(PDF) Managing Vertebrate Pests: Rabbits

Bureau of Resource Sciences

and

CSIRO Division of Wildlife and Ecology

Managing Vertebrate Pests:

Rabbits

Kent Williams, Ian Parer, Brian Coman,

John Burley and Mike Braysher

Australian Government Publishing Service

Canberra

ISBN 0 644 29240 7 (set)

ISBN 0 644 29623 2 (This publication)

This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced

by any process without prior written permission from the Australian Government Publishing Service.

Requests and inquiries concerning reproduction and rights should be addressed to the Manager, Commonwealth

Information Services, Australian Government Publishing Service, GPO Box 84, Canberra ACT 2601.

Scientific editing by Mary Bomford. Cover and publication design by Bob Georgeson, Bureau of Resource Sciences

Design Studio.

Cover photograph by G. Chapman.

Typesetting and diagrams by Henryk Dekker.

The Bureau of Resource Sciences is a professionally independent Bureau established in October 1992 in the Department

of Primary Industries and Energy. Its role is to enhance the sustainable development of Australia’s agricultural,

mineral, petroleum, forestry and fisheries resources and their industries by providing scientific and technical advice

to government, industry and the community.

The CSIRO Division of Wildlife and Ecology is part of Australia's national, independent, scientific organisation,

CSIRO. It's goal is to develop the scientific knowledge required to manage Australia's wildlife, plant and land resources

for ecological sustainability.

Preferred way to cite this publication:

Williams, C.K., Parer, I., Coman, B.J., Burley, J. and Braysher, M.L. (1995) Managing Vertebrate Pests: Rabbits. Bureau

of Resource Sciences/CSIRO Division of Wildlife and Ecology, Australian Government Publishing Service, Canberra.

Author affiliations: K. Williams and I. Parer, CSIRO Division of Wildlife and Ecology; B. Coman, Vernox Pest

Management; J. Burley, Animal and Plant Control Commission of South Australia; M. Braysher, Bureau of Resource

Sciences.

Printed for AGPS by Paragon Printers, Wollongong Street, Fyshwick ACT 2609

This publication, which is one in a series,

provides land managers with ‘best practice’

national guidelines for managing the

agricultural and environmental damage

caused by rabbits. Others in the series

include guidelines for managing feral

horses, foxes, feral goats, feral pigs and

rodents. The publication was developed

and funded jointly by the Vertebrate Pest

Program which is administered by the

Bureau of Resource Sciences, and by the

CSIRO Division of Wildlife and Ecology.

To ensure that the guidelines are widely

accepted as the basis for rabbit

management, comment has been sought

from government including state, territory

and Commonwealth agriculture, environ-

mental and resource management agencies,

and from other land managers, and

community organisations, including the

Australian Conservation Foundation, the

National Farmers’ Federation, the National

Consultative Committee on Animal Welfare,

and the Anangu Pitjantjatjara Aboriginal

Land Council. The Standing Committee on

Agriculture and Resource Management has

endorsed the approach to managing rabbit

damage set out in these guidelines.

There are strongly held conflicting views

among people interested in the

management of rabbits. Some scientists

judge rabbits as Australia’s most pernicious

environmental problem, and wish to see

more resources allocated to their

management. People involved in

commercial or subsistence use of rabbits

are alarmed at the prospect of rabbits being

managed to levels too low to allow such

uses to continue. Economists argue the

spending on rabbit management should be

fully justified in terms of the economic or

environmental returns on such investments,

and are concerned that the information

necessary for this does not exist. People

holding strong animal welfare concerns

hope to see rabbit management and better

control techniques reduce the level of

suffering in rabbits subjected to control

operations. Farmers would like to be sure

that expenditure on rabbit control is not

wasted by rapid reinvasion from adjacent

areas. The authors have had a difficult task

in considering these competing views in

the preparation of these guidelines but

believe they are a significant step forward

in the management of rabbits.

The principles underlying the strategic

management of vertebrate pests have been

described in Managing Vertebrate Pests:

Principles and Strategies (Braysher 1993).

The emphasis is on the management of pest

damage rather than on simply reducing pest

density. A major difficulty faced by the

authors was that despite numerous

historical accounts and studies of rabbits in

Australia, their impact on the environment

Bureau of Resource Sciences/CSIRO iii

FOREWORD

and on agricultural production is poorly

documented. Nevertheless, the weight of

scientific and other information collected

over many decades reinforces the belief

that rabbits are a serious vertebrate pest for

agricultural production and the natural

environment. Demonstration projects

funded under the Vertebrate Pest Program

administered by the Bureau of Resource

Sciences are helping to document the

impact of rabbits in Australia and to test the

effectiveness of different approaches to

management.

The guidelines recommend that,

wherever practicable, management should

concentrate on reducing rabbit density to

low levels and holding it there by routine

maintenance control. The evidence suggests

that, if undertaken as part of a local or

regional group scheme, this is the most cost-

effective way of managing rabbit damage.

While there is hope that rabbit populations

will in the future be controlled by new or

modified micro-organisms acting as

mortality or sterility agents, we cannot

depend on such developments. Until they

are proven it is essential that strong efforts

to control rabbits by conventional means

be maintained.

These guidelines will help land managers

to reduce agricultural losses and

environmental damage through the use of

scientifically-based management that is

humane, cost-effective and integrated with

ecologically sustainable land management.

iv Managing Vertebrate Pests: Rabbits

Neil Williams

Executive Director

Bureau of Resource Sciences

Brian Walker

Chief

CSIRO, Division of Wildlife and Ecology

CONTENTS

FOREWORD iii

ACKNOWLEDGMENTS xi

ACRONYMS AND ABBREVIATIONS xii

GLOSSARY xiii

SUMMARY 1

INTRODUCTION 11

PART ONE: HISTORY, DISTRIBUTION AND BIOLOGY 15

1. HISTORY OF INTRODUCTIONS AND SPREAD 17

Summary 17

1.1 Europe 17

1.2 Australia 18

2. DISTRIBUTION AND ABUNDANCE 21

Summary 21

2.1 Distribution in Australia 21

2.2 Changes in abundance with time and space 22

3. BIOLOGY 26

Summary 26

3.1 The European wild rabbit and its relatives 26

3.2 Body characteristics of the rabbit 27

3.3 Shelter 28

3.4 Behaviour 32

3.5 Dispersal 33

3.6 Social organisation 36

3.7 Parasites, predators and diseases 37

3.8 Nutrition 46

3.9 Reproduction and survival 48

3.10 Population dynamics 51

PART TWO: IMPACTS AND USE 55

4. ECONOMIC AND ENVIRONMENTAL IMPACTS 57

Summary 57

4.1 Introduction 58

4.2 Economic impact 58

4.3 Environmental impact 65

4.4 Resource value and use 82

PART THREE: COMMUNITY ATTITUDES 85

5. ATTITUDES TO RABBIT USE, ANIMAL WELFARE AND NEW

TECHNOLOGY 87

Summary 87

5.1 Community perceptions 87

5.2 Implication of rabbit harvesting for rabbit damage control 90

5.3 Rabbits on Aboriginal lands 91

5.4 Commercial farming of rabbits 91

5.5 Animal welfare 92

5.6 Rabbits as a recreational resource 98

5.7 Pet rabbits 98

5.8 The myth of the superbug 99

Bureau of Resource Sciences/CSIRO v

PART FOUR: TECHNIQUES AND MANAGEMENT 101

6. PAST AND CURRENT MANAGEMENT 103

Summary 103

6.1 Development of rabbit control practices 103

6.2 Current management 107

6.3 Extension and technical advice 110

6.4 Contribution of training 111

7. TECHNIQUES TO MEASURE AND CONTROL RABBIT IMPACT AND ABUNDANCE 114

Summary 114

7.1 Measuring rabbit impact 114

7.2 Measuring rabbit abundance 116

7.3 Use of rabbit impact, distribution and density measurements 121

7.4 Rabbit control techniques 124

7.5 Monitoring techniques 145

7.6 Evaluation techniques 146

PART FIVE: STRATEGIC RABBIT MANAGEMENT 149

8. ECONOMICS OF RABBIT MANAGEMENT 151

Summary 151

8.1 Economic framework 152

8.2 Defining the economic problem and assessing the cost and benefits

of control 152

8.3 Economic framework for strategic, sustained management 160

9. STRATEGIC MANAGEMENT AT THE LOCAL AND REGIONAL LEVELS: PRINCIPLES 169

Summary 169

9.1 Introduction 170

9.2 Defining the problem 171

9.3 Management plan 174

9.4 Implementation 187

9.5 Monitoring and evaluation 188

10. STRATEGIC MANAGEMENT APPROACH APPLIED LOCALLY:

SOME EXAMPLES 191

Summary 191

10.1 Introduction 191

10.2 The strategic approach 192

10.3 Evaluation of the group schemes 197

11. IMPLEMENTING MANAGEMENT 200

Summary 200

11.1 Group action — basis of a national approach? 200

11.2 Requirements for effective local action 204

11.3 Implementation at the national, state and local level 207

PART SIX: FUTURE DIRECTIONS 211

12. DEFICIENCIES IN KNOWLEDGE, TECHNIQUES AND LEGISLATION 213

Summary 213

12.1 Introduction 213

12.2 Biology of the rabbit 214

12.3 Impact in non-agricultural areas 214

12.4 Impact in agricultural areas 215

12.5 Management and monitoring techniques 215

12.6 Administrative procedures and incentives 217

vi Managing Vertebrate Pests: Rabbits

12.7 Training and extension 217

12.8 Animal welfare 219

GENERAL READING 220

REFERENCES CITED 221

APPENDIX A: CONTROL TECHNIQUES 247

A1 Poisoning 247

A2 Warren destruction 254

A3 Removal of surface harbour 255

A4 Fumigation 256

APPENDIX B: STRATEGIC RABBIT MANAGEMENT IN PLANTATION FORESTS 261

B1 Defining the problem 261

B2 Management plan 262

B3 Implementation 265

B4 Monitoring 266

B5 Evaluation 266

APPENDIX C: STRATEGIC RABBIT MANAGEMENT IN CONSERVATION AREAS 267

C1 Defining the problem 267

C2 Management plan 268

C3 Implementation 270

C4 Monitoring 271

C5 Evaluation 271

APPENDIX D: CRITERIA FOR ERADICATION 274

INDEX 275

FIGURES

Figure 1 Strategic approach to managing rabbit damage. 12

Figure 2 Spread of the rabbit in Australia. 19

Figure 3 Rabbit infestation trends in different land types in the Riverina district

of New South Wales after the introduction of myxomatosis. 22

Figure 4 Rainfall, and fluctuations in rabbit populations in different land systems

in western New South Wales. 23

Figure 5 Present distribution of the rabbit in Australia. 24

Figure 6 Surface rabbits, shelter types, squats and warrens 29

Figure 7 Diagrammatic representation of a six-year-old warren at Canberra. 31

Figure 8 Percentage of rabbits consuming bait placed at different distances from

warrens: (a) three days after baiting commenced; and (b) eight days after

baiting commenced.* 33

Figure 9 Effect of adjacent rabbit densities on the number of (a) warrens,

and (b) active entrances in areas cleared of rabbits and warrens

two years previously. 34

Figure 10 Rabbit numbers on a small property at Margaret River in Western Australia. 35

Figure 11 Recolonisation after warren ripping of a 21 000 hectare property in western

New South Wales during the high rainfall years of the mid-1970s.

