Ecological StudiesAnalysis and Synthesis

Edited by

w.o. Billings, Durham (USA) F. Golley, Athens (USA)

O.L. Lange, Wiirzburg (FRG) 1.S. Olson, Oak Ridge (USA)

H. Remmert, Marburg (FRG)

Volume'irl

Photo: I.e. Gleize.

Patrick Duncan

Horses and GrassesThe Nutritional Ecology

of Equids and TheirImpact on the Camargue

With 114 lllustrations

Springer-VerlagNew York Berlin Heidelberg London Paris

Tokyo Hong Kong Barcelona Budapest

Patrick DuncanDirector de RecherchesCentre National de la

Recherche ScientifiqueCentre d'Etudes Biologiques de ChizeVilliers-en-Bois, France

1'hi!; slUdy was carried out al the Station Biologiques de la Tour du Valat.

Poetry excerpts on pp 21, 7S, 98. and 129 are from Roy Campbell: Horses on the Camargue. FranciscoCampbell Custodio and Ad. Donker (Ply) Ltd. Originally published in 1930 by Faber and Faber,Loodo,.

Cover phOlo: C. Feh.

Ubrary of Congress Cataioging-in-Publication DataDuncan, Patrick

Horses and grasses : the nutritional e<:ology of equids and their impact on theCamargue f by Patrick Duncan.

p. em. - (Ecological studies ; v. 87)Includes bibliographical references and index.ISBN-I3: 978-1-4612-7661-6I. Camargue horse-Food. 2. Camargue horse-Ecology. 3. Wild

horses-France-Camargue-Food. 4. Wild horses-France-Camargue­-Ecology. 5. Grassland ocology-France-Camargue. 6. Camarguehorse. 7. Grazing-Environmental aspeclS-France-Camargue.I. TItle. II. Series.SF293.C28D86 1991599. 72'5-dc20 91-4190

CIP

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© 1992 Springer-Verlag New York Inc.Sol\cover reprint of the hardcover 1st edition 1992All righlS reserved. This work may not be translated or copied in whole or in part without the wrinenpennission of the publisher (Springer-Verlag New York. Inc.• I7S Fifth Avenue, New York, NY 10010,USA) except for brief excerplS in connection with reviews or scholarly analysis. Use in connectionwith any form of information slO~ and retrieval, electronic adaptation, computer softwlue, or bysimilar or dissimilar methodology OON lcrwwn or hereafter developed is forbidden.The use of general descriptive names, trade names, trademarks. etc., in this publication, even if theformer are not especially identified, is not 10 be taken as a sign that such names, as understood bythe Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone.

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ISBN-13: 978-1-4612·7661-6DOl: 10.10071978-1-4612-2770-0

e-ISBN-13: 978-1-4612-2770-0

For Alison Duncanwho cares for horses, grasses, and the Camargue

Preface

Grasslands constitute one of the planet's major biomes (Chapter 1, Fig. 1)and have done so for 30 million years (Webb 1977). The plants of grasslandshave coevolved with grazing animals during this period, and this interactionhas shaped the growth-forms, chemical composition, and patterns of repro­duction of the plants (Crawley 1983). In the Pleistocene and Recent periods,the communities of grazing ungulates have been dominated by ruminantssuch as the Bovidae (antelopes, cattle, bisons," etc.), both in wild and do­mestic grazing systems.

The ruminants are a highly successful artiodactyl group which evolvedrecently; before the Pliocene, the commonest ungulates of the grasslands, atleast in some continents, belonged to the order Perissodactyla, rhinocerotidsand, particularly, equids (Simpson 1951, Cifelli 1981). The equids remainednumerically abundant, if species-poor, up to the end of the Pleistocene,especially in the temperate grasslands of North America.

Today there are seven species of equids, all belonging to one genus(Equus; see Chapter 1, Thble 2), compared with 49 genera of Bovidae (Walk­er 1968). The only large populations of wild equids are the Plains zebras ofEast Africa, and kiangs of Mongolia and north-western China. Five ofthe seven species are vulnerable or threatened with extinction, and one of

aLatin names are in Appendix 1.

vii

viii Preface

these, Przewalski's horse, which is closely related to the ancestor of thedomestic horse, is extinct in the wild.

