Wildlife-Habitat Relationships: Concepts and Applications

By Michael L. Morrison, Bruce Marcot and William Mannan

Wildlife-Habitat Relationships goes beyond introductory wildlife biology texts to provide wildlife professionals and students with an understanding of the importance of habitat relationships in studying and managing wildlife. The book offers a unique synthesis and critical evaluation of data, methods, and studies, along with specific guidance on how to conduct rigorous studies.

Now in its third edition, Wildlife-Habitat Relationships combines basic field zoology and natural history, evolutionary biology, ecological theory, and quantitative tools in explaining ecological processes and their influence on wildlife and habitats. Also included is a glossary of terms that every wildlife professional should know.

• Language: English
• Publisher: Island Press
• Release date: Sep 26, 2012
• ISBN: 9781597266338

Michael L. Morrison

Michael L. Morrison, born in 1969, is from Scott, Louisiana, but now lives in Houston, Texas. He read his first novel, Carrie, by Stephen King, at the age of ten, and fell in love with books. He began writing poetry in high school, and moved on to short stories while stationed at National Naval Medical Hospital in Bethesda, Maryland. Over the years, he has shared his poems and stories with family and friends. Just recently, with the support of his family and friends, he published his first novella, The Bird Cages, as an ebook, and he is looking forward to publishing more of his writing in the near future.

Book preview

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ABOUT ISLAND PRESS

Island Press is the only nonprofit organization in the United States whose principal purpose is the publication of books on environmental issues and natural resource management. We provide solutions-oriented information to professionals, public officials, business and community leaders, and concerned citizens who are shaping responses to environmental problems.

In 2006, Island Press celebrates its twenty-second anniversary as the leading provider of timely and practical books that take a multidisciplinary approach to critical environmental concerns. Our growing list of titles reflects our commitment to bringing the best of an expanding body of literature to the environmental community throughout North America and the world.

Support for Island Press is provided by the Agua Fund, The Geraldine R. Dodge Foundation, The Doris Duke Charitable Foundation, The William and Flora Hewlett Foundation, Kendeda Sustainability Fund of the Tides Foundation, The Forrest C. Lattner Foundation, The Henry Luce Foundation, The John D. and Catherine T. MacArthur Foundation, The Marisla Foundation, The Andrew W. Mellon Foundation, The Gordon and Betty Moore Foundation, The Curtis and Edith Munson Foundation, The Oak Foundation, The Overbrook Foundation, The David and Lucile Packard Foundation, The Winslow Foundation, and other generous donors.

The opinions expressed in this book are those of the author(s) and do not necessarily reflect the views of these foundations.

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Copyright © 2006 Michael L. Morrison, Bruce G. Marcot, R. William Mannan

All rights reserved under International and Pan-American Copyright Conventions. No part of this book may be reproduced in any form or by any means without permission in writing from the publisher: Island Press, 1718 Connecticut Ave., NW, Suite 300, Washington, D.C. 20009.

ISLAND PRESS is a trademark of The Center for Resource Economics.

Library of Congress Cataloging-in-Publication data.

Morrison, Michael L.

Wildlife-habitat relationships : concepts and applications / by Michael L. Morrison, Bruce G. Marcot,

and R. William Mannan.—3rd ed.

p. cm.

Includes bibliographical references.

9781597266338

1. Habitat (Ecology) 2. Animal ecology. I. Marcot, Bruce G. II. Mannan, R. William. III. Title.

QH541.M585 2006

591.7—dc22

2006009619

British Cataloguing-in-Publication data available.

Printed on recycled, acid-free paper e9781597266338_i0002.jpg

Design by (to come)