No warrens were ripped on this property in 1974–77. 36

Bureau of Resource Sciences/CSIRO vii

Figure 12 Variations over time in the number of rabbits and predators at Yathong

Nature Reserve in central-western New South Wales. 39

Figure 13 Variation in fox and feral cat populations in relation to changes in rabbit

populations in south-western Western Australia. 40

Figure 14 Recovery of rabbits after drought in an area where predators (feral cats and

foxes) were shot, and where they were not shot in central-western

New South Wales. 40

Figure 15 Abundance of rabbits and the frequency of occurrence of rabbits in

dingo stomachs. 42

Figure 16 The percentage of rabbit in the spring diet of eight species of raptor in

the Mallee region of Victoria. 42

Figure 17 Rabbit abundance indices for areas in England where predator removal

effort was measured. 43

Figure 18 Seasonal variation in the percentage of adult (older than nine months)

females pregnant at five sites in Australasia. 49

Figure 19 Seasonal variation in the survival rate to 24 weeks of young born at

different times of the year. 50

Figure 20 Hypothetical model of central Australian rabbit populations and suggested

strategic application of control measures. 52

Figure 21 Cumulative sedimentation in Burrinjuck (southern tablelands, New South

Wales), Umberumberka (western New South Wales) and Pekina (near

Peterborough, South Australia) Reservoirs. 58

Figure 22 Dung collected from points on eight transects in Coorong National

Park in South Australia. 75

Figure 23 Number of small mammal species extinct or locally extinct since

European colonisation.** 79

Figure 24 A hypothetical example of a simple map a farmer could use to assist

planning rabbit management. 122

Figure 25 Abundance of foxes as determined by spotlight counts at two sites and

the amount of 1080 used in the south-west of Western Australia. 132

Figure 26 Results of an economic survey of 12 station properties in the winter rainfall

zone of Western Australia showing the higher profitability on properties

with lower stocking rates. 155

Figure 27 Experimental costs of control for rabbits at different densities on

a property near Yass, New South Wales. 161

Figure 28 Cost of maintenance control relative to initial control by methods

including or excluding warren ripping. 162

Figure 29 Reduction of rabbit populations by repeated maintenance control in

an experimental program of strategic, sustained management. 162

Figure 30 Declining cost of successive maintenance treatments by phosphine

diffusion fumigation in experimental trials. 163

Figure 31 Growth rate (logistic) of a rabbit population at different sizes. 164

Figure 32 Hypothetical harvest curve for a rabbit population in an area with

a maximum carrying capacity of 1000 rabbits. 164

Figure 33 Use of 1080 poison in two group rabbit control schemes expressed as

a percentage of the initial amount of 1080 used. 176

Figure 34 Strategic, sustained rabbit management. 182

Figure 35 Initial rabbit control treatment. 183

Figure 36 Maintenance rabbit control treatment (one month after initial treatment

and annually thereafter). 184

Figure 37 Treatment for scrub-living rabbits. 185

viii Managing Vertebrate Pests: Rabbits

Figure A1 Map showing adequate trail placement to cater for a substantial rabbit

infestation, Murray Mallee district, South Australia. 249

* The Wildlife Society holds copyright for this figure.

** Reproduced from Search — Science and Technology in Australia and New Zealand with

permission of Control Publications.

TABLES

Table 1 Percentage of New South Wales with rabbits at different levels of

abundance. 24

Table 2 Relative importance of young and older rabbits in the diet of foxes

and feral cats. 38

Table 3 Comparison of stocking rates on a mixed grazing property in the

south-east of South Australia before and after rabbit control. 59

Table 4 Estimated relative grazing pressures in dry sheep equivalents (DSE)

by sheep, goats, kangaroos and rabbits on different land types in the

Broken Hill district. 61

Table 5 Pasture biomass consumed by rabbits. 62

Table 6 Estimates of pasture biomass loss from various densities of rabbits, using

exclosure techniques in Western Australia. 62

Table 7 Increase in production after rabbit control on a 650 hectare property in the

northern Midlands, Tasmania. 63

Table 8 Number of trees and shrubs per hectare at different rabbit densities. 68

Table 9 Percentage basal cover of three vegetation groups and the percentage

of bare ground 12 years after erection of rabbit enclosures. 69

Table 10 Approximate mean LD50 of 1080 poison (sodium monofluoroacetate) for

different groups of native animals with known past and continuing

exposure to naturally occurring fluoroacetates, and for introduced

animals and those native animals with no known past exposure

to this toxin. 76

Table 11 Comparative toxicity of 1080 to various animals. 77

Table 12 Percentage frequency of occurrence of vertebrates and invertebrates

in dingo and fox scats collected at Irving Creek in 1989 and the percentage

frequency of occurrence in dingo stomachs collected in 1969 in the

Petermann Ranges. 80

Table 13 Legislative and organisational responsibilities for rabbit control. 108

Table 14 State and territory objectives for rabbit control management. 109

Table 15 Extension and training needs for successful rabbit control. 112

Table 16 Ideal properties of rabbit poison and properties of commonly-used

rabbit poisons and cholecalciferol. 128

Table 17 Assessment of biological control options. 143

Table 18 Hypothetical examples of benefits of rabbit control for properties

with different stocking rates carrying 4000 DSE. 156

Table 19 Cumulative cost, effectiveness, and index of cost per benefit of

combined treatments in an experimental rabbit control program in the

Yass–Canberra district. 159

Table 20 Hypothetical example in which the annual cumulative costs of two

different rabbit control regimes are compared. 177

Table 21 Some costs of rabbit control associated with the Bathurst Scheme in

New South Wales, 1962–67. 202

Table 22 Materials and services needed for poisoning. 247

Bureau of Resource Sciences/CSIRO ix

Table A2 Choice of technique for poisoning. 248

Table A3 Recommended free-feeding rates. 250

Table A4 Legal restrictions on the use of poisons. 250

Table A5 Recommended poison feeding rates. 252

Table A6 Suitability of equipment for ripping. 254

Table A7 Legal restrictions on the use of fumigants. 256

Table A8 Materials and services needed for fumigation. 257

xManaging Vertebrate Pests: Rabbits

The Vertebrate Pests Committee’s Strategic

Vertebrate Pest Working Group, which is

overseeing the preparation of the

guidelines — Kevin Heinrich, Neil

Hogstrom, John Hicks, Don Pfitzner and

John Auty — provided valuable input and

comments.

Special acknowledgment is given to Mr

Bunny Fennessy and Dr Barney Foran of

the Division of Wildlife and Ecology,

CSIRO, Dr Glen Saunders of NSW

Agriculture and Dr Brian Cooke of the

Animal and Plant Control Commission,

South Australia, for critically reviewing the

manuscript. The late Dr Graeme Caughley

advised on the method of calculating

estimates and standard errors of density

and number of warrens from transect

counts.

Several individuals from the Bureau of

Resource Sciences deserve mention. Dr

Peter O’Brien was a continuing source of

advice. Quentin Hart and Hazel Small

helped edit the manuscript. Deborah

McLeod, Joy Manly, Cass Coleman and

Sarah Martin all helped at various stages

in the preparation of the document.

Dr Richard Williams helped collate the

report and provided input to improve the

quality of the document. Henryk Dekker

redrew many of the figures.

Dr Mary Bomford provided extensive

scientific and other editorial comment and

organised the final collation and

publication of the guidelines.

Many other people and organisations,

too numerous to acknowledge

individually, gave us the benefit of their

experiences by commenting on the

manuscript at various stages of its

evolution. The document was sent for

comment to:

• Commonwealth Department of Primary

Industries and Energy Divisions

• Standing Committee on Agriculture and

Resource Management (SCARM)

• Australian and New Zealand

Environment Council

– Standing Committee on

Conservation

– Standing Committee on the

Environment

• Land and Water Research and

Development Corporation

• Meat Research Corporation

• Rural Industries Research and

Development Corporation

• Australian Wool Research and

Promotion Organisation

• Australian Conservation Foundation

• National Consultative Committee on

Animal Welfare

• National Farmers’ Federation

• Murray Darling Basin Commission

• Australian Veterinary Association

• Anangu Pitjantjatara Land Council

We wish to thank all these groups for their

contributions.

The families of the authors deserve praise

for remaining sane and helpful during its

extended gestation.

Throughout the preparation of this report,

the authors were reminded of the enormous

contribution made by Dr Ken Myers,

previously of CSIRO Division of Wildlife and

Ecology, to our understanding of the rabbit

in Australia. The research which he led with

foresight, dedication and enthusiasm has in

large measure made this report possible.

Bureau of Resource Sciences/CSIRO xi

ACKNOWLEDGMENTS

ACF Australian Conservation

Foundation

ACT Australian Capital Territory

AEDP Aboriginal Employment and

Development Program (now

ARRI)

AHC Australian Heritage

Commission

ANCA Australian Nature

Conservation Agency

(formerly ANPWS)

ANZECC Australian and New Zealand

Environment Conservation

Council

APB Agriculture Protection Board

(Western Australia)

APCB Animal and Plant Control

Board (South Australia)

APCC Animal and Plant Control

Commission (South Australia)

ARRI Aboriginal Rural Resources

Initiative

BRS Bureau of Resource Sciences

CaLM Department of Conservation

and Land Management (New

South Wales)

CALM Department of Conservation

and Land Management

(Western Australia)

CCNT Conservation Commission of

the Northern Territory

CRC Cooperative Research Centre

(Vertebrate Biocontrol Centre)

CSIRO Commonwealth Scientific and

Industrial Research

Organisation

DCNR Department of Conservation

and Natural Resources

(Victoria)

DPIF Department of Primary

Industry and Fisheries

(Tasmania)

DSE Dry sheep equivalent

ERIN Environmental Resources

Information Network

ESD Ecologically Sustainable

Development

ESP Endangered Species Program

GIS Geographic information

system

GMAC Genetic Manipulation

Advisory Committee

Landcare Commonwealth Landcare

Program

LandCare Victorian Landcare Program

NCA Nature Conservation

Authority

NCCAW National Consultative

Committee on Animal Welfare

NFF National Farmers’ Federation

NLP National Landcare Program

NPWS National Parks and Wildlife

Services (various states)

NRIC National Resource

Information Centre

NRMS National Resource

Management Strategy

NSCP National Soil Conservation

Program

NSWAF NSW Agriculture and Fisheries

pers. comm. Personal communication

PMIS Pest management information

system

PPB Pastures Protection Board

ppm Parts per million

RCD Rabbit calicivirus disease

(RCD) also called rabbit

haemorrhagic disease (RHD)

RLPB Rural Lands Protection Board

(New South Wales)

SCARM Standing Committee on

Agriculture and Resource

Management

SCB Soil Conservation Board of

South Australia

SCS Soil Conservation Service of

New South Wales

SSC Strategic, sustained control

SSCAW Senate Select Committee on

Animal Welfare

TAFE Technical and Further

Education

VPC Vertebrate Pests Committee of

SCARM

VPP Vertebrate Pest Program

xii Managing Vertebrate Pests: Rabbits

ACRONYMS AND ABBREVIATIONS

active entrance: a warren entrance that is

being used as distinguished by obvious

rabbit sign

active warren: an occupied warren

acute poison: a substance that kills an

animal quickly, usually within hours,

and after a single dose

anticoagulant: a substance that slows or

prevents blood clotting. Anticoagulants

may be used as poisons to kill pest

animals

antigen: a substance, usually foreign to

the body, that stimulates an animal’s

immune system to make antibodies.

