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SUMMARY

The intro duced European rabbit(Oryctolagus cuniculus) is one of the mostwidely distributed mammals in Australiaand, except for the house mouse (Musdomesticus), the most abundant. Rabbitsoccur mainly south of the Tropic ofCapricorn, and almost anywhere except atthe highest altitudes, in dense forests or onpoorly drained soils.

Rabbits are a major environmental andagricultural pest. Damage to theenvironment is particularly significant insemi-arid and subalpine areas where rabbitand sheep grazing has fundamentally alteredthe ecosystems. Rabbit control poses asignificant animal welfare concern.

These guidelines contain a comprehen-sive review of the history of rabbits inAustralia, their biology, the damage theycause, and past and current management.The attitudes of animal welfare groups,commercial, recreational and Aboriginalrabbit users, and other interest groups areexamined. The authors recommendmanagement techniques and strategies forcontrol, illustrated by four case studies.Deficiencies in knowledge, managementand legislation are identified. The guidelinesare an essential reference and managementguide for policy makers, land managers andothers interested in rabbit management.

Why develop national guidelines?

These guidelines for managing the impactof rabbits have been developed under theVertebrate Pest Program (VPP) which isadministered by the Bureau of ResourceSciences (BRS). The project has beencoordinated by the Vertebrate PestsCommittee (VPC) of the Standing Committeeon Agriculture and Resource Management(SCARM). These rabbit guidelines werefunded by the VPP and the CSIRO. Similarguidelines have been published for feralhorses, and others are being prepared forfoxes, feral goats, feral pigs and rodents.

The purpose of the guidelines is to assistthe development of strategies to reduce thedamage rabbits cause to production andconservation values using the most cost-effective approaches. Ideally, such strategiesare based on reliable, quantitativeinformation about the damage caused bythe pest, the cost of control measures, andthe effect of implementing control onreducing the damage. Despite many decadesof rabbit research we have little reliableinformation of this type for rabbitmanagement. In developing theseguidelines, the authors have used allavailable information, but they have alsohad to make assumptions about rabbitimpact and the efficacy and cost-effectiveness of control techniques. Theseassumptions may need to be changed whenmore reliable information becomesavailable.

The rabbit problem

The results of the many scientific and otherstudies conducted on the effects of rabbits inAustralia indicate that they are probably ourmost serious vertebrate pest, affectingagriculture, the pastoral industries and theenvironment.

There are no reliable figures for the nationalcost of rabbits to agriculture, but the annualloss to the pastoral region of South Australiaalone is estimated at $20 million (1993-94dollars, as are all money values in theseguidelines unless otherwise indicated), anestimate that would be much higher if thereduction in production due to progressivedeterioration of the land could be calculated.The effect on production is most apparent indrier areas where pasture production is lowand rabbit numbers increase to high densitiesand compete with stock. In most higherrainfall areas rabbits can be managed, andare regarded as a moderately expensivenuisance to agricultural production, ratherthan a serious economic pest.

The serious impact of rabbits on nativeflora and fauna is now becoming recognised.Rabbits directly compete with many native

Bureau of Resource Sciences/CSIRO 1

animals for food and shelter and haveextensive effects on native flora throughringbarking, grazing and browsing. Theoverall effects of rabbits on biodiversity arelargely unquantified, though many species ofvertebrates and invertebrates that depend onthe vegetation damaged by rabbits are likelyto be affected.

In the arid zone, rabbit densities belowone rabbit per hectare can preventregeneration of some native plants. Theprogressive deterioration of rangelandecosystems may not be obvious becausemany trees and shrubs are long-lived. Mulga(Acacia aneura), for example, can live for250 years. Tree and shrub populationsbecome senile where rabbits destroy allseedlings. If rabbits are not reduced to verylow numbers in these regions, the decline innative trees and shrubs through lack ofseedling recruitment will continue. Thepotential ecological consequences of thisdecline are expected to include increasederosion and changes to plant and birdcommunities. There may be no safe rabbitdensity for some tree and shrub seedlings.Because other pests, domestic stock andnative herbivores are also involved inbrowsing and grazing native plants,conserving biodiversity in the rangelands willrequire management of the total grazingimpact by all these species.

Rabbits also have an impact onconservation values in higher rainfall areas.For example, rabbits at a density of three perhectare prevented regeneration of sheoak(Allocasuarina verticilliata) and sallow wattle(Acacia longifolia) in the Coorong NationalPark on the coast of South Australia. The effectof rabbits in modifying vegetation inconservation areas, however, has not beensufficiently evaluated for higher rainfall areasand may be unrecognised. It requires long-term evaluation.

Why do rabbits prosper inAustralia?

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 inAustralia is the warren, which providesprotection from weather and predators andenables rabbits to inhabit semi-arid and aridcountry. Contrary to popular belief, rabbitsdo not dig new warrens readily. Althoughthey usually live in warrens, rabbits readilylive above the ground whenever there isadequate shelter. In some areas a highproportion of adult rabbits live mostly aboveground, such as the coastal scrub in south-western Western Australia and parts ofTasmania.

Another reason for the success of therabbit in Australia is the absence of somediseases and parasites that keep its numbersin check in other countries. Moreover, thegenerally dry climate in Australia constrainsthe parasites that are present. Comparedwith Europe and America, Australia has fewpredators and, in particular, lacks wildmustelid species (Mustela spp.) such asweasels and ferrets, which kill young rabbitsin warrens.

Factors affecting rabbit numbers

Rabbit populations in most of Australiafluctuate mainly in response to variation inrainfall. In the drier rangelands, rabbitnumbers increase during favourable seasonsand decline during droughts to around 1%of peak numbers. Therefore long-termtrends are difficult to identify. In some higherrainfall areas, rabbit numbers have fallen inrecent years because of cropping, warrenripping and property development. Rabbitsoften remain abundant in habitats wherethey are difficult to control, such as rockyhills and other refuges.

After the introduction and establishmentof the virus causing myxomatosis in the early1950s, rabbit numbers fell dramatically, andrabbits died out in some marginal habitats.The impact of the disease was greatest inthe semi-arid areas where the carriers(vectors) of the virus, mosquitoes, areseasonally abundant. The impact was lessin those areas where there are few

2 Managing Vertebrate Pests: Rabbits

mosquitoes, such as Tasmania, WesternAustralia and some tableland regions. Theintroduction in 1968 of the European rabbitflea (Spilopsyllus cuniculi), an alternative,more perennial vector, resulted in largereductions in rabbit populations inTasmania, south-western Western Australia,on tablelands, and in parts of SouthAustralia. The 1993 introduction of an arid-adapted Spanish flea (Xenopsyllacunicularis) is intended to cause similarreductions in the drier rangelands, and itsspread and efficacy are currently beingevaluated.

