The Dusky Dolphin: Master Acrobat Off Different Shores

458 Pages·2009·6.92 MB·English

by  Bernd Wursig

The Dusky Dolphin
Master Acrobat off Different Shores
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The Dusky Dolphin

Master Acrobat off Different Shores
Edited by Bernd W ü rsig and Melany W ü rsig

AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD
PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO
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First edition 2010
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Dedication
This book is dedicated to Charlie Walcott, the finest of scientists, naturalists,
mentors, and humanists. We thank you for making our journey possible, and
for always — in direct fashion or in spirit — guiding us along the way. We owe
you more than two life-times of gratitude.
Professor Charles Walcott, Punta Los Conos, Golfo San Jos é , Argentina, 24 December 1973
Bernd and Melany W ü rsig,
Muritai Maui,
Kaikoura, New Zealand,
January 2009
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Contents
Preface i x
About the Editors x v
1. The Dusky Dolphins ’ Place in the Delphinid
Family Tree 1
April D. Harlin-Cognato
2. Dusky Dolphin Life History and Demography 2 1
Frank Cipriano and Marc Webber
3. Dusky Dolphin Trophic Ecology: Their Role in
the Food Web 4 9
Silvana L. Dans, Enrique A. Crespo, Mariano
Koen-Alonso, Tim M. Markowitz, B á rbara Ber ó n
Vera, and Adrian D. Dahood
4. Acoustics of Dusky Dolphins 7 5
Whitlow W.L. Au, Marc O. Lammers, and Suzanne Yin
5. Dusky Dolphins Foraging at Night 9 9
Adrian D. Dahood and Kelly J. Benoit-Bird
6. Dusky Dolphins Foraging in Daylight 1 15
Robin L. Vaughn, Mariana Degrati, and Cynthia J. McFadden
7. Predator Threats and Dusky Dolphin Survival Strategies 1 33
Mridula Srinivasan and Tim M. Markowitz
8. Mating Habits of New Zealand Dusky Dolphins 1 51
Tim M. Markowitz, Wendy J. Markowitz, and Lindsay M. Morton
9. Dusky Dolphin Calf Rearing 1 77
Jody Weir, Sierra Deutsch, and Heidi C. Pearson
vii
viii Contents
10. Sexual Segregation and Genetic Relatedness in
New Zealand 1 95
Deborah E. Shelton, April D. Harlin-Cognato, Rodney L. Honeycutt,
and Tim M. Markowitz
11. Human Interactions with Dusky Dolphins: Harvest,
Fisheries, Habitat Alteration, and Tourism 2 11
Tim M. Markowitz, Silvana L. Dans, Enrique A. Crespo, David J.
Lundquist, and Nicholas M.T. Duprey
12. Human Interactions with Dusky Dolphins: A
Management Perspective 245
Simon Childerhouse and Andrew Baxter
13. Dolphin Swimming and Watching: One Tourism
Operator’s Perspective 2 77
Dennis Buurman
14. Neglected But Not Forgotten—Southern Africa’s
Dusky Dolphins 2 91
Peter B. Best and Michael A. Me ÿ er
15. Patterns of Sympatry in Lagenorhynchus and
Cephalorhynchus : Dolphins in Different Habitats 3 13
Sonja Heinrich, Simon Elwen, and Stefan Br ä ger
16. A Large-brained Social Animal 3 33
Heidi C. Pearson and Deborah E. Shelton
17. Social Creatures in a Changing Sea: Concluding
Remarks 3 55
Bernd W ü rsig
References 3 59
Glossary 415
Index 4 27
Preface
Dusky dolphins (L agenorhynchus obscurus ) are indeed master acrobats, as the
book title states, for they leap in a spectacular variety of ways. There are simple
head-first re-entry leaps that make hardly a splash; side, belly, or backslaps that
are structured to make noise; long distance in-air salmon leaps designed for the
dolphin to travel more rapidly than through the dense medium of water; and
acrobatic leaps, spins, and somersaults that seem to be created for the pure joy
of creation. We call the latter acrobatic leaps “ social, ” and believe that these
indicate high levels of alertness and a “ party-like ” atmosphere that may very
well be important in social mammals for reinforcing existing social bonds and
forging new ones. Curiously, the structure of this book is such that we do not
detail these different leap types in great detail, although leaps are mentioned in
several contexts of behavior throughout. The interested reader may wish to visit
W ü rsig and Whitehead (2009) for a more detailed discussion of aerial behavior.
Acrobatic leaping dusky dolphins leap in sequences, with from 1 or 2
leaps to as many as 36 such leaps during one bout. Whenever a dusky dolphin
starts out with a particular type of acrobatic leap, say a forwards somersault
with a half-body twist to the right, it will keep that same leap during the leap
bout, with no change in repertoire. The 36th leap will be the same as the first,
although one can tell that the dolphin is tiring by “ the end,” just before it quits
leaping and slowly travels at the surface while breathing rapidly. This appears
to be much like the athletic human who starts a sequence of “ chin-ups ” at the
local gymnasium with vigor, but the final attempts to lift the chin above the
exercise bar are arduous indeed, and the human then needs to take a rest. So
it is for the dolphin; it rests, and several minutes later may begin a new leap
sequence, which is hardly ever the same leap type as exhibited before. This
time it may enter the air with a rapid forwards leap followed by a right-sided
body slap onto the water, with final tail slap as it descends, and so on.
We have no (real) idea of what is going on when dusky dolphins engage
in acrobatic “ social ” leaps, but these occur only at levels of high group alert-
ness, and seem to signal (and perhaps incite) “ excitement ” in group members
as a whole. We (W ü rsig and W ü rsig 1980) long-ago attempted to describe leap
types relative to progressions in cooperative “ bait-ball herding ” foraging stages
in Argentina: noiseless head-first re-entry leaps at the initial stages of foraging
are designed for dolphins to come from depth, overshoot the surface, breathe,
and descend to depth again; noisy side-slaps help to frighten and thereby
tighten fish schools once they are at the surface, and possibly also signal other
ix