Bureau of Resource Sciences
Managing Vertebrate Pests: Foxes
Glen Saunders, Brian Coman, Jack Kinnear and Mike Braysher
Australian Government Publishing Service Canberra © Commonwealth of Australia 1995
ISBN 0 644 29240 7 (set) ISBN 0 644 (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.
Credits for cover photograph. Main: C. Marks, DCNR, Victoria. Insert: G. Chapman, CSIRO.
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.
Author affiliations: Glen Saunders, NSW Agriculture; Jack Kinnear, Department of Conservation and Land Management, Western Australia; Brian Coman, Vernox Pest Management; Mike Braysher, Bureau of Resource Sciences.
Publication to be cited as:
Saunders, G., Coman, B., Kinnear, J. and Braysher, M. (1995) Managing Vertebrate Pests: Foxes. Australian Government Publishing Service, Canberra.
Printed for AGPS by Paragon Printers, Wollongong Street, Fyshwick ACT 2609 FOREWORD
This publication, which is one in a series, to their role as pr edators. Despite this provides land managers with ‘best practice’ perception, there is little r eliable information national guidelines for managing the agri- on the effects of fox pr edation on prey cultural and environmental damage caused populations or of the ef fect of fox contr ol by foxes. Others in the series include on the recovery of prey species. The guidelines for managing feral horses, exception is in Western Australia, where rabbits, feral goats, feral pigs and r odents. some field experiments have shown that fox The publication was developed and funded control can lead to the r ecovery of native by the Vertebrate Pest Program in the species, including rock-wallabies, bettongs Bureau of Resource Sciences. Production and numbats. Foxes may also detrimentally of the fox guidelines was aided by financial affect native species such as bir ds of pr ey assistance from the Australian Natur e and large reptiles by competing with them Conservation Agency’s Feral Pests Pr ogram. for food, but such impacts ar e speculative To ensure that the guidelines ar e widely as no studies have been conducted. accepted as the basis for fox management, Less is known about the agricultural comment has been sought fr om state, impact of foxes, although ther e is increasing territory and Commonwealth gover nment evidence that foxes may inflict sever e levels agriculture, environmental and r esource of lamb pr edation which were previously management agencies. Comments wer e also unrecognised. Foxes ar e also implicated in sought from land managers and community deaths and injuries to calves and dairy cattle, and other organisations, including the although this impact has not been Australian Conservation Foundation, the quantified. There is also a small risk that National Farmers’ Federation, the National foxes could have a r ole in the spr ead of Consultative Committee on Animal W elfare, exotic diseases, such as rabies, should such the Anangu Pitjantjatjara Aboriginal Land diseases enter Australia. Council and the Norther n Land Council. The Standing Committee on Agricultur e and There are diverse views about fox Resource Management has endorsed the management. While economists would approach to managing fox damage set out argue that spending on pest contr ol should in these guidelines. be justified in ter ms of the economic r eturns on such investments, this is clearly dif ficult Foxes are widely perceived by the wider when the impacts of foxes for both con - community and by scientists and conser - servation and agricultural values, and the vationists as a thr eat to native species due
Bureau of Resource Sciences iii responses of pr ey populations to fox The principles underlying the strategic control, are poorly quantified. Those with management of vertebrate pests have been an interest in conservation place a high described in Managing Vertebrate Pests: value on the pr otection of native species Principles and Strategies (Braysher 1993). and often consider fox contr ol to be a The emphasis is on the management of pest priority for endanger ed species pr otection. damage rather than on simply r educing pest People interested in hunting foxes for density. The guidelines r ecommend that commercial use or r ecreation want to r etain wherever practical, management should foxes as a r esource. The crash of fox pelt concentrate on achieving clearly defined prices resulting from the actions of the anti- conservation or agricultural pr oduction hunting lobby in Eur ope has r educed objectives. interest in fox harvesting in r ecent years. These guidelines will help land managers People concerned with animal welfar e hope reduce damage to agricultur e and native to ensure that fox contr ol or harvesting is fauna caused by foxes thr ough the use of conducted using humane techniques. The scientifically-based management that is authors have attempted to take all these humane, cost-effective and integrated with divergent views and values into account in ecologically sustainable land management. compiling the guidelines.
Peter O’Brien Acting Executive Director Bureau of Resource Sciences
iv Managing Vertebrate Pests: Foxes CONTENTS
FOREWORD iii ACKNOWLEDGMENTS viii ACRONYMS AND ABBREVIATIONS ix GLOSSARY x SUMMARY 1 INTRODUCTION 7
1. HISTORY 11 Summary 11 1.1 Europe and America 11 1.2 Australia 11
2. DISTRIBUTION AND BIOLOGY 15 Summary 15 2.1 Distribution and abundance 15 2.2 Biology 18
3. ECONOMIC AND ENVIRONMENTAL IMPACTS 27 Summary 27 3.1 Environmental impact 28 3.2 Economic impact 37 3.3 Resource value and use 41
4. RABIES AND FOXES 43 Summary 43 4.1 The disease 43 4.2 Management techniques for rabies contr ol 45 4.3 Implications for Australia 46 4.4 Implications for fox management 47
5. COMMUNITY ATTITUDES AFFECTING FOX MANAGEMENT 48 Summary 48 5.1 Perceptions of the fox 48 5.2 Sport hunting 48 5.3 Animal welfare 49 5.4 Implications of fox harvesting for damage contr ol 54
6. PAST AND CURRENT MANAGEMENT 56 Summary 56 6.1 History 56 6.2 Legislation and coordination of management pr ograms 57
7. TECHNIQUES TO MEASURE AND CONTROL FOX IMPACT AND ABUNDANCE 63 Summary 63 7.1 Introduction 63 7.2 Assessing impact 64 7.3 Measuring fox abundance 68 7.4 Use of fox impact and density measur ements 70 7.5 Control techniques 72
Bureau of Resource Sciences v 8. STRATEGIC MANAGEMENT AT THE LOCAL AND REGIONAL LEVEL 88 Summary 88 8.1 Economic frameworks 89 8.2 Strategic approach 89 8.3 Problem definition 89 8.4 Management plan 90 8.5 Implementation 94 8.6 Monitoring and evaluation 94 8.7 Hypothetical example of strategic management at local and regional level — conservation 95 8.8 Hypothetical example of strategic management at local and regional level — agricultur e 98
9. IMPLEMENTING MANAGEMENT OF FOX DAMAGE 101 Summary 101 9.1 Introduction 101 9.2 Role of gover nment and landholders 101 9.3 Use of community gr oups 102 9.4 Community awareness 104
10. DEFICIENCIES IN CURRENT KNOWLEDGE AND APPROACHES 106 Summary 106 10.1 Introduction 106 10.2 Specific deficiencies 107
REFERENCES 112
APPENDIX A Native species believed to be at risk fr om fox pr edation 126
APPENDIX B Technique for the manufactur e and use of cyanide capsules 127
APPENDIX C Instructions for the use of FOXOF F® baits 128
APPENDIX D Criteria for eradication 132
APPENDIX E Best practice extension in pest management 133
APPENDIX F Economic framework for feral pig management 135
INDEX 139
FIGURES Figure 1 Strategic approach to managing fox damage. 8 Figure 2 Spread of the r ed fox in Australia. 12 Figure 3 Interrelationship between fox and rabbit populations. 13 Figure 4 Relative distribution of foxes and rabbits in Australia. 14 Figure 5 Present-day world distribution of the r ed fox. 16 Figure 6 Variations with time of rabbit and pr edator (cat and fox) numbers in central-western New South Wales. 20 Figure 7 Variation in fox and feral cat numbers in r elation to changes in rabbit numbers in south-wester n Western Australia. 21
vi Managing Vertebrate Pests: Foxes Figure 8 Predator removal experiment conducted over eight years in Western Australia for five colonies of r ock-wallabies. 29 Figure 9 The relative abundance of Rothschild’s r ock-wallaby, before and after fox contr ol in the Dampier Ar chipelago. 30 Figure 10 Percentage capture rate of bettongs after five years of fox contr ol in Tutanning Nature Reserve.31 Figure 11 Numbat sightings in Dryandra State For est between 1979 and 1992. 32 Figure 12 The quantity of 1080 and the number of baits used for fox contr ol in New South Wales between 1980 and 1993. 55 Figure 13 Bounty payments in Western Australia. 57 Figure 14 Determining the cause of lamb death. 66 Figure 15 Example of a simple map of four hypothetical pr operties showing the key factors that landholders should r ecord and use to plan fox management. 71
TABLES Table 1 Density estimates of Australian fox populations. 17 Table 2 Comparison of mean home range estimates for foxes in dif ferent habitats. 22 Table 3 Percentage occurrence and percentage volume of major food items identified in the stomachs of foxes. 23 Table 4 Quantity and value of wild r ed fox pelts supplied during 1982–83 from the major exporting countries involved. 41 Table 5 Number and value of raw fox pelts exported fr om Australia. 41 Table 6 Number of 35 milligram strychnine baits pr epared for fox contr ol in South Australia in 1984–85 to 1990–91. 61 Table 7 State and territory legislative r equirements for fox poisoning. 75
Bureau of Resource Sciences vii ACKNOWLEDGMENTS
The Vertebrate Pests Committee’s Working • Standing Committee on Agricultur e and Group, which is overseeing the pr eparation Resource Management of the guidelines — Peter Allen, Roger • Australia and New Zealand O’Dwyer, John Hicks, Don Pfitzner , Kevin Environment and Conservation Council Heinrich, Neil Hogstrom and John Auty — – Standing Committee on provided valuable input and comments. Conservation – Standing Committee on the Special acknowledgment is given to the Environment following people who made helpful • Land and Water Research and comments on the draft manuscript: Peter Development Corporation Alexander, Peter Bir d, Peter Catling, Terry • Meat Research Corporation Korn, Geoff Lundie-Jenkins, Clive Marks, • Rural Industries Research and Nicky Marlow, Nick Mooney, Glenys Development Corporation Oogjes, Jeff Short, Linton Staples, Jim • International Wool Secretariat Thompson and Paul de T orres. • Australian Conservation Foundation Several individuals from the Bur eau of • National Consultative Committee on Resource Sciences deserve mention. Quentin Animal Welfare Hart and Hazel Small helped edit the • National Farmers’ Federation manuscript and figur es. Deborah McLeod • Murray Darling Basin Commission assisted with pr eparation of the manuscript. • Australian Veterinary Association Mary Bomford provided extensive scientific • Anangu Pitjantjatjara Land Council and other editorial comment. Quentin Hart We wish to thank all these gr oups for their and Mary Bomfor d organised the final contributions. Many other people, too collation and publication. numerous to acknowledge individually, also The draft manuscript was cir culated to the gave us the benefit of their experiences by following organisations for comment: commenting on drafts of the manuscript. The Australian Nature Conservation Agency • Commonwealth Department of Primary provided financial assistance. Industries and Ener gy
viii Managing Vertebrate Pests: Foxes ACRONYMS AND ABBREVIATIONS
ANCA Australian Nature LandCare Victorian Landcare Program Conservation Agency MAFF Ministry of Agriculture, ANZFAS Australian and New Zealand Fisheries and Food (United Federation of Animal Societies Kingdom) APB Agriculture Protection Board NLP National Landcare Program (Western Australia) (now part of the Natural APCC Animal and Plant Contr ol Heritage Trust) Commission (South Australia) PMIS Pest management infor mation AUSVETPLAN Australian Veterinary system Emergency Plan RLPB Rural Lands Pr otection Board AVA Australian Veterinary RSPCA Royal Society for the Association Prevention of Cruelty to BRS Bureau of Resour ce Sciences Animals CALM Department of Conservation SCARM Standing Committee on and Land Management Agriculture and Resour ce (Western Australia) Management CCNT Conservation Commission of VPP Vertebrate Pest Program (BRS) the Northern Territory (now National Feral Animal (now Parks & W ildlife Control Program) Commission of the Norther n Territory) CRC Cooperative Research Centre for Biological Contr ol of Vertebrate Pest Populations CSIRO Commonwealth Scientific and Industrial Research Organisation DCNR Department of Conservation and Natural Resources (Victoria) (now Department of the Natural Resources and the Environment) DEST Department of Envir onment, Sport and Territories ERIN Environmental Resources Information Network ESAC Endangered Species Advisory Committee FPP Feral Pests Program (ANCA) GIS Geographic information system HCAV Hunt Clubs Association of Victoria HIPD Hunting indicator of population density Landcare Commonwealth Landcare Program
Bureau of Resource Sciences ix GLOSSARY
abortifacient: a chemical used to induce endocrine function: the r elease, abortion distribution and ef fects of hormones in ad hoc measures: specially arranged for an animal’s body the purpose endoparasite: animals that live inside anticoagulant: a substance that slows or another animal’s body, such as tapewor ms prevents blood clotting. Anticoagulants and the bacteria in the digestive tract may be used as poisons to kill pest enzootic areas: areas where a disease animals. occurs in wildlife attenuated strains: a weak strain of an European rabbit flea: a flea intr oduced to infectious organism assist the spr ead of myxomatosis biltong: strips of sun-dried, lean meat family group: occupants of a fox territory, biocontrol/biological control agent: a usually composed of a monogamous living organism (or a virus) used to adult pair and their of fspring from the control the population density of previous breeding season; a dominant another species adult pair, subordinate adults and brittilised capsule: a capsule for oral offspring, or other common combinations dosing of animals that has been made forb: a soft herb-like plant with a non- brittle so it will easily shatter when woody stem, especially a pastur e plant eaten but is safe to carry that is not a grass cadastral information: usually includes geographic information system (GIS): property boundaries, land tenur e and acomputer-based system for displaying, roads overlaying and analysing geographic Canidae, canids: the family of animals information such as vegetation, soils, that includes dogs, foxes and wolves climate, land use and animal distributions carcinogenic: cancer causing gestation: pregnancy carrying capacity: the maximum number home range: the area an animal ranges of animals that the r esources available over during its nor mal daily activities in an area of land can support immunosterility: causing an animal to chenopod: plant of the family become sterile by immunising it against Chenopodiaceae. In arid ar eas of one of the pr oteins or hor mones Australia chenopods are mostly salt- involved in the r eproductive process tolerant shrubs such as blue bush and index, indices: a measur e which is salt bush. correlated with a value but is not an crepuscular: animals active at dawn and actual estimate of that value. For dusk example spotlight counts give an index dasyurids: animals in the family of of fox numbers but do not give an carnivorous marsupials Dasyuridae, estimate of total numbers. including quolls, dunnarts, intraperitoneal: into the abdominal cavity antechinuses, planigales, ningauis and intubation: to insert a tube into the Tasmanian devil LD50: the quantity of poison or lethal dose diurnal: animals active during the day that will kill 50% of tr eated animals dystocia: difficult birth macropods: animals in the Macr opodidae endangered species: species in danger superfamily which includes kangar oos, of extinction and whose survival is wallabies, bettongs, rat kangar oos, unlikely if the causal factors leading to potoroos, pademelons and tr ee their decline continue to operate kangaroos
x Managing Vertebrate Pests: Foxes minimum convex polygon: a simple translocation: moving a species to a method for calculating the ar ea different place or habitat enclosed by an animal’s home range. It ultrasound scanning: use of low involves drawing the smallest possible frequency sound to investigate the convex polygon around the outermost internal structure of an animal without locations or sitings of the animal. surgery, used for counting foetuses monoestrus: become reproductively vectors: organisms or substances that ar e receptive only once per year vehicles to spread a biocontrol agent or neophobia: fear of new things disease among animals. For example, nocturnal: animals active at night mosquitoes are vectors of myxomatosis. one-shot oats: technique for poisoning vulnerable species: species believed rabbits using 1080 and oats wher eby likely to become endanger ed in the only one in one hundr ed oat grains near future if the causal factors continue contain 1080 poison, suf ficient to kill an to operate adult rabbit oral delivery: a dose swallowed in food Note: All money values thr oughout the or drink guidelines are in 1993-94 Australian dollars. parturition: birth pelt: the skin and fur, either raw or dr essed population turnover: the average time it takes to replace a generation
RD50: the concentration of a sensory irritant which pr oduces a 50% decr ease in an animal’s br eathing rate recombinant virus: a virus which has been modified by artificial genetic manipulation relict population: a small isolated population of a species that was once more widespread and abundant scat: faeces secondary poisoning: intoxication or death of animals caused by ingestion of other poisoned animals spotlight traverse: a fixed line of travel over which animals in a spotlight beam are counted sylvatic: involving one or mor e wildlife species tarbaby: a technique for killing foxes where 1080 poison in gr ease is squirted into a fox den. The fox dies fr om ingesting the poison gr ease from fur and paws. territory: the area an animal or gr oup of animals defends from intruders tetanic spasms: violent generalised muscular contractions with flailing limbs transect: a rectangular plot in which data collection occurs
Bureau of Resource Sciences xi xii Managing Vertebrate Pests: Foxes implementing control on reducing the SUMMARY damage. We have little r eliable information of this type for fox management. In The introduced European red fox (Vulpes developing these guidelines, the authors vulpes) is widely distributed thr oughout the have used available infor mation, but land southern half of Australia in virtually all managers responsible for fox contr ol will habitats, including urban envir onments. still have to make assumptions about fox Foxes are seen as a major pest species impact and the ef ficacy and cost- threatening the long-term survival of a range effectiveness of contr ol techniques until of native fauna. The r eview of fox damage more reliable information becomes undertaken in developing these guidelines available. It is expected that in planning and confirmed this threat, although scientifically implementing fox management, gover nment quantified information of fox damage is land management agencies will closely based mainly on studies in W estern involve community-based gr oups such as Australia. Foxes ar e also an agricultural pest Landcare. because they pr ey on lambs and other livestock. The fox problem These guidelines contain a compr ehen- sive review of the history of foxes in Within 30 years of their initial r elease in Australia, their biology, the damage they southern Victoria in the 1860s, foxes wer e cause, and past and curr ent management. proclaimed as a pest in some shir es of north- The attitudes of conservationists, animal east Victoria. Pest status was based initially welfare groups, commercial and r ecreational on livestock predation, particularly on hunters, and other inter est groups are newborn lambs. examined. Management techniques and Significant predation by foxes on strategies for fox contr ol are recommended endangered or vulnerable species has long and illustrated by case studies. Deficiencies been suspected; but only in the last decade in knowledge, management and legislation has scientific evidence been pr oduced which are identified. directly incriminates the fox as a major cause of population decline in some species. The best known example is that of the black- Why develop national guidelines? footed rock-wallaby (Petrogale lateralis), These guidelines for managing the impact living in small, r elict colonies in the wheat- of foxes have been developed under the belt of Western Australia. Here, high-level Vertebrate Pest Program (VPP) administered management of local fox populations using by the Bur eau of Resource Sciences (BRS) poisoned baits r esulted in a substantial which is pr oducing a series of pest increase in wallaby numbers. These fox management guidelines in cooperation with removal experiments have now been the Vertebrate Pests Committee. The major repeated in other ar eas and for other wildlife pests being addr essed in the series ar e foxes, species. The evidence suggests that in nearly feral horses, rabbits, feral goats, feral pigs all cases, the r emoval of foxes r esults not and rodents. only in substantial population incr eases but The purpose of the guidelines is to assist a wider use of the habitat by the particular the development of strategies to r educe the prey species concer ned. Circumstantial damage foxes cause to pr oduction and evidence based on fox distribution and faunal conservation using the most cost-ef fective abundance consistently indicates that the fox approaches. Ideally, such strategies ar e is an important pr edator of some smaller based on r eliable, quantitative information wildlife species. about the damage caused by the pest, the The findings concerning fox damage to cost of control measures, and the ef fect of native fauna outlined in these guidelines
Bureau of Resour ce Sciences 1 highlight the need for conservation of Europe and North America ar e agencies in Australia to assess the extent comparable with those obtained fr om of fox damage in ar eas containing wildlife limited studies in some parts of souther n vulnerable to fox pr edation. Where the Australia. This suggests that conditions ar e damage is significant, they should theoretically suitable for the disease to implement fox management using the become established and to persist at least appropriate technique and strategy in southern Australia. Ther e are, however, outlined in these guidelines. Further many strains of the rabies virus overseas decline or extinction of native fauna may and it is not clear which, if any, of these result if this course is not followed. strains might be suited to a wild animal The economic significance of foxes as rabies cycle in Australia which would predators of livestock is uncertain and involve foxes as the main r eservoir host. subject to debate. Recent studies of ewe The likelihood of a smuggled animal fertility using ultrasound scanning for developing rabies and then infecting a wild pregnancy and litter-size testing, suggest fox is low. that the losses of lambs to pr edators are There is a close r elationship between higher than earlier studies indicated. It may fox and rabbit numbers. When rabbit exceed 10% and be as high as 30%. In many populations crash, due to dr ought, instances however, other factors such as myxomatosis or Rabbit Calicivirus Disease starvation, mismothering, difficult birth and (RCD), there will be a lag period until fox cold weather may be of much gr eater numbers decline and adjust to the r educed economic significance to the sheep prey population. The likelihood of industry. These factors may also incr ease increased predation pressure on native the susceptibility of lambs to pr edation by wildlife over this period needs to be foxes. considered. Rabbit numbers may also be Losses of other livestock, particularly affected by foxes. Pr eliminary studies poultry, are probably of far less economic suggest that foxes and feral cats may slow significance. However, with a marked rise the recovery of rabbit populations after in the popularity of specialty stock and they crash due to dr ought or disease. The hobby farms, which have a wider collection potential role of foxes in rabbit contr ol and of poultry and animals susceptible to fox the impact of foxes on native wildlife predation, the cost of such pr edation by following crashes in rabbit populations foxes may be significant to individual needs to be clarified. producers. The fox in Australia carries no diseases Why do foxes prosper in Australia? of serious economic or public health A number of qualities have helped the fox significance, although recently foxes have to successfully colonise Australia including been found to harbour the hydatid parasite, their wide dietary range covering small to requiring continued surveillance of this medium-sized mammals, bir ds, reptiles and situation. Controversy still surrounds the amphibians, insects, carrion, fruit, and possible role of foxes in Australia as a human refuse. Unquestionably, though, the potential wild reservoir host for the rabies rabbit has been a major factor . Wherever virus. In many parts of the norther n rabbits are common they ar e the staple food hemisphere, the fox is the main r eservoir of foxes. The fox also has high r eproductive of this disease and, given the widespr ead success. Although litters ar e small, and distribution of foxes in Australia, the females only br eed once per year , cub possibility of rabies developing as an survival is high and most adults appear to established disease in fox populations breed. With the possible exception of mange cannot be dismissed. Fox density and and distemper, the fox has few serious movement data from rabies enzootic ar eas diseases. It also has few natural enemies.