Manufactured in the United States of America

10 9 8 7 6 5 4 3 2 1

Table of Contents

ABOUT ISLAND PRESS

Title Page

Copyright Page

Table of Figures

List of Tables

Preface

About the Third Edition

Acknowledgments

PART I - Concepts of Wildlife–Habitat Relationships

1 - The Study of Habitat: A Historical and Philosophical Perspective

2 - The Evolutionary Perspective

3 - The Habitat, Niche, and Population Perspectives

PART II - The Measurement of Wildlife–Habitat Relationships

4 - The Experimental Approach in Wildlife Science

5 - Measuring Wildlife Habitat: What to Measure and How to Measure It

6 - Measuring Wildlife Habitat: When to Measure and How to Analyze

7 - Measuring Behavior

8 - Habitats through Space and Time: Heterogeneity and Disturbance

9 - Wildlife in Landscapes: Populations and Patches

10 - Modeling Wild life–Habitat Relationships

PART III - The Management of Wildlife Habitat

11 - Managing Habitat for Animals in an Evolutionary and Ecosystem Context

12 - The Future:New Initiatives and Advancing Education

Afterword

Glossary

About the Authors

Author Index

Subject Index

Island Press Board of Directors

Table of Figures

Figure 2.1

Figure 2.2

Figure 2.3

Figure 2.4

Figure 2.5

Figure 2.6

Figure 2.7

Figure 2.8

Figure 2.9

Figure 3.1A

Figure 3.1B

Figure 3.1

Figure 3.2

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Figure 3.22

Figure 3.23

Figure 4.1

Figure 5.1

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Figure 12.1

List of Tables

Table 1.1

Table 2.1

Table 2.2

Table 3.1

Table 3.2

Table 3.3

Table 3.4

Table 3.5

Table 3.6

Table 3.7

Table 3.8

Table 5.1

Table 5.2

Table 5.3

Table 5.4

Table 6.1

Table 6.2

Table 6.3

Table 6.4

Table 6.5

Table 6.6

Table 6.7

Table 7.1

Table 7.2

Table 7.3

Table 8.1

Table 8.2

Table 8.3

Table 8.4

Table 10.1

Table 11.1

Table 11.2

Table 11.3

Table 12.1

Preface

When we published our first edition of this book in 1992, the world population stood at a bit over 5.44 billion people and was increasing at an annual growth rate of 1.48%, adding 81,404,054 people to the planet annually, according to the United States Census Bureau. When we published our second edition in 1998, there were over 5.92 billion people, and although the annual growth rate had dropped slightly to 1.31%, it was still adding 78,308,546 people annually. As we completed this, our third edition, in early 2005, the planet was bearing over 6.47 billion of us, with an annual rate of increase of 1.14%, or 74,629,207 people. Concomitantly, just in this 14-year wink of an ecological eye, we have seen striking evidence of continued loss or degradation of the scarcest natural environments, including tropical coral reefs, mangrove swamps, ancient forests, and native grasslands, while urban, suburban, agricultural, and degraded lands, and lands dedicated solely to intensive resource production, continue to spread.

We wish for optimism but cannot ignore the crises in wildlife conservation that seem to confront us everywhere these days. Changes in regional and global climates continue to challenge our understanding but cry for action. There are crises of academia as essential expertise in basic taxonomy and systematics has itself become a moribund species; how crucial these skills are, for if we cannot name and catalog organisms, we cannot hope to document and quantify trends and mobilize action to stem extinctions, local and global. Other writers have despaired of how few conservation biologists these days spend much time in the field, and of how natural history as an empirical science and lifestyle seems to be increasingly forgotten. Perhaps the greatest crisis is what Robert Michael Pyle (1992) wrote of as the extinction of experience, a growing personal alienation from nature and loss of intimacy with the very environment that sustains us, for, as he wrote, What is the extinction of the condor to a child who has never known a wren?

We speak of the legacies of ancient forests—large old trees, snags, down logs, and organic material to enrich tomorrow’s soils. As well, we need to consider the legacies of our own knowledge and expertise to help others understand and provide wildlife and habitats for tomorrow. Reliable knowledge comes with rigor and scientific study. However, knowledge without action is as fruitless as never evolving from the primordial soup of ignorance in the first place. Research, as the Oregon political columnist Russell Sadler (1991) once said, is a race between ignorance and irreversible consequences.

While scientists struggle to understand the relations between human-caused environmental changes, biocomplexity, ecosystem resilience, species viability, and resource sustainability, we cannot lose sight of the astounding rapidity with which all these changes are occurring, nor the accelerated need to educate ourselves and others on the effects of our daily living habits. More than ever, we must all redefine ourselves as perennial students of the planet, whether we are senior managers, researchers, or academic students in the traditional sense. There is far more for us to learn than we ever can, as time for stabilizing or restoring wildlife and their habitats has already run out in portions of our wonderful and crowded world. This is what has led us to dedicate this third edition to wildlife students everywhere, the corollary being that learning and mutual education must never cease.

Let us quickly move beyond alarmism, for that shuts off the lines of listening by those publics, politicians, and purveyors we need to reach. Instead, as a wildlife profession, we can assert a positive vision of wildlife conservation that builds on legacies of knowledge and ecosystems alike. As our numbers grow, we can point to incredibly bold new moves in wildlife conservation that beg respect and emulation. India, which has surpassed 1 billion people since our second edition was published, in an attempt to save the last of its parks and wildlife communities has essentially outlawed clear-felling of forests and most sport hunting, and has given nontimber forest resources great economic and social focus. China has instituted policies of family size constraints and a massive reforestation program in many of their degraded and de-sertified lands. The Nature Conservancy has successfully run innovative programs of swapping portions of national debt for conserving critical natural areas in some developing countries. Major ecosystem restoration programs have been instituted, such as those in the Everglades of Florida. Top predators—carnivores—have been successfully reintroduced to Yellowstone National Park and elsewhere. There now are more national parks and sanctuaries, and more recovery plans for threatened and endangered species in place, than ever throughout the world.

Such positive steps toward wildlife and habitat conservation include some extreme measures taken literally in the face of collapsing ecosystems and vanishing species, as well as more evolutionary measures designed to better integrate economies with conservation, such as through burgeoning ecotourism and sustainable ecode-velopment programs. Developed countries also can learn much from conservation measures designed to include participation and ownership by local and native peoples, who often are most in need of reliable and sustainable resources and economic growth and stability.

In this way, wildlife conservation should not be viewed as a pastime of the rich but as a plan for the future for us all. A new vision for a near future in which we truly provide for sustainable resources, provide for ecosystem integrity, and foster the health of our biosphere, likely will demand the courage to seek and accept changes in our daily resource use habits and even to shift the very centers of what we value and how we value what we use. We can employ such positive visions, and successes like the ones cited above, as hallmarks and templates to help further such a future. It is not wildlife versus humanity, jobs versus owls, today’s food versus tomorrow’s inviolate protected area that will foster participation for a sustainable future. Nor will a sustainable future be reached along a gap between the academically educated and the lay public. Only by opening our minds and hearts and all becoming students can we move there together.

The purpose of our first edition was to advance from the point where the many fine, but introductory, texts in wildlife biology left off. Through the second, and now this third, edition, this purpose has not changed. We have further developed this new edition to incorporate the many new ideas that have come our way from several sources. First, we took to heart the independent reviews that appeared in scientific journals. Second, our friends and colleagues showed us their hidden talents as book critics; we also attended to these comments. Finally, we each have tapped into new experiences and studies to present the most current findings, concepts, and visions for future development in research and management.

This book is intended for advanced undergraduates, graduate students, and practicing professionals with a background in general biology, zoology, wildlife biology, conservation biology, and related fields. An understanding of statistics through analysis of variance and regression is helpful, but not essential. Land managers will especially benefit from this book because of its emphasis on the identification of sound research and the interpretation and application of results.

