraduate ecology textbooks, but these subjects are rarely considered in depth. This book summarises some of the latest research into these fascinating adaptations, developing mathematical models whereappropriate and making recommendations for the most urgently needed outstanding areas of enquiry.

Author Biography

Graeme Ruxton has co-written two books, both published by Oxford University Press - 'Living in Groups' (2002) for the Oxford Series in Ecology and Evolution, and the textbook 'Elementary Experimental Design for the Life Sciences' (2003). He is also the author of over 100 scientific articles. His background in physics provides particular strength in the functional aspects of signalling systems discussed in this book. Tom Sherratt is the author of nearly 50 scientific papers on subjects ranging from the evolution of co-operation, to the maintenance of imperfect mimicry and the evolution of warning signals. His practical background in both tropical and temperate entomology (principally damselflies and mosquitoes) has been of great value in evaluating empirical work in this broad field, whilst his wide interests in evolutionary biology and foraging theory complement those of his co-authors in placing empirical findings within an appropriate theoretical context. Mike Speed has worked for over a decade on the role of predator behaviour in the generation of insect warning signals. He is consulting editor for the journal Animal Behaviour and a member of the education committee of the Association for the Study of Animal Behaviour. His publications span theoretical and empirical studies of mimicry and aposematism.

Table of Contents

Introduction	p. 1
Avoiding detection	p. 5
Background matching	p. 7
Why crypsis?	p. 7
Industrial melanism in Biston betularia	p. 9
Background is a multivariate entity	p. 10
Combining background matching with other functions	p. 11
Flicker fusion	p. 12
Polymorphism of background matching forms	p. 12
A case study: polymorphism in Cepaea	p. 13
Polymorphism through neutral selection	p. 13
Positive selection for polymorphism	p. 14
Definitions related to frequency-dependent predation	p. 14
Search images	p. 17
Control of search rate	p. 18
Comparing search image and search rate mechanisms	p. 18
Neutral selection again	p. 19
Coping with multiple backgrounds	p. 20
Masquerade	p. 23
Conclusion	p. 25
Disruptive colouration	p. 26
Introduction	p. 26
Separating disruptive colouration from background matching	p. 27
Empirical evidence	p. 27
Conclusion	p. 29
Countershading and counterillumination	p. 30
Introduction	p. 30
Self-shadow concealment and countershading	p. 30
Direct empirical tests of the advantages of countershading	p. 31
Indirect evidence	p. 33
The naked mole-rat	p. 33
Countershading in ungulates	p. 34
Countershading in aquatic environments	p. 34
Counterillumination in marine animals	p. 35
Countershading in aerial, aquatic, and terrestrial systems	p. 36
Conclusion	p. 37
Transparency and silvering	p. 38
Transparent objects still reflect and refract	p. 38
More reasons why perfect transparency need not translate to perfect crypsis	p. 39
Polarization	p. 39
Other wavelengths of light	p. 40
Snell's window	p. 41
Imperfect transparency can be effective at low light levels	p. 42
Some parts of an organism cannot be made transparent	p. 43
The distribution of transparency across habitats	p. 44
Silvering as a form of crypsis	p. 45
Conclusion	p. 48
Avoiding attack after detection	p. 49
Secondary defences	p. 51
The diversity of secondary defences	p. 51
Costs and benefits of some behavioural and morphological secondary defences	p. 53
Behavioural defences	p. 53
Morphological and other mechanical defences	p. 54
Chemical defences	p. 55
Some characteristics of chemical defences	p. 56
Are chemical defences costly?	p. 59
Costs, benefits, and forms of defence	p. 63
The evolution of defences	p. 64
Evolutionary pathways	p. 64
Theoretical approaches to the evolution of defences	p. 64
Formal modelling of the evolution of defences	p. 67
Summary and conclusion	p. 68
Signalling to predators	p. 70
Introduction	p. 70
Signalling that an approaching predator has been detected	p. 70
Signalling that the prey individual is intrinsically difficult to catch	p. 73
Summary of theoretical work	p. 75
Empirical evidence from predators	p. 75
Stotting by gazelle	p. 75
Upright stance by hares	p. 76
Push-up displays by lizards	p. 77
Singing by skylarks	p. 77
Predator inspection behaviour by fish	p. 77
Calling by antelope	p. 78
Fin-flicking behaviour by fish	p. 78
Studies where predator behaviour is not reported	p. 79
Tail-flicking by rails	p. 79
Tail-signalling by lizards	p. 80
Calling by Diana monkeys	p. 80
Snorting in African bovids	p. 81
Tail-flagging by deer	p. 81
Barking by deer	p. 81
Conclusion	p. 81
The form and function of warning displays	p. 82
Characteristics of aposematic warning displays	p. 82
Aposematism does not require complete avoidance by predators	p. 84
Conspicuous animals are not necessarily aposematic	p. 84
Design of aposematic displays I: why conspicuousness?	p. 85
The opportunity costs of crypsis	p. 87
Forms of secondary defence and the need for conspicuous components of warning displays	p. 87
Design of aposematic displays II: the psychological properties of predators	p. 89
Unlearnt wariness	p. 90
Aposematism and predator learning	p. 94
Memorability	p. 97
Recognition	p. 99
Summary	p. 100
Co-evolution: which came first, conspicuousness or special psychological reponses to conspicuousness?	p. 100
Conclusion: designing a warning display	p. 101
The initial evolution of warning displays	p. 104
