The adaptation of herbivore behaviour to seasonal and locational variations in vegetation quantity and quality is inadequately modelled by conventional methods. Norman Owen-Smith innovatively links the principles of adaptive behaviour to their consequences for population dynamics and community ecology, through the application of a metaphysiological modelling approach. The main focus is on large mammalian herbivores occupying seasonally variable environments such as those characterised by African savannas, but applications to temperate zone ungulates are also included. Issues of habitat suitability, species coexistence, and population stability or instability are similarly investigated. The modelling approach accommodates various sources of environmental variability, in space and time, in a simple conceptual way and has the potential to be applied to other consumer-resource systems. This text highlights the crucial importance of adaptive consumer responses to environmental variability and is aimed particularly at academic researchers and graduate students in the field of ecology.

Norman Owen-Smith is Research Professor in African Ecology and heads the Centre for African Ecology at the University of the Witwatersrand.

Acknowledgements

xi

Acronym and symbol conventions

xiii

Conceptual origins: variability in time and space

1

(12)

Modelling philosophy

2

(2)

Herbivores and vegetation

4

(6)

Modelling technology

10

(1)

Structure of the book

10

(3)

Consumer-resource models: theory and formulation

13

(25)

Basic theory

13

(2)

Descriptive population models

15

(5)

Demographically structured population models

20

(1)

Interactive consumer-resource models

21

(8)

Metaphysiological population models

29

(7)

Overview

36

(2)

Resource abundance: intake response and time frames

38

(23)

Basic theory

39

(3)

Within-patch feeding

42

(5)

Foraging spells

47

(5)

Daily food intake

52

(1)

Half-saturation level for intake

53

(2)

Allometry of food intake

55

(1)

Influences on the form of the intake response

56

(1)

Overview

57

(4)

Resource distribution: patch scales and depletion

61

(24)

Feeding sites

62

(1)

Patch acceptance

63

(2)

Patch departure

65

(10)

Foraging areas

75

(2)

Habitat types

77

(2)

Waterpoint restrictions

79

(1)

Selectivity in foraging

80

(3)

Overview

83

(2)

Resource quality: nutritional gain and diet choice

85

(25)

Diet breadth model

86

(6)

Palatability classes

92

(5)

Evaluating the diet breadth model

97

(8)

Form of the nutritional gain response

105

(3)

Overview

108

(2)

Resource constraints: physiological capacities and costs

110

(26)

Linear programming models

111

(5)

Digestive capacity

116

(9)

Metabolic satiation

125

(2)

Thermal tolerance

127

(4)

Constraints versus cost-benefit isoclines

131

(2)

Truncation of the intake response

133

(1)

Overview

134

(2)

Resource allocation: growth, storage and reproduction

136

(26)

Relative growth potential

137

(5)

Storage

142

(9)

Growth versus storage

151

(2)

Reproduction

153

(5)

Senescence

158

(1)

Flux- versus state-dependent mortality

159

(1)

Overview

160

(2)

Resource production: regeneration and attrition

162

(22)

General production

163

(2)

Grass production model

165

(12)

Browse production

177

(3)

Resource-related dynamics and plants

180

(2)

Overview

182

(2)

Resource competition: exploitation and density dependence

184

(21)

Stocking density models

185

(3)

Growth potential

188

(3)

Alternative models of resource production

191

(11)

Competitive distributions

202

(1)

Resource versus density dependence

203

(1)

Overview

204

(1)

Resource-dependent mortality: nutrition, predation and demography

205

(27)

Mortality function

206

(3)

Observed mortality patterns

209

(15)

Predation

224

(3)

State-dependent mortality

227

(1)

Demographic structure

228

(2)

Overview

230

(2)

Habitat suitability: resource components and stocking densities

232

(32)

Determinants of browser abundance

233

(11)

Range condition and grazer stocking densities

244

(9)

Generic resource types

253

(4)

Overview

257

(7)

Resource partitioning: competition and coexistence

264

(37)

Lotka-Volterra model

265

(1)

Competitive habitat partitioning

266

(3)

Exploitation competition model

269

(10)

Size difference for coexistence

279

(2)

Ecomorphological distinctions

281

(7)

Tradeoffs facilitation and competition

288

(7)

Overview

295

(6)

Population dynamics: resources basis for instability

301

(34)

Interactive herbivore-vegetation dynamics

302

(15)

Soay sheep example

317

(12)

Other ungulate populations

329

(1)

Alternative modelling approaches

330

(2)

Overview

332

(3)

An adaptive resource ecology: foundation and prospects

335

(11)

Retrospective review

335

(2)

Prospects

337

(4)

Broader issues

341

(4)

Overview

345

(1)

References

346

(25)

Index

371

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