Our approach combines basic field zoology and natural history, evolutionary biology, ecological theory, and quantitative tools. We think that a synthesis of these topics is necessary for a good understanding of ecological processes, and hence good wildlife management. We attempt to draw on the best and recent examples of the topics we discuss, regardless of the species involved or its geographic location. We do concentrate on terrestrial vertebrates from temperate latitudes, with a bias toward North America, because this is where much literature has been developed and where our own experience has occurred. However, because it is the concepts that are important, the specific examples are really of secondary importance. Hence our writing can be used by anyone from any location. We did try, however, to bring in examples from amphibians, reptiles, birds, and mammals (both large and small), and from different ecosystems and locations, to help individuals from different backgrounds better understand the application of concepts to their particular interests.

We emphasize the need for critical evaluation of methodologies and their applications in wildlife research. Management decisions all too often are based on data of unknown reliability—that is, from research conducted using biased methods, low sample sizes, and inappropriate analyses. We understand also that, all too often, managers are faced with making decisions using unreliable or incomplete data. The general dearth of monitoring, validation, and adaptive management research forces a vicious cycle. This does not need to—and should not—persist.

To aid both the student and the professional, we have tried to explain fundamental concepts of ecological theory and assessment so that the use of more advanced technical tools is more acceptable, more often sought, and more appropriately applied. Ultimately, the success of conservation efforts depends on gathering, analyzing, and interpreting reliable information on species composition, communities, and habitat. We hope that this book encourages such rigor in concept and practice.

Literature Cited

Pyle, R. M. 1992. Intimate relations and the extinction of experience. In Left Bank #2: Extinction, 61–69. Hillsboro, OR: Blue Heron Publishing.

Sadler, R. 1991. Paper presented at the New Perspectives Conference, USDA Forest Service, Roanoke VA, December 3, 1991.

About the Third Edition

The second edition forms the core of this new work. We have revised much of the text, introduced much new material in each chapter to supplement that previously offered, and updated reference citations throughout.

In Part 1, Chapters 1 through 3 cover central concepts of wildlife–habitat relationships and lay the foundation on which the rest of the book is constructed. Chapter 1 discusses the historical background and philosophical attitudes that have shaped the wildlife profession and influenced how research should be approached. Chapter 2 reviews the evolutionary background against which the current distribution, abundance, and habits of animals developed. In this edition, we defer discussion of keystone species to a broader and updated discussion of key ecological functions of species in Chapter 11. Chapter 3 discusses habitat relationships from the perspective of vegetation ecology and population biology. In Chapter 3, we have updated and substantially expanded our discussion of the niche as it appeared in the second edition. Specifically, we have developed how the study of multiple limiting factors likely holds the key to advancing our study of habitat relationships. We still address population responses, and have expanded our discussion of population viability, genetics, metapopulation dynamics, and related concepts.

In Part 2, Chapters 4 through 10 form the heart of the book and cover measurement and modeling of wildlife–habitat relationships. Chapter 4 discusses fundamental approaches to study design and experimental methodologies, reviewing the philosophy of various ways of gaining reliable knowledge, and the challenges to conducting scientific investigations and having the result be accepted in society. We have added new examples, and new subjects of concern about science are now addressed including information theoretic versus traditional hypothesis testing, and relativism. Chapters 5 and 6 review the many methods that have been used to develop wildlife-habitat relationships, including field methods, data analysis, sampling biases, and data interpretation. We re-organized Chapter 5 to more explicitly encompass analyses across spatial scales, and have updated our discussions of methodologies to include the increasing use of new technologies. Chapter 6 also incorporates discussion of multivariate statistics, which we have updated with additional comments on methods and misuses of the techniques. Although we do not delve heavily into methods of multivariate analyses, we think that we are more effective by emphasizing the concept of multivariate analyses, proper sampling methods, and interpretation of results. We have also added new information on model selection procedures, such as AIC. Chapter 7 covers behavioral sampling and analysis in wildlife research, and has been expanded to include more information on the fundamental causes of an individual’s behavior. Chapters 8 and 9 review characterization of patterns of habitat within landscapes, and population responses, respectively, including habitat fragmentation, study of metapopulations, and landscape ecology, topics that continue to be emphasized by researchers and managers alike. Chapter 8 presents the rationale for a landscape-perspective of habitat relationships, definition and classification of landscapes, basics of landscape ecology, concepts of spatial and temporal scales in ecological study and their implications for managing habitat in landscapes, ways to depict and measure habitat heterogeneity including habitat fragmentation, and reviews disturbance ecology and management implications; all material—concepts, summary of studies, and citations—has been brought up to date since the previous edition. Chapter 9 focuses on population response to landscape conditions and patterns, and reviews how researchers and managers have viewed wildlife response to habitat edges, boundary effects, and succession and climate; provides an updated discussion of population viability, metapopulation dynamics, and effects of population isolation; updates discussions of biogeographic implications of habitat isolation and patterns, species–area relations; and discusses implication for conserving and monitoring wildlife in heterogeneous environments, including utility of habitat corridors. All of this material has been updated since the last edition. Chapter 10 reviews and updates the utility and development of wildlife–habitat relationships models, including discussion of how to select models, depict uncertainty, and implications of prediction errors and model validity for research hypothesis-testing and management decision making. Chapter 10 also updates discussions from the last edition on traditional types of models, and presents a new section on more recent, avant garde wildlife habitat modeling approaches that draw from fields of decision support, Bayesian statistics, and various knowledge-based approaches only recently being developed for wildlife habitat modeling. The chapter also updates a discussion on recent developments in various approaches to modeling land allocations for habitat conservation and on recent results of model validation.