The efficacy of myxomatosis declined inthe 1950s but has remained more or lessconstant since then and myxomatosis stillplays a major role in limiting rabbit numbers.The present density of rabbits in Australiacompared to the situation beforemyxomatosis was introduced is not known.On average, rabbit numbers are thought tobe about 5% of premyxomatosis abundancein the higher rainfall areas and perhaps 25%in the rangelands. Although the resistanceof rabbits to the virus has increased, this hasprobably been balanced by the evolutionof more virulent strains of the virus. Theeffectiveness of myxomatosis in the longterm cannot be predicted, so no relianceshould be placed on its continued efficacy.

Development of a strategicmanagement approach

Colonial governments and their successorsrelied on stringent legislation requiringlandholders to undertake control. Varioustechniques were used, including shooting,poisoning, fencing, and even the intentionalspread of predators such as cats. Mosttechniques were relatively ineffective,although with determination andpersistence, and using rabbit-proof fencesas boundaries, some landholders achievedsustained, low rabbit densities andoccasionally complete local eradication.

Most evidence indicates that successfulrabbit management requires integratedaction at the state, regional and local level.

Land managers need a clear understandingof techniques and goals and they need toaccept responsibility for the action required.Extension programs increase generalawareness and understanding of the damagerabbits cause and what can be done toalleviate the problem. An essential part ofraising public awareness will be well-trainedand motivated state and territory workers.Technical and Further Education Collegescan have an important role in trainingpeople in techniques of extension, damageassessment and control.

What is the strategic approach?

The emphasis in these guidelines is not onkilling rabbits, but rather on their efficientand strategic management to reduce thedamage they cause to production andconservation values in the most cost-effective way. Rabbits are but one factor ina complex and changing agriculturalenvironment that includes a highly variableclimate, fluctuating commodity prices, otheranimal and plant pests, farm stock and theprofitability of farming businesses. Farmersneed to consider investment in rabbitmanagement in the context of investmentin other areas of the farm business unit.Rabbits also need to be considered inrelation to their impact on natural and semi-natural ecosystems, and on the biodiversitywithin them.

A strategic approach to the managementof rabbits developed in these guidelines isbased on four key activities:

Defining the problem — The problem shouldbe defined in terms of rabbit damage andthe reduction in rabbit density required toreduce or prevent the damage.

Developing a management plan — Landmanagers must establish clear objectivesin terms of the desired production orconservation outcome sought. Options forrabbit management include localeradication, strategic management, crisismanagement and no management.Eradication will rarely be a feasible goal.


These guidelines strongly recommendsustained, strategic management as theprincipal management option.

Implementing the plan — A local or regionalapproach to rabbit management is usuallymost effective. This generally requirescoordinated action by individual propertyowners and government and other agencies.

Monitoring and evaluating the program —Monitoring has two aspects. Operationalmonitoring assesses the efficiency of thecontrol operation. Performance monitoringinvolves gathering information to determinewhether the strategy is meeting the desiredlong-term production or conservation goal.

Community attitudes

Various segments of the community seerabbits either as appealing characters fromcartoons and literature, a commercialresource, a subsistence food source, ananimal welfare concern or a major pest. Itis unlikely that these deeply held attitudescan be changed quickly, but the publicneeds to understand the damage caused byrabbits and its implications. Scientists andstate and territory land managementagencies must communicate to legislators,land managers, landholders and the publicthe damage caused by rabbits and ensurethese people have sufficient information tomake appropriate rabbit managementdecisions.

Rabbits as a resource — Rabbits areharvested in the wild and domestic rabbitsare farmed for food and raised as pets andshow animals. The associated industriesare small; for example, the annual valueof wild rabbit harvesting is estimated tobe about $10 million. The promotion ofwild harvesting and other forms ofcommercial use may inhibit effective rabbitmanagement through, for example,providing a case against the introductionof new biological control agents. Theauthors believe the commercial use of wildrabbits has no role to play in managingrabbit impact, mainly because wild rabbit

harvesting is usually from high densityrabbit populations, and this will not reducedensities to a level where damage iseffectively managed.

Aboriginal use of rabbits — Some Aboriginalgroups include rabbits as a major part oftheir diet and perceive them as an integralpart of the land. It is important thatAboriginal communities have accessto information on the long-termconsequences of high rabbit numbers,which may include loss of traditionalvalues as well as ecological impacts. Stateand territory land management authoritiesneed to work closely with Aboriginalpeople to assist them to make land-usedecisions which meet their needs andenable ecologically sustainable land use.

Animal welfare — Some rabbit controlpractices are inhumane. The steel-jawedtrap should be banned. The fumigantchloropicrin should be phased out oncea more humane alternative is found. Whilesome suffering must be expected with theuse of techniques recommended in thisreport, their strategic application wouldminimise suffering by maintaining reducedrabbit populations, thereby minimising theneed for repeated treatments.

Myth of the super bug — The success ofmyxomatosis in the 1950s has causedunrealistic expectations of biologicalcontrol. Consequently many landmanagers may not put much effort intoconventional rabbit management becauseof high hopes of future control by newbiological control agents such asmyxomatosis transmission via the arid-adapted Spanish flea, rabbit calicivirusdisease (RCD), also called rabbithaemorrhagic disease (RHD), and virally-borne immunocontraception. Release ofsuch new agents will be years away,however, even if these research projectssucceed. Virally vectored immuno-contraception in particular, is long-termhigh risk research, and it is too early topredict whether it will be successful. Newtechniques will only complement, notreplace, conventional control, and the


challenge will be to use conventionalcontrol techniques to take maximumadvantage of lowered rabbit densitiesfollowing biological control. Maintenancecontrol was rarely undertaken after therelease of myxomatosis. Land managerscannot afford to rely on the potential ofnew agents to save them from action now.

Impact assessment methods

There is a pressing need for low-costtechniques to assess rabbit impact. Atpresent, managers usually rely on estimatesof rabbit abundance as an indicator ofdamage. There are risks in this approachbecause rabbits, at densities almostundetectable to a casual observer, canprevent regeneration of some native plants.Thus, the perception of low numbers maygive an inaccurate measure of impact.

Rabbit distribution and abundance is bestestimated from counts of semi-permanentfeatures such as warrens and burrowentrances; these counts also indicate theproneness of the land to rabbit infestation.They are not suitable, however, whererabbits are mainly surface dwelling. Here,techniques such as dung and spotlighttransect counts must be used, and these areless reliable.

Rabbit management techniques

Maps which show the relationship betweendistribution and abundance of rabbits andtopographic, soil and other land featuresare an invaluable aid to planning andimplementing rabbit management.

Over most of Australia where rabbits usewarrens, the primary control techniqueinvolves destroying warrens and associatedrefuges, possibly after initial poisoning ifrabbit densities are high. Following primarycontrol, sustained maintenance control bywarren ripping or by fumigation is essential.Using dogs to drive rabbits undergroundincreases the effectiveness of ripping andfumigating. Poisoning without maintenancecontrol provides only short-term relief. The

primary role of poisoning is to reduce rabbitdensity before warren ripping. When rabbitpopulations are reduced by drought ormyxomatosis, managers should takeadvantage of the reduced rabbit populationsto apply other control techniques, to furtherreduce and maintain the low densities.