The initial evolution of aposematism: the problem	p. 104
Stochastic-deterministic scenarios	p. 105
Spatial aggregation	p. 106
Experimental simulations of aggregation effects	p. 108
More complex population and predator models for aposematism	p. 108
Individual selection models	p. 109
Evaluations of predator psychology models	p. 110
Alternatives to the rare conspicuous mutant scenario	p. 111
Sexual selection	p. 111
Defences, optimal conspicuousness and apparency	p. 112
Aposematism originated to advertise 'visible' defences	p. 112
Facultative, density-dependent aposematism	p. 112
Simultaneous evolution of defence and conspicuousness	p. 113
Phylogeny and evolutionary history	p. 113
The evolution of aposematism: a trivial question with interesting answers?	p. 114
The evolution and maintenance of Mullerian mimicry	p. 115
Where Mullerian mimicry fits in	p. 115
Chapter outline	p. 115
A brief early history of Mullerian mimicry	p. 116
Some potential examples of Mullerian mimicry	p. 118
Neotropical Heliconius butterflies	p. 119
European burnet moths	p. 120
Bumble bees	p. 120
Cotton stainer bugs (genus Dysdercus)	p. 122
Poison arrow frogs	p. 122
Experimental evidence for Mullerian mimicry	p. 122
Direct assessments of the benefits of adopting a common warning signal	p. 122
Proportions of unpalatable prey consumed by naive predators in the course of education	p. 124
Models of Mullerian mimicry	p. 126
Questions and controversies	p. 126
Which is the model and which is the mimic?	p. 126
How can mimicry evolve through intermediate stages?	p. 127
Why are mimetic species variable in form between areas?	p. 129
How can multiple Mullerian mimicry rings co-exist?	p. 131
What is the role of predator generalization in Mullerian mimicry?	p. 134
Why are some Mullerian mimics polymorphic?	p. 134
Do Mullerian mutualists only benefit simply from shared predator education?	p. 135
Overview	p. 136
Deceiving predators	p. 137
The evolution and maintenance of Batesian mimicry	p. 139
Scope	p. 139
Taxonomic distribution of Batesian mimicry	p. 140
Examples of Batesian mimicry	p. 140
Comparative evidence for Batesian mimicry	p. 141
Experimental evidence for Batesian mimicry and its characteristics	p. 142
Predators learn to avoid noxious models and consequently their palatable mimics	p. 142
Palatable prey altered to resemble an unpalatable species sometimes survive better than mock controls	p. 143
Batesian mimics generally require the presence of the model to gain significant protection	p. 144
The relative (and absolute) abundances of the model and mimic affects the rate of predation on these species	p. 147
The distastefulness of the model affects the rate of predation on the model and mimic	p. 148
The model can be simply difficult to catch rather than noxious on capture	p. 148
The success of mimicry is dependent on the availability of alternative prey	p. 150
Mimics do not always have to be perfect replicas to gain protection, particularly when the model is relatively common or highly noxious	p. 150
Frequency-dependent selection on Batesian mimics can lead to mimetic polymorphism	p. 151
The theory of Batesian mimicry	p. 152
Questions and controversies	p. 154
Why are not all palatable prey Batesian mimics?	p. 154
Is the spatio-temporal coincidence of the models and mimics necessary?	p. 155
Why is Batesian mimicry often limited to one sex?	p. 156
How is mimicry controlled genetically and how can polymorphic mimicry be maintained?	p. 158
Why are imperfect mimics not improved by natural selection?	p. 159
How does Batesian mimicry evolve, and why do models simply not evolve away from their mimics?	p. 161
What selective factors influence behavioural mimicry?	p. 162
Overview	p. 163
The relationship between Batesian and Mullerian mimicry	p. 164
Context	p. 164
Evidence of interspecific differences in levels of secondary defence	p. 165
Why should weakly defended mimics increase the likelihood that more highly defended models are attacked?	p. 166
Predator hunger	p. 166
Differences in predatory abilities: the 'Jack Sprat' effect	p. 169
Psychological models	p. 169
Observational data on the nature of the relationship between Batesian and Mullerian mimicry	p. 170
Summary	p. 171
Other forms of adaptive resemblance	p. 172
Overview	p. 172
Aggressive mimicry	p. 172
Pollinator (floral) mimicry	p. 174
Intraspecific sexual mimicry	p. 175
Automimicry	p. 176
The phenomenon of automimicry	p. 176
The challenge to theoreticians	p. 179
Summary	p. 182
Deflection and startling of predators	p. 183
Deflection defined	p. 183
Empirical evidence for deflection	p. 183
Lizard tails	p. 183
Tadpole tails	p. 184
Eyespots on fish	p. 185
False head marking on butterflies	p. 187
Weasel tails	p. 190
Summary of empirical evidence for deflective signals	p. 190
How can deflective marking evolve if they make prey easier for predators to detect?	p. 191
Why do predators allow themselves to be deceived?	p. 191
Startle signals	p. 192
General considerations	p. 192
Distress calls as startle signals	p. 193
Visual startle signals	p. 194
Sound generation by moths attacked by bats	p. 195
Summary of empirical evidence	p. 196
Why would predators be startled?	p. 196
Tonic immobility	p. 197
Distraction displays	p. 198
Summary	p. 199
General Conclusions	p. 200
Appendices	p. 202
A summary of mathematical and computer models that deal with Mullerian mimicry
A summary of mathematical and computer models that deal with Batesian mimicry
References	p. 210
Author Index	p. 240
Species Index	p. 243
Subject Index	p. 248
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