2 Managing Vertebrate Pests: Foxes Many fox deaths ar e human induced. Sever e to planning and coordination of mange and the r eduction of rabbit numbers management. It is r ecommended that ef forts due to dr ought and disease have also caused to manage fox damage over lar ge areas significant deaths of foxes in some ar eas. primarily be coor dinated programs using Rural fox density is thought to vary between poisoned baits. These may be laid on the 0.2–7 per squar e kilometre, while they can surface or buried depending on reach 12 per squar e kilometre in urban circumstances or legislative r equirements. areas. Community-based schemes such as Landcare can help to achieve this goal. Foxes rapidly recolonise after contr ol. Development of a strategic Therefore techniques must be applied management approach regularly or tar geted for long-term control Historically, pest contr ol authorities have of damage. For example, ther e may be no encouraged management of fox damage to point in poisoning foxes to pr otect lambs livestock or wildlife in Australia lar gely by at times during the year when no damage the use of bounty schemes. Although is occurring. poisoning, shooting and trapping have been Economic frameworks need to be employed, these wer e usually by individual developed to assist land managers assess landholders. the relative value of alter native fox Traditional forms of bounty payment management strategies. Such frameworks have been shown to be inef fective and most require: definition of the economic pr oblem; fox bounty schemes in Australia have now data on the r elative costs and benefits; and stopped. The only bounty curr ently in place an understanding of why the actions of is the ‘Foxlotto’ scheme used in V ictoria individual land managers may not lead to although this is small scale. Most br oadacre optimal levels of fox contr ol and how such control is thr ough poison baits. At a local problems can be addr essed by land farm level, shooting, particularly night managers and gover nments. shooting with spotlights, driving befor e guns and gassing of br eeding dens is carried out, but the r eduction in fox density is pr obably What is the strategic approach? temporary. The emphasis in these guidelines is not on killing foxes but rather on their ef ficient Research in Western Australia has and strategic management to r educe the demonstrated that foxes can be contr olled damage they cause to pr oduction and using 1080 meat baits without risk to native conservation values. Foxes ar e but one carnivores and omnivor es (for example factor in a complex and changing quolls, bettongs, bandicoots and smaller environment that includes a highly variable dasyurids). While it is conceded that climate, fluctuating commodity prices, elements of the W estern Australian fauna other animal and plant pests, far m stock are 1080 tolerant thus pr oviding a margin and the profitability of far ming businesses, of safety, the extent of this advantage may and the viability of conservation r eserves. have been over emphasised. The procedures Land managers need to consider developed in Western Australia are likely investment in fox management in the to be applicable to other parts of Australia, context of investment in other ar eas of the provided that appr opriate risk assessment land management unit as well as in r elation research is carried out first to deter mine the to their impact on natural and semi-natural species which ar e at risk fr om 1080 ecosystems, and on the biodiversity within poisoning. them. The effective management of fox damage Achieving a strategic appr oach to the over large areas requires greater attention management of foxes and other vertebrate
Bureau of Resour ce Sciences 3 pests involves establishing four key The community generally has little components. These are: knowledge of the biology and damage foxes cause in Australia. Those who speak on the Defining the problem — The problem should need for fox contr ol often call for eradication be defined in ter ms of fox damage and the of foxes thr oughout Australia. This is clearly reduction in fox density r equired to reduce not achievable. Even with the possible or prevent the damage. success of pr esent research into Developing a management plan — Land immunosterility, continuing control will be managers must establish clear objectives required. in terms of the desir ed production or Several of the techniques used to contr ol conservation outcome sought. Options for foxes raise animal welfar e concerns, most fox management include local eradication, notably the use of steel-jawed traps. strategic management, crisis management However, the use of steel-jawed traps has and no management. Eradication will rar ely been wholly or partly banned in many states be a feasible objective. Wher e fox control and territories but hunting with dogs, is shown to be necessary, these guidelines particularly den terriers, continues. Such strongly recommend sustained, strategic hunting is not humane or ef fective, and management as the principal management often causes suf fering to both hunted and option. hunter. A leg-snare device, developed Implementing the plan — A local or r egional recently in Victoria, offers a more humane approach to fox management is usually alternative to steel-jawed traps, particularly most effective. This generally r equires in urban and semi-urban ar eas. However, coordinated action by individual pr operty humaneness of the device depends upon managers and government and other frequent inspection of the snar es and the agencies. Such action limits the extent of early removal of captured animals. Their rapid recolonisation where only small-scale acceptance will ther efore depend on the fox control is implemented. development and enfor cement of minimum inspection standards. Monitoring and evaluating the program — Monitoring has two aspects. Operational Poisoning with 1080 in buried meat baits monitoring assesses the ef ficiency of the is probably the most humane, ef ficient and control operation. Performance monitoring selective method of fox contr ol. Strychnine, involves gathering information to deter mine still registered as a fox poison in some states whether the strategy is meeting the desir ed and territories, is a much less humane poison. long-term production or conservation goal. The humaneness of 1080 is a little unclear , but because foxes ar e highly susceptible to The above approach has been adopted this poison, especially compar ed to most for developing these national guidelines, potential non-target animals, it should and the information in this r eport is continue to be used until a mor e suitable designed to facilitate the development of alternative is found. Cyanide is a humane strategies for managing foxes at the local poison that kills rapidly. Unfortunately, the and regional level. non-target impact of this poison is not well known and ther e are concerns about human Community attitudes safety. Further r esearch is r equired on the possible use of cyanide for fox contr ol. In Australia, as elsewher e, the fox is regarded as a killer, a pest, a r ogue possessed of inordinate cunning, a The future commercial resource, a har mless or even Current research aimed at immuno- beneficial component of the ecosystem, and sterilisation of foxes in Australia as an finally, an honoured object of the chase. efficient form of biocontrol should be
4 Managing Vertebrate Pests: Foxes supported, although it must be r ecognised There is a need for impr oved coordination that this is high-risk, long-ter m research. between agencies and gover nment with Managers will need to r ely on available interests and responsibilities for fox contr ol. techniques for the for eseeable future. The effect of fox pr edation on populations of a range of native species (including birds, reptiles and amphibians) in dif ferent ecosystems needs to be better quantified. At the moment, much of this work is concentrated in Western Australia and little data is available for the r est of the mainland. The relationship between fox densities and impact on pr ey populations in particular needs to be quantified. The predator–prey relationship between foxes and rabbits r equires closer study. Of particular importance is the ef fect of fluctuating rabbit numbers upon the pr ey range of foxes, especially any incr eased pressure upon endanger ed or vulnerable wildlife species as the r esult of a sudden drop in rabbit density. Currently, relatively little is known of fox ecology in Australia and ther e is wide regional variation in habitat, behaviour and population dynamics. Studies ar e required, particularly on population densities and movement across different habitats, so that land managers can use this infor mation to develop appropriate management strategies. Recent evidence suggests that historical studies on lamb pr edation in Australia may have underestimated the economic losses due to foxes. Further studies ar e needed to better quantify the losses. Commonwealth, state and territory governments must critically examine their present legislation and strategies r elating to fox management. While mor e evidence is required about the extent of fox damage to wildlife in parts of Australia other than Western Australia, there is suf ficient evidence that precautionary management of foxes is required in areas with uncommon native species susceptible to foxes. These include the smaller macropods. With the development of Landcare, and other similar community- based groups, it is possible to better coordinate fox management over lar ge areas.
Bureau of Resour ce Sciences 5 6 Managing Vertebrate Pests: Foxes approach to the management of foxes and INTRODUCTION other vertebrate pests involves establishing four key components as shown in Figur e 1. These guidelines for managing foxes ar e one Such an appr oach has been adopted for in a series developed under the V ertebrate developing these national guidelines. Pest Program (VPP) of the Bur eau of Resource Sciences in cooperation with the Vertebrate Pests Committee of the Standing Defining the problem Committee on Agricultur e and Resource Historically, the fox was consider ed a pest Management (SCARM). Others include the but not a significant pr edator of livestock in feral horse, rabbit, feral goat, feral pig and Australia. Recent studies by Lugton (1993) rodents. The need for a new appr oach to have again focused on this aspect of fox vertebrate pest management is described in damage. However, the most important Managing Vertebrate Pests: Principles and change has been the r ecognition that fox Strategies (Braysher 1993), which is a predation of wildlife is a major pr ocess companion book which should be r ead threatening the survival of many native together with these guidelines. Braysher animals. Chapters 1 and 2 outline the history (1993) explains why national guidelines for of the fox in Australia and trace the sour ces managing pest animals wer e developed, the of wild populations. Fr om this historical base, development process, and the principles on what is known about fox biology is then which pest management should be based. presented. The need to focus on damage caused by the pest and not the pest itself is str essed. Chapter 3 reviews the evidence concerning the economic and envir onmental As stated in Braysher (1993), a set of impact of foxes in Australia. These impacts guidelines for all vertebrate pests, taking are not well quantified, and further studies account of the links between them and other are needed to addr ess these deficiencies. aspects of land management, would have been more desirable than the single species approach adopted in the guidelines. This Management plan would have been consistent with the holistic The primary aim of a land manager is to approach to land management advocated meet the desired conservation and/or under the Ecologically Sustainable production outcomes for the land, using Development strategy and Landcar e. practical, cost-effective methods without Although this has not been practicable, all degrading the soil and other natural r esources the guidelines, including this one, consider on which the long-ter m sustainability of the interactions between species and other land depends. The envir onment in which aspects of land management. land managers, including far mers, operate is highly variable. A number of factors The guidelines are principally for state, influence the desir ed outcomes, such as territory and Commonwealth land fluctuating commodity prices, climatic management agencies, so that they can mor e variability including dr ought, plant and effectively manage fox damage thr ough animal pests, grazing pr essure, quality of better coordination, planning and stock and social factors such as the influence implementation of r egional and local of animal welfar e and conservation management programs. The Commonwealth organisations. has a major inter est in the management of vertebrate pests, as a manager of The objective of the national guidelines Commonwealth lands, thr ough such is to encourage the adoption of ‘best practice’ initiatives as the V ertebrate Pest Program, the fox management as distinct fr om reactive National Landcare Program and the National measures by individuals and agencies. ‘Best Strategy for the Conservation of Australia’s practice’ is based on cooperative action and Biological Diversity. Achieving the strategic adoption of a whole pr operty planning
Bureau of Resour ce Sciences 7 approach to management, pr eferably linked management (sustained, targeted or one-off); to a regional or total catchment plan. commercial harvesting and crisis management. The guidelines will have met their purpose if the strategic appr oach they advocate is There are many ways of contr olling foxes, accepted and implemented by a significant but the integration of several techniques in number of agencies and individuals. This a planned way, taking into account overall constitutes the criterion of per formance. land management, fox biology, and other variables will impr ove their effectiveness. The Chapter 4 r eviews management way in which to develop an integrated fox techniques for rabies. management program is described in Chapter A national strategy for managing foxes 8. This chapter also r eviews the elements of includes encouraging the gr oup approach. fox management strategies at local and Community attitudes strongly influence the regional levels, including r ecommended management of foxes, and these issues ar e management techniques and strategies for discussed in Chapter 5. fox control for hypothetical agricultural and conservation systems. Chapter 6 reviews both past and curr ent management and Chapter 7 r eviews techniques for measuring and contr olling fox Implementation impact and abundance. Various management options are discussed in Chapter 8. They At the national level, ‘best practice’ r equires include local eradication; strategic that the various r oles and responsibilities of
Strategic management of foxes at the national level
Defining Management Implementation Monitoring Problem Plan (Section 8.5) and Evaluation (Section 8.3) (Section 8.4) (Section 8.6)
• who has the • objectives • group action • assess control problem • management – ownership • compare over time • real or perceived • options • whole farm/district • techniques • define harmful – local eradication • government • evaluation • impact – strategic role of outcome – economic management – environmental – crisis • measure impact management • mapping – no management • performance • criteria • allocating • management • units • management • strategy
Figure 1: Strategic approach to managing fox damage.
8 Managing Vertebrate Pests: Foxes governments, agencies, gr oups and the management system to r efine the pest individuals are taken into account and management strategy is called lear ning by integrated. Chapter 9 r eviews these issues, doing. and describes how these factors ar e It is expected that community-based integrated into an overall management groups will become incr easingly involved strategy. in the strategic management of vertebrate pests. The guidelines ar e designed to Monitoring and evaluation facilitate the ownership of the pest pr oblem by such local gr oups, and the management Monitoring is an essential part of fox strategy which might be developed and management. Operational monitoring implemented based on them. measures the efficiency of the contr ol strategy, assessing the cost-ef fectiveness of Note: All money values thr oughout the control over time. Chapter 7 r eviews guidelines are in 1993-94 Australian dollars. monitoring requirements. Throughout this document ‘fox’ r efers to Performance monitoring seeks to evaluate the European red fox ( Vulpes vulpes). the outcome of the management plan; that is, whether the conservation or agricultural production targets set initially ar e being met. This is reviewed in Chapter 8. Both forms of monitoring enable managers to decide whether the management strategy needs to be modified.
Strategic management at the local and regional level These guidelines set out best practice fox management at the national level based on current knowledge. They bring together the best available infor mation on effective fox control, as a basis for better management of the damage due to this pest.
Vertebrate Pest Program In the Envir onment Statement of December 1992, the Commonwealth Gover nment provided increased resources to complete preparation of the guidelines for managing Australia’s major vertebrate pest species and to establish key demonstration pr ojects 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 foxes, it is anticipated that ‘best practice’ will evolve based on experience gained fr om undertaking strategic management. Using
Bureau of Resour ce Sciences 9 10 Managing Vertebrate Pests: Foxes 1. History persisted and probably coexisted in Eur ope. As the ice r eceded to the Ar ctic at the end of the last glaciations, the ar ctic fox Summary withdrew to higher latitudes and the corsac 1 Evolutionary origins of the European red fox to the steppes of Russia, whilst the mor e fox (Vulpes vulpes) are uncertain. As a adaptable red fox advanced widely (Lloyd member of the Canidae, it may have evolved 1980). during the Eocene (30–50 million years The history of the r ed fox in North ago), possibly in North America. The fox was America deserves comment. The native r ed first introduced to Australia in the 1860s fox of North America ( V. fulva) is and 1870s for hunting with horses and considered by Churcher (1959) to be the hounds. It occurs naturally only in the same species as V. vulpes. If so, then the northern hemisphere and is found former might be r egarded as a race or throughout most of the Palaearctic region. subspecies of the latter . Certainly, Eur opean In Australia and elsewhere it has been a red foxes wer e introduced into Maryland successful coloniser. Within 30 years of its in the middle of the eighteenth century and initial release in southern Victoria in 1871, later to Long Island (Lloyd 1980). Ther e is the fox attained the status of a pest in evidence that the early distribution of the northern parts of the state. Colonisation was native fox did not extend below 40 ° N probably assisted by the spread of the rabbit latitude and that the intr oduced red fox may in Australia at about the same time. By 1893 have colonised the mor e southern areas as the fox was reported in New South Wales; these were opened up by Eur opean settlers. in 1901 in South Australia; in 1907 in The two subspecies may then have met and Queensland; and in 1912 in Western interbred resulting in a lar ger overall range Australia. By the early 1930s, foxes were to for the species (Lloyd 1980). be found in most habitats all over mainland Australia with the exception of the tropical north. There are no foxes in Tasmania. 1.2 Australia Although newspapers r eported the intr o- 1.1 Europe and America duction of foxes as early as 1855, it is likely that the first successful r eleases took place Fossil records suggest that the family in southern Victoria in 1871 (Rolls 1969). One Canidae, to which foxes belong, evolved of these took place near Geelong in V ictoria, some 30–50 million years ago in the Eocene, where rabbits had been r eleased a few years probably in North America. The Canidae earlier. This may be one of the few examples may come from two separate lines with where a predator and its natural pr ey were foxes and jackals descending fr om introduced at about the same time. T wo fox Cynodictis, and dogs and wolves fr om cubs were shipped from England to Adelaide Amphicyon (Lloyd 1980). in 1869, but their subsequent fate is The evolution of the r ed fox as a distinct unknown. Nonetheless, foxes wer e species is poorly documented. Bones of the apparently common in the Coor ong region animal are rare in all deposits which pr edate of South Australia by 1888. By 1893 the shir es the Stone Age (Zeuner 1963). Thr ee species of Euroa, Benalla and Shepparton (all in of fox, including the r ed fox, occur in the Victoria) had a bounty scheme on fox heads, Pleistocene (11 000 to 1 million years ago) indicating that the new arrivals quickly fauna of Eur ope and, fr om the Middle attained the status of pests. New South W ales Pleistocene, the r ed fox is known fr om the quickly followed suit with the declaration Thames deposits of Grays and Ilford in Essex of foxes as noxious animals at Ar midale, and (Zeuner 1963). In later Pleistocene times the within a few years they wer e reported to be three species (red, corsac and arctic fox) in southern Queensland.
Bureau of Resource Sciences 11 Foxes were first r eported to be in Western tropical north (Figur e 2), was achieved in Australia, west of Eucla, in 1911–12 and 160 100 years. However, the limits ar e not fixed. kilometres west of the South Australian It is likely that the norther nmost limit of border in 1915 (Long 1988). Their spr ead foxes alters with seasonal conditions, in the west was rapid, and some evidence expanding and contracting in r esponse to suggests that they colonised the last of the a run of good seasons or a run of dr ought forested areas of the lower south-west of years. Similarly, Lloyd (1980) has indicated Western Australia at the same time as the that in parts of Gr eat Britain, the distribution rabbit. Colonisation by foxes pr obably and density of foxes seems to have waxed continued well into the 1950s, since Long and waned considerably over the past (1988) records first sightings in the East century. Kimberley in 1968 and at Fitzr oy Crossing ‘Foxes occur throughout in 1958. Australia except for the Thus the fox’s pr esent distribution, which tropical north, Tasmania and covers all of mainland Australia except the some smaller islands.’
1934 1950Ð52 Northern Territory 1930Ð35 1932 1932 1920 1931 Tropic of Capricorn
Western Australia Queensland 1929 1930 South Australia 1925 1916 1920 1910 1920 1907 1901 1911Ð12 1900 1901 1925 1915 1900 1930 1916 New South Wales 1932Ð34 1890 1893 Victoria 1880 1870 1865
0 200 400 600 km Tasmania Frontier of spread
Figure 2: Spread of the r ed fox in Australia (after Jar man 1986).
12 Managing Vertebrate Pests: Foxes 70
60 1
50
40
30
Scalp numbers ('000) 20
10
0
1949 1952 1955 1958 1961 1964 1967 1970 Year
Figure 3: Interrelationship between fox and rabbit populations as demonstrated by decr eased number of fox scalps r eturned for bounty payment in V ictoria following the widespr ead outbreak of myxomatosis in 1951 (after Redhead et al. 1991).
Data from early bounty schemes in annual dispersal distance of 11 kilometr es Australia suggest that the fox spr ead most with exceptional movements up to 30 rapidly across the inland saltbush and kilometres, although this was based on a Mallee country, and mor e slowly in the small sample size. While foxes dispersing forested ranges near the coast (Jar man into an area previously devoid of foxes may 1986). However, in Western Australia, the have dispersed more rapidly than mor e early spread seems to have been along the recent studies indicate, it is concluded that southern coastline with a succession of the early and rapid movement of foxes in sightings from Eucla in 1912 to Geraldton Australia was assisted by deliberate human in 1925 (Long 1988) (Figur e 2). spread of the animal. ‘The rapid spread of foxes in ‘In Australia the spread and Australia was assisted by establishment of foxes was deliberate human introductions closely linked to the spread of to new areas.’ rabbits.’ If it is assumed that all Australian foxes The early history of fox intr oductions to originated from the early intr oductions to Tasmania is poorly documented though Victoria, then data fr om early sightings several introductions have been r ecorded elsewhere on the continent suggest annual (Lever 1985; Statham and Mooney 1991). dispersal distances of up to 160 kilometr es Fortunately, none were successful. per year. This is unlikely, for although The early spread and establishment of dispersal movements of this magnitude have fox populations was closely linked to the been recorded, they ar e the exception rather spread of rabbits. Australian studies on fox than the rule. Recent data on cub dispersal food habits (Section 2.2.7) highlight the in Victoria (Coman et al. 1991) indicates an
Bureau of Resource Sciences 13 Foxes Rabbits
Figure 4: Relative distribution of foxes and rabbits in Australia (after V ertebrate Biocontrol Centre 1992). importance of rabbit in their diet, and the fox scalps began in 1949. Numbers r eturned data on early spr ead of foxes suggest that for payment quickly r ose to a high level but they spread more rapidly wher e rabbits then fell dramatically in 1952–53 when were present. Long (1988) noted that in widespread myxomatosis outbreaks reduced Western Australia, the fox appear ed to the rabbit population to a very low level. follow approximately the same invasion Significantly though, scalp numbers r ose path as the rabbit, although several years again within a few years, possibly indicating later. the ability of foxes to switch to alter native The interrelationship between foxes and food sources. Figure 4 shows the high degr ee rabbits is dramatically illustrated in Figur e3. of overlap between the distribution of rabbits In Victoria, a statewide bounty scheme for and foxes.
14 Managing Vertebrate Pests: Foxes 2. Distribution and predators, although cubs can be taken by biology birds of prey and dogs. Population turnover appears to be rapid, but its causes, partic- ularly in Australia, are poorly understood. Summary Mortality of foxes is thought to be due mainly to the impact of drought on their The red fox is widely distributed throughout prey, principally rabbits, and that caused the southern half of mainland Australia by humans. Mange and distemper may also and can survive in habitats ranging from be significant contributors. arid through to alpine as well as urban. 2 The only limitations on distribution appear Fox groups generally have well-defined to be the presence of dingoes, at least in home ranges with spatially stable borders. some areas, and the tropical climate of The size of a home range depends on the northern Australia. In non-urban areas it productivity of the environment, but varies appears to be most abundant in fragmented from 1600 hectares in Canadian tundra to habitats typically found in agricultural 30 hectares in urban areas. Foxes are landscapes. These offer a wide variety of mostly active from dusk to dawn and rarely cover, natural food and den sites. Density travel more than ten kilometres per day estimates in Australia, although few, range within the home range. Dispersal is from 0.2 adults per square kilometre in common, particularly in sub-adult males. coastal forest up to 12 adults per square It commences in late summer and continues kilometre in urban populations. through to the onset of breeding in winter. Exceptional dispersal distances of over 300 Females reproduce only once a year. kilometres have been recorded with averages Gestation lasts 51–53 days with most cubs of between 2–40 kilometres. born during August and September. Mean litter size is four up to a maximum of about Although predominantly carnivorous, ten. Both sexes become sexually mature the fox is an opportunistic predator and from ten months of age. Although social scavenger with no specialised food require- groups of one male and several vixens do ments. Diet studies conducted in Australia exist, most foxes are thought to have only show sheep taken as carrion, rabbits and one mate. Males may also leave their normal house mice to be the most common food territory temporarily in search of other items. mating opportunities. Overseas the disease most commonly 2.1 Distribution and associated with foxes is rabies, which is only abundance endemic in Europe and North America. Many other infectious diseases occur in foxes, although little is known of their 2.1.1 Worldwide distribution of incidence in Australia, or their impact on foxes population regulation. These include ‘Foxes are now found in mange, canine distemper, parvovirus, several Australian cities.’ toxoplasmosis, canine hepatitis, tularaemia, leptospirosis, staphylococcal infections and The red fox is the most common and encephalitis. Like most carnivores that feed widespread member of its genus, which on a wide range of prey, foxes also carry a includes 11 other species worldwide variety of endoparasites. The incidence of (Clutton-Brock et al. 1976). It occurs helminth parasites, in foxes in particular, naturally in the norther n hemisphere only, has been intensively surveyed in south- where it is distributed thr oughout most of eastern Australia because of their potential the Palaearctic region (Lloyd 1980). Pr esent- transmission to domestic animals. Other day distribution of the r ed fox is pr esented than the dingo, the fox has few natural in Figure 5.