Management is more difficult where aproportion of rabbits dwell on the surface,a situation more common than waspreviously realised. Poisoning and, wherepracticable, refuge destruction are importanttechniques. A major risk with repeatedpoisoning is the development of bait andpoison avoidance, as has occurred inWestern Australia and New Zealand.

Impact of rabbit control on nativewildlife

Predator–prey interactions are complex andlittle is known about those involvingchanges in the abundance of rabbits. Thefollowing hypotheses are based onecological theory and limited experimentaland anecdotal knowledge. Fieldexperiments are needed before morereliable predictions can be made.

When rabbit numbers are greatlyreduced, foxes and cats may turn to nativewildlife as alternative prey in the short term.Such increased predation may occur afterwidespread rabbit control and is similar tothe recurrent increased predation whichoccurs after droughts and myxomatosisoutbreaks. Since rabbits are the primary foodof foxes and cats in most of Australia, a long-term reduction in rabbit density might alsoreduce fox and cat densities, and so reducetheir effect on wildlife in the longer term.Reduced grazing pressure from rabbits mightalso allow vegetation to recover which couldincrease habitat and shelter for wildlife andso reduce predation. Reducing rabbitnumbers could also reduce numbers ofnative birds of prey, as rabbits are the mainfood of many raptors during their breedingseasons. On the basis of these hypotheses,fox and cat control should be implementedfollowing rabbit control in areas containing


susceptible, rare or threatened nativespecies. More information may enable theseprocedures to be modified.

Strategies for reducing rabbitdamage

These guidelines describe strategies formanaging rabbits in four classes of land use:

• high production cropping and grazingland;

• low production rangeland;• forestry plantations; and• conservation areas.

The management option recommendedfor all classes of land use is sustained, strategicmanagement. Ideally, rabbit managementaims to reduce rabbit damage to the levelwhere the benefits of management aregreatest relative to the costs. This approachrequires knowledge of the relationshipbetween rabbit density and the costs andbenefits of management. This is difficult andcostly to determine, and it is unlikely that therabbit, with its high reproductive potential,could be managed with this degree ofprecision.

For most circumstances, it is assumed thatrabbit damage is related to rabbit density,although it is recognised that there is notalways a direct correlation between rabbitnumbers and levels of damage. For example,there is evidence that in the rangelands ofNew South Wales, competition betweensheep and rabbits only occurs when pasturebiomass is less than 250 kilograms per hectare.The relationship between rabbit density andlevel of damage will vary with both the typeof damage being considered and other factors,such as the total grazing impact from allspecies and variation in the vegetation cover.This has implications for the selection ofappropriate management strategies for rabbitsin relation to different land uses and changesin market prices for wool, other commoditiesand for conservation values which are affectedby rabbits.

In the authors’ opinion, based mainly onthe experience of state rabbit control

authorities, data from small-scale field trials,and on rabbit population ecology, reducingand maintaining rabbit populations atminimum densities is more likely to besuccessful and profitable for damagemanagement than some lesser level ofcontrol to densities from which rabbitpopulations can rapidly rebound. Evenwhere resource damage only occurs whenrabbit numbers are high, it may still be mostcost-effective to maintain rabbits at verylow densities at all times. Such a strategycould bring the greatest benefits at the onsetof drought, when the impact of rabbits onboth production and conservation valuesis likely to be high, and when landmanagers may have inadequate time, labouror funds to mount a rabbit control program.The relative cost-effectiveness of aiming forsustained minimum levels as a long-termstrategy will depend on the cost of this levelof rabbit control relative to the benefitsresulting from the control, in comparisonto the cost–benefit ratios of some lesserlevel of control or no control. The initialextra cost of achieving very low rabbitnumbers could be offset by the reducedcosts of continuing control to maintain theselow numbers and reduced impacts.Strategic, sustained management (SSM) toreduce and maintain rabbits at minimumdensities is most likely to be profitable inplaces where uncontrolled rabbit densitieswould usually be moderate or high (greaterthan three rabbits per hectare).

Rabbit control to achieve and maintainminimum densities is also likely to beprofitable in conservation reserves where ahigh value is placed on the resources beingprotected from rabbit damage. In therangelands, the high cost of reducing rabbitsto very low densities might prevent this frombeing a feasible goal. Although there maybe high benefits from rabbit control in suchareas, in terms of increased wool clip andland values, the large areas involved meanthat initial control costs may be high andland managers may lack sufficient funds,especially at times of low wool values.Rabbit control to increase production maynot be profitable in areas which naturally


have low rabbit densities (less than one rabbitper hectare). More information on therelationships between rabbit density anddamage, and between control costs andbenefits, is needed for assessments of themost effective strategies for rabbitmanagement for different areas and land uses,and on the best approaches for integratingrabbit management with other propertyoperations.

A goal of reducing rabbit numbers to asclose to zero as possible and then maintainingthem at that level has the advantage ofproviding land managers with a clear, readilymonitored, long-term goal. This may counterany tendency of land managers to developtolerance to rabbits which could undermineefficient long-term management. Landmanagers need to be committed to a long-term strategy for a successful outcome.

Wherever practicable, SSM includesassessing the effectiveness of the managementprogram in reducing rabbit damage, especiallywhen aiming to protect conservation values.

Local eradication is achievable only inspecial situations such as on small islands andon properties protected by natural barriers orrabbit-proof fences and monitoredcontinuously for reinvasion by rabbits.

Economic frameworks need to bedeveloped to assist in the assessment of therelative value of alternative control strategieswhenever this is feasible. Such frameworksrequire: definition of the economic problem;data on the relative costs and benefits; anunderstanding of why the actions of individuallandholders may not lead to optimal rabbitmanagement; assessment of the means bywhich governments can overcome identifiedmarket failures; and an assessment of thelikely returns from alternative rabbitmanagement strategies.

Implementing rabbit management

For effective rabbit management, landmanagers must be motivated by anawareness of potential or actual rabbitdamage. They need to know what can and

should be done to alleviate it, and to beinvolved at all stages of the managementprocess: planning, implementation,monitoring and evaluation. State andterritory pest management authorities withappropriately trained field staff operatingat the regional and local level have aprimary role in motivating landholders totake appropriate action. Locally-basedschemes such as Landcare groups are aprimary means for governments to workwith landholders. Successful examples ofthis approach include the Bathurst Schemeand the Pine Creek Rangecare Group.Further studies are required, however, todetermine the essential elements ofsuccessful schemes, and whether these willcontinue to operate after governmentassistance is withdrawn.

Public lands — Governments manage largetracts of land infested with rabbits. Whileprivate landholders are required bygovernments to manage rabbits, there isoften no such obligation on governments.Private landholders see this as inequitable.As a minimum, governments shouldmanage and maintain an adequate bufferzone between public and private land toprotect adjacent properties. If there areinsufficient resources for effective,sustained management across all publicland, efforts should be concentrated inhigh-value areas.