In Part 3, Chapters 11 and 12 cover management of wildlife–habitat relationships. Chapter 11 introduces the topic of wildlife and habitat management in the context of ecosystem management. We discuss and illustrate wildlife management goals in an evolutionary and ecological context, and provide all-new material and examples on a broad environmental and functional approach, including an ecographic (mapping) approach to evaluating and managing for key environmental correlates, key ecological functions, and key cultural functions of wildlife. We newly discuss implications for conservation of ecosystem services, thinking beyond wildlife population viability in a community and ecosystem context, and practical approaches to managing for evolutionary potential of wildlife. We also provide an updated discussion of adaptive management and review both failures and successes in this area. Chapter 12 presents a framework for advancing our understanding of wildlife through modified approaches to habitat relationships, raises a call for greater emphasis on the synthetic field of restoration ecology, and makes a plea for improvements to our educational system. We present this material partly as a prescription, and partly as a null model on which we can debate the best means of advancing our profession. In this edition we have refined our recommendations on how wildlife and habitat might be studied if we are to improve our understanding of what determines distribution and abundance, and ultimately leads to the recovery and preservation of species.

New to this edition is a brief glossary of key terms that every wildlifer should know. The book concludes, as did the second edition, with an author index and a general subject index.

Developing this latest edition entailed our extensively reviewing a massive amount of recent literature and discussing concepts, findings, and approaches with many researchers and managers. In one sense, little has changed since the early 20th century; habitat is still the crux and essential foundation for wildlife conservation, although there continue to be rapid advances in approaches to conceptualizing, measuring, modeling, and managing habitat. We have tried to keep pace with such advances in this edition and have prioritized new and expanded discussions on topics with the most promise for successfully understanding and conserving wildlife and habitats.

Lastly, in this volume we have again demonstrated the robust, positive growth rate of new editions, despite our wonderful editor’s decree for density-dependent limits to growth. When pressed, our answer is simply, Knowledge should be boundless.

Acknowledgments

First, we thank Barbara Dean, Executive Editor, Island Press, for guiding this third edition through the publication process. And once again we thank Allen Fitchen, former director of the University of Wisconsin Press, for encouraging us to put our thoughts onto paper and shepherding this project through the first and second editions. Many individuals have reviewed chapters through the three editions of this book, including several additional referees for this volume—Roel Lopez, Tom O’Neil, John Marzluff, Paul Krausman, Shawn Smallwood, Luke George, Bob Steidl, and William Matter; we thank you all for your insights. We also thank Joyce VanDeWater for her diligent and excellent help in finalizing the figures for this edition, and Carly Johnson for formatting and editing our penultimate draft.

Numerous individuals helped shape our views of wildlife biology and science in general; we cannot list them all. We especially appreciate the dialogues shared with our graduate students over the years. In addition, discussions with many ecologists and managers, domestically and internationally, helped us identify recent scientific advances and critical management issues. We also thank the numerous authors whom we have cited in this book for their research efforts and insightful analyses.

We dedicated the first edition of our book to Drs. E. Charles Meslow and Jack Ward Thomas, who taught us that wildlife conservation truly succeeds when practiced with honor, rapport, and rigor. Our second edition was dedicated to the community of field biologists throughout the world who daily tend to the inheritance of succeeding generations. Both of these dedications bear repeating there, for they are both more valid than ever.

We dedicate this edition to wildlife students of the world, including those who learn in academia and those who continue to educate themselves throughout their careers. Though learning will come informed action and the courage and spirit to educate others, thus ensuring the future of wildlife everywhere.

PART I

Concepts of Wildlife–Habitat Relationships

1

The Study of Habitat: A Historical and Philosophical Perspective

It is a good morning exercise for a research scientist to discard a pet hypothesis every day before breakfast. It keeps him young.

KONRAD LORENZ

An animal’s habitat is, in the most general sense, the place where it lives. All animals, except humans, can live in an area only if basic resources such as food, water, and cover are present and if the animals have adapted in ways that allow them to cope with the climatic extremes and the competitors and predators they encounter. Humans can live in areas even if these requirements are not met, because we can modify environments to suit our needs or desires and because we potentially have access to resources such as food or building materials from all over the world. For these reasons, humans occupy nearly all terrestrial surfaces of the earth, but other species of animals are restricted to particular kinds of places.

The distribution of animal species among environments and the forces that cause these distributions have frequently been the subjects of human interest, but for different reasons at different times. The primary purpose of this introductory chapter is to review some of the reasons why people study the habitats of animals and to outline how these reasons have changed over time. We also introduce the major concepts that will be addressed in this book.

Curiosity about Natural History

Throughout recorded history, humans, motivated by their curiosity, have observed and written about the habits of animals. The writings of naturalists were, for centuries, the only recorded sources of information about animal–habitat relationships. Aristotle was among the first and best of the early naturalists. He observed animals and wrote about a wide variety of subjects, including breeding behavior, diets, migration, and hibernation. Aristotle (384–322 BC) also noted where animals lived and occasionally speculated about the reasons why:

A number of fish also are found in sea-estuaries; such as the saupe, the gilthead, the red mullet, and, in point of fact, the greater part of the gregarious fishes. . . . Fish penetrate into the Euxine [estuary] for two reasons, and firstly for food. For the feeding is more abundant and better in quality owing to the amount of fresh river-water that discharges into the sea. . . . Furthermore, fish penetrate into this sea for the purpose of breeding; for there are recesses there favorable for spawning, and the fresh and exceptionally sweet water has an invigorating effect on the spawn. (Aristotle 344 BC)

Interest in natural history waned after Aristotle’s death. Politics and world conquest were the focus of attention during the growth of the Roman Empire, and interest in religion and metaphysics suppressed creative observation of the natural world during the rise of Christendom (Beebe 1988). As a result, little new information was documented about animals and their habitats for nearly 1700 years after the death of Aristotle. Yet, as Klopfer and Ganzhorn (1985) noted, painters in the medieval and pre-Renaissance periods still showed an appreciation for the association of specific animals with particular features of the environment. Fanciful renderings aside, peacocks do not appear in drawings of moors nor moorhens in wheatfields (Klopfer and Ganzhorn 1985, 436). Similar appreciation is seen in artwork from India, China, Japan (e.g., Sumi paintings), and elsewhere during this period. Thus keen observers noticed relationships between animals and their habitats during the Dark Ages, but few of their observations were recorded.