Bureau of Resource Sciences 15 Figure 5: Present-day world distribution of the r ed fox (after Jar man 1986).
The success of the r ed fox in nearly all western Australia by the pr esence of high environments is attributable to a highly densities of dingoes. Sharp boundaries in adaptable and unspecialised lifestyle with density along parts of the New South W ales no specific habitat r equirements (Corbet and border are probably due to the dingo fence Harris 1991). Historical evidence suggests and the displacement of foxes by dingoes. that the red fox has expanded its natural However, in areas of South Australia adjacent range over the last 200 years (Lloyd 1980; to the New South W ales border, foxes appear Voigt 1987) possibly in part due to to be pr esent even where there are high diminished competition with lar ger canids densities of dingoes. Her e, dingoes pr obably such as the wolf ( Canis lupus). Since the influence fox density rather than distribution. mid-1940s, urban foxes have become Only isolated pockets occur in the far north, common in British cities (Harris and Rayner such as the Kimberley r egion of Western 1986) and recently have occupied a number Australia (King and Smith 1985) and the of Australian cities such as Adelaide, Victoria River District and Barkly T ablelands Brisbane, Canberra, Melbourne, Perth and of the Norther n Territory (Wilson et al. 1992). Sydney (C. Marks, D NRE, Victoria, pers. Foxes appear to have r eached the northern comm. 1994). limit of their range as r ecently as the last 30 years (Jarman 1986). The norther n limit of 2.1.2 Australian distribution fox distribution in Australia may r eflect climatic preference. The red fox does not The red fox is found thr oughout the southern occur in the humid tr opical regions of North half of Australia with the exception of America and Asia although other Vulpes Tasmania and Kangar oo Island (Jar man 1986, species do (Wilson et al. 1992). Wilson et al. 1992). It occurs fr om the arid centre to the alps and is also found in urban 2.1.3 Density estimates Australia. In central Australia, its distribution is similar to that of the rabbit, but appears The nocturnal and elusive natur e of the r ed to be limited in some ar eas of easter n and fox makes population density estimates
16 Managing Vertebrate Pests: Foxes Table 1: Density estimates (foxes per square kilometre) of Australian fox populations.
Study Habitat Location Fox density
Coman et al. 1991 Temperate grazing Central Victoria 3.9 Thompson and Fleming 1994 Temperate grazing Northern Tablelands, NSW 4.6–7.2
Newsome and Catling 1992 Dry sclerophyl forest South Coast, NSW 0.2 Newsome and Catling 1992 Semi-arid grazing Western NSW 2.0 2 Marlow 1992 Arid grazing Western NSW 0.9 T. Bubela (Sydney University, Sub-alpine South-east NSW 1.8 pers. comm. 1994)
D. Algar (CALM, WA) and Semi-arid grazing South-west 0.6–0.9 P. Thomson (APB, WA) – pers. Western Australia comm. 1993 C. Marks (DNRE, Vic., pers. Urban Melbourne 0–12 comm. 1994) difficult to determine and often inaccurate. densities are more common in the temperate This is further complicated by the cyclical grazing country of south-eastern Australia. changes in fox densities associated with prey abundance. Their occurrence in such a wide 2.1.4 Habitat preferences variety of habitats also makes it difficult to apply a common census technique, making The worldwide distribution of the red fox, comparisons between different populations ranging from tundra to the desert as well at best, tenuous. Details of population as urban areas, suggests that it can survive estimation techniques are presented in in most environments. How an animal uses Chapter 7. the specific habitats within the confines of its environment (specified by a territory or Estimates of fox densities vary from as home range) is determined by a high as 15 adults per square kilometre in combination of factors including the distri- urban areas of Britain (Harris and Rayner bution of food and water, shelter from 1986; Harris and Smith 1987) to as low as predation and climate, breeding sites and 0.1 adults per square kilometre in tundra the paths which link the various habitat and boreal forest (Voigt 1987). Like all other patches. Identification of habitat require- species, population density depends very ments and how they are used are important much on the productivity of the in the design of effective strategies for environment. managing fox damage. In Australia, fox density is perceived to be highest inside the dingo fence in semi- ‘Worldwide fox distribution arid New South Wales where there is an ranges from tundra to desert. abundance of rabbits and carrion, and Red foxes are not found in lowest along the more heavily timbered tropical climates.’ coast and ranges (Wilson et al. 1992). The Habitat use by urban foxes has been few density estimates which are available studied in a number of British cities (Harris involve only a limited number of relatively 1977; Macdonald and Newdick 1982; Kolb small study sites. These are presented in 1985; Harris and Rayner 1986). The most Table 1. In conflict with the Wilson et al. important urban habitat requirement observation, these figures suggest that higher appears to be that of cover (Harris 1977).
Bureau of Resource Sciences 17 Exposed habitats such as fr ont gardens, can penetrate some distance into them in parkland and playing fields ar e avoided, search of food (Jar man 1986). The r ed fox with undisturbed habitats such as back appears to be absent fr om areas with gardens, rough ground and cemeteries tropical climates, such as Asia, although the preferred. There appears to be a temporal reasons for this ar e unclear. The fox’s habitat pattern, with foxes avoiding habitats at times preference within specific envir onments has when human activity is high. Roads ar e used not been studied in Australia. for travel between habitat patches. This situation may change towards the suburban 2.2 Biology fringes or in urban ar eas interspersed with large tracts of r ough ground or open space The life history of the r ed fox has been (Macdonald and Newdick 1982; Rosatte et extensively studied in the norther n al. 1991). hemisphere (reviewed by Burrows 1968; ‘Foxes are often abundant in Storm et al. 1976; Pils and Martin 1978; Lloyd agricultural areas as they 1980; Zimen 1980; Harris 1986; Henry 1986; offer a wide range of cover, Macdonald 1987; Voigt 1987). However, food and den sites.’ there have been few biological studies of foxes in Australia (Ryan 1976a; Coman 1988; These studies have been made easier in Coman et al. 1991; Phillips and Catling 1991; the urban areas because of the even and Marlow 1992). Most of these studies have clearly defined distribution of habitats and concentrated on the pr edatory relationship the limited areas for travel. However , it is between foxes and the sheep industry, fox more difficult to make clear interpr etations of habitat preferences in rural or wilder ness diet or fox endoparasites. The biological areas. The fox is pr obably most abundant information presented here is therefore in fragmented environments typically found based mainly on observations fr om the in agricultural landscapes because these northern hemisphere. The extent to which offer a wide variety of cover , food and den this information applies to foxes in Australia sites. More uniform, open environments are is unclear, emphasising the need to better less favoured as are heavily for ested or understand the biology of the fox in mountainous areas. Foxes do not live Australia, especially those aspects essential entirely within closed canopy for ests but for developing contr ol strategies.
The European red fox adapted well to Australian habitats. Source: CSIRO
18 Managing Vertebrate Pests: Foxes 2
Foxes use dens for the birth and early caring of cubs. Source: CSIRO
2.2.1 General description and to October with a peak during August in classification south-eastern Australia (McIntosh 1963a; Ryan 1976a), although ther e may be The red fox is a member of the family latitudinal variations as found in the norther n Canidae which includes wolves, jackals and hemisphere (Lloyd and Englund 1973; Stor m coyotes. Males are slightly larger than et al. 1976). R yan (1976a) found sper m or females. Both males and females, but par - spermatids present in males in every month ticularly females, have seasonal variations except January, with peak pr oduction in body weight. Adults have a head and occurring from June to August. Gestation body length of 570–740 mm, a tail length of lasts 51–53 days with most cubs bor n during 360–450 mm and weigh between 4.5–8.3 August and September. kilograms (Coman 1983). ‘Vixens come on heat once a Behavioural traits, which ar e common to year. Cubs are mostly born in many other canids, include the use of dens August and September.’ (commonly enlarged rabbit burrows) for the birth and early caring of cubs; surplus killing Mean litter size is four up to a maximum of prey and caching of food for later of around ten. Cubs ar e suckled until four consumption; predominantly nocturnal and weeks, then pr ogressively weaned onto crepuscular activity; and territorial family solids. Both sexes become sexually matur e groups with juvenile dispersal common. from ten months of age. The number of non- Numerous scent glands, particularly anal breeding vixens in any population is highly sacs, are used to mark territories. They have variable, being most common wher e a wide range of vocalisations, most populations are subject to low levels of commonly heard during the mating season. control and least common wher e mortality rates are high (Corbet and Harris 1991). This may be due to the social suppr ession of 2.2.2 Reproduction reproduction in large groups. In these cases The red fox is monoestrus, vixens coming some non-breeding females may act as on heat only once during the br eeding ‘helpers’, which are so defined because of season and then for only two to thr ee days. their supportive r ole in raising cubs Females are reproductively active fr om July (Macdonald 1979). The mechanisms for this behaviour remain unclear. Foxes are thought
Bureau of Resource Sciences 19 to be largely monogamous. However, endemic, and also in Australia wher e every polygamous social groups of one male and effort is taken to pr event its introduction several vixens do exist, the vixens invariably (Chapter 4). Many other infectious diseases being closely related (Macdonald and Bacon occur in foxes, although little is known of 1982). Males are also known to leave their their incidence in Australia or impact on territory in search of other mating oppor - population regulation. These include tunities, but this occurs during the br eeding mange, canine distemper, parvovirus, season and has minimal management impli - toxoplasmosis, canine hepatitis, tularaemia, cations. leptospirosis, staphylococcal infections and ‘The average litter is four cubs; encephalitis viruses (Voigt 1987). maximum litter is about ten Foxes carry a variety of endoparasites cubs.’ (Lloyd 1980). The incidence of helminth parasites in foxes in particular has been 2.2.3 Diseases and parasites intensively surveyed in south-easter n Australia because of their potential The disease most commonly associated with transmission to domestic animals (Pullar the fox, and one to which the species is 1946; Coman 1973a; Ryan 1976b). Most particularly susceptible, is rabies (W andeler prevalent are Taenia pisiformis, T. serialis, et al. 1974; Macdonald 1980). It is a major Spirometra erinacei, Dipylidium caninum, public health concer n throughout Europe Toxocara canis, Uncinaria stenocephala and North America wher e the disease is and Ancylostoma caninum.
Drought 6000
4000 Rabbits
2000 Spotlight counts in 18 km
50
Predators
0 0 J JJDJJJDJJ 1979 1980 1981
Figure 6: Variations with time of rabbit and pr edator (cat and fox) numbers at Y athong Nature Reserve in central-western New South Wales (after Newsome et al. 1989)
20 Managing Vertebrate Pests: Foxes ‘Foxes can carry rabies and of dog ticks ( Ioxodes holocyclus). This other diseases, although fox suggestion warrants further study. rabies has so far been kept out of Australia.’ 2.2.4 Mortality factors In some parts of the world foxes ar e an important end host for the hydatid The red fox has few natural pr edators, tapeworm (Echinococcus granulosus). although cubs can be taken by bir ds of prey Although thousands of foxes have been and dogs (Corbet and Harris 1991) and ther e examined for signs of this parasite in is circumstantial evidence that dingoes may 2 Australia, it has only been found in influence the distribution of foxes (Section afewanimals, and then at low levels. 2.1.2). In Australia, dingoes ar e known to Consequently, it is assumed that foxes do kill and eat adult foxes (P . Bird, APCC, SA not play an important r ole in the life cycle pers. comm. 1993). Population tur nover of Echinococcus in rural Australia despite appears to be rapid, but causes, particularly their susceptibility to this parasite. The in Australia, ar e poorly understood (Coman situation is less clear in urban ar eas where 1983). In a sample of 317 foxes killed by it appears that even a few infected foxes ar e hunters in south-easter n Australia, it was a risk to human health (Jenkins and Craig found that 54% of animals wer e less than 1992). one year old and 71% less than two years old with few (4%) animals surviving beyond Ectoparasites known to occur in Australia, four years (Coman 1988). and which ar e found on foxes in the norther n hemisphere (Corbet and Harris 1991), ‘Most foxes are killed by people include fleas ( Spilopsyllus cuniculi, Pulex or the effects of drought.’ irritans, Ctenocephalides canis), ticks (Ixodes Most deaths are believed to be due to ricinus) and mites ( Sarcoptes scabiei, human intervention and the impact of Demodex folliculorum, Notoedres spp., drought on their main pr ey, rabbits. Storm Otodectes cyanotis and Linguatula serrata). et al. (1976), in a North American study, Ringworm (Microsporum) is also r ecorded reported that more than 80% of tagged foxes occasionally. In a r ecent study, Phillips and died as a r esult of shooting, trapping or r oad Catling (1991) suggested that the observed kills. Harris (1978), in a survey of British low fox density in rainfor ests of souther n urban fox mortality found that 61% of adults coastal New South Wales may be due to mortality resulting from the high incidence died from road accidents, 18% wer e delib-
Flea introduced
25 200 20 Foxes 150 Rabbits 15
100 10
Rabbits per km 50 5 Cats Cats/foxes per 100 km 0 0 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982
Figure 7: Variation in fox and feral cat numbers in r elation to changes in rabbit numbers in south- western Western Australia (after King and Wheeler 1985). Ther e was an incr eased incidence of myxomatosis following the intr oduction of the Eur opean rabbit flea.
Bureau of Resource Sciences 21 Table 2: Comparison of mean home range estimates (minimum convex polygons) for foxes in different habitats.
Habitat Home range (ha) Reference
Tundra (British Columbia) 1611 Jones and Theberge 1982 Farmland (Ontario) 900 Voigt and Tinline 1980 Farmland (Victoria) 610 Coman et al. 1991 Alpine (New South Wales) 550 Bubela 1993 Forest (New South Wales) 416 Phillips and Catling 1991 Farmland/woodland (Western Australia) 340 D. Algar (CALM, WA) and P. Thomson (APB, WA) – pers. comm. 1993 Forest/urban (West Germany) 133 Zimen 1984 Urban (England) 30 Saunders et al. 1993 erately killed by man, 10% died from disease, Myers and Parker 1975a, b; Newsome et al. 3% from fights, less than 1% from parturition 1989; King and Wheeler 1985; Redhead et deaths and the remainder (7%) from al. 1991). During the lag time, foxes are misadventure or unknown causes. Sarcoptic believed to prey heavily on the remaining mange is a significant mortality factor rabbits and on native fauna. The role foxes (Trainer and Hale 1969; Pils and Martin play in regulating rabbit density, and the 1978; Tullar and Berchielli 1982), as of implications of managing or not managing course is rabies where it is endemic foxes for native wildlife during rabbit (Macdonald 1980). Secondary poisoning as management programs, is unclear and needs a result of pest control programs, principally further investigation. 1080 control of rabbits, is not uncommon ‘We need to know more about (McIlroy 1981) as is primary poisoning from how foxes affect rabbit and baits intended for larger carnivores such as wildlife populations.’ dingoes (McIlroy 1986). The number of baits distributed intentionally for fox control in Australia has risen dramatically in recent 2.2.5 Movements and home range years. This is possibly due to decreased Red fox family groups generally occupy well- hunting pressure as a result of the collapse defined home ranges with non-overlapping, in the fur trade and increasing concern for adjoining and stable borders (Storm 1965; the damage they cause to native wildlife Ables 1969; Sargeant 1972; Pils and Martin populations and agricultural production 1978; Voigt and Macdonald 1984). (Chapter 3). Overlapping home ranges reported in some ‘Rabbits are the main prey of studies are thought to be due to inadequate foxes in the southern pastoral data collection and analysis or to the study areas of Australia.’ animals being closely related (Voigt 1987). However, Doncaster and Macdonald (1991) In the southern pastoral zones of observed continually drifting territories in an Australia, rabbits are the principal prey of urban fox population. The combined foxes and feral cats. When rabbit evidence from studies of scent marking, populations crash, either due to drought social encounters and movement patterns (Figure 6) or outbreaks of myxomatosis suggests that home ranges are the same as (Figure 7), fox and feral cat populations also territories (Henry 1979; Macdonald 1979). collapse after a lag period (Brooker 1977;
22 Managing Vertebrate Pests: Foxes ‘Fox family groups usually the size of the territory. An urban fox with occupy well-defined home a home range of 30 hectares is able to visit ranges.’ all boundaries two to three times in a night (Saunders et al. 1993). In contrast, Sargeant A home range is generally proportional (1972) found that rural foxes with home in area to the amount of resources it ranges of 250–750 hectares required two contains. Foxes in habitats with abundant weeks to cover the entire territory. These food sources have smaller home ranges differences may result in varying levels of (Harestad and Bunnell 1979; Lindstedt et al. encroachment between neighbours as well 1986). The variation in fox home range size 2 as the extent of social contacts. Apart from as implied by resource productivity in this, the most common incidences of foxes different environments is shown in Table 2. disregarding territorial boundaries occur as Voigt and Macdonald (1984) proposed that a result of dispersal behaviour or adult males the pattern of mortality and the extent of searching for mating opportunities. Daily seasonal climatic variation also contributed travelling distances by resident adults within to home range size, and concluded that red their territories rarely exceed ten kilometres, foxes are so variable in their behaviour that with most activity between dusk and dawn any extrapolations to an area based on (Voigt 1987; Saunders et al. 1993). studies from another should be viewed with caution. This means that fox management, ‘Adult foxes rarely travel more especially in terms of baiting intensity and than ten kilometres per day.’ the size of fox-controlled buffer zones needed for the protection of a specific area, 2.2.6 Dispersal needs careful consideration (Section 7.5). Dispersal by the red fox has been studied The extent to which foxes can patrol and extensively in Europe and North America hence maintain a territory is influenced by
Table 3: Percentage occurrence and percentage volume of major food items identified in the stomachs of foxes by Coman (1973b) (first figure) and Croft and Hone (1978) (second figure).
Food item % Occurrence % Volume
Sheep 31, 29 20, 19
Rabbit 39, 25 35, 20 House mouse 26, 15 14, 10
Macropod species 3, 1 2, 1 Possum species 7, 1 5, 1
Pig 1, 5 1, 5 Fox 3, 1 1, 1
Cattle 1, 2 1, 1 Domestic poultry 1, 4 1, 3
Bird species 19, 9 5, 5 Insects 36, 37 8, 12
Other invertebrates 7, 11 1, 4 Cold-blooded vertebrates 3, 5 1, 2
Plant material 57, 38 3, 12
Bureau of Resource Sciences 23 because of the importance of this behaviour predator of sheep and native fauna to the spread of rabies (Phillips et al. 1972; (McIntosh 1963b; Martensz 1971; Ryan and Steck and Wandeler 1980). The majority of Croft 1974; Brunner et al. 1975; Seebeck dispersal occurs in sub-adult foxes, partic - 1978; Bayly 1978; Gr een and Osborne 1981; ularly males, commencing in late summer Triggs et al. 1984; Brunner and W allis 1986; and continuing through to the onset of Baker and Degabriele 1987; W allis and breeding in winter. Brunner 1987; Catling 1988; Br own and ‘The greatest movement of Triggs 1990; Lunney et al. 1990; McKay foxes occurs when young 1994). Two of the most compr ehensive in males disperse.’ terms of areas covered were those of Coman (1973b); and Cr oft and Hone (1978). These A variety of dispersal patter ns have been involved the examination of over 2000 fox revealed in radio-tracking studies. These stomachs from throughout Victoria and New suggest two distinct phases: sudden, quick South Wales. The most common items ar e and mainly straight line travel followed by presented in Table 3, although ther e were slower, less directed movements that persist numerous regional and seasonal variations until the animal establishes the boundaries within and between studies. Assuming of its new territory (Zimen 1984). A series energy intake is best r eflected by per centage of exploratory trips prior to the main volume, sheep (believed to be mostly taken dispersal event are also common. All of as carrion), rabbit and the house mouse ar e these phases occur over a r elatively short the most important food items to the fox on period. Longer dispersal distances ar e a statewide scale. Similar observations have associated with less pr oductive environ- been reported from fox populations in the ments. Exceptional movements of over 300 northern hemisphere (Sequeira 1980). Foxes kilometres have been r ecorded in North also have some distaste for food items such America and 100 kilometr es in Europe as insectivore and car nivore meat, although (Corbet and Harris 1991). Mean dispersal cannibalism of litter mates or pr edation by distances are much smaller than this, ranging vixens on other litters is not uncommon from 2.8–43.5 kilometr es for males and (Macdonald 1977). 1.8–38.6 kilometres for females (T rewhella ‘’Foxes are opportunistic et al. 1988). In Australia, Coman et al. (1991) predators and scavengers with in central Victoria, observed a mean no specialised food dispersal distance of 11 kilometr es based requirements.’ on a study of 13 dispersing animals. Marlow (1992) monitored the dispersal of five female Sargeant (1978) quantified the pr ey foxes which dispersed a mean distance of demands of captive foxes. Cubs began to 3.5 kilometres. In a r ecent study in south eat prey four weeks after birth. Ther eafter, western Australia, Marlow and Thomson prey consumption averaged 197 and (WA CALM and APB, pers. comm. 1995) 271grams per cub per day for weeks 5–8 observed mean juvenile dispersal in males and 9–12 r espectively, and 363 grams per of 43 km (n=7, range 9–170 km) and females cub per day for the post-denning period. of 15 km (n=6, range 6–22 km). Feeding by adults averaged 321 grams per adult per day. Fr ee water was not needed 2.2.7 Diet by either cubs or adults. Saunders et al. (1993) constructed a generalised model to Although predominantly carnivorous, the estimate the daily ener gy expenditure, red fox is an opportunistic pr edator and excluding direct costs of r eproduction, for scavenger with no specialised food r equire- urban foxes. Based on yearly averages for ments. There have been several studies on this study, an adult male r equired 2001 the diet of the fox in Australia mainly kilojoules per day which was the equivalent because of concern about its r ole as a of 372 grams of wild mammal or 524 grams
24 Managing Vertebrate Pests: Foxes of scavenged meat. The implications of Midwest (Sargeant 1972; Storm et al. 1976) these food r equirements, particularly during and Ontario, Canada (Voigt and Macdonald the post-denning period, to pr ey biomass 1984) were found to be typically occupied within the family gr oup territory ar e by only one adult pair of foxes along with substantial. Sargeant (1978) estimated this their litter of cubs which eventually to be equivalent to 18.5 kilograms per squar e dispersed. Although not well documented, kilometre (two adults and five cubs). most observations suggest that this is also ‘Sheep taken as carrion, the predominant family group composition rabbits and house mice are the throughout Australia. Macdonald (1979, 2 main food of foxes.’ 1981), von Schantz (1981) and Mulder (1985) found that in ar eas with more food and other While diet studies indicate the range of resources, family groups tended to be lar ger, prey consumed by foxes, diet studies alone consisting of one adult male and up to are not a r eliable indication of the extent of several vixens. Within these groups, vixens damage caused by foxes. Some endanger ed were usually related and only the dominant native species may occur only rar ely in the female produced a litter. Subordinate diet, but foxes may be having a significant females are recognised as ‘helpers’ which impact on their populations. Conversely, may feed, guard, groom and play with the other species that occur consistently in the cubs of the br eeding vixen (Macdonald fox diet may be in suf ficient numbers that 1979). Where more than one vixen br eeds they can tolerate long-ter m fox predation within the one family gr oup, communal without any r esulting decline in population denning and car e of young may occur (T ullar densities. The damage that fox pr edation et al. 1976). The pr esence of only a few causes to native fauna can only be solitary males in these mor e productive areas quantified by scientifically designed and suggests higher male mortality (V oigt 1987). replicated studies where fox predation is Von Schantz (1981) also concludes that it is reduced and the r esponse of the pr ey is in the best inter est of the dominant pair to monitored. The r esults of such studies ar e first expel male of fspring as they have the outlined in Section 3.1. least to contribute to the raising of ‘Fox predation does not subsequent litters. necessarily have a significant effect on the populations of 2.2.9 Conclusion prey species.’ ‘Relatively little is known about the ecology of foxes in 2.2.8 Social organisation Australia.’ A combination of aggr essive and non- Red foxes ar e highly adaptable and occupy aggressive encounters, scent marking and a wide range of habitats. Likewise, they vocalisations are used to maintain fox show considerable variation in their territories (Sargeant 1972; Niewold 1980; behaviour, population density, r eproduc- Voigt and Macdonald 1984). Most tive potential and diet between these encounters are due to dispersal or adult habitats. Macdonald (1981) ar gued that these males trespassing on neighbouring territories in search of receptive females. To a lesser differences arose largely from the effects of extent, females can r eturn to their territory two group variables: the patter n of resource of birth and some foxes will explor e neigh- availability, such as the abundance and bouring territories per haps in search of food dispersion of available food or the distrib- (Niewold 1980; Voigt and Macdonald 1984; ution of cover or dens; and the intensity and Mulder 1985). pattern of mortality. Voigt (1987) suggested The composition of family gr oups varies that the extent of seasonal climatic variation with habitat. Lar ge territories in the American also contributed to these variations. This is
Bureau of Resource Sciences 25 particularly likely to be the case in Australia where the fox can be found fr om desert to alps (Figure 2). Because of these variations, accurate prediction of the behaviour of a fox population, particularly without baseline information, is dif ficult if not impossible. Relatively little is known of fox ecology in Australia. Studies are required, particularly on population densities and movement across different habitats, so that land managers can make soundly based decisions on appropriate management strategies.