Legislation — Legislation should clearlystate the responsibility of land managersfor rabbit management and facilitateappropriate action. Equally important isthe ability and commitment to enforce thelegislation. Legislation is also needed toregulate the use of toxic chemicals.

Who should implement control? — Manyaspects of rabbit management requiretrained, experienced advisers andoperators. While some landholders andland managers have skills in rabbitmanagement, those without such skillsmay wish to be trained. Where this isimpracticable, hire of government servicesor use of contractors is an alternative.


Training — States and territories which donot have the resources and expertise totrain field staff may be able to accesstraining programs in states such as SouthAustralia and Western Australia, whichcould recover costs for this service.Training in rabbit control needs to be partof integrated vertebrate pest managementwhich, in turn, is part of a holisticapproach to management. This documentand the associated documents on othervertebrate pests may be useful in trainingvertebrate pest managers.

Research needs

The basic biology of the rabbit is well known.Less is known about the interaction betweenrabbit numbers and production losses anddisruption of ecosystems. Research prioritiesare:

Impact — (1) Rangelands: measure rabbitimpacts on native vegetation includingregeneration, and on pastoralism; (2)rangelands and cropping areas: quantify therelationship between rabbit density andimpact; and (3) conservation areas: measurerabbit impact on native vegetation, includingregeneration, and on fauna for all climaticregions.

Monitoring — Develop low-cost techniquesfor rapid assessment of: (1) rabbit impact oncrops, native vegetation, native fauna andsoil; and (2) rabbit abundance wherewarrens and burrows are little used byrabbits.

Economics — Determine cost–benefit analysesof different levels of rabbit control for bothcropping and grazing lands. Examine thecost-effectiveness of various combinationsof control techniques and prescriptions forcontrol.

Traditional control — Determine optimalmethods for controlling rabbits that live inscrub, rocky areas and on steep slopes;improve humaneness of techniques,particularly fumigation; improve baitingtechniques and target specificity; developalternative toxins; reduce impact on

predators and native fauna; and improveintegration with other farm managementpractices.

Biological control — Further development ofmyxomatosis and rabbit calicivirus disease(RCD): host/vector/virus interactions; strainvariants and manipulation; mass productionof virus; and improved knowledge oftransmission by vectors.

Creating an appropriate adminis-trative environment

An appropriate administrative environmentis crucial to the success of strategic rabbitmanagement. The following are keyactivities:

• Review the adequacy of existinglegislation, policies and institutionalarrangements for the formulation anddelivery of programs for managingrabbits and other vertebrate pests at alllevels of government.

• Improve humaneness by prohibitingsteel-jawed traps and phasing outchloropicrin.

• Review and improve effectiveness ofsupport for Landcare groups and otherland management groups, consistentwith 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 rabbitmanagement as capital improvement ofproperty values.

Training and extension

Attention to training and extension isessential, with the following as keyactivities:

• Update training courses and manualson vertebrate pest management toinclude information contained in theseguidelines and to integrate rabbitmanagement with other aspects of landand property management through theproperty planning process.


• Investigate feasibility of courses onrabbit control being included in thecurricula of appropriate tertiaryinstitutions.

• Coordinate approaches of the variousstates and territories to cooperate ondevelopment of pest managementinformation systems, and on interstatetraining of vertebrate pest controlofficers.

Enlisting community support

Rabbit management in Australia needswidespread public support for success;education is the key to this. Educationalpackages for schools should be reviewedand, where necessary, expanded orimproved.

Extension and advisory services toLandcare and other land managementgroups should be augmented. Theseservices are essential to improve communityand land manager understanding of researchfindings, to engender a sense of ownershipof the problem and to place rabbit damagein the context of ecologically sustainabledevelopment.


INTRODUCTION

These guidelines for managing the impactof rabbits have been developed under aproject managed by the Bureau of ResourceSciences (BRS) and coordinated by theVertebrate Pests Committee (VPC) of theStanding Committee on Agriculture andResource Management (SCARM). Theproject is funded by the BRS and the CSIRO.Similar guidelines have been published forferal horses, and others are being preparedfor foxes, feral goats, feral pigs and rodents.

These guidelines are primarily for state andterritory land management agencies to use inconsultation with private land managers andother interest groups, to prepare state,regional and local strategies for reducing theimpact of rabbits on agricultural productionand the environment. The guidelines shouldbe read and used in conjunction withManaging Vertebrate Pests: Principles andStrategies (Braysher 1993), which explainswhy the guidelines were developed, theiraims, the development process, their use andthe principles of pest management.

Various interest groups were consultedduring preparation of these guidelines,notably state and territory land managementagencies, the National Farmers’ Federation(NFF), the Australian ConservationFoundation (ACF), the National ConsultativeCommittee on Animal Welfare (NCCAW), theAustralian Veterinary Association (AVA), andthe Anangu Pitjantjatjara Aboriginal LandCouncil.

Effective rabbit management, particularlyin the rangelands, is central to the successof a number of Commonwealth Governmentconservation programs, including theEcologically Sustainable Development (ESD)Strategy, the Endangered Species Program(ESP) and the Decade of Landcare (whichincorporates the National ResourceManagement Strategy (NRMS), the NationalLandcare Program (NLP), and the OneBillion Trees and Save the Bush Programs).

Consistent with the holistic approach toland management advocated under the

Ecologically Sustainable DevelopmentStrategy and Landcare, all the managementguidelines for feral animals, including thisone, consider interactions between all pests,other species and aspects of landmanagement. A holistic and integratedapproach to management is necessary forAustralia’s rangelands, where rabbits andmany other vertebrate pests are common.

The guidelines should assist state andterritory land management agencies to moreeffectively manage pest damage throughbetter coordination, planning andimplementation of regional and localmanagement programs. Achieving thestrategic management of rabbits and otherpest animals involves four key components(Figure 1):

Defining the problem — Ideally the problemshould be defined in terms of rabbit damageand the reduction in rabbit density requiredto reduce or prevent the damage.Unfortunately the relationship betweenrabbit density and damage has not beenquantified in most cases. Until researchestablishes this relationship, most managerswill rely on measuring the abundance anddistribution of rabbits or warrens, andassume that damage is directly related torabbit abundance.

Developing a management plan — Landmanagers must establish clear objectives interms of the desired production orconservation outcome sought. Options forrabbit management include localeradication, strategic management, crisismanagement and no management.Eradication will rarely be a feasible goal.These guidelines strongly recommendsustained, strategic management as theprincipal management option. The choiceof initial and maintenance controltechniques in the management strategy willdepend mainly on whether the rabbitsshelter in surface cover or in undergroundwarrens or burrows.

Implementing the plan — A local or regionalapproach to rabbit management is usuallymost effective. This generally requires


coordinated action by individual propertyowners and government and other agencies.

Monitoring and evaluating the operation —Monitoring has two aspects. Operationalmonitoring assesses the efficiency of thecontrol operation. Performance monitoringinvolves gathering information to determinewhether the strategy is meeting the desiredlong-term production or conservation goal.Both forms of monitoring help determinewhether the management strategy shouldbe modified.