The study of natural history was renewed in the seventeenth and eighteenth centuries. Most naturalists during this period, such as John Ray (1627–1705) and Carl Linnaeus (1707–1778), were interested primarily in naming and classifying organisms in the natural world (Eiseley 1961). Explorers made numerous expeditions into unexplored or unmapped lands during this period, often with the intent of locating new trade routes or identifying new resources. Naturalists usually accompanied these expeditions or traveled on their own, collecting and recording information about the plants and animals they observed. Many Europeans during this period also collected feathers, eggs, pelts, horns, and other parts of animals for collection cabinets. Some cabinets were serious scientific efforts, but most were not. Nevertheless, new facts about the existence and distribution of animals worldwide were gathered during this time, and the resulting advances in knowledge generated considerable curiosity about the natural world.

During the nineteenth century, naturalists continued to describe the distribution of newly discovered plants and animals, but they also began to formulate ideas about how the natural world functions. Charles Darwin (1809–1882) was among the most prominent of these naturalists. His observations of the distributions of similar species were one set of facts among many that he marshaled to support his theory of evolution by natural selection (Darwin 1859). The work of Darwin is highlighted here, not only because he recorded many new facts about animals, but also (and more importantly) because the theory of evolution by natural selection forms the framework and foundation of the field of ecology.

Curiosity about Ecological Relationships

In the early 1900s, curiosity about how animals interact with their environment provided the impetus for numerous investigations into what are now called ecological relationships. Interest in these relationships initially led to detailed descriptions of the distribution of animals along environmental gradients or among plant communities. Merriam (1890), for example, identified the changes that occur in plant and animal species on an elevational gradient, and Adams (1908) studied changes in bird species that accompany plant succession. Biologists living in this period postulated that climatic conditions and availability of food and sites to breed were the primary factors determining the distributions of animals they observed (see Grinnell 1917a).

Biologists in the early to mid-1900s, however, recognized that the distribution of some animals could not be explained solely on the basis of climate and essential resources. David Lack (1933) was apparently the first to propose that some animals (in this case, birds) recognize features of appropriate environments, and that these features are the triggers that induce animals to select a place to live. Areas without these features, according to Lack, generally will not be inhabited, even though they might contain all the necessary resources for survival. Lack’s ideas gave birth to the concept of habitat selection and stimulated considerable research on animal–habitat relationships during the next 60 years.

Svardson (1949) developed a general conceptual model of habitat selection, and Hilden (1965) later expressed similar ideas. Their models characterized habitat selection as a two-stage process in which organisms first use general features of the landscape to select broadly from among different environments, and then respond to subtler habitat characteristics to choose a specific place to live. Svardson (1949) also suggested that factors other than those associated with the structure of the environment influence selection. For example, whether an animal stays or leaves a particular place could be influenced by conspecifics (Butler 1980), interspecific competitors (Werner and Hall 1979), and predators (Werner et al. 1983), as well as by features of the environment that are directly or indirectly related to resources needed for survival and reproduction. Habitat selection, therefore, has come to be recognized as a complicated process involving several levels of discrimination and spatial scales and a number of potentially interacting factors. Study of these factors and the behaviors involved in habitat selection has resulted in a wealth of information about why we find animals where we do (see Stauffer [2002] for an overview of the recent history of habitat studies).

The distribution of animals is also intimately tied to the concept of niche. This concept has been defined in multiple ways over time (see e.g., Schoener 1989; Griesemer 1992; Pianka 1994 for historical overviews) and continues to be the subject of much discussion. Grinnell (1917b) formally introduced the term when he was attempting to identify the reasons for the distribution of a single species of bird. His assessments included spatial considerations (e.g., reasons for a close association with a vegetation type), dietary dimensions, and constraints placed by the need to avoid predators (Schoener 1989). Thus, in this view, the niche included both positional and functional roles in the community. Elton (1927) later described the niche as the status of an animal in the community and focused on trophic position and diet. Views of the niche articulated by Grinnell and Elton are often contrasted, but Schoener (1989) argued that they had much in common, including the idea that a niche denotes a place in the community, dietary considerations, and predator-avoiding traits. Hutchinson (1957) articulated the multivariate nature of the causes of animal distribution in his presentation of the n-dimensional niche. In this view, niche dimensions are represented by multiple environmental gradients. A given species (or population) can exist in only a subset of the conditions defined by all the gradients (its potential or fundamental niche) but may be further restricted in distribution (its realized niche) by predators and competitors. Odum (1959) viewed the niche as the position or status of an organism in an ecosystem resulting from its behavioral and morphological adaptations. His idea of the niche was dependent on both where an organism lives and what it does, but he separated, to some degree, habitat from niche with the analogy that an organism’s address is its habitat and its profession is its niche. More recent ideas about the niche (e.g., MacArthur and Levins 1967; Levins 1968; Schoener 1974) consider niche axes as resources (i.e., those important for an animal) and niche as the combination of several utilization distributions along those axes. The point of our brief review of the concept of the niche is to illustrate that, although the term can be viewed in a variety of ways, most concepts include elements that are traditionally considered part of habitat. Thus studies designed to describe or define an animal’s niche (of which there have been many) almost always elucidate animal–habitat relationships as well.