26 Managing Vertebrate Pests: Foxes 3. Economic and reduced, in order to prevent increased fox environmental predation on native fauna. Foxes undoubtedly exert some control over rabbits, impacts but not when conditions are favourable for growth of rabbit populations. In areas where Summary native wildlife are at significant risk from fox predation, fox management should be The fox has long been recognised as a considered as part of rabbit control. serious threat to Australian native fauna, but until recently, this has been based The economic impact of foxes in mainly on anecdotal and circumstantial Australia has been poorly studied but the evidence. For example, foxes have been principal losses almost certainly involve identified as a factor limiting the success of newborn lambs. Earlier studies on the seven out of ten mainland reintroductions causes of lamb loss generally dismiss 3 of native fauna. predation as being insignificant on a state or national level. More recent evidence The best evidence of the primary role foxes suggests that foxes may take from 10–30% play in population regulation of some native of lambs in some areas. fauna comes from Western Australia. Fox control resulted not only in substantial Positive economic impacts of the fox increases in the populations of some relate entirely to the value of fox pelts. In marsupials, but also in wider habitat use. the recent past, high export prices for fox However, for some native species, other pelts provided significant income for factors beside predation may be operating. Australia, but the market fluctuates widely For example, it has been shown that factors and current pelt sales are low. The impact which affect food for malleefowl chicks may of commercial harvesting upon fox numbers also need to be addressed in addition to and fox damage during the years of high predation. pelt prices is unknown, but some anecdotal evidence suggests that numbers have risen There is debate about the extent to which since the high-level harvesting ceased. foxes are a useful biocontrol agent for rabbits, and whether there is a need to One important social aspect of fox manage foxes when rabbit populations are predation in Australia is its potential impact
Phascogale species are believed to be at risk from fox predation. Source: Applied Biotechnologies
Bureau of Resource Sciences 27 on ecotourism. Many of Australia’s wildlife last 200 years; a further 43 species ar e judged species that are vulnerable to fox predation to be either endanger ed or vulnerable are unique and constitute an important (Commonwealth Endangered Species tourism asset. Advisory Committee (ESAC) Report 1992). ‘The impact of foxes on wildlife 3.1 Environmental impact has probably been exacerbated The fox has long been r ecognised as a serious by habitat modification and threat to populations of native wildlife. fragmentation.’ Finlayson (1961) for example described how, Undoubtedly the causes ar e complex. over a 25 year period, r egions in central The ESAC (1992) r eport discusses a suite Australia were being stripped of its smaller of threatening processes including habitat wildlife species by incr easing populations of loss; habitat change and degradation; foxes. Similarly, the decline of species such impact of intr oduced animals and plants; as the brush-tailed r ock-wallaby (Petrogale disease; exploitation; and climatic change. penicillata) on mainland Australia is A threatening process which has r ecently frequently attributed to pr edation by foxes come to light is the impact of pr edation by (Le Souef and Burr ell 1926; Wakefield 1954 foxes on native marsupials and on the as cited in Short and Milkovits 1990). Such malleefowl (Leipoa ocellata). Except for observations were, however, mostly based on some detailed studies of fox pr edation on anecdotal and circumstantial evidence. It was a limited range of W estern Australian native not until recent studies such as those of mammals and some work by Priddel (1991) Kinnear et al. (1988) and Priddel (1989) quantified the extent of fox impact on wildlife on malleefowl, ther e is little quantitative that land managers began to call for mor e information on the damage foxes cause to effective management of foxes. native fauna (Pech et al. 1995). However , there is a considerable number of anecdotal ‘Foxes can pose a serious and observational r eports. Consequently, threat to populations of native the examples in these guidelines ar e heavily animals.’ biased toward Western Australia although Because Australian native fauna did not it is likely that the fox is having a similar co-evolve with the fox, susceptible pr ey impact in other parts of Australia. species may have few strategies to avoid predation by this animal. Further more, the 3.1.1 Fox removal studies in impact of the fox on wildlife has pr obably Western Australia been exacerbated by habitat fragmentation and modification since Eur opean settlement In Western Australia, the impact of fox (Mansergh and Marks 1993). predation on some marsupials has been ‘Because they did not co-evolve examined in a series of pr edator removal with the fox, Australian native experiments (Kinnear et al. 1988 and animals may have few unpublished works; Friend 1990; Morris strategies to avoid fox 1992). Such experiments have yielded predation.’ substantial and consistent population increases by a variety of marsupial species. Compared to other continents, the The results suggest that not only has ther e damage to Australian wildlife since Eur opean been substantial population incr eases, but settlement has been catastr ophic and unpar- alleled other than for some island faunas. At also a wider use of the habitat when the least 20 species of Australian mammals have predation pressure is lowered. Some r esults become extinct. This r epresents about one- from these predator removal experiments half of the world’s mammal extinctions in the are described below.
28 Managing Vertebrate Pests: Foxes Rock-wallabies (Petrogale lateralis) and three colonies served as experimental controls (no fox contr ol). All populations wer e Rock-wallabies were once common throughout south-west Western Australia. By periodically assessed befor e and after fox 1979 only six isolated colonies existed and control. these were in decline (Kinnear et al. 1988). After eight years, the populations subject In a pr edator removal experiment, foxes wer e to fox control increased four to fivefold (Figure controlled using 1080 baits in two colonies;
8a Querekin Census No Fox Control 8d Mount Caroline Census Fox Control from 1982 20 60 50 15 3 40 10 30 20 5 10 Wallaby numbers Wallaby numbers Wallaby 0 0 1978 1980 1983 1986 1988 1990 1978 1980 1983 1986 1988 1990 Year Year
8b Tutakin Census No Fox Control 8e Nangeen Hill Census Fox Control from 1982 20 120 100 15 80 10 60 40 5 20 Wallaby numbers Wallaby numbers Wallaby 0 0 1978 1980 1983 1986 1988 1990 1978 1980 1983 1986 1988 1990 Year Year
8c Sales Rock Census No Fox Control 60 50 40 30 20 10 Wallaby numbers Wallaby 0 1978 1980 1983 1986 1988 1990 Year
Figure 8: Predator removal experiment conducted over eight years in W estern Australia for five colonies of r ock-wallabies (Petrogale lateralis). Three colonies received no treatment (Figure 8a,b,c), while foxes wer e controlled in two other colonies (Figur e 8 d,e) (after Kinnear et al. 1988). Note: Variable y-axis scales used for wallaby numbers at different sites.
Bureau of Resource Sciences 29 8d,e). Those not subject to fox contr ol on Rothschild’s rock-wallabies in the Dampier remained the same, or fluctuated and then Archipelago (J. Kinnear, unpub.). This wallaby declined (Figure 8a,b,c). A thir d population is endemic to W estern Australia and is in an area having no fox contr ol was reduced restricted to the Pilbara and Gascoyne r egions. to a single, barr en female. Rock-wallabies Foxes have invaded Dolphin Island (which have since been r eintroduced into one site carries P. rothschildi) by crossing a narrow (Querekin) in association with fox contr ol, passage that separates the island fr om the and their numbers have incr eased. mainland (the Burrup Peninsula). Enderby Island has rock-wallabies but is fox fr ee. Rothschild’s rock-wallabies (Petrogale Abundance indices derived fr om standard rothschildi) spotlight traverses showed a marked difference in rock-wallaby abundance Another fox removal experiment was between Dolphin Island and fox-fr ee Enderby conducted to determine the impact of foxes Island. For every thr ee hours of spotlighting
1979 1990 Dampier Archipelago N
Western Australia
Perth 27
Dolphin Island 56 58 1 No fox After fox control control
Fox free Enderby Island Dampier
Karratha
051015 20 km
Scale
Figure 9: The r elative abundance of Rothschild’s r ock-wallaby (Petrogale rothschildi), before and after fox control in the Dampier Ar chipelago. Enderby Island is fox fr ee while foxes had invaded Dolphin Island by cr ossing the narr ow passage that separates it fr om the mainland (J. Kinnear , unpub.).
30 Managing Vertebrate Pests: Foxes 3
Although foxes have been implicated in the demise of the malleefowl, other factors are thought to be involved including habitat modification. Source: D. Priddel, NSW NPWS
50 55 14 N
0 44 21.5 12 30 17 1.8 20 6 Means of sampled sites
3
20 11 8 0 5 0 1984 12 1989 3 0 1 km
Figure 10: Percentage capture rate of bettongs ( Bettongia penicillata) after five years of fox contr ol in Tutanning Nature Reserve. Light gr een columns show the captur e rate prior to fox contr ol; dark green columns show the captur e rate following five years of fox contr ol in the r eserve (J. Kinnear, unpub.).
Bureau of Resource Sciences 31 12
10
Whole of Dryandra baited 8
Part of Dryandra baited
6
4 Numbat sightings per 100 km
2
0 1979 81 82 83 84 85 87 88 89 90 91 92 Year
Figure 11: Numbat (Myrmecobius fasciatus) sightings in Dryandra State For est between 1979 and 1992. Fox control program implemented in 1982 (J.A. Friend, CALM, W A, pers. comm. 1992). on fox-free Enderby, approximately 60 rock- bandicoot, between 1971 and 1975. T ammars wallabies were sighted, while on Dolphin (Macropus eugenii), bettong and brushtail Island (with foxes) only one r ock-wallaby possums (Trichosurus vulpecula) declined was sighted. to very low numbers. The bettong, which was The spotlight traverses wer e repeated after formerly abundant in the r egion, but thought a period of fox contr ol using 1080 baiting on to be extinct because none wer e reported Dolphin Island. Following fox contr ol on this during a ten-year period, was located but island, the sightings incr eased by nearly thirty- found to be in very low numbers. In 1984, fold (Figure 9). Thus, r emoval of foxes fr om the reserve was trapped for bettongs and Dolphin Island resulted in a marked incr ease seven were captured and r eleased. Captures of rock-wallabies on the island. were successful only at two sites characterised by dense cover (Figur e 10).
Bettong (Bettongia penicillata) ‘Fox control resulted in increased numbers and Tutanning Nature Reserve (2200 hectar es) is distribution of bettongs in a a natural bush r emnant in the wheatbelt of Western Australian reserve.’ Western Australia, about 150 kilometr es south- east of Perth. The r eserve lost three species A baiting program for foxes was of marsupials, a numbat, a possum and a implemented and maintained for five years.
32 Managing Vertebrate Pests: Foxes In 1989, the r eserve was trapped again and numbats, bettongs and brushtail possums 63 bettongs wer e caught for appr oximately appeared to have incr eased. Tammar the same trapping ef fort. Prior to fox contr ol wallabies, once thought to be extinct, ar e now there were no captures on some trap lines. commonly seen in some ar eas. After fox contr ol the capture rate of bettongs increased and was as high as 55% of traps 3.1.2 Evidence from south-east set in some ar eas. To summarise, not only Australia did fox control result in a population increase, it also enabled the bettong to In New South Wales, fox r emoval has been occupy and r eproduce successfully in a shown to increase malleefowl survival. larger proportion of the r eserve (Figure 10). Priddel (1991, page 3) states: ‘Populations Tammar wallaby and brushtail possum in New South Wales are in drastic decline numbers also incr eased. and imminent danger of extinction ... The most significant threat to the survival of the 3 Numbats (Mymecobius fasciatus) malleefowl in New South Wales is the introduced fox (Priddel 1989)... the threat Dryandra State Forest (more than 10 000 posed by the fox can be reduced by a hectares) is a pocket of r emnant bushland campaign of intensive baiting’. in the wheatbelt near Narr ogin, about 175 kilometres south-east of Perth. It is a highly ‘Fox removal has been shown significant conservation site because of the to increase malleefowl survival persistence of the numbat within its in New South Wales.’ boundaries. During the 1970s, the numbat In a further study and fr om earlier reports, population declined to a low level (Friend Priddel and Wheeler (1990) concluded that 1990). Similarly, tammar wallabies, bettong feral cats and foxes wer e a major factor and brushtail possum wer e also uncommon. influencing the survival of this species. During monthly trapping and spotlight However, it was shown that contr ol of surveys over two years (1969–70) ther e predators alone was not suf ficient to ensure were few records of these species and the survival of malleefowl chicks (Priddel 1991). trapping success was less than 2% (A. He states:‘Other factors are implicated in the Burbidge, CALM, WA, pers. comm. 1992). demise of malleefowl, namely stock, goats, Additional efforts to trap bettongs in 1975 rabbits and fire’. were unsuccessful. Fire opens the canopy and incr eases the ‘Numbats and other native vulnerability of malleefowl to avian pr edators animals increased in Dryandra (Priddel and Wheeler 1990). Food is a limiting State Forest after foxes were factor (Priddel 1991) on Y athong Nature baited.’ Reserve, New South Wales. The study showed A fox removal program was implemented that newly hatched chicks, which wer e in 1982 in a selected portion of Dryandra State released into mallee wher e foxes have been Forest. The 1080 baiting was undertaken controlled, starved unless given supplemen- monthly, over five years. Numbats incr eased tary food. significantly within the baited ar ea, but not Phillips and Catling (1991) studied the outside the baited ar ea (Friend 1990). In 1989 home range and activities of foxes in a the whole of Dryandra was tr eated with 1080 wilderness area of coastal south-easter n meat baits. Since then numbats have incr eased Australia. Small and medium-sized mammals substantially (Figure 11). were abundant and comprised 52% of the Following fox contr ol, bettongs appeared diet of foxes. Such high pr ey densities ar e in to increase in numbers within the baited ar ea, contrast to the Western Australian situation, and after thr ee years of r egular 1080 baiting but fox densities (and pr esumably predation of the whole Dryandra State For est area, pressure) were judged to be low.
Bureau of Resource Sciences 33 During studies of the distribution and have been successfully r eintroduced into abundance of fauna in two for ested regions, wheatbelt reserves in concert with 1080 one in the north, and the other in the south baiting programs. In another ar ea of Western of eastern New South Wales (P.C. Catling, Australia, subsequent r esearch (Friend 1990) in preparation), foxes wer e found to be recently identified a second limiting factor abundant in all 13 study sites of the souther n apart from fox predation. A numbat r eintro- region. At the same time small wallabies duction experiment into a natur e reserve in were not found, quolls wer e present in only Western Australia had not been as successful one area, and bandicoots in six ar eas, both as previous wheatbelt introductions despite at very low abundance. In contrast, of the fox control. There is evidence that pr edation ten northern study sites, foxes wer e only by feral cats became the limiting factor . It is found in four, at approximately half the not known why cat pr edation is a significant abundance found in the south. Small mortality factor in this semi-desert setting. wallabies and quolls wer e present in nine Feral cats in this ar ea seem less inclined than areas, bandicoots in seven ar eas, and all foxes to take baits. It is subjective observation were mostly at high abundance. which also suggests that cats may incr ease in density following the r emoval of foxes. Norman (1970) studied fox pr edation in short-tailed shearwater (Puffinus tenuirostris) Recent studies in the Gibson Desert of colonies in Victoria. He found pr edation rates Western Australia appear to confir m these to be generally low (less than 2%) but could observations (Christensen and Burr ows, in not identify unconfirmed kills nor the extent press). Feral cat numbers incr eased fourfold to which viable individuals wer e being when fox control was initiated whilst ther e removed from the colony. Hor nsby (1981) was no change in cat numbers in a observed one instance of fox pr edation on a neighbouring site where no fox contr ol was juvenile euro (Macropus robustus) as well as undertaken. several attempted kills of yellow-footed r ock- ‘Feral cat numbers may wallabies in the Flinders Ranges of South increase when foxes are Australia. removed.’ Regular inspection of tortoise nesting sites The impact on native fauna of a fox along the Murray River in South Australia management program which eliminates showed that 93% of eggs wer e taken by foxes foxes but favours other pr edators, such as (Thompson 1983). It was also found in this feral cats, r equires more study. It needs to study that the age structur e of tortoise species be carefully considered in the development in the Murray contained a dispr oportionately of a fox management strategy. large number of old individuals, which was attributed to egg losses. As older individuals die and with juvenile r ecruitment restricted 3.1.4 Evidence from areas lacking by fox predation, tortoise populations along foxes the Murray will continue to decline. Manipulative predator removal experiments, A list of native species believed to be at such as those discussed above, pr ovide risk from fox predation is pr esented at strong evidence that fox pr edation is a major Appendix A. threatening process for Australian native fauna. In addition, ther e is considerable 3.1.3 Impact of fox removal on circumstantial evidence that is consistent other predators with these experimental findings. In the absence of the fox, ar eas such as the wet In Western Australian, numbats have tropics (Torresian Biogeographic Region), increased from low densities during fox Tasmania, Kangaroo Island and numer ous baiting programs (Section 3.1.1), and numbats smaller islands, appear to carry intact and
34 Managing Vertebrate Pests: Foxes abundant faunas (Johnson et al. 1989). This zone. Foxes were implicated in the failur e is despite the pr esence of feral cats and other to establish one colony, and feral cats wer e impacts such as significant habitat loss. implicated in another colony. Fir e caused Conversely, in the pr esence of the fox, ther e the loss of another population. is a history of extinction and major changes in the distribution of surviving mammal 3.1.6 Impact on traditional lands species over wide ar eas of the Australian continent. Other factors, however , such as In the desert r egions, traditional Aboriginal the absence of rabbits in some ar eas, could living patterns persisted well into the twentieth also account for the curr ent abundance of century. Burbidge and McKenzie (1989) have native fauna in some ar eas free from foxes. shown that in the W estern Australian desert ‘Predator removal studies regions, mammal extinctions have been provide strong evidence that common and widespr ead. The disappearance 3 fox predation is a major of many mammals coincided with the time threatening process for that Aborigines left the desert r egion. Australian native fauna.’ Burbidge and Mackenzie (1989) r eported that foxes did not become established in many areas until after the mammals had gone. They 3.1.5 Impact of foxes on suggested that the subsequent change in the reintroductions of native fire regime as evidenced by an incr eased fauna incidence of wide-scale wildfir es was a major cause of the decline in those species. They In a r eview of attempts to r eintroduce suggest that in the absence of traditional macropod species in Australia (Short et al. Aboriginal burning practices, which in the 1992), foxes wer e identified as a factor limiting past generated habitat mosaics and a system the success of seven out of ten mainland r ein- of fire breaks, the fauna was not only deprived troductions. They also found that r eintro- of essential habitat but also made mor e ductions to islands and mainland sites which vulnerable to predators. had predators such as foxes and cats, had a success rate of only 8%. In stark contrast, the Attempts to r e-establish rufous hare- success rate of r eintroductions to island sites wallabies into the desert r egions have been which had no pr edators was 82%. Per haps thwarted principally by high levels of the most convincing example of fox pr edation predation, foxes in one case, and feral cats presented by these authors involved the in another (Sharp 1992). Reintr oductions of reintroduction of Parma wallabies ( Macropus some semi-arid fauna ar e doomed to fail parma) to a site at Robertson in easter n New without fox and feral cat management, South Wales. A total of 45 animals wer e although other factors such as appr opriate released (12 fitted with radio transmitter cover, food and other essential r esources collars). Three weeks after translocation the no doubt ar e also important. However, there heads and thoraxes of two wallabies, which is no effective method for wide-scale had been buried by foxes, wer e found one predator control in the semi-arid r egion. to two kilometr es from the point of r elease. Sustained poisoning of foxes in strategic Of the 26 car casses eventually recovered, 24 areas is currently the only method that is were buried (typical caching behaviour of known to be ef fective. foxes). Within two months, no collar ed animals remained alive, and within thr ee 3.1.7 Fox competition with native months all 45 wallabies ar e believed to have fauna been taken by foxes. Sharp (1992) identified several factors Although the r ole of the fox as a pr edator of affecting attempts to r e-establish rufous hare- wildlife is well r ecognised, there is little wallabies (Lagorchestes hirsutus) in the arid known about its impacts as a competitor .
