The Rules of the Flock: Self-Organization and Swarm Structure in Animal Societies

140 Pages·2020·15.182 MB·English

by  Helmut Satz

THE RULES OF THE FLOCK

THE RULES OF
THE FLOCK
Self-Organization and Swarm
Structure in Animal Societies
Helmut Satz
1
1
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© Helmut Satz 2020
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First Edition published in 2020
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British Library Cataloguing in Publication Data
Data available
Library of Congress Control Number: 2019947625
ISBN 978–0–19–885339–8
DOI: 10.1093/oso/9780198853398.001.0001
Printed and bound by
CPI Group (UK) Ltd, Croydon, CR0 4YY
Preface
The past fifty years have witnessed the emergence of a new field of
scientific research: the study of swarm behavior. The question
which led to these studies is immediately evident: how is it pos-
sible that large numbers of simple individuals, each interacting
only with a few near-by neighbors, produce dramatic large-scale
collective behavior? Flocks of birds execute striking swarm
maneuvers above us in the sky; schools of fish do the same in the
depths of the sea. Glow worms in the Asian jungle perform light
displays in which thousands of individual bugs radiate in perfect
synchronization. These and various other, similar phenomena
have led mathematicians and physicists to join forces with their
colleagues from biology in the attempt to show that the under-
lying structure of animal swarms is in fact quite universal and
many ways similar to that studied in the physics of many inter-
acting particles. It is found that the formation and structure of a
bird swarm is very much like the magnetization pattern of a piece
of iron, in which the spins of most of the atoms suddenly point in
the same direction. And the synchronization of the glow worm
radiation is shown to use mechanisms quite similar to those lead-
ing to the radiation of light by a laser.
On the other hand, ants, bees and other social insects have
developed very efficient collective schemes for the solution of
various problems, such as finding the shortest path between two
points—schemes which since some decades have found their use
in human logistics as well. And in addition, their swarm structure
gives a new meaning to what survival of the fittest means.
Evolution has here led to swarm constructs which completely
modify the individual members: they are no longer autonomous
animals, but have instead become parts of a superorganism, with
specific functions and specific benefits. While an independent
existence for members of mammal herds or bird flocks may have
vi Preface
its difficulties, it is completely impossible for the members of
social insect states, where collective efforts are necessary not only
for the existence of the state, but for that of each member as well.
What about human societies? Although the behavior of these
is much more complex, there exist features which are evidently
also the result of self-organization. In particular, evolution led to
the creation of language as a tool to describe abstract as well as
concrete aspects; this tool allowed the planning and organization
which resulted in the human dominance over the entire Earth.
The aim of this book is to describe the swarm behavior of
animal societies and then confront it with the counterparts in
physics and informatics. It is meant to address a general reader-
ship and it will therefore use very little and only very simple
math em ati cs; also the physics and biology involved will be on a
level accessible to non-specialists. We humans experience a deep
sense of wonder when we see a whirling swarm of birds or a
glistening school of fish, and a feeling of great amazement at the
achievements of ant or bee states. The book wants to show that
such feelings become still enhanced when we learn how the striking
performances come about, when we see that in fact they follow
general patterns which nature uses in the inanimate world as well.
It is a pleasure to thank Irene Giardina for helpful comments
on the STARFLAG project, to Johannes Fritz for providing pho-
tos of the Waldrapp project and to Susette von Reder for help in
preparing the manuscript.
Helmut Satz
Bielefeld, March 2019
Contents
1. Introduction 1
2. The Eighth Plague 8
3. The Onset of Connectivity 15
4. The Birds of Rome 19
5. Spins and Magnets 27
6. The Rules of the Flock 34
7. Complexity and Criticality 42
8. Fiery Clouds in the Jungle 51
9. The Audible Silence 56
10. Coupled Oscillators 60
11. Laser Beams 65
12. The Way to Go 71
13. How to Fly 79
14. Avian Aerodynamics 89
15. The Ant State 95
16. Kin Selection: My Sister’s Keeper 102
17. Of Bees and Flowers 110
18. Communication and Language 115
19. Epilogue 122
Bibliography 127
Person Index 129
Subject Index 130

1
Introduction
The locusts have no king, yet all of them go forth in ranks.
The Bible, Proverbs 30:27
Moses led the people of Israel from Egypt to the Promised
Land. Caesar’s legions conquered Europe. Genghis Khan’s hordes
threatened the Occident. Napoleon’s army reached Moscow.
The history of mankind always records that many were led by a
few who ruled and decided. This has also had a formative effect
on our view of the collective behavior in nature. When many
“unimportant” individual objects combine to form a unified
larger body, we are always ready to look for a king, a leader, a
central initiator. But much of nature does not operate that way:
locusts, bees, ants, fish, starlings, antelopes and many other ani-
mals form functioning societies, swarms, schools, flocks, herds and
more, and yet these societies have no king, no ruler.
The whole is more than the sum of its parts—that is well known
at least since Aristotle. And that great builders can combine many
small bricks to construct magnificent cathedrals has also been
shown often enough. But that many small identical entities can
come together completely on their own, without any initiator,
without any plan, to create a new form, endowed with its own,
special properties, that is a rather novel discovery in natural sci-
ence. The key words are emergence and self-organization. Locusts, up
to a certain point solitary individuals, suddenly come together to
form immense swarms that darken the sky and devour all that is
edible. Thousands of fireflies in the Asian jungle send out absolutely
synchronized light signals, all flash at the same instant, without
The Rules of the Flock: Self-Organization and Swarm Structures in Animal Socities. Helmut Satz,
Oxford University Press (2020). © Helmut Satz. DOI: 10.1093/oso/9780198853398.001.0001