Antibodies react with antigens in the

body and can prevent the development

of disease

biomass: the weight of living material in a

specified area; often the amount of plant

material covering an area of ground

cadastral data: usually includes property

boundaries, land tenure and roads

calcareous: containing or like calcium

carbonate

canids: members of the dog family

cementum: a thin, bonelike tissue that

covers the root of a tooth

conservation values: aspects of the

natural environment that society wants

to protect, such as endangered species,

wilderness and biological diversity

coumarins: a class of chemical

compounds; some of which are used as

vertebrate poisons (anticoagulants)

coupe: a forest plantation management

unit containing trees of the same age

cumulative poison: a poison that builds

up in an animal’s body with successive

doses or continued exposure. Usually

more than one dose is required to cause

death

discount rate: difference in value

between present and future benefits.

Calculating discount rates involves using

the reverse equation to that used for

calculating interest rates on invested

money

dry sheep equivalent (DSE): the number

of animals that eat the same amount of

pasture as a non-breeding, non-pregnant

ewe. For example, 12–16 rabbits are

usually considered to be one DSE

ecotone: boundary region between

different ecosystems, such as between

forest and grassland

ectoparasite: a parasite that lives on the

outside of an animal’s body. Examples

are fleas, ticks and lice

El Niño: name of a warm ocean current

that appears intermittently off the coast

of Ecuador and Peru. This is now

recognised as part of a global climatic

event that happens about every 3–6

years and typically lasts 12–15 months.

It is associated with abnormally dry

weather in much of eastern Australia

enclosure: an area of land fenced round to

keep in wanted animals

endoparasites: parasites that live inside an

animal’s body, such as tapeworms and

the bacteria in the digestive tract

enzyme: a substance that promotes natural

chemical reactions in the body without

itself being used up or changed in the

process

epizootic: the occurrence or outbreak of

a disease in a population or region at

a much higher level than normally

expected

exclosure: an area of land fenced round to

keep out unwanted animals

felids: members of the cat family

Bureau of Resource Sciences/CSIRO xiii

GLOSSARY

fibrin: an insoluble fibrous protein produced

during blood clotting

forb: a soft herb-like plant with a non-woody

stem, especially a pasture plant that is not

a grass

geographic information system (GIS):

a computer-based system for displaying,

overlaying and analysing geographic

information such as vegetation, soils,

climate, land use and animal distributions

gross margin: the difference between the

returns from the sale of a product from

a farming enterprise minus the running

costs. It excludes capital components such

as the purchase of machinery

hypothermia: unnaturally low body

temperature in warm-blooded animals

immunocontraceptive: same as

immunosterilant

immunocontraceptive virus: a virus that

causes an immune response leading to

temporary or permanent sterility in

infected animals

immunosterilant: a substance that triggers

an immune reaction that causes sterility in

a treated animal; acts as a contraceptive

knockdown: a control action that markedly

reduces population size over a short time

LD50: the quantity of a poison that will kill

50% of treated animals

leporids: animals of the rabbit and hare

family

macropores: spaces in the soil that improve

water penetration

mediterranean regions: regions with a

climate similar to Mediterranean Europe,

with hot, dry summers and cool, wet

winters. In Australia these regions are

around Adelaide and south of Perth

metabolic poison: a substance that is toxic

to an animal’s basic body functions

through interfering with biochemical

processes, such as oxygen transport

micro-arthropods: small insects, mites etc.

mustelids: weasels, ferrets etc.

myxomatosis: a disease caused by the

myxoma virus that was introduced to

Australia as a biological control agent for

rabbits. The disease is effective in reducing

rabbit populations in areas of moderate

and high rainfall

neophobia: fear of new objects in the

environment

net present value: discounted present value

of all financial benefits produced by a

project, minus the discounted value of the

costs incurred

one-off control: a control measure that is

implemented only once although it may

have long-term or ongoing effect

parenchyma: essential or specialised

supporting tissue of an organ

phosphorylation: attachment of a

phosphate molecule to sugar groups. An

essential biochemical reaction in plants

and animals

primary poisoning: the death of animals

that ingest the poison (see secondary

poisoning)

quadrats: small plots of land used for sample

measurements of such items as plants or

dunes

rabbit calicivirus disease: an exotic viral

disease that causes high death rates in

rabbits. It is presently being investigated as

a potential biological control agent for

rabbits in Australia. Also called rabbit

haemorrhagic disease

run-on areas: places where water tends to

accumulate and which are moister and

more productive than surrounding areas

scat: faeces

second generation anticoagulant: a new

class of anticoagulant poison developed to

control pests that have developed

resistance to first generation

anticoagulants. Warfarin and pindone are

first generation. Bromodialone and

brodifacoum are second generation. In

contrast to first generation anticoagulants

repeated ingestion may not be necessary

to cause death

secondary poisoning: intoxication or death

of animals caused by ingestion of other

poisoned animals

senescent: post-reproductive age

sign: any evidence of the recent presence of

an animal such as dung, scratch and dig

marks etc.

spotlight transect counts: a count of the

number of nocturnal animals seen in the

beam of a spotlight along a set or random

xiv Managing Vertebrate Pests: Rabbits

transect. An estimate of population density

can be extrapolated from this based on the

length/width of the transect

squat: a shallow depression in long

vegetation or under fallen timber where

a rabbit takes shelter

sterilising agent: a substance that causes

treated animals to become sterile; a

contraceptive

stop: a shallow burrow dug by a pregnant

female rabbit in which to have her litter.

The entrance to a stop is covered with soil

and is difficult to detect

tarbaby: a technique for killing rabbits

where 1080 poison in grease is squirted

into a rabbit warren. The rabbit dies from

ingesting the poisoned grease while

grooming the grease from fur and paws

thermoregulation: control of body

temperature using a combination of

external (e.g. the sun) and internal heat

sources (metabolism)

total grazing pressure: the amount of

pasture removed by all grazing animals

present, including wildlife, domestic stock

and insects. In practice, insects are usually

not included in the calculation

transect: a rectangular plot in which data

collection occurs

type locality: site at which the original

specimen used to describe a species was

collected

Note: All money values throughout the

guidelines are in 1993-94 Australian dollars

unless otherwise indicated.

Bureau of Resource Sciences/CSIRO xv

SUMMARY

The intro duced European rabbit

(Oryctolagus cuniculus) is one of the most

widely distributed mammals in Australia

and, except for the house mouse (Mus

domesticus), the most abundant. Rabbits

occur mainly south of the Tropic of

Capricorn, and almost anywhere except at

the highest altitudes, in dense forests or on

poorly drained soils.

Rabbits are a major environmental and

agricultural pest. Damage to the

environment is particularly significant in

semi-arid and subalpine areas where rabbit

and sheep grazing has fundamentally altered

the ecosystems. Rabbit control poses a

significant animal welfare concern.

These guidelines contain a comprehen-

sive review of the history of rabbits in

Australia, their biology, the damage they

cause, and past and current management.

The attitudes of animal welfare groups,

commercial, recreational and Aboriginal

rabbit users, and other interest groups are

examined. The authors recommend

management techniques and strategies for

control, illustrated by four case studies.

Deficiencies in knowledge, management

and legislation are identified. The guidelines

are an essential reference and management

guide for policy makers, land managers and

others interested in rabbit management.

Why develop national guidelines?

These guidelines for managing the impact

of rabbits have been developed under the

Vertebrate Pest Program (VPP) which is

administered by the Bureau of Resource

Sciences (BRS). The project has been

coordinated by the Vertebrate Pests

Committee (VPC) of the Standing Committee

on Agriculture and Resource Management

(SCARM). These rabbit guidelines were

funded by the VPP and the CSIRO. Similar

guidelines have been published for feral

horses, and others are being prepared for

foxes, feral goats, feral pigs and rodents.

The purpose of the guidelines is to assist

the development of strategies to reduce the

damage rabbits cause to production and

conservation values using the most cost-

effective approaches. Ideally, such strategies

are based on reliable, quantitative

information about the damage caused by

the pest, the cost of control measures, and

the effect of implementing control on

reducing the damage. Despite many decades

of rabbit research we have little reliable

information of this type for rabbit

management. In developing these

guidelines, the authors have used all

available information, but they have also

had to make assumptions about rabbit

impact and the efficacy and cost-

effectiveness of control techniques. These

assumptions may need to be changed when

more reliable information becomes

available.

The rabbit problem

The results of the many scientific and other

studies conducted on the effects of rabbits in

Australia indicate that they are probably our

most serious vertebrate pest, affecting

agriculture, the pastoral industries and the

environment.

There are no reliable figures for the national

cost of rabbits to agriculture, but the annual

loss to the pastoral region of South Australia

alone is estimated at $20 million (1993-94

dollars, as are all money values in these

guidelines unless otherwise indicated), an

estimate that would be much higher if the

reduction in production due to progressive

deterioration of the land could be calculated.

The effect on production is most apparent in

drier areas where pasture production is low

and rabbit numbers increase to high densities

and compete with stock. In most higher

rainfall areas rabbits can be managed, and

are regarded as a moderately expensive

nuisance to agricultural production, rather

than a serious economic pest.

The serious impact of rabbits on native

flora and fauna is now becoming recognised.

Rabbits directly compete with many native

Bureau of Resource Sciences/CSIRO 1

animals for food and shelter and have

extensive effects on native flora through

ringbarking, grazing and browsing. The

overall effects of rabbits on biodiversity are

largely unquantified, though many species of

vertebrates and invertebrates that depend on

the vegetation damaged by rabbits are likely

to be affected.

In the arid zone, rabbit densities below

one rabbit per hectare can prevent

regeneration of some native plants. The

progressive deterioration of rangeland

ecosystems may not be obvious because

many trees and shrubs are long-lived. Mulga

(Acacia aneura), for example, can live for

250 years. Tree and shrub populations

become senile where rabbits destroy all

seedlings. If rabbits are not reduced to very

low numbers in these regions, the decline in

native trees and shrubs through lack of

seedling recruitment will continue. The

potential ecological consequences of this

decline are expected to include increased

erosion and changes to plant and bird

communities. There may be no safe rabbit

density for some tree and shrub seedlings.

Because other pests, domestic stock and

native herbivores are also involved in

browsing and grazing native plants,

conserving biodiversity in the rangelands will

require management of the total grazing

impact by all these species.