Hunting Animals for Food and Sport

The earliest humans relied, in part, on killing animals for survival, and they undoubtedly recognized and exploited the patterns of association between the animals they hunted and the kinds of places where these animals were most abundant. Use of fire by Native Americans altered the ecosystems in which they lived (Botkin 1990) and influenced (probably intentionally) the number of animals they hunted. Similarly, people who later made an economic living by trapping and hunting, or could afford the luxury of hunting for sport, knew where to find animals and probably speculated accurately about the habitat features that influenced the abundance of game species. Marco Polo reported, for example, that in the Mongol Empire in Asia, Kublai Khan (AD 1215–1294) increased the number of quail and partridge available to him for falconry by planting patches of food, distributing grain during the winter, and controlling cover (Leopold 1933). This advanced system of habitat management suggests a general understanding of the habitat requirements of target game species, but it is unlikely that the information was obtained through organized studies of habitat use. Also, the men who hunted and trapped for subsistence or sport rarely recorded their knowledge about habitats for posterity.

Not until people began to attempt to apply biology systematically to the management of game as a crop in the early 1900s did they realize that science had accumulated more knowledge of how to distinguish one species from another than of the habits, requirements, and inter-relationships of living population (Leopold 1933, 20). The absence of information about habitat requirements of most animals and the desire to increase game populations by manipulating the environment stimulated detailed investigations of the habitats and life histories of game species. H. L. Stoddard’s work on bobwhite quail (Colinus virginianus), published in 1931, and Errington and Hammerstrom’s work on pheasants, published in 1937, exemplify early efforts of this kind.

Studies similar to Stoddard’s have been conducted on most game animals in North America from 1930 through the present day (e.g. Bellrose 1976; Wallmo 1981; Thomas and Toweill 1982), but many of these studies only summarize general habitat associations and do not identify critical habitat components. Since the early 1980s, the number of hunters has increased while undeveloped land available for managing wild animal populations has decreased. The need to manage populations more intensively is therefore great, and detailed knowledge of habitat requirements is essential for this task. Studies of the habitat requirements of game animals continue to be conducted, as one can easily see by reviewing recent scientific journals on wildlife management.

Public Interest and Environmental Laws

Human activities have dramatically disturbed natural environments in North America and throughout the world. These disturbances have been associated primarily with the rapid increase in the size of the human population and the exploitation of natural resources, including wild animals, for human use. Interest in wild animals by the general public also increased during this period, and concern about the negative effects of human activities on animal populations and other aspects of the natural environment eventually led to the passage of laws in the United States that were designed to aid management of wild animals or reduce environmental degradation. The following summary pertains to U.S. history; it is beyond the scope of the text to review public interest and environmental law in other nations.

Public interest early in the century focused on game animals, and some laws passed in the 1930s reflected this interest. The Migratory Bird Hunting Stamp Act of 1934 and the Pittman-Robertson Federal Aid in Wildlife Restoration Act of 1937, for example, primarily taxed sportsmen and provided funds for management of waterfowl and other hunted species (see table 1.1). As noted in the previous section, information needed for management of these species stimulated efforts to describe and quantify their habitats.

An increase in environmental awareness during the 1960s and 1970s broadened the scope of the kinds of animals about which the general public was concerned. Animal species not hunted for sport and without any other apparent economic utility were also perceived as having value. (The ethical rationales underlying these values are discussed in the next section.) Among the laws passed during this period were the National Environmental Policy Act (1969), the Endangered Species Conservation Act (1973), the Federal Land Policy and Management Act (1976), and the National Forest Management Act (1976) (Bean 1977; see also table 1.1). Legislators designed these laws, in part, to ensure that all wildlife species and other natural resources were considered in the planning and execution of human activities on public lands. Knowledge of the habitats of animal species is obviously required before the effects of an environmental disturbance can be fully evaluated, before a refuge for an endangered species can be designed, or before animal habitats can be maintained on lands managed under a multiple-use philosophy. Biologists responded to the need for information about habitat requirements by studying, often for the first time, numerous species of nongame animals and by developing models to help predict the effects of environmental changes on animal populations (e.g., Verner et al. 1986).

Public interest in the nonconsumptive use of animals has not waned in recent years. In the United States in 2001, 66 million people over 16 years of age spent over $38.4 billion observing, feeding, or photographing wildlife (U.S. Fish and Wildlife Service 2003). The funding mechanisms for managing animals in the United States, however, have not kept pace with the broadening umbrella of public interest. Many state fish and game agencies have developed nongame management programs that emphasize identifying and managing habitats, but these programs are often limited by inadequate funding, and the sources of funds are, with rare exception, not broad based or user related. In Arizona, for example, the nongame program is funded by a fixed percentage of the funds generated by the state lottery.

Efforts to increase the funding base for managing nongame animals and their habitats were initiated in the mid-1990s, when legislation was written that called for a federal tax on outdoor equipment, such as binoculars and tents, used in activities associated with the nonconsumptive enjoyment of wildlife. Funds generated by this act, like those from the Pittman-Robertson Federal Aid in Wildlife Restoration Act, would have been distributed to the states on a matching basis. This initial effort failed, but similar legislation is currently being promoted (e.g., the Teaming with Wildlife initiative). Legislation of this kind, if made into federal law, would distribute the burden of paying for wildlife management among those who most benefit, and would allow state agencies to manage more thoroughly the habitats of a wide variety of species. It would also stimulate the acquisition of information about those habitats.

Table 1.1. Important U.S. legislation stimulating the study, preservation, or management of animal habitat

Source: Based in part on Gilbert and Dodds (1987,17).