Bureau of Resource Sciences 35 Either competition or pr edation by foxes district of the Norther n Territory (Wilson et could threaten the viability of wildlife al. 1992). The consequences for native fauna populations reduced by habitat loss and mod- of these or other populations of foxes ification. Morris (1992) suggests foxes may spreading more widely are unknown, but compete with the chuditch or wester n quoll could be significant. (Dasyurus geoffroii) for food in jarrah for est in Western Australia. Foxes can also pr ey on 3.1.9 The fox as a predator of young chuditch. A pr eliminary unreplicated rabbits test suggested that poisoning foxes with 1080 may allow chuditch to incr ease. Parer (1977), Wood (1980) and Newsome et al. (1989) conclude that the fox, in 3.1.8 Environmental conjunction with other pr edators, can consequences of potential restrict rabbit populations under certain range expansion circumstances. Pech et al. (1992) defined these as being: ‘at low rabbit densities, foxes The fox has the potential to expand its range are capable of regulating rabbits, while at to include Tasmania, Kangaroo Island and high rabbit densities, rabbits escape from other islands with suitable habitat. W ere this predator regulation and foxes would not to occur it would pr obably have major have a significant impact on rabbit detrimental impacts on the native fauna of numbers’. these islands, particularly in T asmania where ‘Foxes are not effective at probable consequences of fox pr edation are controlling rabbit numbers in obvious for such pr ey species as the easter n good seasons.’ quoll, bandicoots, bettong and gr ound parrot. Other consequences, such as This prediction fits the historical patter n. competition between foxes and other Foxes have been pr esent in Australia for species, are less certain, but the fox could more than a hundr ed years and during this be a strong threat to the T asmanian devil. period rabbit plagues wer e commonplace. ‘If foxes were introduced to If this model is corr ect, the fox may be Tasmania, Kangaroo Island or viewed as beneficial by r educing the other smaller islands they frequency of rabbit outbr eaks, or by could cause considerable extending the interval between outbr eaks damage.’ by restraining rabbit population gr owth rates. In essence, when rabbit densities ar e There have been several unsuccessful low, fox pr edation may under certain cir - attempts to introduce the fox into T asmania cumstances limit rabbit population gr owth. (Statham and Mooney 1991). The origin of a fox killed near Launceston in 1972 is still It may be concluded on the basis of this unknown. It would be r elatively easy for model that the fox is capable of exer cising people to make further attempts. All lar ger a measure of biological contr ol on the rabbit Australian islands have r egular sea and air populations. However, the fox is not an traffic, making irr esponsible, deliberate ef forts effective biocontrol agent, because it cannot at introduction almost inevitable in the long prevent the build up of rabbit numbers as term. Early detection would be unlikely in a result of favourable conditions, and it has isolated locations. minimal impact at high rabbit densities. The important question is whether the r ole that Whether foxes could spr ead further north foxes play in rabbit contr ol outweighs the is uncertain. There are records of foxes in the damage foxes cause to native wildlife. The Kimberley region of Western Australia (King answer is likely to vary depending on r egion and Smith 1985) and an isolated population and circumstances. For example, in exists on Killarney station in the Victoria River broadacre cropping land and other ar eas
36 Managing Vertebrate Pests: Foxes where there are few native wildlife species controlling rabbits with and without fox susceptible to fox pr edation, it may be management is r equired. advantageous to maintain fox pr edatory pressure on rabbits by not using 1080 3.2 Economic impact poisoning to manage rabbits. It has been clearly demonstrated that foxes ar e highly susceptible to secondary poisoning fr om 3.2.1 Harmful economic impacts eating 1080-poisoned rabbits (Bir chfield 1979; Christensen 1980; King et al. 1981; Within a few decades of their intr oduction, McIlroy and Gifford 1991). It would be foxes were regarded as an agricultural pest necessary to deter mine that susceptible as is evidenced by the numer ous bounty native wildlife are not likely to be pr esent. schemes in place ar ound the tur n of the century. Although records are lacking, it was ‘Foxes are highly susceptible to certainly predation upon newborn lambs 3 secondary poisoning from which quickly ear ned the fox a bad eating 1080-poisoned rabbits.’ reputation. Sheep, and especially lambs, Where native wildlife is at significant risk being of relatively small size and lacking from fox predation, use of 1080 on rabbits to aggression, are more prone to predator cause secondary poisoning of foxes may be attack than many other livestock species. warranted, though its ef ficacy is uncertain. Further, sheep management often involves Christensen (1980) linked rabbit contr ol with unsupervised grazing in lar ge holdings. 1080 to an incr eased abundance in native Under these conditions, it is not surprising marsupials in Western Australia. Conversely, that high losses of lambs to pr edators are when the use of 1080 was r educed following often claimed. Even so, the r ole of the fox the introduction of the Eur opean rabbit flea as a predator of otherwise viable lambs is in Western Australia, populations of native subject to much contr oversy and further marsupials such as bettongs, wallabies and conclusive studies are required. numbats declined. A better understanding of ‘Soon after it was introduced, the relationship between rabbits, foxes and the fox was regarded as an feral cats and impact on native wildlife from agricultural pest.’
Fox predation on lambs may be significant on some properties. Source: R. Knox, APB
Bureau of Resource Sciences 37 Curiously, one of the first r eports of fox Australia, only 2.7% would have survived damage in Australia r elated not to the animal if a pr edator had not attacked; starvation itself but to the rather cavalier attitude of accounted for almost half of the mortalities. some early hunt clubs who, in the course of A similar study in New South W ales pursuing their quarry, damaged the fences (McFarlane 1964) indicated that of some and walls of early settlers (Rolls 1969). 3000 lamb carcasses examined, almost half were mutilated by pr edators but a maximum In published studies the fox has histori - of 9.7% actually died because of pr edator cally been perceived as an insignificant attack. A pr oportion of the latter would have predator of livestock (Fennessy 1966; Hone been weak or moribund lambs so that only et al. 1981) and hence ther e has been little 2% of the total lamb cr op was assessed as development of appropriate management having been killed by pr edators. strategies. This situation is beginning to change, partly as a r esult of the fox’s curr ent ‘Rogue foxes can cause high high profile as a pr edator of endanger ed losses of otherwise viable native species, but also due to a new lambs.’ emphasis on intensive management and the Not all lamb mortality studies dismiss protection of stud flocks, plus the sudden predation as being of secondary significance withdrawal of commercial fox harvesting and in some situations, foxes and other operations. Added to this is a pr omoted predators can cause heavy losses (Moule awareness of risks associated with fox 1954; Smith 1964; T urner 1965; McDonald involvement in the potential spr ead of 1966). However, these unusually high losses rabies. This elevated status of the fox as a can often be attributed to cir cumstances threat to the agricultural community has peculiar to a single flock or a small ar ea of occurred in the continuing absence of country (Coman 1985). These include a high conclusive data on fox damage and the cost proportion of twinning, particular lines of and benefits of management. ewes which exhibit poor mothering ability, ‘Ultrasound studies suggest and the proximity of optimal fox habitat. that fox predation on lambs There is evidence that individual killer foxes may be more important than become habituated to the killing of lambs was previously believed.’ (Rowley 1970). Such foxes can cause serious losses in individual flocks and both T urner While there have been few published (1965) and Moor e et al. (1966) describe such studies which show foxes as significant events. predators of lambs, general causes of lamb mortality have been well studied (for example Studies in Australia show that fr eshly Rowley 1970). These past surveys indicated killed livestock are an infr equent dietary that the biggest single factor in lamb losses item. However, feeding on carrion, notably appeared to be associated with the birth sheep and lamb car casses is common, process or as a r esult of poor mater nal care, particularly in winter (Catling 1988). For with primary predation causing the death of example, Alexander et al. (1967) found that an otherwise healthy lamb being only of the main fox activity amongst lambing minor significance. Rowley (1970) points out sheep was centred upon scavenging for that most of the important factors involved in foetal membranes. Ther e were some timid poor lambing percentages are inconspicu- attempts to attack live lambs but of 36 fox ous, whereas damage inflicted by pr edators sightings in the flock, only one attack on a is usually highly visible, commonly leading live lamb was r ecorded. Ewes were the sheep-owner to over estimate the generally undisturbed by the pr esence of importance of predators. the foxes. These findings wer e supported by the study of Mann (1968) wher e the Dennis (1965b) showed that of 4417 dead exclusion of foxes by fencing did not r educe lambs collected and inspected in W estern lamb mortality.
38 Managing Vertebrate Pests: Foxes Nonetheless, many of these past investi - foxes are common and wher e lambing is gations probably underestimate the role of early in the season. High lamb losses can foxes as pests in the sheep industry. In occur where lambing is out of step with or dietary studies, identification of soft tissue isolated from neighbouring flocks. material from lamb carcasses is difficult There are a number of potential pr edators unless wool is pr esent. It is also possible of lambs, including feral pigs, dingoes and that many lambs ar e killed without being foxes. Predator wounds of lambs vary in eaten, or killed and cached, to be eaten later characteristics and it is often dif ficult to as carrion. identify the pr edator from the wound ‘Foxes can account for up to inflicted. Rowley (1970) pr oduced a useful 30% of lamb deaths in some key for identifying pr edators from wounds areas.’ on lambs. Taken in combination with the post-mortem techniques developed by Pregnancy diagnosis in ewes using 3 Dennis (1965a) and others, an estimate can ultrasound has become mor e common, and be made of the damage caused by foxes in the early data fr om these ultrasound studies the sheep industry. However , the techniques suggests that fox pr edation may be much rely on the r ecovery of all lambs killed by more important than pr eviously believed. foxes and, as explained above, this is not For example, a r ecent study at the always possible. Rutherglen Research Institute, Victoria (J. Reeves, Rutherglen Research Institute, Although no quantitative studies have Victoria, pers. comm. 1993) indicated that been undertaken, r ecent observations also foxes took 7% of all lambs pr eviously suggest the fox is a pr edator of cattle (K. recorded as foetuses pr esent in a flock of Smith, RLPB, Moss Vale, NSW, pers. comm. 896 ewes. Importantly, many of the lambs 1994). Reported instances ar e sporadic and taken were completely r emoved from the mostly restricted to small rural subdivisions paddock immediately after birth, and on semi-urban fringes. When it occurs, therefore would not have been r ecorded however, the ef fect of fox pr edation is using conventional methods for estimating substantial — calves dying as a dir ect result lamb loss. While losses of this magnitude of predation or cows having to be put down may be insignificant to some graziers, they as a result of fox attacks during calving. are obviously important to br eeders of valuable stud stock. While the losses may ‘The fox is a legendary poultry be insignificant at a r egional or national thief, but poultry in intensive level, the operation of r ogue foxes on farms are well protected from individual properties can sometimes cause foxes.’ very high losses of otherwise viable lambs. Losses of other far m livestock to foxes In a recent study of fox pr edation on are probably not of economic significance, lambs in wester n New South Wales, Lugton although the pr owess of the fox as a poultry (1993) presents data indicating a high loss thief is legendary. T oday, most commercial of otherwise viable lambs to pr edators, poultry farming operations use intensive or principally foxes. Between 1985 and 1992 battery farming and the animals ar e generally Lugton observed lamb pr oduction and lamb well protected. Usually it is the small backyar d losses on five pr operties. He also r eviewed poultry flock which suf fers, but while of major information from other sources. On the concern to the individual operator , these basis of his own studies and those of others losses are not of serious economic signifi - involved in sheep pr oductivity trials, Lugton cance. Foxes ar e also a significant pr oblem suggests that in some sheep gr owing areas, for some commer cial emu and ostrich far ms. predation may account for up to 30% of all Fox predation on newbor n goat kids is lamb mortalities. He concludes that fox common but the level of loss is not consider ed predation has a lar ge impact in ar eas where significant at a national level. For high-value
Bureau of Resource Sciences 39 commercial cashmere herds, however, losses the potential impact of fox pr edation upon to individual enterprises due to fox pr edation the aesthetic quality of fauna parks, on kids can be high. wilderness areas and reserves. Because of the uniqueness of much of Australia’s fauna, Foxes can be a major nuisance to those reserves, parks or wilder ness areas in landholders, especially ‘hobby’ or ‘weekend’ which tourists ar e able to view uncommon farmers through loss of household or hobby or distinctive wildlife ar e a valuable stock. Loss of a few ducklings or a newbor n resource, both in economic and aesthetic goat kid can cause genuine distr ess to terms. owners. There has been incr easing demand on vertebrate pest contr ol agencies to supply There is no practical method for assessing poison baits for fox contr ol to pr event these the economic impact of foxes on wildlife losses. although it may be considerable, particu - larly for ecotourism. The inter est shown by In summary, the r ole of the fox as a international tourists towards Australia’s predator of livestock is not well understood, fauna such as kangar oos, koalas and despite a number of studies of lamb mortality. penguins, both in zoos and wildlife parks The importance of fox pr edation on lambs as well as in the wild, ar e an indication of as a cause of significant economic losses will the potential of this industry. vary from district to district and fr om time to time. While the mor e recent studies indicate ‘Where foxes are controlled in that foxes may be mor e important as a Dryandra State Forest, livestock predator than first thought, the spotlight tours to view native losses are probably lower than those caused mammals are becoming by a combination of natural factors including popular.’ starvation, mismothering, dystocia and In South Australia, the W arrawong adverse weather. Sanctuary, run by Dr John W amsley, has Further studies are required to assess the demonstrated that native fauna — such as importance of predation by foxes to lamb wallabies, potoroos, bettongs and bandicoots losses. Emphasis in these studies needs to be — protected by fox-proof enclosures can on examining possible links between be shown to the public by ‘display feeding’. predation levels and a range of factors Foxes and cats have been eliminated fr om including local density of foxes, r ole of other within the park and a fox and cat-pr oof fence predators, the importance of killer foxes, erected and supplementary feeding proximity of flocks to heavy cover , flock size provided. Guided gr oups of visitors can view and duration of lambing, br eed of ewes, a range of smaller native mammals in a semi- incidences of twinning, possible seasonal natural setting, which in other cir cumstances differences in predation pressure, and lambing would rarely if ever be seen. shelter. Projects funded under the V ertebrate With fox management, ther e is potential Pest Program (see Introduction) will pr ovide to display native mammals in the wild to a substantial information on the impact of foxes receptive public. For example, in Dryandra on livestock production. State Forest spotlight tours of the for est are There are no comprehensive data available becoming popular since the population on the costs of fox contr ol in Australia. The recoveries of the numbat (a diur nal species major costs would be the pr eparation and now seen fr equently), the bettong and the field delivery of poison baits (Section 7.5.2). brushtail possum. Thirty bettongs per hour are commonly seen. In Dryandra village, a 3.2.2 Ecotourism rustic collection of woodcutter dwellings now used as tourist lodgings, as many as 30 An emerging issue associated with the wild bettongs can be seen near dusk management of fox damage in Australia is congregating at the feeding site. It is possible
40 Managing Vertebrate Pests: Foxes for a person to sit quietly amongst a group Table 4: Quantity and value of wild red fox of bettongs and watch them busily and pelts supplied during 1982–83 from the major noisily foraging for scattered wheat grains. exporting countries involved (after Ramsay 1994). Persistent control has greatly reduced the number of foxes on Phillip Island and their Country Unit value Number Value likely impact on little penguin (Eudyptula ($A) of pelts ($A) minor) populations. For the period 1987–92, 202 foxes were destroyed while in the same Australia 23.20 350 981 8 152 000 period 499 penguins were identified as Canada 57.03 88 800 5 063 000 having been killed by foxes (M. Hayes, USA 57.03 445 630 25 414 000 DCNR, Victoria, pers. comm. 1993). Although other factors such as pollution are probably Note: Australian figures refer to exports only; figures for other more important, the risk foxes pose to an countries include internal use. North American figures include 3 estimated annual $50 million tourist industry pelts from farmed foxes. is significant. These examples demonstrate the potential have since dropped considerably. This for wildlife to attract tourists. National parks decline is due to a number of factors provide an ideal venue for the tourist including the vagaries of fashion, increased industry to exploit a worldwide interest in supplies from other countries and Australia’s unique wildlife. In selected areas, campaigns by the anti-fur lobby. The figures fox management may allow reconstruction in Table 5 represent only saleable pelts. The of some of the mammal fauna that formerly total harvest of foxes in any one year would existed, provided other population-limiting be higher. As an example, in some years factors are not operating. 10–20% of foxes can have severe mange (B. Coman unpublished data). These pelts Ecotourism ventures may be an effective and an unknown percentage of pelts badly element of an integrated approach to damaged by bullets would not be sent to managing Australia’s endangered or markets. vulnerable wildlife. By combining wildlife rehabilitation programs with economically ‘Low export prices for fox viable ecotourism ventures, income earned pelts has discouraged can be used to maintain or increase the commercial harvesting.’ protected areas. The commercial harvest for fox pelts in Australia occurs during autumn and winter 3.3 Resource value and use in the south-east of the continent. The fur industry estimates that about 60% of fox In the past, Australia has been one of the pelts supplied to the trade comes from New world’s most important exporters of fox pelts. Tables 4 and 5 show that the sale of Table 5: Number and value of raw fox pelts fox pelts can generate significant export exported from Australia (after Ramsay 1994). income. ‘There is no evidence that Calendar Number Unit Percentage harvesting foxes for pelts had year of pelts value used a significant impact on auctioned ($A) locally reducing the damage they cause.’ 1986 109 271 22.23 18.4 1987 105 654 21.40 20.6 Unfortunately overseas demand fluctuates 1988 101 982 9.80 17.8 widely, and although the industry flourished 1989 44 145 10.46 19.0 in the first half of the last decade, prices 1990 56 427 8.39 9.6
Bureau of Resource Sciences 41 South Wales, 30% fr om Victoria and the remainder from South Australia. Most foxes are killed at night using high-power ed rifles in conjunction with power ful spotlights. A smaller percentage is taken via fox drives or the use of den dogs. The use of steel- jawed traps for commer cial hunting is uncommon. The annual harvest of fox pelts varies widely and usually r eflects the export price. This is shown in T able 5 where the total number of fox pelts auctioned at the Melbourne market varied fr om 109 000 in 1986 to 44 000 in 1989.
42 Managing Vertebrate Pests: Foxes 4. Rabies and foxes The only r eported instance of rabies in Australia was in T asmania in 1867, a small outbreak which was quickly eradicated Summary (Pullar and McIntosh 1954). Rabies is one Rabies is a major threat to Australia, of the most fear ed of human infectious particularly if it becomes established in wild diseases due to the distr essing clinical foxes. At present the two main foci of sylvatic symptoms, the inevitability of death once rabies are in Western Europe and North symptoms appear and the severity of past America, both characterised by a high treatments. The number of people dying incidence of the disease in fox populations from rabies worldwide is estimated at (up to 85% of diagnosed cases). In these areas between 20 000 and 75 000 per year , while it is considered that in the absence of foxes, the number of people tr eated because of sylvatic rabies could not be maintained by exposure to rabid animals is between other wild species. This is due to the high 500000 and three million (MacInnes 1987; susceptibility of foxes to rabies, and the Fenner et al. 1987; W andeler et al. 1988). behaviour and structure of fox populations ‘The only reported instance of which ensure the disease is readily spread rabies in Australia was a and maintained. The two approaches small outbreak in Tasmania in 4 presently employed to control fox rabies are 1867 which was quickly population reduction and vaccination. In eradicated.’ areas where rabies is endemic, elimination of the disease through vaccination may be the more economically, socially and 4.1.1 Description scientifically acceptable. However, in The rabies virus belongs to a gr oup known Australia, assuming initial distribution of the as the lyssaviruses within the family disease is limited as is the number of vectors Rhabdoviridae. The disease, which principally involved, population reduction is seen as the affects the central nervous system, is thought better alternative. If rabies became established in foxes, the distribution and to infect all species of mammal and is nearly abundance of the species in Australia would always fatal (Kaplan et al. 1986). The most make control operations a daunting if not common route for rabies transmission is by a impossible task. Other wild host populations bite from a rabid animal. Rabies virus, like all including dingoes and bats could also other viruses, needs living host cells in order become involved, perhaps further to replicate and survive. The tissues of an complicated by the as yet unknown animal that has died fr om rabies lose their susceptibility of other native species. The infectivity at a rate that varies with the initial implications of this scenario are that in the virus content and the envir onmental influence first instance, efforts should concentrate on (Wandeler 1980). preventing the entry of rabies into Australia and secondly, if it does, strategies should be in place to rapidly eliminate the disease at ‘Rabies transmission is its point of introduction. usually by a bite from a rabid animal.’
4.1 The disease There are two main epidemiological ‘Rabies occurs on all cycles of rabies: urban, with the domestic continents except Australia dog as primary host; and sylvatic with one and Antarctica.’ or more wildlife vectors involved. Cases of human rabies ar e relatively rare in developed Rabies occurs on all the continental land countries where the urban cycle has virtually masses with the exception of Australia and been eliminated. Antarctica (MacInnes 1987; Blancou 1988).