Rabbits also have an impact on

conservation values in higher rainfall areas.

For example, rabbits at a density of three per

hectare prevented regeneration of sheoak

(Allocasuarina verticilliata) and sallow wattle

(Acacia longifolia) in the Coorong National

Park on the coast of South Australia. The effect

of rabbits in modifying vegetation in

conservation areas, however, has not been

sufficiently evaluated for higher rainfall areas

and may be unrecognised. It requires long-

term evaluation.

Why do rabbits prosper in

Australia?

Rabbits have a high reproductive potential.

Adult females produce 15–40 young a year,

but only 1–10% survive past the first year.

The key to the success of the rabbit in

Australia is the warren, which provides

protection from weather and predators and

enables rabbits to inhabit semi-arid and arid

country. Contrary to popular belief, rabbits

do not dig new warrens readily. Although

they usually live in warrens, rabbits readily

live above the ground whenever there is

adequate shelter. In some areas a high

proportion of adult rabbits live mostly above

ground, such as the coastal scrub in south-

western Western Australia and parts of

Tasmania.

Another reason for the success of the

rabbit in Australia is the absence of some

diseases and parasites that keep its numbers

in check in other countries. Moreover, the

generally dry climate in Australia constrains

the parasites that are present. Compared

with Europe and America, Australia has few

predators and, in particular, lacks wild

mustelid species (Mustela spp.) such as

weasels and ferrets, which kill young rabbits

in warrens.

Factors affecting rabbit numbers

Rabbit populations in most of Australia

fluctuate mainly in response to variation in

rainfall. In the drier rangelands, rabbit

numbers increase during favourable seasons

and decline during droughts to around 1%

of peak numbers. Therefore long-term

trends are difficult to identify. In some higher

rainfall areas, rabbit numbers have fallen in

recent years because of cropping, warren

ripping and property development. Rabbits

often remain abundant in habitats where

they are difficult to control, such as rocky

hills and other refuges.

After the introduction and establishment

of the virus causing myxomatosis in the early

1950s, rabbit numbers fell dramatically, and

rabbits died out in some marginal habitats.

The impact of the disease was greatest in

the semi-arid areas where the carriers

(vectors) of the virus, mosquitoes, are

seasonally abundant. The impact was less

in those areas where there are few

2Managing Vertebrate Pests: Rabbits

mosquitoes, such as Tasmania, Western

Australia and some tableland regions. The

introduction in 1968 of the European rabbit

flea (Spilopsyllus cuniculi), an alternative,

more perennial vector, resulted in large

reductions in rabbit populations in

Tasmania, south-western Western Australia,

on tablelands, and in parts of South

Australia. The 1993 introduction of an arid-

adapted Spanish flea (Xenopsylla

cunicularis) is intended to cause similar

reductions in the drier rangelands, and its

spread and efficacy are currently being

evaluated.

The efficacy of myxomatosis declined in

the 1950s but has remained more or less

constant since then and myxomatosis still

plays a major role in limiting rabbit numbers.

The present density of rabbits in Australia

compared to the situation before

myxomatosis was introduced is not known.

On average, rabbit numbers are thought to

be about 5% of premyxomatosis abundance

in the higher rainfall areas and perhaps 25%

in the rangelands. Although the resistance

of rabbits to the virus has increased, this has

probably been balanced by the evolution

of more virulent strains of the virus. The

effectiveness of myxomatosis in the long

term cannot be predicted, so no reliance

should be placed on its continued efficacy.

Development of a strategic

management approach

Colonial governments and their successors

relied on stringent legislation requiring

landholders to undertake control. Various

techniques were used, including shooting,

poisoning, fencing, and even the intentional

spread of predators such as cats. Most

techniques were relatively ineffective,

although with determination and

persistence, and using rabbit-proof fences

as boundaries, some landholders achieved

sustained, low rabbit densities and

occasionally complete local eradication.

Most evidence indicates that successful

rabbit management requires integrated

action at the state, regional and local level.

Land managers need a clear understanding

of techniques and goals and they need to

accept responsibility for the action required.

Extension programs increase general

awareness and understanding of the damage

rabbits cause and what can be done to

alleviate the problem. An essential part of

raising public awareness will be well-trained

and motivated state and territory workers.

Technical and Further Education Colleges

can have an important role in training

people in techniques of extension, damage

assessment and control.

What is the strategic approach?

The emphasis in these guidelines is not on

killing rabbits, but rather on their efficient

and strategic management to reduce the

damage they cause to production and

conservation values in the most cost-

effective way. Rabbits are but one factor in

a complex and changing agricultural

environment that includes a highly variable

climate, fluctuating commodity prices, other

animal and plant pests, farm stock and the

profitability of farming businesses. Farmers

need to consider investment in rabbit

management in the context of investment

in other areas of the farm business unit.

Rabbits also need to be considered in

relation to their impact on natural and semi-

natural ecosystems, and on the biodiversity

within them.

A strategic approach to the management

of rabbits developed in these guidelines is

based on four key activities:

Defining the problem — The problem should

be defined in terms of rabbit damage and

the reduction in rabbit density required to

reduce or prevent the damage.

Developing a management plan — Land

managers must establish clear objectives

in terms of the desired production or

conservation outcome sought. Options for

rabbit management include local

eradication, strategic management, crisis

management and no management.

Eradication will rarely be a feasible goal.

Bureau of Resource Sciences/CSIRO 3

These guidelines strongly recommend

sustained, strategic management as the

principal management option.

Implementing the plan — A local or regional

approach to rabbit management is usually

most effective. This generally requires

coordinated action by individual property

owners and government and other agencies.

Monitoring and evaluating the program —

Monitoring has two aspects. Operational

monitoring assesses the efficiency of the

control operation. Performance monitoring

involves gathering information to determine

whether the strategy is meeting the desired

long-term production or conservation goal.

Community attitudes

Various segments of the community see

rabbits either as appealing characters from

cartoons and literature, a commercial

resource, a subsistence food source, an

animal welfare concern or a major pest. It

is unlikely that these deeply held attitudes

can be changed quickly, but the public

needs to understand the damage caused by

rabbits and its implications. Scientists and

state and territory land management

agencies must communicate to legislators,

land managers, landholders and the public

the damage caused by rabbits and ensure

these people have sufficient information to

make appropriate rabbit management

decisions.

Rabbits as a resource — Rabbits are

harvested in the wild and domestic rabbits

are farmed for food and raised as pets and

show animals. The associated industries

are small; for example, the annual value

of wild rabbit harvesting is estimated to

be about $10 million. The promotion of

wild harvesting and other forms of

commercial use may inhibit effective rabbit

management through, for example,

providing a case against the introduction

of new biological control agents. The

authors believe the commercial use of wild

rabbits has no role to play in managing

rabbit impact, mainly because wild rabbit

harvesting is usually from high density

rabbit populations, and this will not reduce

densities to a level where damage is

effectively managed.

Aboriginal use of rabbits — Some Aboriginal

groups include rabbits as a major part of

their diet and perceive them as an integral

part of the land. It is important that

Aboriginal communities have access

to information on the long-term

consequences of high rabbit numbers,

which may include loss of traditional

values as well as ecological impacts. State

and territory land management authorities

need to work closely with Aboriginal

people to assist them to make land-use

decisions which meet their needs and

enable ecologically sustainable land use.

Animal welfare — Some rabbit control

practices are inhumane. The steel-jawed

trap should be banned. The fumigant

chloropicrin should be phased out once

a more humane alternative is found. While

some suffering must be expected with the

use of techniques recommended in this

report, their strategic application would

minimise suffering by maintaining reduced

rabbit populations, thereby minimising the

need for repeated treatments.

Myth of the super bug — The success of

myxomatosis in the 1950s has caused

unrealistic expectations of biological

control. Consequently many land

managers may not put much effort into

conventional rabbit management because

of high hopes of future control by new

biological control agents such as

myxomatosis transmission via the arid-

adapted Spanish flea, rabbit calicivirus

disease (RCD), also called rabbit

haemorrhagic disease (RHD), and virally-

borne immunocontraception. Release of

such new agents will be years away,

however, even if these research projects

succeed. Virally vectored immuno-

contraception in particular, is long-term

high risk research, and it is too early to

predict whether it will be successful. New

techniques will only complement, not

replace, conventional control, and the

4Managing Vertebrate Pests: Rabbits

challenge will be to use conventional

control techniques to take maximum

advantage of lowered rabbit densities

following biological control. Maintenance

control was rarely undertaken after the

release of myxomatosis. Land managers

cannot afford to rely on the potential of

new agents to save them from action now.

Impact assessment methods

There is a pressing need for low-cost

techniques to assess rabbit impact. At

present, managers usually rely on estimates

of rabbit abundance as an indicator of

damage. There are risks in this approach

because rabbits, at densities almost

undetectable to a casual observer, can

prevent regeneration of some native plants.

Thus, the perception of low numbers may

give an inaccurate measure of impact.

Rabbit distribution and abundance is best

estimated from counts of semi-permanent

features such as warrens and burrow

entrances; these counts also indicate the

proneness of the land to rabbit infestation.

They are not suitable, however, where

rabbits are mainly surface dwelling. Here,

techniques such as dung and spotlight

transect counts must be used, and these are

less reliable.

Rabbit management techniques

Maps which show the relationship between

distribution and abundance of rabbits and

topographic, soil and other land features

are an invaluable aid to planning and

implementing rabbit management.

Over most of Australia where rabbits use

warrens, the primary control technique

involves destroying warrens and associated

refuges, possibly after initial poisoning if

rabbit densities are high. Following primary

control, sustained maintenance control by

warren ripping or by fumigation is essential.

Using dogs to drive rabbits underground

increases the effectiveness of ripping and

fumigating. Poisoning without maintenance

control provides only short-term relief. The

primary role of poisoning is to reduce rabbit

density before warren ripping. When rabbit

populations are reduced by drought or

myxomatosis, managers should take

advantage of the reduced rabbit populations

to apply other control techniques, to further

reduce and maintain the low densities.

Management is more difficult where a

proportion of rabbits dwell on the surface,

a situation more common than was

previously realised. Poisoning and, where

practicable, refuge destruction are important

techniques. A major risk with repeated

poisoning is the development of bait and

poison avoidance, as has occurred in

Western Australia and New Zealand.

Impact of rabbit control on native

wildlife

Predator–prey interactions are complex and

little is known about those involving

changes in the abundance of rabbits. The

following hypotheses are based on

ecological theory and limited experimental

and anecdotal knowledge. Field

experiments are needed before more

reliable predictions can be made.

When rabbit numbers are greatly

reduced, foxes and cats may turn to native

wildlife as alternative prey in the short term.

Such increased predation may occur after

widespread rabbit control and is similar to

the recurrent increased predation which

occurs after droughts and myxomatosis

outbreaks. Since rabbits are the primary food

of foxes and cats in most of Australia, a long-

term reduction in rabbit density might also

reduce fox and cat densities, and so reduce

their effect on wildlife in the longer term.