Ethical Concerns

Another impetus for studying habitat partly underlies the public interest and environmental laws outlined in the previous section and relates to an ethical concern for the future of wildlife and natural communities (Schmidtz and Willott 2002). This concern is, in part, a humanistic one, insofar as the health of natural systems affects our use and enjoyment of natural resources in the broadest sense. From a utilitarian viewpoint, the world is also our habitat, and its health directly relates to our own. The ethical concern, however, transcends humanism in that wildlife and natural communities are intrinsic to the world in which we have evolved and now live. Writers of legal as well as ethical literature have argued that nonhuman species have, in some sense, their own natural right to exist and grow (e.g., Stone 1974, 1987). The study of wildlife species and their habitats in this context may deepen our appreciation for and ethical responsibility to other species and natural systems.

Why should we be concerned about species and habitats that offer no immediate economic or recreational benefits? Several rather standard philosophical arguments offer complementary and even conflicting rationales. One viewpoint argues for conserving species and their environments because we may someday learn how to exploit them for medical or other benefits (future option values). Another viewpoint argues for preserving species for the unknown (and unknowable) interests of future generations; we cannot speak for the desires of our not-yet-born progeny, who will inherit the results of our management decisions.

Generally, a traditional conflict has pitted ethical humanism against humane moralism. Ethical humanism, as championed by Guthrie, Kant, Locke, More, and Aquinas, argues that animals are not worthy of equal consideration; animals are not up to human levels in that they do not share self-consciousness and personal interests. In effect, this argument allows us to subjugate wildlife and their habitats. Kant argues as much. He advanced his idea on a so-called deontological theme (from the Greek de-ont, that which is obligatory). That is, rights—specifically human rights—allow us to view animals as having less value because they are less rational (or are arational); we humans have the duty to manage species and the freedom to subjugate them.

On the other hand, humane moralism, as championed in part by Christopher D. Stone, Jeremy Bentham (of the animal liberation movement), and Peter Singer, argues that animals deserve the focus of ethical consideration. According to this argument, humans are moral agents. Animals and, by extension, their habitats require consideration equal to that given humans, even if they do not ultimately receive equal treatment.

There is also a third ethical stance, one that may serve as an impetus for studying and conserving wildlife and their habitats: an ecological ethic. The ecological ethic, as proposed by J. Baird Callicott, was most eloquently advanced by Leopold (1949) in his A Sand County Almanac, although elements of his philosophy (and much fuller philosophical expositions) can be traced to Henri Berson, Teilhard de Chardin, and John Dewey. The focus of ethical consideration in this view is on both the individual organism and the community in which it resides. Concern for the community is the essence of Leopold’s ecological ethic, a holistic ethic that focuses on the relationships of animals with each other and with their environment.

Leopold wrote of soil, water, plants, animals, oceans, and mountains, calling each a natural entity. In his view, animals’ functional roles in the community, not solely their utility for humans, provide a measure of their value. By extension, then, to act morally, we must maintain our individual human integrity, our social integrity, and the integrity of the biotic community.

Following such an ecological ethic, a concern for the present and future conditions of wildlife and their habitats motivates the writing of this book. The sad history of massive resource depletion, including extinctions of plant and animal species and the large-scale alteration of terrestrial and aquatic environments, must, in our view, strengthen a commitment to further understanding wildlife and their habitats. Understanding is the necessary prelude to living truly by an ecological ethic.

Concepts Addressed

This book covers both theoretical and applied aspects of wildlife–habitat relationships, with an emphasis on the theoretical framework under which researchers should study such relationships. An appropriate way to begin a preview of the concepts covered in subsequent chapters is to define the term habitat. A review of even a few papers concerned with the subject will show that the term is used in a variety of ways. Frequently, habitat is used to describe an area supporting a particular type of vegetation or, less commonly, aquatic or lithic (rock) substrates. This use probably grew from the term habitat type, coined by Daubenmire (1976, 125) to refer to land units having approximately the same capacity to produce vegetation.

We, however, view habitat as a concept that is related to a particular species, and sometimes even to a particular population, of plant or animal. Habitat, then, is an area with a combination of resources (like food, cover, water) and environmental conditions (temperature, precipitation, presence or absence of predators and competitors) that promotes occupancy by individuals of a given species (or population) and allows those individuals to survive and reproduce. Habitat of high quality can be defined as those areas that afford conditions necessary for relatively successful survival and reproduction over relatively long periods when compared with other environments. (We recognize, though, that the habitats of some animals are ephemeral by nature, such as early seral stages or pools of water in the desert after heavy rains.) Conversely, marginal habitat promotes occupancy and supports individuals, but their rates of survival and reproduction are relatively low, or the area is usually suitable for occupancy for relatively short or intermittent periods. Thus quality of habitat is ultimately related to the rates of survival and reproduction of the individuals that live there (Van Horne 1983), to the vitality of their offspring, and to the length of time the site remains suitable for occupancy.

Understanding why a particular population or species occupies only a specific area in a region or why it occupies only a specific continent requires more than just knowledge of the organism’s environmental needs and ecological relationships. Explanations for an animal’s distribution also require an understanding of its evolutionary history, the climatic history of the area, and even the history of the movements of landmasses. We provide in chapter 2 an overview of the forces, factors, and processes that determine why animals are found where they are and how they came to be there. The information presented emphasizes that both past and present conditions can play significant roles in defining the habitat of an animal. In short, we provide in chapter 2 the evolutionary perspective and conceptual framework we feel are necessary before the study of habitat can proceed successfully.

