Ecology of small mammals

From their largely descriptive beginnings about a half century ago, studies on the ecology of small mammals have mushroomed in number, scope, content and complexity. Yet strangely, or perhaps not so strangely if one considers the extent and complexity of ecological interactions, the main problems for which the early workers sought answers still defy complete analysis, and basic hypotheses remain untested if not even untestable. The same holds true for so many branches of animal ecology that it seems to be the complexity of the concepts that frustrates efforts rather than the subject species. Like all branches of science, small mammal ecology has been subject to a series of fashionable approaches, one following another as tech­ nology penetrates previously impregnable regions. Doubtless the future development of our science will be punctuated by wave upon wave of new endeavour in whole fields that are perhaps even yet unidentified. Answers to the complex questions which ecologists ask do not come easily. Increasingly though, they arise in direct proportion to the efforts expended upon their elucidation. Many studies have achieved such a high level of elegance, in terms of manpower and apparatus, that there is a feeling that questions asked when such resources are unavailable are not worth asking. Nothing could be further from the truth. Many a complex model has failed fully to explain the phenomenon for which it was construc­ ted because of a lack of basic field data on the species' natural h~story.

1 Life-history strategies.- 1.1 Introduction.- 1.2 Evolution and life-history strategies.- 1.2.1 Individual selection.- 1.2.2 Kin selection.- 1.2.3 Group selection.- 1.3 Demographic components of life-history strategies.- 1.3.1 Theoretical considerations.- 1.3.2 Empirical data.- 1.4 Energetic components of life-history strategies.- 1.4.1 The evolution of food habits and food niche breadth.- 1.4.2 The evolution of energy metabolism: homeothermy v. heterothermy.- 1.5 Behavioural components of life-history strategies.- 1.5.1 The evolution of habitat selection.- 1.5.2 The evolution of social organization.- 1.6 Summary.- 1.7 Acknowledgements.- 1.8 References.- 2 Population processes in small mammals.- 2.1 Introduction.- 2.2 Distribution.- 2.2.1 ‘Macrodistribution’.- 2.2.2 ‘Microdistribution’.- 2.3 Abundance.- 2.3.1 Density.- 2.3.2 ‘Income and expenditure’.- 3 The stability and instability of small mammal populations.- 3.1 Introduction.- 3.2 The regulation of small mammal populations.- 3.2.1 Theoretical background.- 3.3 Case studies of change in small mammal populations.- 3.3.1 Change in numbers of mice and voles in Wytham Woods over 30 years.- 3.3.2 Regulation of wood mice in Wytham Woods 1948–66.- 3.3.3 The story of the house mouse (Mus musculus).- 3.3.4 Cyclic species.- 3.4 Conclusions.- 3.5 References to Chapters 2 and 3.- 4 Community structure and functional role of small mammals in ecosystems.- 4.1 Introduction.- 4.2 Characterization of ‘small mammals’ as a single state variable.- 4.3 Characterization of ‘small mammals’ as different state variables.- 4.4 The structure of small mammal faunas.- 4.4.1 Taxonomic composition.- 4.4.2 Species diversity.- 4.4.3 Relative abundance.- 4.4.4 Biomass and density.- 4.4.5 Ecological diversity.- 4.5 Some ecological characteristics of small mammals.- 4.6 Evaluation of transfer functions which link the component ‘small mammals’ to other system variables.- 4.6.1 Consumption: its direct impact and the functional relationships between vegetation and primary consumers.- 4.6.2 Consumption: its indirect impact and the functional relationships between primary consumers and primary producers.- 4.6.3 Activities other than consumption: their impact and the functional relationships between primary consumers and abiotic state variables.- 4.6.4 Small mammals as secondary consumers: their impact and functional relationships with other consumer state variables.