In most cases, rabbit impact on oneproperty or area is influenced by theirpresence in neighbouring properties orareas. Thus the problem is often one that isshared by many people or agencies whoneed to cooperate to find a solution.

The objective of these guidelines is tochange rabbit management from crisismanagement by individuals and agenciesto strategic management based oncooperative action. Adopting a wholeproperty approach to management,preferably linked to a regional or totalcatchment plan, is advocated. The strategicapproach to rabbit management involvesencouraging a group approach in an initialcontrol campaign and following this withsustained control measures.

The criterion for success of theseguidelines will be the acceptance andimplementation of the strategic managementapproach to the rabbit problem by asignificant number of agencies andindividuals.


DefiningProblem

(Section 9.2)

• real or perceived• define harmful • impact

– economic– environmental

• mapping• measure and• assess impact

ManagementPlan

(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 ‘bestpractice’ pest management, the Govern-ment, in its Environment Statement ofDecember 1992, provided increasedresources to the Vertebrate Pest Program(VPP) to complete preparation of theguidelines for managing Australia’s majorvertebrate pest species and to establish keydemonstration projects to facilitate adoptionof best practice pest management. Projectswill draw on the management strategiesoutlined in the relevant guidelines for eachspecies. For most species, including rabbits,it is anticipated that best practice will evolvebased on experience gained fromundertaking strategic management. Usingthe management system to refine the pestmanagement strategy is called learning bydoing. Each of the guidelines will bereviewed periodically as knowledge of thestrategic management approach increases.

It is expected that community-basedgroups will become increasingly involvedin the strategic management of vertebratepests. The guidelines are designed tofacilitate the ownership of the pest problemby such local groups, and the managementstrategy which might be developed andimplemented based on them. Accordingly,preference in funding under the VPP is givento projects which involve collaborationbetween a number of appropriategovernment and/or non-governmentagencies and involve community-basedgroups in their design and implementation.

The VPP supports projects which addressthe impact pests have on primaryproduction. The complementary Feral PestProgram administered within the AustralianNature Conservation Agency (ANCA) givespriority to strategic pest management inareas primarily used for conservation. Thereare strong linkages between the programs,and projects which address both agriculturaland conservation damage due to pests maybe jointly funded.

Note: All money values throughout theguidelines are in 1993-94 dollars unlessotherwise indicated.


PART ONE

HISTORY, DISTRIBUTION AND BIOLOGY

1

1. History ofIntroductions andSpread

SummaryDuring the last ice age the range of theEuropean rabbit contracted to the warmestparts of southern Spain and France. Therabbit appeared to be a disappearing speciesbefore man reversed its fortunes sodramatically. It is now found over most ofEurope, on three other continents and onmore than 800 islands.

In mainland Australia rabbits establishednear Geelong in Victoria following the firstknown release of wild stock in 1859. Theirspread was rapid and was aided by thepresence of burrows of native species, thepaucity of predators, the modifications tothe natural environments made for farmingand occasionally by their deliberatetransport.

1.1 Europe

Members of the family Leporidae (rabbitsand hares) first appeared in the late Eocene(40–70 million years ago) in Asia and NorthAmerica (Dawson 1981) and arrived inEurope during the Miocene (10–25 millionyears ago). The genus Oryctolagus was firstrecorded in Spain during the middlePliocene period. Two European subspecieshave been distinguished, O. cuniculuscuniculus from southern France (averageadult weight 1500 g) and O. cuniculushuxleyi from Spain (average adult weight1000 g). Recent evidence based onmitochondrial DNA has revealed that thetwo subspecies diverged more than onemillion years ago (Biju-Duval et al. 1991).During the last ice age the European rabbitwas largely restricted to the warmest partsof Spain and southern France and its majorspread did not commence until historicaltimes. Domestic rabbits were derived fromthe French subspecies by monks some timebetween the fifth and tenth centuries(Sandford 1992).

Rabbits were introduced to Englandfrom France soon after the Normanconquest in the eleventh century. Rabbitsremained scarce outside rabbit farms(called warrens) until the nineteenthcentury. At that time free-livingpopulations increased due to changes infarming practices, the planting ofhedgerows and an increase in the mortalityof rabbit predators due to hunting by thenobility and trapping by tenant farmers.Colonisation took some 900 years inEngland and Wales and was still notcomplete in Scotland in 1950 (Sheail 1971).

The Spanish subspecies was transportedaround the eastern Mediterranean as earlyas 1500 BC by Phoenician traders. In Romantimes Spain was renowned for its rabbits andthe name of the country ‘Hispania’, later‘Espana’, is thought to be derived from aSemitic word denoting rabbits. In the firstcentury BC, the inhabitants of the islands ofMinorca and Majorca asked EmperorAugustus for the help of the Roman army incontrolling the impact of rabbits on theircrops and trees (Barrett-Hamilton 1911;Harting 1986). The French subspecies ofrabbit were often liberated on islands toprovide food for shipwrecked sailors; theyare now present on some 800 islandsthroughout the world (Flux and Fullagar1992).

Free-living rabbits were rare in France inthe sixth century but many colonies wereheld in enclosures or on islands for huntingpurposes, and rabbits were often transportedto start new colonies. Introductions weremost successful on islands, perhaps becauseof high predator pressure elsewhere. Therabbit’s colonisation of France was notcompleted until the nineteenth century andrange expansion is still occurring elsewherein Europe although the species may now beclose to its ultimate limits.

The rabbit was introduced into Italy in thefirst century AD but the populations becameextinct. Present populations near Padua,Milan and Pisa are all the result of recentintroductions. There are no rabbits in Greeceor elsewhere in the eastern Mediterranean


1

although they were undoubtedly introducedmany times. The reasons for the slow rateof spread and for so many failedintroductions in Europe are unknown.However, the French subspecies seems torequire intense agricultural and pastoraldevelopment for it to thrive and maintainitself in the wild.

The relationship of the rabbit to peopleis unique. It is farmed for meat and fibre andis a laboratory animal, a significant pest, amajor game species, a household pet, a story-book character and a star in animatedcartoons. It is the only farmed animaldomesticated in historical times and the onlypest mammal whose densities have beenmuch reduced by biological control. Theownership of rabbits by the Lord of themanor and the persecution of poachers arecredited with being the main cause of theradicalisation of the lower classes in England

and a cause of the French revolution(Hopkins 1985). During the depression inAustralia, and during the second world warin Europe, the rabbit was the main sourceof animal protein for many people. The scaleof the impact of the rabbit in Australia isconsidered to be unique in the history ofwild animal introductions.

1.2 Australia

Domestic rabbits arrived in Australia withthe First Fleet in 1788. The first feralpopulations were in south-eastern Tasmaniawhere they numbered in the thousands onsome estates by 1827. The first person tointroduce wild rabbits to the Australianmainland was Thomas Austin, anenthusiastic sportsman and member of anacclimatisation society. He also introducedhares. Twenty-four rabbits arrived from


Rabbit numbers reached high levels in south-eastern Australia prior to the introduction ofmyxomatosis. Bounties and the market for rabbit meat and fur, combined with the highnumbers 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 wereput in enclosures at Austin’s property,‘Barwon Park’, near Geelong. Some werereleased or escaped soon after. One ofAustin’s descendants suggests that therewere only 13 rabbits, some of which werecaught in the wild and some of which werehutch-bred.