Reduced grazing pressure from rabbits might

also allow vegetation to recover which could

increase habitat and shelter for wildlife and

so reduce predation. Reducing rabbit

numbers could also reduce numbers of

native birds of prey, as rabbits are the main

food of many raptors during their breeding

seasons. On the basis of these hypotheses,

fox and cat control should be implemented

following rabbit control in areas containing

Bureau of Resource Sciences/CSIRO 5

susceptible, rare or threatened native

species. More information may enable these

procedures to be modified.

Strategies for reducing rabbit

damage

These guidelines describe strategies for

managing rabbits in four classes of land use:

• high production cropping and grazing

land;

• low production rangeland;

• forestry plantations; and

• conservation areas.

The management option recommended

for all classes of land use is sustained, strategic

management. Ideally, rabbit management

aims to reduce rabbit damage to the level

where the benefits of management are

greatest relative to the costs. This approach

requires knowledge of the relationship

between rabbit density and the costs and

benefits of management. This is difficult and

costly to determine, and it is unlikely that the

rabbit, with its high reproductive potential,

could be managed with this degree of

precision.

For most circumstances, it is assumed that

rabbit damage is related to rabbit density,

although it is recognised that there is not

always a direct correlation between rabbit

numbers and levels of damage. For example,

there is evidence that in the rangelands of

New South Wales, competition between

sheep and rabbits only occurs when pasture

biomass is less than 250 kilograms per hectare.

The relationship between rabbit density and

level of damage will vary with both the type

of damage being considered and other factors,

such as the total grazing impact from all

species and variation in the vegetation cover.

This has implications for the selection of

appropriate management strategies for rabbits

in relation to different land uses and changes

in market prices for wool, other commodities

and for conservation values which are affected

by rabbits.

In the authors’ opinion, based mainly on

the experience of state rabbit control

authorities, data from small-scale field trials,

and on rabbit population ecology, reducing

and maintaining rabbit populations at

minimum densities is more likely to be

successful and profitable for damage

management than some lesser level of

control to densities from which rabbit

populations can rapidly rebound. Even

where resource damage only occurs when

rabbit numbers are high, it may still be most

cost-effective to maintain rabbits at very

low densities at all times. Such a strategy

could bring the greatest benefits at the onset

of drought, when the impact of rabbits on

both production and conservation values

is likely to be high, and when land

managers may have inadequate time, labour

or funds to mount a rabbit control program.

The relative cost-effectiveness of aiming for

sustained minimum levels as a long-term

strategy will depend on the cost of this level

of rabbit control relative to the benefits

resulting from the control, in comparison

to the cost–benefit ratios of some lesser

level of control or no control. The initial

extra cost of achieving very low rabbit

numbers could be offset by the reduced

costs of continuing control to maintain these

low numbers and reduced impacts.

Strategic, sustained management (SSM) to

reduce and maintain rabbits at minimum

densities is most likely to be profitable in

places where uncontrolled rabbit densities

would usually be moderate or high (greater

than three rabbits per hectare).

Rabbit control to achieve and maintain

minimum densities is also likely to be

profitable in conservation reserves where a

high value is placed on the resources being

protected from rabbit damage. In the

rangelands, the high cost of reducing rabbits

to very low densities might prevent this from

being a feasible goal. Although there may

be high benefits from rabbit control in such

areas, in terms of increased wool clip and

land values, the large areas involved mean

that initial control costs may be high and

land managers may lack sufficient funds,

especially at times of low wool values.

Rabbit control to increase production may

not be profitable in areas which naturally

6Managing Vertebrate Pests: Rabbits

have low rabbit densities (less than one rabbit

per hectare). More information on the

relationships between rabbit density and

damage, and between control costs and

benefits, is needed for assessments of the

most effective strategies for rabbit

management for different areas and land uses,

and on the best approaches for integrating

rabbit management with other property

operations.

A goal of reducing rabbit numbers to as

close to zero as possible and then maintaining

them at that level has the advantage of

providing land managers with a clear, readily

monitored, long-term goal. This may counter

any tendency of land managers to develop

tolerance to rabbits which could undermine

efficient long-term management. Land

managers need to be committed to a long-

term strategy for a successful outcome.

Wherever practicable, SSM includes

assessing the effectiveness of the management

program in reducing rabbit damage, especially

when aiming to protect conservation values.

Local eradication is achievable only in

special situations such as on small islands and

on properties protected by natural barriers or

rabbit-proof fences and monitored

continuously for reinvasion by rabbits.

Economic frameworks need to be

developed to assist in the assessment of the

relative value of alternative control strategies

whenever this is feasible. Such frameworks

require: definition of the economic problem;

data on the relative costs and benefits; an

understanding of why the actions of individual

landholders may not lead to optimal rabbit

management; assessment of the means by

which governments can overcome identified

market failures; and an assessment of the

likely returns from alternative rabbit

management strategies.

Implementing rabbit management

For effective rabbit management, land

managers must be motivated by an

awareness of potential or actual rabbit

damage. They need to know what can and

should be done to alleviate it, and to be

involved at all stages of the management

process: planning, implementation,

monitoring and evaluation. State and

territory pest management authorities with

appropriately trained field staff operating

at the regional and local level have a

primary role in motivating landholders to

take appropriate action. Locally-based

schemes such as Landcare groups are a

primary means for governments to work

with landholders. Successful examples of

this approach include the Bathurst Scheme

and the Pine Creek Rangecare Group.

Further studies are required, however, to

determine the essential elements of

successful schemes, and whether these will

continue to operate after government

assistance is withdrawn.

Public lands — Governments manage large

tracts of land infested with rabbits. While

private landholders are required by

governments to manage rabbits, there is

often no such obligation on governments.

Private landholders see this as inequitable.

As a minimum, governments should

manage and maintain an adequate buffer

zone between public and private land to

protect adjacent properties. If there are

insufficient resources for effective,

sustained management across all public

land, efforts should be concentrated in

high-value areas.

Legislation — Legislation should clearly

state the responsibility of land managers

for rabbit management and facilitate

appropriate action. Equally important is

the ability and commitment to enforce the

legislation. Legislation is also needed to

regulate the use of toxic chemicals.

Who should implement control? — Many

aspects of rabbit management require

trained, experienced advisers and

operators. While some landholders and

land managers have skills in rabbit

management, those without such skills

may wish to be trained. Where this is

impracticable, hire of government services

or use of contractors is an alternative.

Bureau of Resource Sciences/CSIRO 7

Training — States and territories which do

not have the resources and expertise to

train field staff may be able to access

training programs in states such as South

Australia and Western Australia, which

could recover costs for this service.

Training in rabbit control needs to be part

of integrated vertebrate pest management

which, in turn, is part of a holistic

approach to management. This document

and the associated documents on other

vertebrate pests may be useful in training

vertebrate pest managers.

Research needs

The basic biology of the rabbit is well known.

Less is known about the interaction between

rabbit numbers and production losses and

disruption of ecosystems. Research priorities

are:

Impact — (1) Rangelands: measure rabbit

impacts on native vegetation including

regeneration, and on pastoralism; (2)

rangelands and cropping areas: quantify the

relationship between rabbit density and

impact; and (3) conservation areas: measure

rabbit impact on native vegetation, including

regeneration, and on fauna for all climatic

regions.

Monitoring — Develop low-cost techniques

for rapid assessment of: (1) rabbit impact on

crops, native vegetation, native fauna and

soil; and (2) rabbit abundance where

warrens and burrows are little used by

rabbits.

Economics — Determine cost–benefit analyses

of different levels of rabbit control for both

cropping and grazing lands. Examine the

cost-effectiveness of various combinations

of control techniques and prescriptions for

control.

Traditional control — Determine optimal

methods for controlling rabbits that live in

scrub, rocky areas and on steep slopes;

improve humaneness of techniques,

particularly fumigation; improve baiting

techniques and target specificity; develop

alternative toxins; reduce impact on

predators and native fauna; and improve

integration with other farm management

practices.

Biological control — Further development of

myxomatosis and rabbit calicivirus disease

(RCD): host/vector/virus interactions; strain

variants and manipulation; mass production

of virus; and improved knowledge of

transmission by vectors.

Creating an appropriate adminis-

trative environment

An appropriate administrative environment

is crucial to the success of strategic rabbit

management. The following are key

activities:

• Review the adequacy of existing

legislation, policies and institutional

arrangements for the formulation and

delivery of programs for managing

rabbits and other vertebrate pests at all

levels of government.

• Improve humaneness by prohibiting

steel-jawed traps and phasing out

chloropicrin.

• Review and improve effectiveness of

support for Landcare groups and other

land management groups, consistent

with the National Landcare Program.

• Review policies on land subdivision.

• Investigate introduction of caveats on

land titles relating to removal of rabbits.

• Investigate means by which financial

institutions can value effective rabbit

management as capital improvement of

property values.

Training and extension

Attention to training and extension is

essential, with the following as key

activities:

• Update training courses and manuals

on vertebrate pest management to

include information contained in these

guidelines and to integrate rabbit

management with other aspects of land

and property management through the

property planning process.

8Managing Vertebrate Pests: Rabbits

• Investigate feasibility of courses on

rabbit control being included in the

curricula of appropriate tertiary

institutions.

• Coordinate approaches of the various

states and territories to cooperate on

development of pest management

information systems, and on interstate

training of vertebrate pest control

officers.

Enlisting community support

Rabbit management in Australia needs

widespread public support for success;

education is the key to this. Educational

packages for schools should be reviewed

and, where necessary, expanded or

improved.

Extension and advisory services to

Landcare and other land management

groups should be augmented. These

services are essential to improve community

and land manager understanding of research

findings, to engender a sense of ownership

of the problem and to place rabbit damage

in the context of ecologically sustainable

development.

Bureau of Resource Sciences/CSIRO 9

INTRODUCTION

These guidelines for managing the impact

of rabbits have been developed under a

project managed by the Bureau of Resource

Sciences (BRS) and coordinated by the

Vertebrate Pests Committee (VPC) of the

Standing Committee on Agriculture and

Resource Management (SCARM). The

project is funded by the BRS and the CSIRO.

Similar guidelines have been published for

feral horses, and others are being prepared

for foxes, feral goats, feral pigs and rodents.

These guidelines are primarily for state and

territory land management agencies to use in

consultation with private land managers and

other interest groups, to prepare state,

regional and local strategies for reducing the

impact of rabbits on agricultural production

and the environment. The guidelines should

be read and used in conjunction with

Managing Vertebrate Pests: Principles and

Strategies (Braysher 1993), which explains

why the guidelines were developed, their

aims, the development process, their use and

the principles of pest management.

Various interest groups were consulted

during preparation of these guidelines,

notably state and territory land management

agencies, the National Farmers’ Federation

(NFF), the Australian Conservation

Foundation (ACF), the National Consultative

Committee on Animal Welfare (NCCAW), the

Australian Veterinary Association (AVA), and

the Anangu Pitjantjatjara Aboriginal Land

Council.

Effective rabbit management, particularly

in the rangelands, is central to the success

of a number of Commonwealth Government

conservation programs, including the

Ecologically Sustainable Development (ESD)

Strategy, the Endangered Species Program

(ESP) and the Decade of Landcare (which

incorporates the National Resource

Management Strategy (NRMS), the National

Landcare Program (NLP), and the One

Billion Trees and Save the Bush Programs).