The situation of domestic horses is very different. In spite of the inven­tion of the internal combustion engine, there are still millions of them. Theyare used for transport and traction in the less-developed parts of the world,and for leisure activities in developed countries. In every continent, domes­tic horses have escaped and established feral populations. Where low humandensities have meant that these feral populations have been left uncontrolledfor some time, as in North America and Australia, they have become soabundant as to be perceived as pests by some people.

Equids therefore pose two contrasting management problems: how toconserve and increase the sizes of the populations of threatened wild species,and how to reduce the feral populations efficiently and humanely so thatthey are in balance with the, often artificial, ecosystems in which they live.To succeed, management must be based on a thorough understanding of theequids, their feeding and social behavior, and on the ways they interact withthe plant communities they live in and from.

The ecology and behavior of ruminants and their interactions with plantcommunities have been thoroughly studied for economic reasons. Equidsare much less well known. In the Camargue, France, a herd of horses wasexperimentally released into a nature reserve and allowed to increase withouthuman intervention. This book brings together the results of this long-termstudy. It is written as a contribution to our understanding of the interactionsbetween grasslands and one of the herbivores which shaped and shapesthem. I hope that it will prove useful not only to specialists in this field, butalso to the community of people working to save the wild species and tomanage the feral populations of equids.

Acknowledgments

Working on the horses in the Camargue was a formative and exciting experi­ence for a young zoologist, especially when based at the Station Biologiquede la Tour du Valat with a team of people who possess a remarkable under­standing of the ecology of the delta. They and many people outside thestation, by sharing their knowledge and skills and giving of their time, havemade this project possible. Space does not allow each to be mentionedindividually here, but their contributions are no less appreciated.

The people of the Camargue, who have conserved the horses and themarshes, taught me about their animals when, thanks initially to Jean­Claude "Coco" Gleize, I rode with them to fetch their herds of cattle fromthe marshes. They showed me what it means to live integrated managementin a European wetland, the difficult double act of conservation and develop­ment. Jacques Mailhan, in particular, has always been interested in ourapproach to the ecological role of the horses and cattle and helped in manyways.

Bettina von Goldschmidt and Professor B. Tschanz had the idea of thisstudy; Dr. Luc Hoffmann put it into effect with the technical assistance ofRene Lambert and broadened the original concept to cover the ecologicalimpact of horses on the wetlands. The study was funded by the FondationTour du Valat, and administered successively by Michel Pont and Jean PaulThris. Pierre Jouventin and the Centre National de la Recherche Scientifiqueprovided support in the final stages. The patience and understanding of all

ix

x Acknowledgments

these people for a research project involving many different people, often onshort stays, was essential.

Professor Fran~ois Bourliere, Tim Clutton-Brock, and John Krebshelped the study over many years and in many ways; I am very grateful tothem. I benefited, too, from discussions with all the coworkers mentioned inthe book, as well as with Steve Albon, Joel Berger, Monique Borgerhoff­Mulder, Sylviane Boulot, Tim Caro, Michel Doreau, Joshua Ginsberg,Morris Gosling, Sandy Harcourt, Paul Harvey, Michel-Antoine Leblanc,Thierry Lecomte, William Martin-Rosset, Patricia Moehlman, Ian Nich­olson, Marion Petrie, Jacques Poissonnet, Rory Putman, Dan Rubenstein,Y. Ruckebusch, Mike Scott, Kelly Stewart, and P.L. Toutain. lain Gordonprovided stimulating discussion and constructive criticism at a crucial stage.

I am particularly grateful to Coco Gleize, who monitored and managedthe herd throughout the period. His knowledge of horses and of the Ca­margue, his efficiency and dedication to his work allowed many difficulttasks to be carried out with ease. The field data were collected with theunstinting help of many colleagues, as well as Coco Gleize: Melanie Barclay,Peter Elliott, Sandrine Ferrazzini, Laurence Mallinson, Eleanor Mayes, Pa­mela Moncur, and Jamie Skinner, whose learning curve covered even Pro­ven~al, provided valuable assistance over relatively long periods. For permis­sion to use unpublished data, I am grateful to Pamela Cowtan, ChrisGakahu, Pierre Heurteaux, Rene Lambert, Martin Levertin, Pamela Mon­cur, and Steve Skelton; and especially to Tom Foose.