Bureau of Resource Sciences 43 4.1.2 Present worldwide status (Wandeler 1980). An infected fox may not show symptoms until a period of high Many rabies epidemics have been r ecorded, stress such as dispersal, mating or birth with the dog acting as the main host and which also happen to be the periods of primary transmitter of the infection to man greatest contact between foxes (T inline (Kaplan 1985). In developed countries, the 1988). Following incubation ther e is a advent of cheap and ef fective rabies symptomatic period, typically of 3–5 days, vaccines (Sikes 1975) which allowed for throughout which the virus is usually large-scale vaccination campaigns, coupled secreted (Sikes 1962). Despite a limited with the control of stray dogs, have amount of evidence it appears that the effectively eliminated the dog as a vector number of foxes encounter ed by a rabid of rabies between 1945 and 1960 (T ierkel fox would be the same as if it wer e healthy, 1975). Urban rabies now occurs principally and that the rate at which these contacts in parts of Africa, the Indian subcontinent, are made would be incr eased by the South-East Asia, and Central and South heightened activity of rabid foxes America where there are communities (Macdonald and Bacon 1982). associated with large numbers of unvacci - nated or stray dogs (Geering 1992). While the characteristics of rabies within the fox ensur e that it is per haps the most Without the fox, it is doubtful that sylvatic susceptible wild animal, the behaviour and rabies would occur over most of the geo- structure of fox populations also ensur e graphical range of the disease with the that the disease is r eadily spread and possible exception of South-East Asia. A maintained. In particular, dispersal by sub- number of wildlife vectors ar e involved, adult foxes is believed to be r esponsible although it is usually only one species which for the autumn peak in the cases of fox is responsible for perpetuating the disease in rabies and for the long distance pr ogression a particular region (Geering 1992). of the disease (T oma and Andral 1977; Artois and Andral 1980). During the mating 4.1.3 Fox rabies season (winter), males may also stray fr om their own territories in sear ch of breeding At present the two main foci of sylvatic opportunities. Territories vacated by the rabies are in Western Europe and North death or movement of a pr evious occupant America. The disease is both characterised can be incorporated into adjacent, higher by a high incidence of rabies in fox density territories (Macdonald 1980). At populations, with up to 85% of diagnosed other times of the year ther e is limited cases in all species (W andeler et al. 1974), between-territory contact (Macdonald and and by the cyclic natur e of the disease. The Bacon 1982). This in tur n limits spread and latter is related to seasonal peaks in fox slows down the pr ogression of rabies reproduction (Müller 1971). W ithout the fox, (Wandeler 1980). The high r eproductive it is doubtful whether sylvatic rabies could capacity of foxes coupled with the be maintained by other wild species either continual turnover of territories means that singly or collectively (Lloyd 1980). The areas affected by rabies will be r epopulated westward spread of rabies in Eur ope has in a r elatively short time, thus cr eating a been at approximately 25–60 kilometres per new population of susceptible animals for year (Moegle et al. 1974). the next wave of the disease (T inline 1988). The fox rabies virus has several unique Comprehensive reviews of the natur e and characteristics including high rates of mode of action of rabies and the r ole of infection and viral excr etion and a low wildlife in its transmission can be found in frequency of post-infection immunity. The Baer (1991), Wandeler et al. (1974), Kaplan incubation period in various laboratory et al. (1986), Steck and W andeler (1980), trials has ranged between 4–181 days Zimen (1980), Macdonald (1980), Bacon
44 Managing Vertebrate Pests: Foxes (1985), MacInnes (1987), Campbell and Their usefulness for stopping or slowing Charlton (1988) and O’Brien and Berry (1992). the spread of rabies has been contr oversial. Zimen (1980) points out that the fluctua - 4.2 Management techniques tions in the incidence of rabies during disease outbreaks may equally be due to for rabies control the normal fluctuations in the incidence of The primary aim of rabies contr ol programs fox rabies rather than the ef forts to reduce is to pr otect humans from infection and fr om population density. He concluded that economic loss (Wandeler 1988). This can be mortality of foxes caused by rabies far attained by a drastic r eduction in the fox outweighed all ef fects of human induced population or by mass immunisation of the fox mortality. Despite substantial ef forts in host species, principally foxes. In both cases France, Germany, Poland and other parts the aim is to r educe the number of susceptible of Europe, as well as North America, foxes to below the thr eshold density of animals traditional control methods have failed to which is necessary to maintain rabies in the halt the spread of fox rabies (Linhart 1960; wild (Anderson et al. 1981). Epidemiological Johnston and Beauregard 1969; Wandeler evidence from Europe suggests that the et al. 1974; T oma and Andral 1977; threshold density lies in the range of 0.2–1.0 Macdonald 1980). Wandeler (1988) suggests 4 foxes per squar e kilometre (Müller 1971; Bogel that for the fox, human contr ol has long et al. 1976 and 1981; Steck and W andeler 1980; been the most important mortality factor Macdonald 1980) with 1.0 being the most and that foxes adapted well to this situation. frequently quoted value (Anderson et al. 1981). This resilience to human contr ol, coupled with the high r eproductive potential and carrying capacity of foxes in rural and urban 4.2.1 Rabies control in endemic environments, are the pr obable causes for areas the failure of fox population r eduction The current practice in Eur ope and North efforts in halting the spr ead of rabies. Bacon America of treating fox rabies epidemics by and Macdonald (1980) also ar gue that the oral vaccination is r elatively recent (Black killing of foxes can be counterpr oductive and Lawson 1970; Baer et al. 1971). Prior to to rabies contr ol because the disruption to this, reducing fox density was consider ed fox social systems r esults in a gr eater degree the only option. This was based on the of movement into new territories and an following premises (Wandeler 1988): increase in aggr essive contacts between foxes. • rabies always disappeared from areas where the disease itself and contr ol efforts had reduced the fox population density to 4.2.2 Vaccination a low level; The first field evaluation of oral vaccination of foxes using attenuated (weak) vaccines was • rabies did not penetrate into r egions which carried out in Switzerland with chicken heads had a tradition of small game hunting as bait (Steck et al. 1982). The trial was where foxes wer e considered a pest and considered successful with two subsequent systematically destroyed; and rabies outbreaks halted and no evidence that the vaccine strain had become established in • areas with low carrying capacities for foxes wild or domestic animals. Similar campaigns such as marshland and alps wer e barriers quickly followed in Belgium (Br ochier et al. to rabies. 1988), Germany (Wachendörfer et al. 1985; Schneider et al. 1985), France (Artois et al. Traditional methods for r educing fox 1987), Italy, Luxembourg and Austria populations for rabies contr ol are trapping, (Schneider et al. 1988) and in Canada shooting, gassing of dens and poisoning. (MacInnes et al. 1988; Johnston et al. 1988).
Bureau of Resource Sciences 45 Recent advances in cloning and gene foxes was only 49%. Anderson (1991) also expression have led to the development of concludes that an overall immunisation of a new generation of rabies vaccines, the 81% may be suf ficient to prevent the spr ead recombinant virus vaccines. The duration of of rabies in low to moderate density fox immunity conferred by this r ecombinant populations (such as the two per squar e virus (a minimum of 12 months) corr esponds kilometre in these trials) but for higher to the length of pr otection required for fox densities in the or der of four per squar e vaccination in the field (Schneider and Cox kilometre, a 90% coverage would be 1988). More importantly, and unlike the necessary to block transmission. attenuated strains, there is no evidence of residual rabies in a variety of non-tar get 4.2.3 Baiting systems animals (Rupprecht and Kieny 1988; W iktor et al. 1984). The first field applications of Whichever strategy is applied, a bait incor - recombinant vaccine baits took place in porating either a vaccine or a toxin needs to Belgium (Pastoret et al. 1988; Br ochier et al. be delivered to fox populations for the 1991). Following the final distribution of bait, purpose of rabies contr ol. Baits such as horse vaccine-induced immunity was evident in meat, tallow and chicken heads have long 81% of the foxes sampled. been used in fox contr ol, mostly in association with poisons such as 1080 (sodium mono- flu- In south-eastern Ontario, rabies has his- oroacetate) and strychnine. Oleyar and torically shown peaks of incidence over a 3.5 McGinnes (1974) and Allen (1982) also used year cycle. The last such peak was in the first ground beef and pork coated in granulated quarter of 1986 (T inline 1988). However, since sugar to deliver chemosterilants to wild foxes. the aerial vaccine baiting of foxes, the In Great Britain the pr esent Ministry of incidence of rabies in foxes has declined to Agriculture, Fisheries and Food (MAFF) its lowest level in 30 years. Most of the cases recommendations for population r eduction which do occur ar e across the Ottawa River in urban foxes in the event of a rabies outbreak from Quebec, which is experiencing a major is for the distribution of day-old chicks injected rabies epizootic (R. Rosatte, Ontario Ministry with a gelatine solution of strychnine (C. of Natural Resources Rabies Unit, pers. comm. Cheeseman, MAFF, Great Britain, pers. comm. 1994). 1993). With the relatively recent advent of These trials indicate that the eventual orally administered rabies vaccines, the eradication of sylvatic rabies in endemic ar eas development of baits specifically for this is possible, although the r esults still need to purpose has r eceived a great deal of attention. be treated with caution. Anderson (1991) points out that in these latter trials (and similarly in nearly all pr evious evaluations of 4.3 Implications for wildlife vaccination campaigns) the experi - Australia mental design failed to include comparable The risk of fox rabies ever being intr oduced non-treatment areas in which baits wer e not to Australia is low. Rabies could only be distributed. This does not allow for the cyclical brought into the country via an infected nature of rabies in fox populations to be fully animal, and with strict quarantine contr ols taken into account in the trial r esults. Voigt over legal imports, the major risk is (1987) also raised this pr oblem but acknowl- obviously from smuggling or illegal landings edges that in the contr ol of rabies a non- (Garner 1992). Such imports may not be treatment area is generally not possible. Ther e rare, although the likelihood of a smuggled is also a need to impr ove upon the low level animal becoming rabid is pr obably low and of immunisation achieved in juvenile animals. with limited opportunities for it to be a In the second baiting period of the trials threat to other animals (For man 1993). This reported by Br ochier et al. (1991) which was however does not pr eclude the possible prior to dispersal, bait uptake by juvenile introduction of sylvatic rabies to Australia.
46 Managing Vertebrate Pests: Foxes The uncertainty of the origins of existing If rabies became established in foxes, the epizootics in Europe with the suggestion distribution and abundance of the species that it was the r esult of adaptation of the in Australia would make contr ol operations canine virus to foxes (Blancou 1985) also a daunting if not impossible task. Other wild shows that the behaviour of a disease such host populations including dingoes and bats as rabies is not pr edictable. Finally there is could also become involved, per haps further the even less likely event that rabies could complicated by the as yet unknown suscep- be deliberately r eleased as was thr eatened tibility of other native species. The implica- by terrorists in the United Kingdom in 1989 tions of this scenario ar e that in the first (Wilson 1992). instance, rabies should not be allowed to enter ‘The risk of fox rabies ever Australia and secondly, if it does, strategies being introduced into Australia should be in place to rapidly eliminate the is low.’ disease at its point of intr oduction. Through the use of simulation models of Circumstances will determine which sylvatic rabies, Pech and Hone (1992) also approach to rabies contr ol is selected. In ar eas highlight the need for ef ficient disease sur- where rabies is alr eady endemic, elimination veillance systems to be in place. Assuming of the disease thr ough vaccination may be rabies was first detected in foxes and the more economically, socially and scientifically 4 reporting rate of rabid foxes was the same as acceptable. However, population reduction that for Gr eat Britain, Bacon (1981) estimated is seen to be the better alter native where the that 100–200 foxes might contract rabies before disease is pr esently absent such as in Australia authorities could be 95% certain of being and Great Britain, assuming, of course, that informed. Pech and Hone (1992) suggest that detection of its intr oduction is rapid so that this may take 4–7 months fr om the time of distribution is r estricted, as are the number introduction which might allow rabies to of carriers of the disease involved. spread between 5–35 kilometr es from the Furthermore, should rabies be intr oduced to initial point of infection. The further the disease Australia the use of vaccines would be spreads before it was detected the less likely prohibited until such time that evidence was that existing fox contr ol methods would available of their safety in the Australian prevent rabies from becoming endemic. environment (AUSVETPLAN Disease Strategy for Rabies 1991). Existing contingency plans for the contr ol of fox rabies in Australia 4.4 Implications for fox therefore rely on population r eduction management techniques (AUSVETPLAN Emer gency Operations Manual, W ild Canid and Felid It is inappropriate to initiate lar ge-scale fox Control 1991). These involve the aerial and management programs on the basis of exotic ground distribution of poison baits (1080, disease risk alone. However , land managers strychnine and cyanide) supported by should be awar e of the r ole that the fox can trapping, den fumigation, shooting, exclusion play in the spr ead and maintenance of rabies fencing and harbour destruction. Coman if the disease was intr oduced to this country. (1992) attempted to implement these In terms of understanding the likely behaviour techniques in simulated rabies outbr eaks in of fox rabies in Australia which is essential Victoria with limited success. This was partly for contingency planning, the gr eatest due to a lack of r esources which would not information gap r emains the accurate be the case in the r eal event. However, there assessment of fox distribution and abundance. were still obvious deficiencies in techniques Similarly, we also know very little about which require further development. The achievable rates of population r eduction by failure of a policy of population r eduction in poison baiting, pr eferred baits for dif ferent endemic rabies areas similarly cannot be environments or appropriate bait application disregarded. techniques.
Bureau of Resource Sciences 47 5. Community attitudes possessed of inor dinate cunning, a har mless affecting fox or even beneficial component of the fauna management and an honour ed object of the chase. The idea of endowing animals with the characteristics, particularly the failings, of Summary humans, and having them enact imaginary Perceptions of the fox as a pest depend very dramas which ridicule the faults of man has much on individual backgrounds and upon been popular with writers as early as Aesop deep-seated historical perceptions of the fox and as late as W alt Disney. Even in the bible, as a ruthless and cunning exploiter. These the fox is cast as being deceitful, ‘Oh Israel, perceptions can hinder development of a thy prophets are like the foxes of the desert’ rational approach to managing this animal. (Ezekiel 13:4). This tr end can be traced through history, per haps reaching its zenith Historically, the fox has been important in Medieval times when Reynard the fox for hunting, a tradition that remains in became a popular story character . Australia today with many hunt clubs and other, less formal methods for hunting foxes. Unfortunately, much of the myth It is unlikely that recreational hunting can associated with such tales has become effectively control fox damage, although installed in what might be ter med recreational hunters may assist individual contemporary popular ecology in Australia, landholders by removing problem animals. where foxes are seen as cunning and ruthless exploiters of wildlife and smaller domestic There has been little attention to the animal livestock species. As a r esult, it is often welfare aspects of fox management in difficult to separate fact fr om opinion and Australia. However, there can be no doubt opinion from myth. It has only been in the that some current control techniques cause last decade that scientific evidence r elating pain and suffering to the animal. The ethics to the ef fects of fox pr edation on Australian of hunting foxes with hounds or other dogs wildlife has been collected (Chapter 3). is beyond the scope of this strategy since the technique is not recognised as a method of ‘The fox is variously regarded damage control. Of the poisons used for fox as a killer, a pest, a cunning control in Australia, cyanide (currently used rogue, a harmless component of only experimentally) is probably the most the fauna , or an honoured humane and strychnine the least humane. object of the chase.’ Information on the humaneness of 1080 in There are a wide range of per ceptions members of the Canidae is equivocal but, about the economic impact of foxes. It is because of the very high sensitivity of foxes important that accurate infor mation on the to this poison, it has an advantage over the impact of foxes is obtained and commu- other two poisons used because of its relative nicated to the general public and to land target-specificity. Shooting with high-powered managers in particular, so that they can rifles is a humane method of fox control, but make informed decisions concer ning the the use of rim-fire rifles and shotguns need for fox management. increases the risk of maiming and slow death. 5.2 Sport hunting 5.1 Perceptions of the fox Attitudes and policies towards foxes and their 5.2.1 Traditional hunting management are, almost certainly, colour ed by historical perceptions of the animal. At The tradition of riding with hounds is one different times in our history it has been which early English colonists transferr ed to variously regarded as a killer, a pest, a r ogue Australia and, in fact, is the main r eason for
48 Managing Vertebrate Pests: Foxes the introduction of the fox to this country dislodged are either killed with shotguns or (Chapter 1). coursed with lar ge lurcher dogs. The first true hunt clubs wer e Finally, the sport shooting of foxes, established in the 1850s although the usually at night with high-power ed rifles, is Adelaide Hunt dates back to 1842. It is a common recreational sport in many parts doubtful whether these early clubs hunted of southern Australia. Such shooting is also foxes, the mor e likely quarry being native the main method employed in the harvesting species (Rolls 1969). Curr ently there are of wild fox pelts, but many shooters will 23 listed Hunt Clubs in Australia (Camer on- take foxes by this technique without any Kennedy 1991) but the sport appears to expectation of commercial gain fr om the be expanding. All states except sale of fox pelts. Queensland and the Norther n Territory In many districts, r ecreational shooters have established Hunt Clubs. This includes with high-powered rifles are invited onto Tasmania which is fox fr ee. The existence farms just prior to or during the lambing of hunt clubs in fox-fr ee areas indicates season. The r esultant localised reduction in that the hunt is essentially a social fox numbers may give some temporary institution and the pr esence of the quarry respite to lamb pr edation losses. is of secondary importance. Recreational fox hunting often r equires Traditional fox hunting pr obably specialised firearms and ammunition. In contributes little to the management of fox addition, hunters undoubtedly contribute damage. Clubs see themselves primarily as in other ways to local and r egional sporting and social or ganisations. economies although the extent of this has 5 Unlike other for ms of recreational fox not been estimated. hunting (see below), hunting with horses and hounds is highly or ganised and 5.3 Animal welfare includes a Hunt Committee, Master of Hounds and Field Master . Clubs usually have strict rules and guidelines. The Hunt 5.3.1 General Clubs Association of V ictoria, for example, has a detailed code of rules for fox hunting Animal welfare groups aim to pr otect animals (HCAV 1988). from cruelty and impr oper exploitation, encourage the considerate tr eatment of animals, and denounce practices per ceived 5.2.2 Other forms of recreational as causing animals unnecessary str ess. The hunting Australian and New Zealand Federation of Battues or fox drives ar e still common in Animal Societies (ANZFAS) accepts that fr om some rural communities. Her e, groups of time to time some feral animals may cause individuals meet, generally on an infor mal agricultural or envir onmental damage, and basis, and use unar med beaters (often with that in these situations ther e is a case for dogs) to drive foxes into a waiting line of pest control (ANZFAS 1990). However, their guns. Usually it is only small ar eas of prime view is that only humane methods conducted fox cover that ar e treated. under the supervision of r elevant ‘Shooting of foxes, usually at government authorities, and within sound night with high-powered rifles, long-term population reduction programs, are is a common sport in southern acceptable. Australia.’ The cruelty r elated to the use of various Another common technique of fox fox control techniques relies essentially on hunting is the use of small terrier dogs to subjective assessments. In fact, a clear flush foxes fr om dens. Animals thus definition of humaneness is dif ficult. The
Bureau of Resource Sciences 49 authors have used the definition used in The use of small terriers as den dogs and Section 3.3 of the Australian Code of Practice larger lurcher dogs for coursing foxes is, for the Care and Use of Animals for Scientific likewise, more of a sport rather than a Purposes — ‘Pain and distress cannot be control tool. In the case of den dogs, the evaluated easily in animals, and therefore terriers as well as the foxes often r eceive investigators must assume that animals severe bite wounds. Fighting between fox experience pain in a manner similar to and terrier can often be pr olonged, and not humans’. all foxes bolt immediately fr om the den and into the waiting guns. Similarly the use of Generally speaking, the humaneness of larger dogs for coursing foxes is question - techniques associated with the management able on animal welfar e grounds. Death of of introduced pest species in Australia has the downed fox can often take several received little attention, with most emphasis minutes, and again, the dogs themselves being placed upon the methods used to cull can receive serious bite wounds. native species such as kangar oos and wallabies. The Sub-committee on Animal Welfare of the Standing Committee on 5.3.3 Sport and commercial Agriculture and Resource Management has shooting produced Codes of Practice for some feral The humaneness of shooting as a contr ol animals but not for pr edators (Sub-committee technique for foxes depends almost entir ely on Animal Welfare 1991). Sometimes in the on the skill and judgement of the shooter . case of the intr oduced predators, there is a High-powered rifles of calibr es from .17 up tendency to justify r elatively inhumane control to .243 ar e commonly used. Generally, techniques on the basis that the pr edators shooting with high-power ed rifles is a themselves inflict pain and suf fering on their humane technique for fox destruction. These prey. This argument is commonly, but in the rifles are generally fitted with power ful author’s opinion, wrongly used by some telescopic sights and ar e used for a stationary graziers to justify the setting of steel-jawed target only. Under these conditions, rapid traps for wild dog contr ol. death from head shots or chest shots is Both the RSPCA Australia and ANZF AS are usual. In those few cases wher e the animals strongly opposed to the hunting of animals are wounded rather than killed outright, the for sport. In the case of vertebrate pests like massive wounds caused by these high- the fox, they r ecognise the need for velocity projectiles usually result in death management measures but oppose the use within a few minutes. of non-specific baiting or the use of toxins which may cause suf fering (RSPCA 1985). ‘Skilled shooting with a high- powered rifle is generally a humane technique for fox 5.3.2 Riding with hounds and destruction.’ other forms of dog hunting The less powerful .22 calibre, rim-fire Since the use of dogs (with or without rifles should not be used for fox contr ol hounds) cannot be r egarded as a method because of the gr eater risk of non-lethal of broadacre fox contr ol, it requires little wounding. comment in these guidelines. A detailed The humaneness of shooting foxes with defence of fox hunting has been pr epared shotguns rather than rifles is mor e difficult by the Hunt Clubs Association of V ictoria to judge. Here, the weapons ar e most (HCAV 1988). commonly used upon a running tar get, and ‘Hunting foxes with dogs is the opportunity for non-lethal wounding is more of a sport than a control much greater. Factors that af fect the method.’ humaneness of the technique include the size of shot used and the gauge of the per day over five days pr oduced ulceration shotgun, distance over which shot travels, and permanent damage to the r espiratory skill of the operator , and presence or system (Buckley et al. 1984). T oxicity of absence of thick cover . In general ter ms, chloropicrin is primarily influenced by the only 12-gauge weapons utilising heavy shot effects on the small and medium br onchi (No.2 or BB size) should be used at distances of the lung, with death r esulting from of up to 35 metr es — sufficiently close to respiratory failure (Clayton and Clayton allow deep penetration of the shot into the 1981). The speed at which this will occur critical lethal ar eas (brain, chest cavity). depends upon the concentration of the gas and the exposur e time. 5.3.4 Den fumigation ‘Chloropicrin causes extended suffering and is not a humane Although not widely used, the intr oduction control agent.’ of lethal gas into fox dens is sometimes used as a contr ol technique. Most Although no work has been published commonly, the technique is used to destr oy on the ef ficacy of chloropicrin as a fox den young pups in br eeding dens. In Australia fumigant, some parallels might be expected only two fumigants ar e used, chlor opicrin with the use of this chemical in rabbit (trichloronitromethane) or phosphine gas warrens. Oliver and Blackshaw (1979) generated from aluminium phosphide, observed that chloropicrin was unevenly although carbon monoxide cartridges ar e distributed in a rabbit warr en when it was being considered for use as a mor e humane introduced without a power fumigator , at fumigant for den fumigation in V ictoria (C. particular points in the warr en. The gas, 5 Marks, DCNR, V ictoria, pers. comm. 1994). being heavier than air , will sink and collect at low spots in the warr en. Concentrations in these ar eas have been shown to build up Chloropicrin to levels of 5 ppm in a few hours, causing This is a non-flammable and colourless liquid the rabbits to move to ar eas in the warr en which vaporises slowly at r oom temperature containing higher and mor e immediately (sea level) (Sexton 1983). It is a str ong sensory lethal concentrations of the gas. irritant which causes pr ofuse watering of the Gleeson and Maguire (1957) suggested eyes, nasal passages and intense irritation of that chloropicrin has a delayed ef fect on the respiratory tract (Chapman and Johnson rabbits which have been exposed to sub- 1925; TeSlaa et al. 1986). Chlor opicrin was lethal but acute doses. This was typically widely used during the First W orld War as a observed in rabbits which escaped fr om chemical warfare agent (T imm 1983). fumigated warrens. These were sometimes Measurement of sensory irritation has found to have died, appar ently from the been attempted in mice ( Mus domesticus) by effects of the gas, some weeks after initial measuring the decr ease in r espiration rate exposure. Similar r esults are likely in foxes. upon exposure to a sensory irritant (Alarie In summary, chloropicrin is not a humane 1981). A commonly used measur ement is the agent for fox contr ol. The symptoms seen concentration of an irritant which pr oduces in live animals of other species and the a 50% decr ease in an animal’s r espiration pathological changes seen in autopsied rate (RD ) and this has been suggested as 50 animals suggest that some suf fering occurs the level of irritation which may r esult in over periods of several hours or , in the case respiratory injury following r epeated or of animals escaping fr om dens, possibly extensive exposure (Kane et al. 1979). days. Power fumigators, which quickly for ce
The RD 50 for mice when exposed to the gas through all parts of the den, might chloropicrin was found to be 7.98 ppm. decrease the time to death, and ther efore Chronic exposure at this level for six hours the duration of suf fering.