Important elements of the habitat of an animal are often provided by vegetation. Changes in vegetation can, therefore, alter habitat conditions. Understanding how the structure and composition of vegetation influence the quantity and quality of habitat features is central to understanding the distribution and abundance of animals. We begin chapter 3 with a review of the patterns and processes associated with plant succession and the relationships between animals and vegetative change. We also initiate in chapter 3 a discussion of how the concepts of niche and habitat relate to one another, and we emphasize the importance of focusing investigations of habitat on the resources that allow animals to survive and reproduce and on ecological relationships that may constrain access or use of those resources. We end chapter 3 with a discussion of factors that can influence the dynamics and viability of populations, including how they may be distributed (e.g., the concept of metapopulation), their genetic makeup, movements of animals within and among them, and the influences of other organisms, such as nonnative species and humans.

Studying wildlife–habitat relationships requires knowledge of the scientific method. We review in chapter 4 activities involved in the scientific method and some of the controversial issues associated with its application in ecology and wildlife science. For example, we emphasize in this chapter the need for students and professional biologists to understand the difference between research and statistical hypotheses. We also review weaknesses in traditional statistical null hypothesis tests and discuss alternative approaches. We end chapter 4 with an evaluation of the strengths and weaknesses of laboratory and field experiments and offer some general strategies for how to proceed with investigations of wildlife–habitat relationships.

Identifying what constitutes habitat of a population or species is the impetus underlying many activities in wildlife science and management. Designing studies that identify habitat conditions requires considerable thoughtfulness about the needs and perceptual abilities of the species under investigation, the spatial scale at which the study is to be conducted, and the methods for measuring environmental features. We provide in chapter 5 a review and analysis of what elements of the environment might be measured in studies of habitat and a discussion of the methods commonly used to measure them.

The assessment of what to measure in wildlife habitat and how to measure it, in chapter 5, is followed in chapter 6 with a consideration of when to take the measurements. We focus in chapter 6 on the importance of timing in determining what constitutes habitat. Use of resources by animals can vary on several temporal scales, including time of day, stage of breeding cycle, season of the year, and between years. Deciding which scale or scales to address in a study will obviously influence its design. Evaluation of the numerous factors that can influence whether an animal occupies a given area lends itself to the use of multivariate statistical techniques. We end chapter 6 with a review of the use of these techniques in conceptualizing, analyzing, and understanding wildlife–habitat relationships.

Patterns of resource use detected in animal populations are products of the behaviors of individual animals. We present in chapter 7 the theoretical framework that forms the basis for investigating animal behavior as it relates to habitat. We also review the principal methods used to measure animal behavior. Assessment of diet and foraging behavior is a focus of this chapter because an animal’s survival and productivity depend heavily on acquiring food.

Some animals may select habitat through a hierarchical process that begins on broad spatial scales or large geographic extents. Furthermore, the distribution of patches of environmental resources (e.g., vegetation types) across the landscape can influence the dynamics of populations and elements of community structure. We review in chapter 8 the basic tenets of landscape ecology, and emphasize that landscape, like habitat, is best viewed as a species-specific concept. We describe different aspects of scale, including geographic extent, map resolution, time, biological organization, and administrative hierarchy, and how these aspects can be integrated in landscape ecology. We also discuss in this chapter how animals may respond to different kinds of disturbances and the resulting heterogeneity of resources in patchy landscapes. Associated with this discussion is a review of the management challenges presented by patchy or fragmented environments; this review includes an assessment of the value of retaining remnant patches of natural environments and some level of connectivity between them. In chapter 9, we continue the discussion of wildlife and landscapes but focus on the specific responses of organisms, species, populations, and communities to landscape dynamics.

Models of wildlife–habitat relationships are used for a variety of purposes, including: (1) as descriptions of current levels of understanding; (2) assessing the relative importance of environmental features in the distribution and abundance of organisms; (3) identifying weaknesses in current understanding; and (4) generation of testable hypotheses about animals and systems of interest. In chapter 10, we review the types of models used in the study and management of wildlife and their habitats, and examine how scientific uncertainty affects the use of these models. We also discuss how models can be developed, calibrated, and tested.

The earth and the natural resources on it are changing rapidly, primarily as a result of human use and exploitation. In the future, management of natural resources, including wildlife, will likely require approaches that conceptually force us to think on broader spatial, temporal, and ecological scales. We discuss in chapter 11 the possibility of managing wildlife in an ecosystem context and suggest that the traditional concept of habitat may need to be broadened beyond the basics of food, cover, and water to include ideas such as the ecological roles of other species, abiotic conditions, and natural disturbance regimes. We also suggest that the traditional notion of wildlife may need to be broadened to encompass the full array of biota present in an ecosystem. We propose in this chapter an enhanced approach to depicting, modeling, and predicting the status and condition of wildlife in ecosystems, and advocate the rigorous use of adaptive management as a foundation for land use decisions.

Changes in environmental conditions on Earth, advances in technological devices and analytic methods, and the potential need for new philosophical and conceptual approaches in research and management require that wildlife biologists do their best to keep abreast of new ideas. We discuss in chapter 12 several ideas that may assist us in advancing our understanding of wildlife–habitat relationships. We suggest that the scale on which we conduct research and management be examined rigorously, and explore potential ways that the concept of niche may help focus research in the future. We also call for a more complete integration of the overlapping fields of wildlife ecology and management, conservation biology, and restoration ecology. Changes in the way we educate students and professionals must precede integration of this kind, and we end chapter 12 with some suggestions for how these changes may be initiated.

Our view of the world and how it works is likely to shift over time as current explanations are replaced by better ones. The second edition of this book was motivated by the evolution of ideas presented in the first. Similar shifts in thinking motivated this third edition. However, our ideas about dealing with changes in the world remain the same. We hope that, no matter what changes occur, our readers—current or future conservationists in the broadest sense—remain tied to an ecological land ethic and continue the pursuit of providing vital, productive habitats for wildlife and humans alike.

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2

The Evolutionary Perspective

Although we may not fully understand the