The work on horseflies benefited greatly from discussions with and inputfrom Dick Hughes and Jeff Waage; that on social behavior from Anne­Marie Monard, and from Sue Wells and Claudia Feh, who also made majorcontributions to the collection of data on the use of time and habitats, inaddition to their own work. Marc du Lac kindly lent us the Marechalbalance for years. I am grateful to him and to the many people from Tour duValat and from further afield who made it possible to round up a herd ofhorses gone feral.

Data analysis was initially carried out at the Centre de Recherches enInformatique et Gestion (Universite de Montpellier), and benefited from thehelp of Y. Escouffier and his colleagues. Thereafter, Vincent Boy providedvaluable, efficient, and reliable help, as did Steve Albon, with the analysisof growth of the animals and the plants. Kees de Groot provided unbelieva­bly patient tutoring on WordPerfect.

Tim Clutton-Brock was kind enough to invite me to spend two sabbati­cals at the Large Animal Research Group at Cambridge. These stays provid­ed a wealth of ideas in an ideal atmosphere for writing-up. I also am gratefulto the President of Wolfson College for a Visiting Fellowship, to ProfessorGabriel Horn (Department of Zoology), and to Dr. Paul Howell.

If the fieldwork was usually fun and the analysis interesting, writing thisbook was a toil which would never have been finished without the help of

Acknowledgments xi

Melanie Barclay, Marie-Antoinette Diaz, Chantal Heurteaux, Olga Ni­konova, and Josiane Xuereb. Jacqueline Crivelli and Georges Vlassis were agreat help with some elusive references, and Line Jouventin with the figures.Her professional eye saved some from a fate worse than death-being incom­prehensible. Christiane Mauget gave great help with the index.

The text was improved by the comments of Vincent Boy, ProfessorBourliere, Tim Clutton-Brock, Alain Crivelli, Rudi Drent, Claudia Feh,Patrick Grillas, lain Gordon, Dirk Kreulen, Anne-Marie Monard, Bettinavon Goldschmidt, and two anonymous referees; the remaining faults aremine.

I am grateful to Claudia Feh, Coco Gleize, Jamie Skinner and M. Jean­Pierre Violet for permission to use their photographs.

The permission of Francisco Campbell to reprint excerpts of RoyCampbell's poetry is deeply appreciated.

Working with the production team at Springer-Verlag was fun: thanks forthe considerable help you gave.

My greatest debt is to Alison Duncan who, in addition to computerizingand analyzing some of the data, got the figures into shape, mastered wordprocessing and computerized bibliography programs for the text, and editedthe manuscript. She was very observant and patient, though less so than Job,which is perhaps a good thing.

Preface

Contents

Vll

3

21

53

75

98

Section A. Introduction and Background

1. Grasslands and Grazing Ungulates

2. The Horses and the Camargue

Section B. Harvesting Nutrients

3. Extracting Nutrients from Plant TIssues

4. Diets-Their Botanical Composition and Nutritional \1lIue

5. Foraging Behavior

Section C. Nutrient Use

6. Social Organization, Mating System, and Feeding Behavior 129

7. Reproduction and Growth 152

Section D. Equids and Their Habitats

8. The Impact of Grazing on the Plants and Animals of the Camargue 173

9. Equids in Grazing Systems 195

xiv Contents

Appendixes

Appendix 1. Latin Names and Common Names ofExtant Mammaland Bird Species to which Reference Is Made in the Text 207

Appendix 2. The History and Management ofCamargue Horses 210

Appendix 3. Climate 219

Appendix 4. Vegetation 222

Appendix S. Parasites 225

Appendix 6. Methods Used for the Study of the Horses' Diets, FoodIntake, and Digestion 237

Appendix 7. Methods Used for the Study of Social Behavior 247

Appendix 8. Parentage of the Horses in the Thor Do Valat Herd1974-1979 250

Appendix 9. The Methods Used for the Study of Reproduction andGrowth 252

Appendix 10. Methods Used for the Study of the Horses; Impact onthe Vegetation 254

References 259

Index 281