Bureau of Resource Sciences 51 Phosphine (Hydrogen phosphide) upon gas concentrations in the dens and, under moist conditions with ample tablets This is a colourless gas, about 20% heavier used, the time to death may be short. than air, which is pr oduced by the action of water on aluminium or magnesium phosphide. Because hydrogen phosphide is 5.3.5 Trapping — steel-jawed and a highly flammable gas it is pr epared as a solid snare tablet with ammonium carbamate which will, Steel-jawed trapping is now used upon generation of the phosphine, pr oduce infrequently for fox contr ol in Australia. Very carbon dioxide and ammonia and thus reduce often, where foxes are caught in steel-jawed the risk of gaseous combustion of the traps, they ar e set for other species, phosphine (Sexton 1983). especially wild dogs and rabbits. The In humans, the gas does not appear to method is clearly inhumane and it is of little cause sensory irritation and is characterised value as a contr ol technique, being time by a slight garlic-like odour . It is a systemic consuming and relatively non-specific. It is poison which depresses the central nervous desirable that steel-jawed traps for fox system and respiratory function (Sexton 1983). control be either banned or r estricted in Inhibition of vital cell enzymes is pr obably those states and territories wher e such caused by the action of phosphine upon bone trapping is still allowed. marrow and organ tissues (Klimmer 1969). Although there is a diverse range of In a concentration of 2000 ppm, the gas mechanical trapping devices used to r eplace is rapidly lethal to humans in less than one the standard leg-hold, steel-jawed trap, minute (Sexton 1983). At 400 ppm it is lethal none of these has been specifically designed to rabbits in 30 minutes (Jokote 1904, quoted for foxes. As an example, six designs of in Oliver and Blackshaw 1979). Unlike spring traps have been appr oved by the chloropicrin, chronic exposure at low levels Ministry of Agricultur e, Fisheries and Food (1–2.5 ppm for over thr ee weeks) gives no in the United Kingdom for use on specified evidence of subacute or chr onic poisoning mammals but none of these ar e suitable (Klimmer 1969). for the taking of foxes (Bateman 1982). A soft catch trap (V ictor Oneida, USA) has Oliver and Blackshaw (1979) found that been extensively investigated, used and rabbits could remain immobile during lethal recommended in the USA, wher e it is exposures, indicating that the chemical is not regarded as both ef fective and humane. a sensory irritant to them. The actual pain and suffering caused in rabbits is not known, ‘Steel-jawed traps are but in humans the symptoms often include inhumane and are not effective nausea, abdominal pain, headache and for fox control.’ convulsions with ensuing coma (World Health The soft catch trap has been used Organisation, undated). extensively in New South W ales as part of a Oliver and Blackshaw (1979) measur ed major research program on fox ecology and phosphine gas concentrations in rabbit the effects of imposed sterility (McIlr oy et al. warrens following the administration of 1994). In one continuous period of seven aluminium phosphide tablets. Their r esults months, a total of appr oximately 14000 trap suggest that the time taken to achieve nights produced a trapping success of one maximum gas concentration in the warr en fox per 150 trap nights (Kay et al. 1995). Soft can be many hours and that it is lar gely catch traps have also been used with some governed by the availability of moistur e. success to catch dingoes in Queensland. In summary, it is concluded that phosphine In Victoria, a leg-hold snar e trap initially is more humane than chlor opicrin. Again, designed to r eplace the earlier gin trap for the length of suf fering or discomfort depends wild dog control, is ef fective for capture of
52 Managing Vertebrate Pests: Foxes foxes. The device uses a snar e thrower which blooded ones, herbivor es more tolerant tightens a thick but pliable wir e noose around than carnivores, and bir ds less affected than the animal’s leg. While this device causes less mammals. The LD 50 for mammals varies bone and tissue damage than the steel-jawed between 0.1 milligrams per kilogram and trap, some str ess is involved and fr equent 10milligrams per kilogram, with foxes being inspection of snar e lines is r equired to prevent amongst the most susceptible. suffering in captured animals. The trap is ‘1080 is relatively target- regarded by the RSPCA, V ictoria as a mor e specific with foxes being highly humane alternative to the steel-jawed trap (P . susceptible to the poison.’ Barber, RSPCA, Victoria, pers. comm. 1992) and is per haps the only technique curr ently There is no detailed study of 1080 available for the selective r emoval of foxes poisoning of foxes, but general observations in urban ar eas. However, setting of these suggest that the symptoms exhibited ar e snares is time consuming and a r elatively similar to those seen in dogs (L. Staples, inefficient method for lar ge-scale control. It Applied Biotechnologies, Victoria, pers. is recommended for use only in localised, comm. 1992). In this species, Chenowith and semi-urban and urban situations wher e other Gilman (1946) describe a latent period of conventional means of contr ol, such as one to two hours during which the animal shooting and poisoning, cannot be used. Their is apparently normal. The onset of central humane use depends on fr equent inspection nervous system stimulation is shown by and clearance, and until standar ds for this ar e sudden appearance of hyper -excitability, the established and enforced, they ar e likely to animal running about and vocalising be unacceptable on animal welfar e grounds. vigorously. Within a few minutes, hyper - 5 excitability gives way to convulsions. Barking 5.3.6 Poisoning and panting persist during the convulsive period which may last for up to two hours and end in r espiratory failure. It is significant Sodium mono-fluoroacetate (1080) that anaesthetised animals still show evidence of extr eme central nervous system Sodium mono-fluoroacetate (1080) inhibits stimulation so that the behaviour of the citrate and succinate metabolism in the animal does not necessarily indicate extr eme tricarboxylic acid cycle by the for mation of pain or suf fering. On this basis, it is dif ficult fluorocitrate. The inhibition by fluor ocitrate to draw any conclusions r egarding the is thought to be primarily r esponsible for degree of suffering experienced by foxes the toxicity of 1080 (Atzert 1971). However , poisoned with 1080. Kun (1982) has conducted experiments which suggest that 1080 has other modes of ANZFAS is opposed to the use of 1080, action in the mitochondria. particularly for car nivores and omnivores, preferring that cyanide be used if r esearch Irrespective of the exact mode of action, finds it to be suitable. However , there is a the end r esult is a loss of ener gy, an strong view that 1080 is the most suitable accumulation of fluorocitrate in body cells poison presently available for widespr ead and a disturbance of central nervous system fox management. It is r elatively target- activity and heart function. Death r esults specific with foxes being highly susceptible from progressive depression of the central to the poison. It is especially useful in nervous system, ending with either cardiac Western Australia and other r egions where failure or convulsive r espiratory arrest as native fauna ar e relatively tolerant to it due the terminal event. to the natural occurr ence of 1080 in the The toxicity of 1080 varies markedly in environment. Studies have also shown that different animal classes and even between it rapidly degrades in water and soil. It also and within genera. Generally, cold-blooded shows no significant, long-ter m accu- vertebrates are more tolerant than war m- mulation in body tissues (Eason 1992).
Bureau of Resource Sciences 53 Strychnine advantage of pr oducing rapid death so that fox carcasses can be r etrieved for inspection. Strychnine is an indole alkaloid derived fr om Either potassium or sodium cyanide can be the seeds of the South-East Asian plant used and the chemical is nor mally encap- Strychnos nux vomica. The LD for 50 sulated in wax to pr event premature decom- strychnine in tested species varies fr om 0.5–3 position in baits (Section 7.5.2). milligrams per kilogram, with members of the Canidae family being among the mor e Because of its rapid action cyanide can susceptible species. Strychnine acts upon the be considered as a humane poison. Its use central nervous system and essentially for routine fox baiting r equires further inves - prevents normal functioning of muscle tissue. tigation, particularly in the methods of pr e- The earliest signs of poisoning ar e sentation and the likely impact on non-tar get nervousness, tenseness and pr ogressively fauna. Because cyanide salts decompose developing stiffness. Violent tetanic spasms rapidly in the pr esence of moisture to may occur spontaneously or be initiated by produce hydrogen cyanide, ther e are various stimuli such as touch, sound or problems of user safety which will r equire sudden bright light. The animal finds it careful investigation. impossible to stand, and falls rigidly to its side with legs stiff and outstr etched, neck and back 5.4 Implications of fox arched, ears erect and the lips pulled back harvesting for damage from the teeth. Initially the spasms ar e inter- control mittent, but they soon become mor e frequent. Spasms become continuous and death r esults Despite a considerable harvest rate in some from spasms of the diaphragm and asphyxia, years, there is no evidence that this rate of usually within an hour of the start of clinical removal had a significant impact upon the signs (Seawright 1989). In July 1991, a level of damage caused by foxes. This Working Group of the National Consultative contrasts with the view of many landholders Committee on Animal Welfare recommended and hunters that since the decline in fox pelt that the sale and use of strychnine be banned prices, the density of foxes has risen sharply in Australia (Department of Primary Industries as has the damage they cause. The and Energy 1992). perception of incr eased risk of fox damage since the decline in pelt prices is supported Cyanide by the figur es for the amount of 1080 poison used for fox contr ol in some ar eas. As an Cyanide inhibits oxidative enzyme systems example, Figure 12 shows the dramatic and causes death fr om anoxia. Acute increase in use of fox baits in New South cyanide intoxication is characterised by Wales during the second half of the last rapid, deep breathing; irregular, weak pulse; decade (J. Thompson, Department of Lands, salivation; muscular twitching and spasms; Queensland, pers. comm. 1994). However , staggering gait; coma; and death (Seawright this might also r eflect, in part, an incr ease 1989). The cyanides ar e particularly rapid in livestock commodity prices, an incr ease in their action and death usually occurs fr om in the numbers of livestock vulnerable to a few minutes to an hour after the onset of attack, and changes to r egulations governing clinical signs. The clinical course will occupy the use of fox baits (Thompson et al. 1991). only a few minutes in the most acute cases The recent concerns about fox pr edation (Jubb et al. 1985). Even with subacute doses, on wildlife (Section 3.1) may also have the course of intoxication rar ely exceeds 45 contributed. minutes and most animals that live for two hours after the onset of signs will r ecover. There was no decline in the high take of foxes in the mid-1980s as might have been Cyanide has been used experimentally expected if the harvest was having a in Australia for fox contr ol and has the significant impact on fox density (T able 5).
54 Managing Vertebrate Pests: Foxes 2500 400
350
2000 300
250 1500
200
1000 150 Grams of 1080
100 500 Approximate number of baits ('000) 50
0 0 1980 81 82 83 84 85 86 87 88 89 90 91 92 93 Year
Figure 12: The quantity of 1080 and the number of baits used for fox contr ol in New South W ales 5 between 1980 and 1993 (updated fr om Thompson et al. 1991).
However, it is not clear whether the harvesting during this time r epresented a constant catch-effort each year or whether the areas of land hunted for foxes varied from year to year. At best, commer cial harvesting provides only sporadic r elief from fox damage since the level of hunting activity r eflects the highly variable return from pelt sales.
Bureau of Resource Sciences 55 6. Past and current foxes were extensively hunted for their pelts, management but as discussed in Section 3.3, evidence suggests that this was mer ely a harvest and did little to r educe overall fox density. Summary However in its defence, many landholders believe that ther e has been an incr ease in Historically, management of fox damage in fox damage associated with the decline of Australia has relied on the payment of the commercial fox take. Ther e is no quan - bounties, coupled with a range of control tifiable assessment of the extent of damage. techniques including shooting, poisoning and trapping. The fox is widely regarded as an agricultural pest although less 6.1.1 Bounty systems emphasis is placed on its management The payment of a bounty or bonus upon compared with other pests such as the rabbit presenting proof of the destruction of a pest and feral pig. In most states and territories, animal has been fr equently used against legislative provisions require the control of foxes (Rolls 1969; Lloyd 1980; Whitehouse foxes by landholders; these are rarely if ever 1977). Bounties were first offered in 1893, enforced. some 20 years after foxes wer e first Although there is a growing awareness introduced to Australia (Rolls 1969). In by conservation authorities of the environ- Western Australia, bounties wer e paid mental impact of foxes, without the active during 1928–56 (Gooding 1955). Figur e 13 participation of the agricultural community, presents the data fr om the scheme as a plot effective fox management over large areas of the number of fox scalps submitted for will not be possible. At present, most fox payment against time (years). Fr om the control programs are either initiated to upward trend in the number of scalps it can protect enterprises at critical times of the be implied that the bounty scheme had little year such as at lambing, or to enhance impact on fox numbers. Indeed, conven - survival of native species through reduced tional bounty systems have been shown to fox predation rates. Government agencies be an inef fective form of pr edator control. mostly recommend the use of poisons The reasons for this ar e numerous (Smith (strychnine or 1080) to reduce fox 1990) and include fraudulent practices, populations with other options including failure to provide long-term relief from pest shooting, trapping, fumigation or impact, high costs, and selective r emoval of adjustments to farming practices. surplus animals. Often bounty hunters tar get Coordinated management programs the area where pests are in gr eatest density involving several properties, and where and most easily caught. This is usually not applicable a range of land uses, is the area where control is most needed uncommon despite receiving a higher profile (Whitehouse 1977). in recent times. No systematic evaluation of these programs or of individual control ‘Bounties have been ineffective operations has been undertaken except in for controlling foxes.’ Western Australia. Fairley (1968 quoted in Whitehouse 1977) comprehensively reviewed bounties as a 6.1 History means for managing foxes in Norther n Ireland. He concluded that bounties wer e Historically, a range of management ineffective. Many of the foxes killed by techniques has been used to try and manage people would have died of natural causes. fox damage. These include hunting; Animals taken under bounty schemes ar e shooting; poisoning with strychnine, cyanide usually the young inexperienced animals and 1080; and fox drives. These techniques which are yet to br eed. For example, half are outlined in Chapter 7. During the 1980s, the dingoes caught ar e less than one year
56 Managing Vertebrate Pests: Foxes 50 000
45 000
40 000
35 000
30 000
25 000
20 000 Bounty payments ($)
15 000
10 000
5 000
0 1928 1931 1934 1937 1940 1943 1946 1949 1952 1955 Year 6 Figure 13: Bounty payments in Western Australia. The upwar d trend in payments demonstrates that bounties are not an ef fective method of fox contr ol. If the system wer e effective a decline in payments would be evident (modified fr om Gooding 1955). old and 78% less than two years old prerequisite of an enfor ceable and (Whitehouse 1977). Just because lar ge widespread management policy. Ther e is a numbers of pests ar e killed does not mean growing awareness by conservation that the pest population declines. authorities of the envir onmental impact of foxes, and Western Australia in particular has 6.2 Legislation and made a significant investment in fox contr ol to protect threatened mammals in several key coordination of areas. Other states ar e investigating similar management programs action. For example, South Australia is Although the fox is r egarded as a pest species studying the ef fectiveness of fox management in all states and territories, ther e is less to protect yellow-footed rock-wallabies in the emphasis placed on its management North Flinders Ranges. compared to some other vertebrate pests such The value of fox pelts until r ecent times as the rabbit and feral pig. This may in part was also suf ficiently high that commer cial be due to the per ception that foxes have little harvesting was seen as a cost-ef fective impact on agricultural pr oduction; a usual management strategy which in many ar eas
Bureau of Resource Sciences 57 absolved the largest group of af fected 6.2.1 Commonwealth landholders, the lamb pr oducers, from the Government (Australian need to undertake their own contr ol. Nature Conservation Although there are legislative provisions in Agency) most states and territories to r equire the management of foxes by landholders, these The Commonwealth Gover nment is involved are rarely if ever enfor ced. Despite this, in the management of feral animals dir ectly government agencies actively encourage fox through its responsibilities as a manager of management through advisory, training and Commonwealth lands, and indir ectly through research services. In practice, fox its responsibilities under the Endangered management is mostly r eactionary either to Species Protection Act 1992. Under this Act, protect enterprises at critical times of the year administered by the Australian Natur e such as lambing or kidding, or to enhance Conservation Agency (ANCA), foxes have the survival of native species thr ough reduced been listed as a key thr eatening process. predation rates. At the time of writing, the Accordingly, there is a r esponsibility to only systematic evaluation of the ef fective- prepare a Threat Abatement Plan for the ness of fox management has been in W estern impact of foxes on endanger ed or vulnerable Australia. species, and to ensur e its implementation within areas of Commonwealth r esponsi- ‘Fox control is the bility. responsibility of the landholder — whether private or 6.2.2 Northern Territory government.’ (Conservation Commission of the Northern Territory) The following is a summary of the pr esent legislative status and management policy The fox is classed as a pest under the for the fox thr oughout Australia. This Territory Parks and Wildlife Conservation includes prescribed methods of contr ol Act 1988. Unless a pest contr ol area is which in most cases involves the use of declared for the fox, ther e is no obligation poisons. Because of their toxicity and on a landholder to take action. At pr esent, potential for misuse both to the detriment foxes are only managed in ar eas where of humans and non-tar get fauna, the use of endangered species r elease programs are poisons is normally regulated under state being conducted. In most of these cases, and territory legislation. In all states and conventional 1080 baiting is used (Section territories, landholders and gover nment 7.5.2). There is virtually no dir ect landholder agencies also have the option of using other involvement in fox contr ol although some management techniques such as shooting, foxes are poisoned as a r esult of dingo trapping, exclusion fencing, fumigation, or baiting operations. adjustments to farming practices. While most state authorities issue advisory notes on 6.2.3 Western Australia these techniques, their use is gover ned by (Agriculture Protection other less specific legislation such as fir earm Board) or animal welfare acts. The fox is a declar ed animal under the Agriculture and Related Resources ‘Because of their toxicity and Protection Act 1976. They can only be potential for misuse, the use of imported or kept under high-security poisons is regulated by conditions, and their numbers in the wild legislation.’ are required to be contr olled. The Agriculture Protection Board (APB) pr ovides advice to landholders for fox contr ol in response to requests and will help and supplied by the APB. Results fr om coordinate district campaigns and supply research have r ecently led to the pr oduction baits. Despite the fox being a declar ed of operational guidelines for fox contr ol. animal under legislation, a management The guidelines detail r ecommended policy is not actively enfor ced. procedures for identifying the need for fox control and planning, pr eparation and Baits made from beef crackle and implementation of 1080 baiting pr ograms. containing either 1080 or strychnine may In 1990–91, 56 000 baits wer e supplied for be purchased from the APB by landholders this purpose. From very crude estimates, for use in fox contr ol. Alternatively, the cost to APB of field involvement with manufactured dried meat baits containing foxes in 1991–92 was appr oximately 1080 can be pur chased with the authority $250000 (M. Sexton, APB, WA, pers. comm. of the APB, or landholders can make their 1992). own baits with strychnine tablets or powder . For coordinated campaigns, APB District Officers will inject fr esh meat baits with 6.2.4 Australian Capital Territory 1080 or insert a one-shot oat into a bait. (ACT Parks and Regulations specify pr ovisions relating to Conservation Service) the manufacture, handling, storage, Foxes are an unprotected animal under the transport and authority for the use of 1080. Nature Conservation Act 1980. Foxes can Landholders are required to notify the be taken or killed without a per mit. occupier of every adjacent pr operty of the However, a permit is required to keep, sell, intention to lay baits and the period and import or export foxes. Routine fox location of baiting prior to laying the baits. management is conducted within Recommendations govern the use of these Tidbinbilla Nature Reserve to pr otect captive baits on private land and include er ection populations of waterbirds and small of signs, distance r estrictions for the laying macropods. Fox control on agricultural land of baits (such as in r elation to urban ar eas is undertaken by the landholder , primarily or water storages), and tethering or burying by shooting although mor e recently Foxoff of baits. Other r ecommended management baits have been used. techniques are exclusion fencing, 6 modification to animal husbandry such as shed lambing of valuable stock, trapping 6.2.5 Queensland (Department of (steel-jaw and snar e), fumigation and den Lands, Land Protection destruction, and shooting. Branch) The APB encourages and assists gr oups The fox is a declar ed animal under the Rural of neighbouring landholders to participate Lands Protection Act 1985, and as such it in coordinated management campaigns. is the duty of owners and occupiers of land They also undertake a limited amount of to destroy it. However, the legislation is not contract poisoning on behalf of landholders. enforced for foxes. Department of Lands A more recent development has seen district field officers provide advice and for mal groups of landholders or ganising fox direction for the contr ol of foxes thr oughout shooting drives. The Western Australian Queensland. They also issue 1080 baits for Department of Conservation and Land fox control. Authorised contr ol officers may Management carries out fox contr ol use strychnine baits to contr ol foxes, but programs on selected ar eas of land under these baits cannot be issued to landholders. its management. To date this work has been The use of strychnine is discouraged in primarily for r esearch purposes, targeting favour of 1080. Meat baits ar e generally used. specific areas and fauna species known or Landholders can purchase strychnine fr om thought to be at risk fr om fox predation. pharmacists following the issue of a per mit The 1080 meat baits used ar e manufactured from the Health Department. Use of 1080
Bureau of Resource Sciences 59 baits is regulated on private lands and the accordance with established r egulations user must abide by conditions of use r elating including use of pr escribed baits, burying to notifying neighbours, distance r estric- the bait, distance r estrictions for the laying tions and erection of signs. of baits such as in r elation to urban ar eas or water storages, notification of It is illegal to intr oduce, keep or sell foxes neighbours, and erection of signs. Other except where permits are issued for scientific approved control techniques are trapping or educational purposes. The fox is (cage or tr eadle snare) and shooting. In the recognised as a thr eat to agricultur e and past, there was no coor dination of fox management programs operate thr oughout management on private lands. However , the state, particularly in coastal or sheep this is changing in conjunction with the producing areas. In national parks bor dering development of mass pr oduced, long shelf- the Queensland coast, foxes ar e believed to life 1080 baits. DCNR is about to implement have a significant impact on coastal nesting a series of coor dinated control campaigns turtles, and annual contr ol campaigns ar e using these baits. These will be supported conducted. Some fox contr ol may be carried by advice on how best to undertake fox out as part of wild dog contr ol, particularly management. Main emphasis is placed on in the southern part of the state. the integration of contr ol techniques into a Foxes are recognised as an incr easing preventative management pr ogram before problem in urban ar eas and a significant the fox becomes a pr oblem. For the year effort has been made to publicise the 1991–92, DCNR allocated appr oximately detrimental impact of the species on $450 000 for fox contr ol on public land (R. domestic and native animals. In addition Waters, DCNR, Victoria, pers. comm. 1992). to poisoning, trapping (using cage traps in Recently DCNR initiated ‘Foxlotto’ which urban areas) and shooting ar e also is open to far mers, professional shooters recommended as control techniques. and shooting clubs. This scheme is a Coordinated management campaigns ar e variation of the bounty system. Upon not common and fox contr ol is usually in presenting a fox scalp or entir e pelt, shooters response to individual r equests for receive a lottery ticket and enter a draw for assistance. a range of monthly and annual prizes. In 1992, over 15 000 scalps wer e presented 6.2.6 Victoria (Department of under this scheme, a quantity which appears Conservation and Natural relatively small compared to the 35 000 pelts Resources) taken from Victoria in 1986 (30% of the 110000 total for Australia). Nevertheless, Foxes are declared vermin under the this scheme has potential to develop Catchment and Land Protection Act 1994, awareness about fox damage and what can which establishes responsibility for their be done to alleviate it. control with owners and occupiers of land. Despite this, no notice has ever been issued On public land, coordinated management compelling a landholder to contr ol foxes. campaigns are carried out to pr otect a variety Under the Act it is also an of fence for any of indigenous species fr om fox predation. person or institution to keep live foxes in These include little ter ns (Bairnsdale), Victoria without a per mit. penguins (Phillip Island and Port Campbell), eastern barred bandicoots (Hamilton and Where foxes ar e identified as being a Gellibrand Hill) and lyr ebirds (Sherbrooke). problem, the Department of Conservation Fox predation on native wildlife is listed as and Natural Resources (DCNR) will issue a potentially threatening process under the 1080 meat baits, pr eferably the manufac- provisions of the Flora and Fauna tured Foxoff bait or alter natively cooked Guarantee Act 1988. This requires the liver or similar. These must be used in development of an Action Plan which sets
60 Managing Vertebrate Pests: Foxes out effective management techniques to Table 6: Number of 35 milligram strychnine prevent or overcome damage due to this baits prepared for fox contr ol in South Australia threatening process. in 1984–85 to 1990–91.