Consistent with the holistic approach to

land management advocated under the

Ecologically Sustainable Development

Strategy and Landcare, all the management

guidelines for feral animals, including this

one, consider interactions between all pests,

other species and aspects of land

management. A holistic and integrated

approach to management is necessary for

Australia’s rangelands, where rabbits and

many other vertebrate pests are common.

The guidelines should assist state and

territory land management agencies to more

effectively manage pest damage through

better coordination, planning and

implementation of regional and local

management programs. Achieving the

strategic management of rabbits and other

pest animals involves four key components

(Figure 1):

Defining the problem — Ideally the problem

should be defined in terms of rabbit damage

and the reduction in rabbit density required

to reduce or prevent the damage.

Unfortunately the relationship between

rabbit density and damage has not been

quantified in most cases. Until research

establishes this relationship, most managers

will rely on measuring the abundance and

distribution of rabbits or warrens, and

assume that damage is directly related to

rabbit abundance.

Developing a management plan — Land

managers must establish clear objectives in

terms of the desired production or

conservation outcome sought. Options for

rabbit management include local

eradication, strategic management, crisis

management and no management.

Eradication will rarely be a feasible goal.

These guidelines strongly recommend

sustained, strategic management as the

principal management option. The choice

of initial and maintenance control

techniques in the management strategy will

depend mainly on whether the rabbits

shelter in surface cover or in underground

warrens or burrows.

Implementing the plan — A local or regional

approach to rabbit management is usually

most effective. This generally requires

Bureau of Resource Sciences/CSIRO 11

coordinated action by individual property

owners and government and other agencies.

Monitoring and evaluating the operation —

Monitoring has two aspects. Operational

monitoring assesses the efficiency of the

control operation. Performance monitoring

involves gathering information to determine

whether the strategy is meeting the desired

long-term production or conservation goal.

Both forms of monitoring help determine

whether the management strategy should

be modified.

In most cases, rabbit impact on one

property or area is influenced by their

presence in neighbouring properties or

areas. Thus the problem is often one that is

shared by many people or agencies who

need to cooperate to find a solution.

The objective of these guidelines is to

change rabbit management from crisis

management by individuals and agencies

to strategic management based on

cooperative action. Adopting a whole

property approach to management,

preferably linked to a regional or total

catchment plan, is advocated. The strategic

approach to rabbit management involves

encouraging a group approach in an initial

control campaign and following this with

sustained control measures.

The criterion for success of these

guidelines will be the acceptance and

implementation of the strategic management

approach to the rabbit problem by a

significant number of agencies and

individuals.

12 Managing Vertebrate Pests: Rabbits

Defining

Problem

(Section 9.2)

• real or perceived

• define harmful

•impact

– economic

– environmental

• mapping

• measure and

•assess impact

Management

Plan

(Section 9.3)

• objective

• management

•options

– local eradication

– strategic

–management

– crisis

–management

– no management

• performance

•criteria

• allocating

•management

•units

• management

•strategy

Implementation

(Section 9.4)

• group action

– ownership

• whole farm/district

• government role

Monitoring

(Section 9.5)

• operational

•efficiency

• performance

•against objectives

• evaluation

•of outcome

Strategic management of rabbits at the national level

Figure 1: Strategic approach to managing rabbit damage.

To encourage the adoption of ‘best

practice’ pest management, the Govern-

ment, in its Environment Statement of

December 1992, provided increased

resources to the Vertebrate Pest Program

(VPP) to complete preparation of the

guidelines for managing Australia’s major

vertebrate pest species and to establish key

demonstration projects to facilitate adoption

of best practice pest management. Projects

will draw on the management strategies

outlined in the relevant guidelines for each

species. For most species, including rabbits,

it is anticipated that best practice will evolve

based on experience gained from

undertaking strategic management. Using

the management system to refine the pest

management strategy is called learning by

doing. Each of the guidelines will be

reviewed periodically as knowledge of the

strategic management approach increases.

It is expected that community-based

groups will become increasingly involved

in the strategic management of vertebrate

pests. The guidelines are designed to

facilitate the ownership of the pest problem

by such local groups, and the management

strategy which might be developed and

implemented based on them. Accordingly,

preference in funding under the VPP is given

to projects which involve collaboration

between a number of appropriate

government and/or non-government

agencies and involve community-based

groups in their design and implementation.

The VPP supports projects which address

the impact pests have on primary

production. The complementary Feral Pest

Program administered within the Australian

Nature Conservation Agency (ANCA) gives

priority to strategic pest management in

areas primarily used for conservation. There

are strong linkages between the programs,

and projects which address both agricultural

and conservation damage due to pests may

be jointly funded.

Note: All money values throughout the

guidelines are in 1993-94 dollars unless

otherwise indicated.

Bureau of Resource Sciences/CSIRO 13

PART ONE

HISTORY, DISTRIBUTION AND BIOLOGY

1

1. History of

Introductions and

Spread

Summary

During the last ice age the range of the

European rabbit contracted to the warmest

parts of southern Spain and France. The

rabbit appeared to be a disappearing species

before man reversed its fortunes so

dramatically. It is now found over most of

Europe, on three other continents and on

more than 800 islands.

In mainland Australia rabbits established

near Geelong in Victoria following the first

known release of wild stock in 1859. Their

spread was rapid and was aided by the

presence of burrows of native species, the

paucity of predators, the modifications to

the natural environments made for farming

and occasionally by their deliberate

transport.

1.1 Europe

Members of the family Leporidae (rabbits

and hares) first appeared in the late Eocene

(40–70 million years ago) in Asia and North

America (Dawson 1981) and arrived in

Europe during the Miocene (10–25 million

years ago). The genus Oryctolagus was first

recorded in Spain during the middle

Pliocene period. Two European subspecies

have been distinguished, O. cuniculus

cuniculus from southern France (average

adult weight 1500 g) and O. cuniculus

huxleyi from Spain (average adult weight

1000 g). Recent evidence based on

mitochondrial DNA has revealed that the

two subspecies diverged more than one

million years ago (Biju-Duval et al. 1991).

During the last ice age the European rabbit

was largely restricted to the warmest parts

of Spain and southern France and its major

spread did not commence until historical

times. Domestic rabbits were derived from

the French subspecies by monks some time

between the fifth and tenth centuries

(Sandford 1992).

Rabbits were introduced to England

from France soon after the Norman

conquest in the eleventh century. Rabbits

remained scarce outside rabbit farms

(called warrens) until the nineteenth

century. At that time free-living

populations increased due to changes in

farming practices, the planting of

hedgerows and an increase in the mortality

of rabbit predators due to hunting by the

nobility and trapping by tenant farmers.

Colonisation took some 900 years in

England and Wales and was still not

complete in Scotland in 1950 (Sheail 1971).

The Spanish subspecies was transported

around the eastern Mediterranean as early

as 1500 BC by Phoenician traders. In Roman

times Spain was renowned for its rabbits and

the name of the country ‘Hispania’, later

‘Espana’, is thought to be derived from a

Semitic word denoting rabbits. In the first

century BC, the inhabitants of the islands of

Minorca and Majorca asked Emperor

Augustus for the help of the Roman army in

controlling the impact of rabbits on their

crops and trees (Barrett-Hamilton 1911;

Harting 1986). The French subspecies of

rabbit were often liberated on islands to

provide food for shipwrecked sailors; they

are now present on some 800 islands

throughout the world (Flux and Fullagar

1992).

Free-living rabbits were rare in France in

the sixth century but many colonies were

held in enclosures or on islands for hunting

purposes, and rabbits were often transported

to start new colonies. Introductions were

most successful on islands, perhaps because

of high predator pressure elsewhere. The

rabbit’s colonisation of France was not

completed until the nineteenth century and

range expansion is still occurring elsewhere

in Europe although the species may now be

close to its ultimate limits.

The rabbit was introduced into Italy in the

first century AD but the populations became

extinct. Present populations near Padua,

Milan and Pisa are all the result of recent

introductions. There are no rabbits in Greece

or elsewhere in the eastern Mediterranean

Bureau of Resource Sciences/CSIRO 17

1

although they were undoubtedly introduced

many times. The reasons for the slow rate

of spread and for so many failed

introductions in Europe are unknown.

However, the French subspecies seems to

require intense agricultural and pastoral

development for it to thrive and maintain

itself in the wild.

The relationship of the rabbit to people

is unique. It is farmed for meat and fibre and

is a laboratory animal, a significant pest, a

major game species, a household pet, a story-

book character and a star in animated

cartoons. It is the only farmed animal

domesticated in historical times and the only

pest mammal whose densities have been

much reduced by biological control. The

ownership of rabbits by the Lord of the

manor and the persecution of poachers are

credited with being the main cause of the

radicalisation of the lower classes in England

and a cause of the French revolution

(Hopkins 1985). During the depression in

Australia, and during the second world war

in Europe, the rabbit was the main source

of animal protein for many people. The scale

of the impact of the rabbit in Australia is

considered to be unique in the history of

wild animal introductions.

1.2 Australia

Domestic rabbits arrived in Australia with

the First Fleet in 1788. The first feral

populations were in south-eastern Tasmania

where they numbered in the thousands on

some estates by 1827. The first person to

introduce wild rabbits to the Australian

mainland was Thomas Austin, an

enthusiastic sportsman and member of an

acclimatisation society. He also introduced

hares. Twenty-four rabbits arrived from

18 Managing Vertebrate Pests: Rabbits

Rabbit numbers reached high levels in south-eastern Australia prior to the introduction of

myxomatosis. Bounties and the market for rabbit meat and fur, combined with the high

numbers of rabbits, made rabbit trapping a profitable industry.

Source: NSWAF (duplicated from print: circa 1948, Cowra)

Photo 8*

positional only

England on Christmas Day 1859 and were

put in enclosures at Austin’s property,

‘Barwon Park’, near Geelong. Some were

released or escaped soon after. One of

Austin’s descendants suggests that there

were only 13 rabbits, some of which were

caught in the wild and some of which were

hutch-bred.

‘Domestic rabbits arrived in

Australia with the First Fleet

in 1788.’

In 1866, 14 253 rabbits were shot on

‘Barwon Park’. Initially, rabbits spread

slowly from ‘Barwon Park’ and from a

second release point at Kapunda in South

Australia, taking about 15 years to reach

the New South Wales border (Rolls 1969;

Stodart and Parer 1988). Fifteen years later

they were into Queensland, and by 1900

they were in Western Australia and the

Northern Territory (Figure 2). The rate of

advance varied from 10–15 kilometres a

year in the wet and forested country to over

100 kilometres a year in the rangelands.

The rate of spread was mostly faster than

in New Zealand and in Argentina, where

it was about 10–15 kilometres a year. It was

the fastest rate of any colonising mammal

anywhere in the world (Caughley 1977),

although it was closely matched by the fox

(Vulpes vulpes) and the hare (Lepus

europaeus) in Australia (Jarman 1986a, b).