‘Domestic rabbits arrived inAustralia with the First Fleet

in 1788.’

In 1866, 14 253 rabbits were shot on‘Barwon Park’. Initially, rabbits spreadslowly from ‘Barwon Park’ and from asecond release point at Kapunda in SouthAustralia, taking about 15 years to reach

the New South Wales border (Rolls 1969;Stodart and Parer 1988). Fifteen years laterthey were into Queensland, and by 1900they were in Western Australia and theNorthern Territory (Figure 2). The rate ofadvance varied from 10–15 kilometres ayear in the wet and forested country to over100 kilometres a year in the rangelands.The rate of spread was mostly faster thanin New Zealand and in Argentina, whereit was about 10–15 kilometres a year. It wasthe fastest rate of any colonising mammalanywhere in the world (Caughley 1977),although it was closely matched by the fox(Vulpes vulpes) and the hare (Lepuseuropaeus) in Australia (Jarman 1986a, b).The fox crossed from Victoria into New


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Figure 2: Spread of the rabbit in Australia (no data available for Tasmania) (after Stodart andParer 1988).

South Wales 13 years after the rabbit andentered Queensland from the New Englanddistrict at the same time as the rabbit; itentered Queensland in the far west 24 yearsafter the rabbit.

As in Europe, human changes to thenatural environment made it more suitablefor rabbits. Rabbits moved up river systems,which were the first areas selected bypastoralists (Strong 1983). Felled timberprovided abundant rabbit harbour, and thegrazing of perennial grasses by domesticstock made the grasses more nutritious andavailable to rabbits. The introduction ofmore nutritious annual grasses and forbs ofMediterranean origin, which have a seasonalgrowth cycle more in tune with the rabbit’sbreeding season, also helped. Thenorthward spread of rabbits in Queenslandthis century is the result of improvementsin the nutritionally poor tropical pasturesand the planting of winter crops (Parer 1987;Stodart and Parer 1988).

‘The rate of spread of therabbit in Australia was the

fastest of any colonisingmammal anywhere in the

world.’

As the Australian environment wasmodified by people, many native speciesand the hare went through one brieferuptive phase, but only the rabbit remainedat high densities (Jarman and Johnson 1977;Lunney and Leary 1988). The presence ofburrows of native species (Vombatus spp.,Bettongia lesueur, Macrotis lagotis,Lagorchestes hirsutus) aided its spread, asdid the wholesale destruction of predators.At ‘Barwon Park’ in 1866 the shooting tallywas 448 hawks, 23 wedgetail eagles, 622native cats and 32 feral cats (Rolls 1969). Inthe early stages of the rabbit’s spread, onlyshort, shallow warrens were dug, but withthe arrival of the fox deep warrens had tobe excavated (Abbott 1913; Matthams 1921;Gooding 1956; Tunbridge 1991).


2. Distribution andAbundance

SummaryRabbits are one of the most widelydistributed and abundant mammals inAustralia. South of the Tropic of Capricornthey occur almost everywhere except at thehighest altitudes, in dense forests or oncertain soil types. North of the Tropic ofCapricorn their distribution is morefragmented, they are often restricted to deepor shaded warrens on the more fertile soilsin run-on areas, or to areas with a shallowwatertable.

After the introduction of myxomatosis in1950, rabbit numbers fell by about 95% inmost of southern Australia and by almost100% in marginal habitats. The impact ofthe disease was greatest in semi-arid areaswhere mosquitoes are seasonally abundant,and least in the more arid rangelands andon the tablelands where mosquitoes are lessabundant. The present density of rabbits inAustralia compared to the density beforemyxomatosis is not known. On average,rabbit densities may be about 5% ofpremyxomatosis densities in the higherrainfall areas and perhaps 25% in therangelands. In the more arid rangelands,numbers increase during favourableseasons and decline during droughts toaround 1% of peak numbers. Because ofthese large fluctuations it is difficult todiscern any long-term trend. In higherrainfall areas, numbers are generallydecreasing due to the expansion of cropping,the increased use of warren ripping andproperty development. Numbers may beincreasing in some districts in locationssuch as rocky hills where control is difficult.

2.1 Distribution in Australia

South of the Tropic of Capricorn rabbits canoccur almost anywhere except in denseforests, on black soil plains or above 1500metres (Parker and Bults 1967; Parer andLibke 1985). North of the Tropic of

Capricorn their distribution is fragmented.Tall tropical grasslands are nutritionallyinadequate for rabbits, and pasture growthoccurs at the wrong time for rabbit breeding.In the arid tropics, rabbits must contendwith short breeding seasons, high warrentemperatures, dry pastures on infertile soilsand mineral deficiencies and imbalances(Cooke 1977a; Parer 1987). In these areasrabbits also have problems with waterbalance and thermoregulation and are oftenrestricted to deep or shaded warrens on themore fertile soils in run-on areas, or to areaswith a shallow watertable.

In the more arid areas below the Tropicof Capricorn, local distributions of rabbitschange dramatically with time. After a runof good seasons, rabbits may be abundantover an entire region. During severedroughts they disappear completely fromsome land systems and their range contractsto refuge areas where there are large, deepwarrens alongside drainage channels ordried-up swamps (Myers and Parker 1975a, b).

‘Rabbits prefer well-drainedsoils — they are not found inblack cracking soils which

become waterlogged.’

Soils are a major factor influencing localand regional distribution (Parker et al. 1976;Parer and Libke 1985). Warrens are largerand more dense in the deeper soils on lowerslopes and flats. These areas are also the mostproductive areas for domestic stock and areimportant for drought fodder (Mutze 1991).Rabbits prefer well-drained soils. Warrensare never found on black cracking soils whichbecome waterlogged and the few rabbitsliving on this soil type breed in hollow logs.Warren density is higher on deep sands thanon shallow sands (Matsumoto 1985). Thismay be due to fox predation or totemperature effects (Wood 1980; Parer andLibke 1985). Rabbits are absent from thePilbara and Ashburton districts of WesternAustralia due to a combination of shallowsoils and a nutritionally deficient pasture(Newsome 1975; King 1990).


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Before myxomatosis, rabbits were notdistributed evenly over southern Australia.Even in the climatically favourable Riverinadistrict in New South Wales they were atmoderate or high densities over only 35–40%of the district (Myers 1962). Aftermyxomatosis was successfully introduced,their distribution changed dramatically inthe Riverina. Within a few years they hadalmost disappeared from the flat orundulating country and had retreated to thewell-drained sandy areas or to the rocky,timbered hills (Figure 3). Similar butunrecorded changes in local distributionprobably occurred over much of Australia.