- 4.6.5 Small mammals as prey items: their impact and functional relationships with other consumer state variables.- 4.7 Energy budgets.- 4.7.1 Assimilation and digestion.- 4.7.2 Production.- 4.7.3 Respiration.- 4.7.4 Energy budget models.- 4.7.5 Energy budgets in an ecosystem context.- 4.8 The role of small mammals in ecosystems.- 4.9 References.- 5 Ecological importance of small mammals as reservoirs of disease.- 5.1 Introduction.- 5.2 Zoonoses involving small mammals.- 5.2.1 Bacterial zoonoses.- 5.2.2 Rickettsial zoonoses.- 5.2.3 Viral zoonoses.- 5.2.4 Fungal zoonoses.- 5.2.5 Protozoal zoooses.- 5.2.6 Helminth zoonoses.- 5.3 Epidemiology of human diseases involving small mammals.- 5.3.1 Foci of infection.- 5.3.2 Spread of infections from foci.- 5.3.3 Models of the spread of disease.- 5.4 The importance of small mammals as reservoirs of disease.- 5.4.1 Overall assessment.- 5.4.2 Problems of assessing the role of small mammals as reservoirs of disease.- 5.5 The control of diseases with small mammal reservoirs.- 5.6 Conclusions.- 5.7 References.- 6 Importance of small mammals as pests in agriculture and stored products.- 6.1 Introduction.- 6.2 Main types of small mammal problems.- 6.2.1 Damage by Microtus arvalis and subsidiary microtines to field crops of temperate regions.- 6.2.2 Major threats to cultivated trees: debarkers, root-cutters and seed depredators.- 6.2.3 Pests emerging from the soil: hamsters, ground squirrels, gerbils, pocket gophers and moles.- 6.2.4 Murid rodents: depredators of cereals and other subsistence crops.- 6.2.5 Rodent damage to tropical cash crops.- 6.2.6 Rodent damage to stored products and structure.- 6.3 Principal means of combating small mammal damage.- 6.3.1 Introduction to control problematics.- 6.3.2 Habitat manipulation and related methods as intentional rodent control measures.- 6.3.3 Exclusion methods and rodent deterrents.- 6.3.4 Reductional control methods.- 6.4 Towards integrated control programmes.- 6.4.1 Introduction.- 6.4.2 Identification of the problem and the pest.- 6.4.3 Determination of the control thresholds.- 6.4.4 Selection of control measures.- 6.4.5 Follow-up of the efficacy of control operations.- 6.4.6 Need for international co-ordination of efforts.- 6.5 References.- 7 Ecology of bats.- 7.1 Habitat.- 7.1.1 Structural and functional requirements.- 7.1.2 Ecological factors: control through ambient influence.- 7.1.3 Foraging strategies.- 7.1.4 Daytime shelters during the active life.- 7.1.5 Hibernation.- 7.2 Diet.- 7.2.1 Food specializations.- 7.2.2 Water intake.- 7.2.3 The position of bats in food chains.- 7.3 Reproduction.- 7.3.1 Sexual cycles.- 7.3.2 Effect of reproduction.- 7.4 Population.- 7.4.1 Population size.- 7.4.2 Population structure.- 7.4.3 Population changes.- 7.5 Community.- 7.6 Relations.- 7.6.1 The role of bats in ecosystems.- 7.6.2 Bats and man.- 7.7 Acknowledgements.- 7.8 References.- 8 Ecology of small marsupials.- 8.1 Introduction.- 8.1.1 Distinctive features of marsupial reproduction.- 8.2 Breeding strategies of polytocous marsupials.- 8.2.1 American opossums.- 8.2.2 Australian bandicoots.- 8.3 Semelparity — an unique strategy.- 8.3.1 Life-history of Antechinus species.- 8.3.2 Cause of synchronous death of males.- 8.3.3 Significance of semelparity.- 8.3.4 Response to fire.- 8.4 Contrasting strategies of arboreal leaf eating marsupials.- 8.4.1 Ringtail possum and greater glider.- 8.4.2 Brush possum and bobuck.- 8.4.3 Concept of forest dependent species.- 8.4.4 Response to forestry practices.- 8.5 The ecology of invasion — the brush possum in New Zealand.- 8.5.1 Introduction and establishment.- 8.5.2 Effects on indigenous forest.- 8.5.3 Forest influence on the possum population.- 8.5.4 Possums, cattle and tuberculosis.- 8.4 The ecology of extinction — small marsupials of the inland plains of Australia.- 8.5 Acknowledgements.- 8.6 References.