The fox crossed from Victoria into New

Bureau of Resource Sciences/CSIRO 19

1

0 200 400 600 km

Known frontier of spread

1860 Victoria

Tasmania

1870

1880

1870

1890

1880

1900

1890

1910

1920

1910

New South Wales

Queensland

South Australia

1980

Northern Territory

1910

1920

Western Australia

1920

1910

1890

1920

Tropic of Capricorn

Assumed frontier of spread

Figure 2: Spread of the rabbit in Australia (no data available for Tasmania) (after Stodart and

Parer 1988).

South Wales 13 years after the rabbit and

entered Queensland from the New England

district at the same time as the rabbit; it

entered Queensland in the far west 24 years

after the rabbit.

As in Europe, human changes to the

natural environment made it more suitable

for rabbits. Rabbits moved up river systems,

which were the first areas selected by

pastoralists (Strong 1983). Felled timber

provided abundant rabbit harbour, and the

grazing of perennial grasses by domestic

stock made the grasses more nutritious and

available to rabbits. The introduction of

more nutritious annual grasses and forbs of

Mediterranean origin, which have a seasonal

growth cycle more in tune with the rabbit’s

breeding season, also helped. The

northward spread of rabbits in Queensland

this century is the result of improvements

in the nutritionally poor tropical pastures

and the planting of winter crops (Parer 1987;

Stodart and Parer 1988).

‘The rate of spread of the

rabbit in Australia was the

fastest of any colonising

mammal anywhere in the

world.’

As the Australian environment was

modified by people, many native species

and the hare went through one brief

eruptive phase, but only the rabbit remained

at high densities (Jarman and Johnson 1977;

Lunney and Leary 1988). The presence of

burrows of native species (Vombatus spp.,

Bettongia lesueur, Macrotis lagotis,

Lagorchestes hirsutus) aided its spread, as

did the wholesale destruction of predators.

At ‘Barwon Park’ in 1866 the shooting tally

was 448 hawks, 23 wedgetail eagles, 622

native cats and 32 feral cats (Rolls 1969). In

the early stages of the rabbit’s spread, only

short, shallow warrens were dug, but with

the arrival of the fox deep warrens had to

be excavated (Abbott 1913; Matthams 1921;

Gooding 1956; Tunbridge 1991).

20 Managing Vertebrate Pests: Rabbits

2. Distribution and

Abundance

Summary

Rabbits are one of the most widely

distributed and abundant mammals in

Australia. South of the Tropic of Capricorn

they occur almost everywhere except at the

highest altitudes, in dense forests or on

certain soil types. North of the Tropic of

Capricorn their distribution is more

fragmented, they are often restricted to deep

or shaded warrens on the more fertile soils

in run-on areas, or to areas with a shallow

watertable.

After the introduction of myxomatosis in

1950, rabbit numbers fell by about 95% in

most of southern Australia and by almost

100% in marginal habitats. The impact of

the disease was greatest in semi-arid areas

where mosquitoes are seasonally abundant,

and least in the more arid rangelands and

on the tablelands where mosquitoes are less

abundant. The present density of rabbits in

Australia compared to the density before

myxomatosis is not known. On average,

rabbit densities may be about 5% of

premyxomatosis densities in the higher

rainfall areas and perhaps 25% in the

rangelands. In the more arid rangelands,

numbers increase during favourable

seasons and decline during droughts to

around 1% of peak numbers. Because of

these large fluctuations it is difficult to

discern any long-term trend. In higher

rainfall areas, numbers are generally

decreasing due to the expansion of cropping,

the increased use of warren ripping and

property development. Numbers may be

increasing in some districts in locations

such as rocky hills where control is difficult.

2.1 Distribution in Australia

South of the Tropic of Capricorn rabbits can

occur almost anywhere except in dense

forests, on black soil plains or above 1500

metres (Parker and Bults 1967; Parer and

Libke 1985). North of the Tropic of

Capricorn their distribution is fragmented.

Tall tropical grasslands are nutritionally

inadequate for rabbits, and pasture growth

occurs at the wrong time for rabbit breeding.

In the arid tropics, rabbits must contend

with short breeding seasons, high warren

temperatures, dry pastures on infertile soils

and mineral deficiencies and imbalances

(Cooke 1977a; Parer 1987). In these areas

rabbits also have problems with water

balance and thermoregulation and are often

restricted to deep or shaded warrens on the

more fertile soils in run-on areas, or to areas

with a shallow watertable.

In the more arid areas below the Tropic

of Capricorn, local distributions of rabbits

change dramatically with time. After a run

of good seasons, rabbits may be abundant

over an entire region. During severe

droughts they disappear completely from

some land systems and their range contracts

to refuge areas where there are large, deep

warrens alongside drainage channels or

dried-up swamps (Myers and Parker 1975

a, b).

‘Rabbits prefer well-drained

soils — they are not found in

black cracking soils which

become waterlogged.’

Soils are a major factor influencing local

and regional distribution (Parker et al. 1976;

Parer and Libke 1985). Warrens are larger

and more dense in the deeper soils on lower

slopes and flats. These areas are also the most

productive areas for domestic stock and are

important for drought fodder (Mutze 1991).

Rabbits prefer well-drained soils. Warrens

are never found on black cracking soils which

become waterlogged and the few rabbits

living on this soil type breed in hollow logs.

Warren density is higher on deep sands than

on shallow sands (Matsumoto 1985). This

may be due to fox predation or to

temperature effects (Wood 1980; Parer and

Libke 1985). Rabbits are absent from the

Pilbara and Ashburton districts of Western

Australia due to a combination of shallow

soils and a nutritionally deficient pasture

(Newsome 1975; King 1990).

Bureau of Resource Sciences/CSIRO 21

1

Before myxomatosis, rabbits were not

distributed evenly over southern Australia.

Even in the climatically favourable Riverina

district in New South Wales they were at

moderate or high densities over only 35–40%

of the district (Myers 1962). After

myxomatosis was successfully introduced,

their distribution changed dramatically in

the Riverina. Within a few years they had

almost disappeared from the flat or

undulating country and had retreated to the

well-drained sandy areas or to the rocky,

timbered hills (Figure 3). Similar but

unrecorded changes in local distribution

probably occurred over much of Australia.

Rabbit numbers tend to be low in much

of the sheep–wheat zone. In closely settled

districts, cropping, pasture improvement,

poisoning and warren destruction restrict

high rabbit densities to places where

vehicle access or warren destruction is

difficult.

2.2 Changes in abundance

with time and space

Although rabbit densities are rarely known

precisely, references in this document to

low, medium and high rabbit densities

denote, approximately, less than 1.0, 1–4

and more than four rabbits per hectare

respectively. Spotlight transect counts of

low, medium and high rabbit densities in

open country with low pasture are

approximately less than 5, 6–30 and more

22 Managing Vertebrate Pests: Rabbits

1951 1952 1953 1954 1955 1956 1957 1958 1959 1960

20

80

100

Open flat or undulating country with light timber

Creek frontages and swamps

Stands of pine and box on sandy soils

Habitat types and their infestation (%) Percentage of region infested

0

10

20

30

40

Figure 3: Rabbit infestation trends in different land types in the Riverina district of New South

Wales after the introduction of myxomatosis (after Myers 1962).

than 30 rabbits per spotlight kilometre

respectively.

‘On average, the number of

rabbits in higher rainfall

areas may be 5% of pre-

myxomatosis levels; in arid

areas the figure may be

around 25%.’

In the rangelands where rainfall is less

than 300 mm, numbers build up after a series

of good seasons and then collapse during

drought (Figure 4) (Myers and Parker 1975

a, b; Newsome et al. 1989). The collapse is

due to the low water and energy content in

the available forage and/or to depletion of

available pasture by rabbits and stock.

Numbers may then remain low for some

years. The rate of resurgence depends on

rainfall, predator numbers and warren

availability. In sand dunes 99% of warrens

can disappear in a drought and population

recovery is slower than in stony areas where

warrens are more permanent (Figure 4).

Rabbit densities tend to be higher and

fluctuate less in the more lightly grazed parts

Bureau of Resource Sciences/CSIRO 23

1

0

100

200

300

69686766656463 Year

(c) stony tablelands

Active entrances per km2

0

200

400

600

69686766656463 Year

(d) sand dunes

Active entrances per km2

0

200

400

600

69686766656463 Year

(b) stony plains with massive

red sands

Active entrances per km2Rainfall (mm)

(a) rainfall

Year 6968676665646362616059585756

0

100

200

300

400

500

600

Figure 4: Rainfall and fluctuations in rabbit populations in different land systems in western New

South Wales. Graphs for: (a) rainfall; (b) stony plains with massive red sands (rangelands); (c)

stony tablelands; (d) sand dunes (after Myers and Parker 1975a).

of a paddock that are distant from stock

watering points (Newsome 1993). In semi-

arid areas populations decline but do not

collapse in droughts except locally where

there are very high rabbit populations (Parer

1977).

Besides varying between years, rabbit

populations have an annual cycle. The low

numbers at the beginning of the breeding

season increase by a factor of 2–5 to a peak

towards the end of the breeding season

(Gilbert et al. 1987).

The current density of rabbits in Australia

compared to the situation before

24 Managing Vertebrate Pests: Rabbits

Table 1: Percentage of New South Wales with

rabbits at different levels of abundance (after

Croft 1990).

Density* 1980 1985

Nil 34.7 23.7

Low 33.5 42.0

Medium 21.7 21.7

High 10.1 12.6

* Low: a few holes, some signs of scratching and dung.

Medium: active warrens present, some rabbits visible,

considerable signs.

High: abundant active warrens, many signs, rabbits

visible any time.

Figure 5: Present distribution of the rabbit in Australia. Bold stipple — widespread and common;

light stipple — scattered populations; dots — isolated populations (after Myers et al. 1989). The

density of the rabbit across its range varies considerably over time due to factors such as drought,

myxomatosis and human control.

myxomatosis is not known. Averaged over

good and bad years the numbers in better

rainfall country may be 5% of the

premyxomatosis numbers; in the arid zone

the figure may be 25% (Myers 1962).

Estimates of rabbit densities after

myxomatosis for 27 sites ranged from 2–97

per hectare with an average of three per

hectare (Wood et al. 1987).

In general, high rabbit numbers over

large areas are found only in those areas

where management is difficult or neglected,

or in some rangeland areas where control

is not obligatory (Northern Territory) or

the legislation is not enforced because

control is perceived to be uneconomic.

‘The areas where rabbits are a

major problem for economic

or conservation reasons are

the southern third of the

Northern Territory, the

northern three-quarters of

South Australia, western New

South Wales and the Nullarbor

Plain in Western Australia.’

The areas where rabbits are a major

problem for economic or conservation

reasons are the southern third of the

Northern Territory, the northern three-

quarters of South Australia, western New

South Wales and the Nullarbor Plain in

Western Australia. Rabbits are low in

numbers throughout most of the

sheep–wheat zone because the area is flat,

largely cleared, occasionally cultivated and

the warrens are accessible and easily

ripped. In higher rainfall country the main

problem areas have a patchy distribution

and are usually found on land with steep

hillsides, gullies with steep sides, large

rocks, abundant fallen timber, or low

scrubby vegetation. In 1980 and 1985,

65–68% of New South Wales had few or no

rabbits and 10–13% had high numbers

(Table 1). The distribution of rabbits in

Australia is shown in Figure 5.