Rabbit numbers tend to be low in muchof the sheep–wheat zone. In closely settled

districts, cropping, pasture improvement,poisoning and warren destruction restricthigh rabbit densities to places wherevehicle access or warren destruction isdifficult.

2.2 Changes in abundancewith time and space

Although rabbit densities are rarely knownprecisely, references in this document tolow, medium and high rabbit densitiesdenote, approximately, less than 1.0, 1–4and more than four rabbits per hectarerespectively. Spotlight transect counts oflow, medium and high rabbit densities inopen country with low pasture areapproximately less than 5, 6–30 and more


1951 1952 1953 1954 1955 1956 1957 1958 1959 1960

20

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Creek frontages and swamps

Stands of pine and box on sandy soils

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Figure 3: Rabbit infestation trends in different land types in the Riverina district of New SouthWales after the introduction of myxomatosis (after Myers 1962).

than 30 rabbits per spotlight kilometrerespectively.

‘On average, the number ofrabbits in higher rainfallareas may be 5% of pre-

myxomatosis levels; in aridareas the figure may be

around 25%.’

In the rangelands where rainfall is lessthan 300 mm, numbers build up after a seriesof good seasons and then collapse duringdrought (Figure 4) (Myers and Parker 1975

a, b; Newsome et al. 1989). The collapse isdue to the low water and energy content inthe available forage and/or to depletion ofavailable pasture by rabbits and stock.Numbers may then remain low for someyears. The rate of resurgence depends onrainfall, predator numbers and warrenavailability. In sand dunes 99% of warrenscan disappear in a drought and populationrecovery is slower than in stony areas wherewarrens are more permanent (Figure 4).Rabbit densities tend to be higher andfluctuate less in the more lightly grazed parts


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Figure 4: Rainfall and fluctuations in rabbit populations in different land systems in western NewSouth 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 stockwatering points (Newsome 1993). In semi-arid areas populations decline but do notcollapse in droughts except locally wherethere are very high rabbit populations (Parer1977).

Besides varying between years, rabbitpopulations have an annual cycle. The lownumbers at the beginning of the breedingseason increase by a factor of 2–5 to a peaktowards the end of the breeding season(Gilbert et al. 1987).

The current density of rabbits in Australiacompared to the situation before


Table 1: Percentage of New South Wales withrabbits at different levels of abundance (afterCroft 1990).

Density* 1980 1985

Nil 34.7 23.7Low 33.5 42.0Medium 21.7 21.7High 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, rabbitsvisible 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). Thedensity 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 overgood and bad years the numbers in betterrainfall country may be 5% of thepremyxomatosis numbers; in the arid zonethe figure may be 25% (Myers 1962).Estimates of rabbit densities aftermyxomatosis for 27 sites ranged from 2–97per hectare with an average of three perhectare (Wood et al. 1987).

In general, high rabbit numbers overlarge areas are found only in those areaswhere management is difficult or neglected,or in some rangeland areas where controlis not obligatory (Northern Territory) orthe legislation is not enforced becausecontrol is perceived to be uneconomic.

‘The areas where rabbits are amajor problem for economicor conservation reasons are

the southern third of theNorthern Territory, the

northern three-quarters ofSouth Australia, western NewSouth Wales and the Nullarbor

Plain in Western Australia.’

The areas where rabbits are a majorproblem for economic or conservationreasons are the southern third of theNorthern Territory, the northern three-quarters of South Australia, western NewSouth Wales and the Nullarbor Plain inWestern Australia. Rabbits are low innumbers throughout most of thesheep–wheat zone because the area is flat,largely cleared, occasionally cultivated andthe warrens are accessible and easilyripped. In higher rainfall country the mainproblem areas have a patchy distributionand are usually found on land with steephillsides, gullies with steep sides, largerocks, abundant fallen timber, or lowscrubby vegetation. In 1980 and 1985,65–68% of New South Wales had few or norabbits and 10–13% had high numbers(Table 1). The distribution of rabbits inAustralia is shown in Figure 5.

In higher rainfall areas numbers areprobably decreasing due to propertydevelopment and the increasing use of

warren ripping (Nolan 1981). In some areasof Victoria, however, where control isdifficult, the increase in rabbit numbers isreflected in the ten-fold increase in the useof 1080 poison during the last decade(I. Nolan, Keith Turnbull Research Institute,pers. comm. 1992). In Queensland, rabbitnumbers in a million hectare area aroundStanthorpe/Inglewood/Texas/Goondiwindiseem to have decreased for reasons thatare not obvious. Commencing in 1964, theQueensland Rabbit Control Authority, thefunctions of which are now undertaken bythe Land Protection Branch of theDepartment of Lands, employed 12operators who were continuouslypoisoning. The overall infestation declinedto such an extent that by 1983 only fiveoperators were employed for spotpoisoning. However, because of the greatvariations in rabbit numbers with seasonalconditions, it is difficult to detect any long-term trend over much of the rangelands.


1

3. Biology

Summary

The European wild rabbit belongs to thefamily Leporidae which has 52 species ofhares and rabbits living in grassland andsavanna ecosystems on four continents.Unlike hares, which rely on speed andendurance to elude predators, the variousspecies of rabbits live near dense cover towhich they flee when threatened. TheEuropean wild rabbit is the only rabbit thatconstructs large warrens, and is the onlyspecies of rabbit that can live in opengrassland, because the warren provides thecover it requires.

The optimum habitat for rabbits inAustralia is the intermediate rainfall zone,where parasite numbers are low, droughtsare uncommon and breeding seasonsrelatively long. Rabbits occasionally do wellin Australia’s hot arid zones even thoughphysiologically they are not well adapted toarid conditions. When some greenvegetation is available, they readily find thehigh protein, high water content diet theyneed to survive and reproduce. The key totheir success in most environments, butparticularly in the arid zone, is their abilityto build warrens. The warren protectsrabbits from predators and climaticextremes. However, during prolongeddrought when food quality and quantitydecline their populations crash.

Survivors of a population crash tend tobe adult rabbits. After the breaking of adrought, rabbit populations are held at lowdensities for several years by a combinationof native predators, foxes and feral cats. Itis not until fox and feral cat numbersdecline some time after the crash of therabbit population, and good seasons return,that rabbit numbers build up again. Undergood conditions, an adult female canproduce 30–40 young a year.

Adult rabbits live as territorialmonogamous pairs, or in social groups ofup to ten individuals with separate

hierarchies for males and females. Malesfight to defend females and females fight todefend access to breeding sites withinwarrens. As many more young males thanfemales disperse, the warren is a heritagepassed on by adult females to femaleoffspring. Resident rabbits rarely move morethan 200 metres from their warren. Majorcauses 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 in1950 there was a rapid increase in theresistance of rabbits to the disease and adecline in the lethality of the common fieldstrains. Both resistance and virulenceappeared to stay steady from 1960 to 1975.In this period, field death rates were about40–60%. Since 1975 there has been anincrease in both resistance of the rabbit tothe virus and the killing capacity of thevirus, perhaps as a result of the introductionof the European rabbit flea. These two trendstend to compensate each other, and overalldeath rates from myxomatosis may not havebeen affected.

3.1 The European wildrabbit and its relatives

The European wild rabbit (Oryctolaguscuniculus) belongs to the family Leporidae(Myers et al. 1987). The leporid (rabbit andhare) family consists of: (1) hares andjackrabbits (Lepus) — 29 species in Europe,Asia, Africa and central and north America;(2) cottontail rabbits (Sylvilagus) —13species in the Americas, the closest relativesof the European wild rabbit are the cottontailrabbits; (3) European wild rabbit(Oryctolagus) — one species in Europe; and(4) eight other genera of rabbits with a totalof ten species in Asia, Africa and theAmericas.

The European rabbit was originallyclassified as a rodent in the genus Lepus.The name Oryctolagus comes from theGreek orukter (digging tool) and lagos(hare) and the Latin word cuniculus denotes


both a rabbit and an underground passage.The type locality for O. cuniculus is inGermany. The English name rabbit, orrabett, is of French origin and originallyapplied only to young rabbits. The namefor an older rabbit was cony (Barrett-Hamilton 1911).

Rabbits and hares inhabit open grassland,savanna and shrub-steppe. About fivespecies of rabbits construct warrens withmore than one entrance; only the Europeanwild rabbit makes large warrens. Leporidsshare with marsupials the unusualanatomical feature of the scrotum being infront of the penis. Body weight of rabbitsand hares ranges from 0.4–4 kilograms, witha mean of about two kilograms. Maximumrunning speed is correlated with body size(Cowan and Bell 1986); the larger hares relyon speed to escape predators, and thesmaller rabbits depend on reaching thesafety of some form of cover. They have apivotal role in the predator–prey complexin most of the world’s grassland ecosystems.Because of their size and fecundity, they arefood for most birds of prey and for a wholerange of mammalian predators as small asweasels (60–120 g) or as large as cheetahs(60 kg). It is generally considered that rabbitand hare populations are regulated largelyby predation on, and dispersal of, younganimals (Edwards et al. 1981; French andHeasley 1981; Henderson 1981; Stevens andWeisbrod 1981; Wagner 1981; Wolff 1981).

Hares have a gestation period of 37–46days and have small litters (two to three)which are born fully-furred and mobile inrudimentary above-ground nests. Incontrast, rabbits have a gestation period ofabout 30 days and have large litters (four toseven) of blind, deaf and almost nakedyoung in short burrows or in elaborateabove-ground nests. All leporids visit theiryoung only once a day and feed them forabout five minutes; this is thought to be astrategy to minimise the amount of scentwhich could attract predators. Mortality,particularly in the young, is high.

Although leporids do not usuallyconsume a high proportion of the primary

production, that proportion may be a largefraction of the highly digestible plants(Wagner 1981).

The only leporid in Australia, apart fromthe wild rabbit, is the European hare (Lepuseuropaeus). Despite the much larger size ofthe hare, the rabbit dominates it inaggressive encounters and female rabbitskill young hares (Evans and Thompson1972; Flux 1981; Mykytowycz 1981). Thereis often an inverse correlation betweenrabbit and hare densities (Rothschild andMarsh 1956; Evans and Thompson 1972;Flux 1970; Broekhuizen 1975).

3.2 Body characteristics ofthe rabbit

European wild rabbits typically have grey-brown back fur and a white-grey belly. Malesand females are similar in size andappearance, except that males have a slightlybroader head. Colour variants usuallycomprise less than 2% of the population,although sandy coloured rabbits are commonin some arid areas, and black rabbits arecommon in the high country in Tasmania(Barber 1954). Rabbits have a major moultin spring and a minor moult in autumn. Darkpatches on the inside of the skin indicate theprogress of the moult (Stodart 1965). Juvenilerabbits moult at three months of age; theyfrequently have a white star on their forehead


1

The most common form of the European wildrabbit, 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 arecovered in fur which protects the foot padsfrom excesses of heat and cold and enablesthe rabbit to move very quietly. The eyesare placed to the sides of the head and areslightly protruding so that the rabbit haspanoramic vision. The rabbit has a sensorypad partly concealed by hairy folds of skinat the entrance of each nostril, and a Y-shaped groove extends from the upper lipto the nose.

Rabbits have 16 teeth in the upper jawand 12 in the lower. There are two pairs ofupper incisors; the second smaller incisorsare behind the first, a feature thatdistinguishes leporids from rodents. Theincisors grow continuously. The cementumof the incisors is thicker in the front than atthe rear and because of differential wear theyare worn to a sharp chisel shape.

At birth the young weigh 35 g each. Bythe time they first emerge from the warrenat 21 days they have increased their bodyweight by 600% to 210 g each. The totalweight of a litter of six at emergence is 80%of the normal weight of the mother. Apartfrom nursing there is no obvious parentalcare. Up to 900 g, weight gain is essentiallylinear (10 g/day), so body weight can beused to age rabbits under 900 g using theequation age (days) = weight (g) ÷ 10 (Parer1977; Daly 1979; Wheeler and King 1980).The most accurate method of estimating theage of a rabbit is from the weight of the driedeye lens which grows throughout life (Myersand Gilbert 1968; Wheeler and King 1980).

3.3 Shelter

In Australia, wild rabbits live in a variety ofsituations which can be classified broadlyby the amount of surface cover that isavailable to them. Where cover is dense andabundant rabbits tend to dig only smallwarrens and live mainly on the surface(Section 3.3.2). Large warrens occur mainlyin open country such as cleared land, grazedpasture and arid areas. Vegetation in theparts of Australia occupied by rabbits rangesfrom (1) shrub (scrub and bracken thickets),

either with or without an overstorey of trees;(2) patches of dense scrub interspersed withpatches of grassland in various proportions;(3) savanna woodland with extensivegrassland; (4) grasslands of varyingvegetation density; through to (5) short orsparse grass with varying extents of bareground (Figure 6). This variation invegetation cover can be viewed as acontinuum in which the range or abundanceof surface cover varies. As surface cover getsless, warrens become larger and the rabbitsdepend increasingly on underground shelter(Figure 6).

3.3.1 The warren

‘Although the rabbit makes the warren, itis the warren that makes the rabbit’(Andrewartha and Birch 1984).

Contrary to popular opinion, rabbits do notreadily dig new warrens, except on sandysoils (Parer 1977; Cowan 1987a). In newlycolonised areas without warrens a rabbitwill generally live in what is called a squat— a shallow depression in long vegetationor under fallen timber. A squat-dwellingpregnant female will dig a shallow burrow,a stop, in which to have her litter. Theentrance to the stop is covered with soiland is difficult to detect. Separate tunnelsmay be dug within a stop for successivelitters and the stop is then called a warren(Mykytowycz et al. 1960).


Warren complexes are generally larger inmore open country, with a greater proportionof rabbits living underground (as indicatedin Figure 6). Source: CCNT

photo 10*positional only


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