In higher rainfall areas numbers are

probably decreasing due to property

development and the increasing use of

warren ripping (Nolan 1981). In some areas

of Victoria, however, where control is

difficult, the increase in rabbit numbers is

reflected in the ten-fold increase in the use

of 1080 poison during the last decade

(I. Nolan, Keith Turnbull Research Institute,

pers. comm. 1992). In Queensland, rabbit

numbers in a million hectare area around

Stanthorpe/Inglewood/Texas/Goondiwindi

seem to have decreased for reasons that

are not obvious. Commencing in 1964, the

Queensland Rabbit Control Authority, the

functions of which are now undertaken by

the Land Protection Branch of the

Department of Lands, employed 12

operators who were continuously

poisoning. The overall infestation declined

to such an extent that by 1983 only five

operators were employed for spot

poisoning. However, because of the great

variations in rabbit numbers with seasonal

conditions, it is difficult to detect any long-

term trend over much of the rangelands.

Bureau of Resource Sciences/CSIRO 25

1

3. Biology

Summary

The European wild rabbit belongs to the

family Leporidae which has 52 species of

hares and rabbits living in grassland and

savanna ecosystems on four continents.

Unlike hares, which rely on speed and

endurance to elude predators, the various

species of rabbits live near dense cover to

which they flee when threatened. The

European wild rabbit is the only rabbit that

constructs large warrens, and is the only

species of rabbit that can live in open

grassland, because the warren provides the

cover it requires.

The optimum habitat for rabbits in

Australia is the intermediate rainfall zone,

where parasite numbers are low, droughts

are uncommon and breeding seasons

relatively long. Rabbits occasionally do well

in Australia’s hot arid zones even though

physiologically they are not well adapted to

arid conditions. When some green

vegetation is available, they readily find the

high protein, high water content diet they

need to survive and reproduce. The key to

their success in most environments, but

particularly in the arid zone, is their ability

to build warrens. The warren protects

rabbits from predators and climatic

extremes. However, during prolonged

drought when food quality and quantity

decline their populations crash.

Survivors of a population crash tend to

be adult rabbits. After the breaking of a

drought, rabbit populations are held at low

densities for several years by a combination

of native predators, foxes and feral cats. It

is not until fox and feral cat numbers

decline some time after the crash of the

rabbit population, and good seasons return,

that rabbit numbers build up again. Under

good conditions, an adult female can

produce 30–40 young a year.

Adult rabbits live as territorial

monogamous pairs, or in social groups of

up to ten individuals with separate

hierarchies for males and females. Males

fight to defend females and females fight to

defend access to breeding sites within

warrens. As many more young males than

females disperse, the warren is a heritage

passed on by adult females to female

offspring. Resident rabbits rarely move more

than 200 metres from their warren. Major

causes of death are drought, parasites,

rabbit management programs, myxo-

matosis, and predators such as dingoes,

birds of prey, goannas, foxes and feral cats.

After the introduction of myxomatosis in

1950 there was a rapid increase in the

resistance of rabbits to the disease and a

decline in the lethality of the common field

strains. Both resistance and virulence

appeared to stay steady from 1960 to 1975.

In this period, field death rates were about

40–60%. Since 1975 there has been an

increase in both resistance of the rabbit to

the virus and the killing capacity of the

virus, perhaps as a result of the introduction

of the European rabbit flea. These two trends

tend to compensate each other, and overall

death rates from myxomatosis may not have

been affected.

3.1 The European wild

rabbit and its relatives

The European wild rabbit (Oryctolagus

cuniculus) belongs to the family Leporidae

(Myers et al. 1987). The leporid (rabbit and

hare) family consists of: (1) hares and

jackrabbits (Lepus) — 29 species in Europe,

Asia, Africa and central and north America;

(2) cottontail rabbits (Sylvilagus) —13

species in the Americas, the closest relatives

of the European wild rabbit are the cottontail

rabbits; (3) European wild rabbit

(Oryctolagus) — one species in Europe; and

(4) eight other genera of rabbits with a total

of ten species in Asia, Africa and the

Americas.

The European rabbit was originally

classified as a rodent in the genus Lepus.

The name Oryctolagus comes from the

Greek orukter (digging tool) and lagos

(hare) and the Latin word cuniculus denotes

26 Managing Vertebrate Pests: Rabbits

both a rabbit and an underground passage.

The type locality for O. cuniculus is in

Germany. The English name rabbit, or

rabett, is of French origin and originally

applied only to young rabbits. The name

for an older rabbit was cony (Barrett-

Hamilton 1911).

Rabbits and hares inhabit open grassland,

savanna and shrub-steppe. About five

species of rabbits construct warrens with

more than one entrance; only the European

wild rabbit makes large warrens. Leporids

share with marsupials the unusual

anatomical feature of the scrotum being in

front of the penis. Body weight of rabbits

and hares ranges from 0.4–4 kilograms, with

a mean of about two kilograms. Maximum

running speed is correlated with body size

(Cowan and Bell 1986); the larger hares rely

on speed to escape predators, and the

smaller rabbits depend on reaching the

safety of some form of cover. They have a

pivotal role in the predator–prey complex

in most of the world’s grassland ecosystems.

Because of their size and fecundity, they are

food for most birds of prey and for a whole

range of mammalian predators as small as

weasels (60–120 g) or as large as cheetahs

(60 kg). It is generally considered that rabbit

and hare populations are regulated largely

by predation on, and dispersal of, young

animals (Edwards et al. 1981; French and

Heasley 1981; Henderson 1981; Stevens and

Weisbrod 1981; Wagner 1981; Wolff 1981).

Hares have a gestation period of 37–46

days and have small litters (two to three)

which are born fully-furred and mobile in

rudimentary above-ground nests. In

contrast, rabbits have a gestation period of

about 30 days and have large litters (four to

seven) of blind, deaf and almost naked

young in short burrows or in elaborate

above-ground nests. All leporids visit their

young only once a day and feed them for

about five minutes; this is thought to be a

strategy to minimise the amount of scent

which could attract predators. Mortality,

particularly in the young, is high.

Although leporids do not usually

consume a high proportion of the primary

production, that proportion may be a large

fraction of the highly digestible plants

(Wagner 1981).

The only leporid in Australia, apart from

the wild rabbit, is the European hare (Lepus

europaeus). Despite the much larger size of

the hare, the rabbit dominates it in

aggressive encounters and female rabbits

kill young hares (Evans and Thompson

1972; Flux 1981; Mykytowycz 1981). There

is often an inverse correlation between

rabbit and hare densities (Rothschild and

Marsh 1956; Evans and Thompson 1972;

Flux 1970; Broekhuizen 1975).

3.2 Body characteristics of

the rabbit

European wild rabbits typically have grey-

brown back fur and a white-grey belly. Males

and females are similar in size and

appearance, except that males have a slightly

broader head. Colour variants usually

comprise less than 2% of the population,

although sandy coloured rabbits are common

in some arid areas, and black rabbits are

common in the high country in Tasmania

(Barber 1954). Rabbits have a major moult

in spring and a minor moult in autumn. Dark

patches on the inside of the skin indicate the

progress of the moult (Stodart 1965). Juvenile

rabbits moult at three months of age; they

frequently have a white star on their forehead

Bureau of Resource Sciences/CSIRO 27

1

The most common form of the European wild

rabbit, with grey-brown back fur and a white-

grey belly. Source: G. Chapman, CSIRO

photo 1*

positional only

which is lost at this moult. The feet are

covered in fur which protects the foot pads

from excesses of heat and cold and enables

the rabbit to move very quietly. The eyes

are placed to the sides of the head and are

slightly protruding so that the rabbit has

panoramic vision. The rabbit has a sensory

pad partly concealed by hairy folds of skin

at the entrance of each nostril, and a Y-

shaped groove extends from the upper lip

to the nose.

Rabbits have 16 teeth in the upper jaw

and 12 in the lower. There are two pairs of

upper incisors; the second smaller incisors

are behind the first, a feature that

distinguishes leporids from rodents. The

incisors grow continuously. The cementum

of the incisors is thicker in the front than at

the rear and because of differential wear they

are worn to a sharp chisel shape.

At birth the young weigh 35 g each. By

the time they first emerge from the warren

at 21 days they have increased their body

weight by 600% to 210 g each. The total

weight of a litter of six at emergence is 80%

of the normal weight of the mother. Apart

from nursing there is no obvious parental

care. Up to 900 g, weight gain is essentially

linear (10 g/day), so body weight can be

used to age rabbits under 900 g using the

equation age (days) = weight (g) ÷ 10 (Parer

1977; Daly 1979; Wheeler and King 1980).

The most accurate method of estimating the

age of a rabbit is from the weight of the dried

eye lens which grows throughout life (Myers

and Gilbert 1968; Wheeler and King 1980).

3.3 Shelter

In Australia, wild rabbits live in a variety of

situations which can be classified broadly

by the amount of surface cover that is

available to them. Where cover is dense and

abundant rabbits tend to dig only small

warrens and live mainly on the surface

(Section 3.3.2). Large warrens occur mainly

in open country such as cleared land, grazed

pasture and arid areas. Vegetation in the

parts of Australia occupied by rabbits ranges

from (1) shrub (scrub and bracken thickets),

either with or without an overstorey of trees;

(2) patches of dense scrub interspersed with

patches of grassland in various proportions;

(3) savanna woodland with extensive

grassland; (4) grasslands of varying

vegetation density; through to (5) short or

sparse grass with varying extents of bare

ground (Figure 6). This variation in

vegetation cover can be viewed as a

continuum in which the range or abundance

of surface cover varies. As surface cover gets

less, warrens become larger and the rabbits

depend increasingly on underground shelter

(Figure 6).

3.3.1 The warren

‘Although the rabbit makes the warren, it

is the warren that makes the rabbit’

(Andrewartha and Birch 1984).

Contrary to popular opinion, rabbits do not

readily dig new warrens, except on sandy

soils (Parer 1977; Cowan 1987a). In newly

colonised areas without warrens a rabbit

will generally live in what is called a squat

— a shallow depression in long vegetation

or under fallen timber. A squat-dwelling

pregnant female will dig a shallow burrow,

astop, in which to have her litter. The

entrance to the stop is covered with soil

and is difficult to detect. Separate tunnels

may be dug within a stop for successive

litters and the stop is then called a warren

(Mykytowycz et al. 1960).

28 Managing Vertebrate Pests: Rabbits

Warren complexes are generally larger in

more open country, with a greater proportion

of rabbits living underground (as indicated

in Figure 6). Source: CCNT

photo 10*

positional only

Bureau of Resource Sciences/CSIRO 29

1

Figure 6: Surface rabbits, shelter types, squats and warrens. Rabbits remain above ground more where surface shelter is abundant. Warrens are

more common and larger where surface shelter is sparse. (Figure drawn by Fleur Sheard)

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