6.2.7 South Australia (Animal and Year Number of Baits Plant Control Commission) (35 mg/bait) The fox is a pr oclaimed animal under class 1984–85 23 771 5a of the Animal and Plant Control Act 1985–86 91 629 1986. The Act pr ohibits the keeping, 1986–87 79 400 movement, sale and r elease of foxes. Other 1987–88 185 829 provisions require a landholder to contr ol 1988–89 88 286 foxes, although this pr ovision is not pr esently 1989–90 90 486 enforced. 1990–91 43 857 The Animal and Plant Contr ol Commission (APCC) is r equired to develop, implement 6.2.8 New South Wales (NSW and advise on coor dinated programs for the Agriculture) control of proclaimed animals. The fox is recognised as a thr eat to both agricultur e The fox is not a declar ed noxious animal and native wildlife, but until r ecently was under the Rural Lands Protection Act 1989 given low priority in comparison to other having been deleted fr om the list in 1977. pest animals. This was in r ecognition of the dif ficulty in enforcing a legislative r equirement to control Prior to 1993, strychnine was the only foxes. Under proposed legislation (Non- poison available for baiting foxes in South Indigenous Animals Act), the fox will be Australia but has since been phased out in placed in category 5 which includes all favour of 1080. The number of appr ovals animals which are recognised as widespread given to landholders for the pur chase of pests. There is no r estriction on the keeping, strychnine to contr ol foxes and the associated transport or sale of foxes in New South number of baits pr epared by them between Wales. 6 1985 and 1991 ar e presented in Table 6. The estimated yearly expenditur e on fox Despite this, the fox is consider ed a control with strychnine by landholders and significant agricultural and envir onmental government agencies in 1992 was $250 000 pest. In recognition of this, NSW Agricultur e (M. Williams, APCC, SA, pers. comm. 1992). and Rural Lands Pr otection Boards actively participate in services aimed at assisting The amount of fox baiting carried out in landholders and other gover nment agencies South Australia has incr eased dramatically to control fox populations. Coor dinated fox since the intr oduction of 1080. This is control programs are encouraged, undoubtedly due in part to per ceptions that principally to better r egulate the use of toxic foxes may be having a mor e important baits and to r educe the threat to non-target effect on domestic stock and wildlife than animals. Because of this concer n, there have previously recognised, but is also a r esult been recent amendments to the National of a gr eater emphasis on a gr oup approach Parks and Wildlife Act 1974, which requires to fox baiting. Gr oup participation through a Fauna Impact Statement to r esolve conflicts existing networks such as Landcar e has between pest animal contr ol programs and encouraged many landholders to take part the potential impact of these on endanger ed in large baiting campaigns. Bait materials fauna (Korn et al. 1992). commonly used include injected meat, liver , fish, fowl heads and eggs, and Foxof f man- Rural Lands Protection Boards issue 1080 ufactured baits. baits consisting of either manufactur ed baits,
Bureau of Resource Sciences 61 fowl heads, and 100 gram pieces of fr esh meat or offal for fox contr ol. Recently ther e has been a consistent incr ease in the amount of 1080 used for fox contr ol in New South Wales, rising from 57 grams in 1980 to 2000 grams in 1993. This is equivalent to an increase in the number of baits fr om approx- imately 2050 to 330 000 (Figur e 12). Use of 1080 baits is r egulated and users are required to abide by certain r equire- ments including distance r estrictions in relation to human habitation, notification to the public about use of poison, and er ection of signs. No other poison is r egistered for fox control although there is believed to be significant illegal use of various lethal chemicals such as phosdrin. The only other recommended control techniques ar e exclusion fencing, flock management and shooting.
6.2.9 Tasmania (Department of Environment and Land Management and Department of Primary Industry and Fisheries) The fox is a pr escribed creature under the National Parks and Wildlife Act 1970 and vermin under the Vermin Destruction Act 1950. Under these Acts it is an of fence to bring a fox into the state, keep one in captivity or allow one to go at lar ge in the state. Also the Vermin Destruction Act requires land occupiers to suppr ess and destroy vermin. All reported sightings ar e investigated by the Parks and W ildlife Service and/or Department of Primary Industry and Fisheries, initially by interview, and then if justified by field surveys. The last fox known to have been killed in the wild was a young vixen in 1973 which was of unknown origin.
62 Managing Vertebrate Pests: Foxes 7. Techniques to suitable lethal technique. It can be made measure and control target-specific to foxes through choice of bait, strict control of 1080 content and bait fox impact and placement, for example by burying it. In abundance Western Australia, dried 1080 meat baits have been shown to be very effective for fox control Summary and are likely to be in other parts of Australia. However before they are extensively used Damage and abundance — A large range elsewhere, the applicability, especially in of native fauna are susceptible to fox relation to non-target kills, needs to be assessed. predation. Fox gut analysis provides an Research to develop an effective biocontrol indication of species at potential risk, but agent to manage foxes offers some promise. not the extent of predation pressure. Survey However, it is breaking new ground and has techniques to identify the distribution and to address difficult scientific, technical and abundance of vulnerable species before and biological problems. Consequently, the after fox removal is the most reliable method research must be considered high-risk and for land managers to assess damage. It is long-term. important to be aware that factors other than fox predation may affect prey abundance. Techniques for monitoring prey 7.1 Introduction density include pitfall and small mammal traps, spotlight and animal track counts. ‘The aim of fox management should be to reduce to an The major agricultural damage due to acceptable level the foxes is lamb loss. However many other agricultural and environmental factors cause lamb loss including difficult damage foxes cause.’ birth, poor mothering, cold exposure and predation by other pests such as feral pigs. Techniques are described in this chapter for A guide is presented to help to distinguish assessing fox impact as well as for planning, between the various factors causing lamb implementing and then monitoring the loss. effectiveness of management pr ograms. Details are provided separately for The primary aim of fox management is environmental and agricultural situations to protect native fauna or increase lamb where differences in objectives and production. The success of fox management procedures exist. Many of the techniques should be guided by direct measure of these described in this chapter have been 7 parameters. Sometimes, such as for scientific developed and tested only in W estern research, fox density needs to be estimated. Australia where considerable ef forts have Techniques include breeding den counts in been placed on fox contr ol in recent years. early summer, scent stations, track and In some cases this will r esult in strategies spotlight counts. which are geographically specific, and this Maps, from simple hand-drawn charts, needs to be taken into account until similar to sophisticated geographic information work is conducted in other parts of systems, are useful for recording the Australia. Land managers should car efully distribution and relative density of foxes and assess the applicability of W estern Australian vulnerable prey in an area, and for techniques to other ar eas. planning control. The principal objective of fox Control techniques — Techniques include management, where the need for contr ol is trapping, shooting, poisoning, den fumigation, identified, is to r emove or r educe to an exclusion fencing and changed farming acceptable level the damage foxes cause to practices. Poisoning using 1080 is the most production and conservation values.
Bureau of Resource Sciences 63 7.2 Assessing impact fox and pr ey interactions or by indir ect surveys of fox food habits such as scat or stomach content analysis. These, however , 7.2.1 Introduction are not always an accurate indication of Effective fox management r equires the predation pressure on thr eatened species. extent of fox damage to be quantified either More important would be to monitor the as lost agricultural pr oduction, or for distribution and abundance of native species conservation, the degree to which the using established survey techniques suitable population of native animals is suppr essed. to Australian conditions. Cooperrider et al. For some pest species such as the feral pig, (1986) provides details of a wide range of where the relationship between pest density techniques. Other techniques include those and damage is known for some for ms of relating to soil plots and small mammal damage, indicators of abundance can be a trapping (Newsome and Catling 1979), bird useful correlate of impact. This corr elation counts (Braithwaite et al. 1989), and in is not known for foxes. In addition ther e is Environmental Impact Statements pr epared no simple, reliable technique for estimating by CSIRO Division of W ildlife and Ecology fox density for a range of habitat types and (for example Shodde et al. 1992), although prey density. Consequently, this makes the latter, while excellent infor mation, are changes in population parameters of the not readily available. potential prey species in r esponse to ‘Diet studies do not necessarily predator control the only r eliable method reflect the impact of foxes on for estimating the extent of fox damage. prey populations.’ ‘Accurate assessment of fox Survey techniques suited to dif ferent damage allows management faunal groups are as follows: strategies to be targeted more effectively.’ • Amphibians and reptiles – timed, random or set transect counts (species can be identified by sight or 7.2.2 Environmental impact call) assessment – terrestrial pitfall or aquatic cage traps In Section 3.1 it is concluded that foxes ar e • Mammals major pests of wildlife over much of Australia. – grid trapping with spring-set box traps However, the extent of this impact has not or pitfall traps (small mammals) been widely quantified. The few studies – wire cage traps (medium size mammals) which exist are from restricted geographic – track counts on raked plots (medium to regions and with only a few native species. large mammals) Unfortunately, it may take many years to – set transect surveys, either walked, or accurately quantify the extent of fox damage covered by vehicle or helicopter; using to wildlife in which time mor e species may spotlights or nightscopes at night (lar ge be driven towards extinction. In the absence mammals and arboreal mammals) of any clear evidence, the land manager must assume adverse impact wher e foxes are • Birds known to interact with populations of – mist nets significant or endangered native species, – set transect surveys (species identified including a range of small to medium-sized by sight or call) animals such as gr ound-nesting birds, – spotlight counts (nocturnal species) dasyurids, bandicoots, possums, smaller If native animal populations ar e declining wallabies and rodents (Appendix A). or restricted to mar ginal habitats, based on Initially, an indication of fox pr edation real or assumed prior infor mation, all factors can be identified by dir ect observation of which might be r esponsible need to be
64 Managing Vertebrate Pests: Foxes considered. Causes other than fox pr edation • cold exposure which becomes appar ent might include habitat fragmentation and when large numbers of lambs die coincident degradation, changes to fir e regime, with periods of adverse weather; competition with introduced species, disease • starvation/mismothering due to factors such or hunting. While this infor mation is being as failure of the ewe to bond with her lambs, gathered, an indication of the extent of fox accidental separations after bonding, udder impact may be gained thr ough changes in the defects and competition with litter mates. distribution and abundance of pr ey species These can only be assessed by dir ect following the r emoval of foxes. Pr eliminary observation; information may be obtained by pilot contr ol studies, with suitable contr ols, which monitor • extremely high or low birth weights which the responses of selected pr ey species. The predispose lambs to death fr om birth injury, results of such pilot studies would pr ovide cold exposure or starvation; and an indication as to whether fox contr ol is a • predation based on cir cumstantial evidence valid management strategy for the thr eatened such as unexplained low lamb marking, species. presence of predators and car casses showing mutilation. 7.2.3 Agricultural impact assessment A decision tree can be used to deter mine the causes of lamb deaths (Figur e 14a). If predation is suspected of being the major Introduction factor, and various potential pr edators are The major agricultural impact due to foxes present, the impact of each species needs is predation of lambs (Section 3.2.1). to be deter mined. The following signs ar e Because the fox hunts mostly at night, dir ect useful (Figure 14b; Rowley 1970; Anon observations of them killing lambs ar e rare. 1991): There are also a number of other pr edators • Was the lamb alive when attacked? Attacks which can be involved, including dingoes, on live animals r esult in bleeding at the wild dogs and feral pigs. Befor e wound site, with subsequent clotting for ming commencing a fox management pr ogram, dark haemorrhagic areas. Dead animals do it is necessary to establish that the fox is not bleed. A lamb bor n alive shows a distinct implicated and is causing significant blood clot at the exposed end of the umbilical economic losses. artery and a lamb bor n dead shows no clot. ‘The major agricultural impact Whether the lamb had walked or not is 7 of foxes is predation on indicated by whether hoof cover is wor n on newborn lambs.’ the soles of the feet (Figur e 14b [5]); • If alive, was the lamb sick or healthy? Lamb losses attributable to predation Examination of the lungs will show a clear by foxes difference between successful br eathing, To determine the extent of fox pr edation light pink and healthy; compar ed to lungs on lambs, it is necessary in the first instance which have not been pr operly aerated being to determine the principal causes of lamb dark and liverish in colour (Figur e 14b [4]). loss. The following constraints on lamb Lambs are born with protective, soft survival can be identified (Alexander 1984): membranes covering the sole of the hooves (Figure 14b [5]). These ar e rapidly lost when • dystocia or difficult birth which is r elated they begin to walk. In nor mal lambs the fat to birth weight and pelvic size of the ewe. around the heart and kidneys is fir m, white Lambs lost to this cause generally show and lacking in obvious blood vessels. When evidence of haemorr hage in the central a lamb fails to feed these fat r eserves become nervous system; soft, gelatinous and dark plum r ed in colour.
Bureau of Resource Sciences 65 (a) Decision tree
Have adult Have lamb sheep been Probably not carcasses attacked or No No killed by been eaten severely predator. or mutilated? injured? [1]
Ye s
Has carcass Has attack Has lamb Probably been entirely No been No breathed? [4] No born dead. eaten except confined for skin and to orifices? [3] some bones? [2] Ye s
Probably Has lamb No born dead walked? [5] or very weak.
Ye s
Any signs Probably of No dead when bleeding? attacked. Ye s Ye s Ye s
Ye s
Have fat Probably reserves Ye s starved. been utilised? [6]
No
Probably Is milk No starved. present in intestine? [7]
Ye s
Probably Probably Probably Probably not foxes. feral birds viable when Dingoes or pigs. of prey. killed. Foxes dogs are or dogs likely indicated. cause. [8]
Figure 14: (a) Decision tree for deter mining the cause of lamb death (after Agricultur e Protection Board, Western Australia 1990); (b) Observable indicators which can be used to help deter mine the cause of lamb death.
66 Managing Vertebrate Pests: Foxes (b) Observable indicators
[1] Severe neck wounds on adult sheep [5] Foot of a still-born lamb with intact sole indicating dingo or wild dog attack. membrane (left) and foot from lamb that has Source: NSW Agriculture walked (right). Source: J. Plant, NSW Agriculture
[2] Extensive mutilation and consumption of [6] Stifle (knee) joint showing breakdown of lamb carcass indicating the possibility of feral body fat (i.e. lamb has starved). pig predation. Source: Queensland RLPB Source: J. Plant, NSW Agriculture
7
[3] Lamb with eye picked out by birds post– [7] Milk in small intestine of lamb that has mortem. Source: J. Plant, NSW Agriculture suckled (right); empty intestine of still-born or weak lamb (left). Source: J. Plant, NSW Agriculture
[4] Unexpanded, heavy, dark-red lung of a still- [8] Fine puncture marks in skin indicating born lamb. possible fox predation. Source: J. Plant, NSW Agriculture Source: J. Plant, NSW Agriculture
Bureau of Resource Sciences 67 Similarly, successful feeding is demonstrat - of most land managers, making it dif ficult to ed by milk in the stomach and gut (Figur e decide whether or not it is economically 14b [7]); and justified to undertake fox management. • What species of animal was responsible A rigorously designed experimental for the predation? Wounding by mammals assessment of the full impact of the fox on involves biting often with matching agricultural production is necessary. It should punctures on opposite sides of the limb or include the costs and benefits of fox contr ol trunk. The car cass is usually moved fr om (Section 10.2.1). the site of death. Feeding by bir ds of pr ey Land managers must make their own best is characteristically on the upper side only, assessment of lamb pr edation by foxes based at the site wher e the lamb died and usually on examination of car casses and considera- involves attacks to the eyes, mouth, navel, tion of all causes of lamb loss. Comparison nose and anus (Figure 14b [3]). Attacks of production figures with similar ar eas where by foxes (and dogs) ar e often characterised there is no known pr edation may also pr ovide by a large number of lambs killed or a guide, although the influence of other factors mutilated in the one night. When this such as weather and ram fertility also need occurs the majority of car casses are usually to be taken into account. left in the paddock. Depending on what part of the body is first attacked, typically As is the case for thr eatened native fauna the neck ar ea is crushed with evidence of (Section 7.2.2), it may be feasible to conduct canine puncture marks on the inside of the pilot studies to test the impact of foxes on lamb skin or the muzzle of the lamb is livestock by appr opriately designed regional mutilated or bitten of f. Puncture marks can experiments. Fox contr ol and non-treatment be used to dif ferentiate wild dog or dingo sites would be necessary, and the r esultant attacks from fox as the latter has a very lambing success would need to be measur ed. slender jaw (Figure 14b [8]). The distance separating the canine teeth on foxes (25–32 7.3 Measuring fox mm) is considerably less than in most dogs (Lloyd 1980). Although the haemorr hage abundance resulting from a broken neck will be obvious in post-mortem examination, the 7.3.1 Introduction lesions resulting from bites in other ar eas of the body may not show exter nally or Abundance can be measur ed in three ways: internally by ventral inspection. For con- as the number of animals in a population, firmation of fox or dog pr edation the as the number of animals per unit of ar ea carcass needs to be fully skinned. (absolute density), and as the density of one population relative to that of another (r elative density) (Caughley 1977). For an elusive Assessing the extent of fox predation animal such as the r ed fox, population size As indicated above, diagnosis of fox pr edation or absolute estimates of abundance ar e is possible by examination of car casses. In difficult to obtain and usually inaccurate. In some situations where foxes ar e active in most situations, estimates of r elative lambing paddocks few car casses can be found abundance will be suf ficient for an initial despite significant predation (Lugton 1987). census of the fox population and to then It is difficult to accurately deter mine the full evaluate the success or otherwise of extent of fox pr edation. Ultrasound foetal management programs. Numerous census counts to establish the maximum r eproduc- techniques are available, the most useful tive potential of the flock combined with an being discussed below. T echnique selection assessment of all causes of lamb loss including depends on the habitat and available disease and mismothering is necessary. This resources. Cyclical changes in fox densities would be beyond the r esources and expertise associated with prey abundance or disease
68 Managing Vertebrate Pests: Foxes can further complicate estimates of fox many inbuilt inaccuracies (Zimen 1980), par - density (Lindstrom 1980; Macdonald 1980). ticularly that hunting r ecords are as much In instances wher e foxes were previously dependent on hunting habits and intensity thought to be absent (for example T asmania, as on fox population density, and may under - Kangaroo Island, far north Australia) it may estimate the fox population by 50–75% (Steck be necessary to confir m sitings through and Wandeler 1980). identification of footprints, scats, hair , fox Scent stations or track counts use chemical vocalisations etc. (see T riggs 1984; Newton- attractants or baits placed r egularly at points Fisher et al. 1993; Brunner and Coman 1974; along established routes of travel (Roughton Morrison 1981 for guidance). and Sweeny 1982; Phillips 1982). The ‘Estimates of fox abundance presence of fox tracks in a one-metr e circle are difficult to obtain and of sifted dirt placed ar ound each scent station usually inaccurate.’ is considered as a visit. This pr ocess is repeated over three to five consecutive days 7.3.2 Breeding den counts to calculate an index for the activity of foxes. To the land manager wishing to gain some Breeding den counts is consider ed to be initial understanding of fox distribution and the only accurate method to deter mine fox abundance and the short-ter m effect of a density, provided the size of family gr oups management program, the most appr opriate and social organisation is known (T rewhella technique is spotlight counting. Spotlight et al. 1988). This technique is especially counts can be particularly useful in the case useful in urban ar eas where householders of open country (Newsome et al. 1989) can help identify the location of all br eeding where a large area is being consider ed for earths (Harris 1981; Page 1981), or in fox control. Foxes are counted at night fr om uniform rural habitats by systematic a vehicle with the aid of a spotlight. For searches (Insley 1977; Pelikan and V ackar consistency between counts and to gain 1978; Coman et al. 1991). Dens ar e most maximum access to foxes in the management prominent in early summer when cubs area, fixed length transects should be become active, trampling the surr ounding carefully planned before commencing the area and accumulating pr ey debris and survey. All foxes seen within a sear ch droppings around the entrance (Kolb 1982). distance either side of the vehicle, say 100 Aerial survey techniques can be metres, are counted. This distance will vary employed to identify br eeding earths in very according to sightability in dif ferent habitats. open habitats (Sargeant et al. 1975). The dis- A reliable index of the population size 7 advantages of this technique ar e that in most will require a minimum of thr ee counts on habitats dens ar e difficult to locate or may consecutive nights. In order to gain a be confused with rabbit burr ows. Dens ar e consistent level of pr ecision, and where occupied annually for a limited time, making resources permit, counts should be r epeated them useful only for measuring changes in until they give similar indices. A rule of the population fr om one year to the next. thumb when deter mining the number of counts is for the standar d error of the counts 7.3.3 Relative density estimates to be within 10% of the mean. Possible sources of variation between counts should Estimates of r elative population densities can be kept as low as possible. For example, be obtained by a variety of indir ect measures. conducted by the same person, fr om the These include the hunting indicator of same vehicle and height, travelling at the population density or HIPD (W andeler et al. same speed and close to the same time each 1974), used commonly in Eur ope to calculate night. Some caution should be attached to threshold densities for rabies transmission spotlight counts as they tend to be biased (Anderson et al. 1981). These estimates have towards including naive younger animals.
Bureau of Resource Sciences 69 7.3.4 Population manipulation they native wildlife or lambs. The pr ocess index of recording assessments is not necessarily an aid to interpr etation but rather a way of Absolute density can be derived fr om relative ensuring that all the r elevant information is density estimates measured before and after documented. It is also a way of ensuring a known number of animals ar e removed that information is recorded in a convenient from the population (Caughley 1977; form for transferring onto maps or com - Eberhardt 1982). This technique is useful in puterised databases. determining the ef fectiveness of a management program. The only limitations ‘The relationship between fox are: density and impact is largely unknown.’ • the number of foxes killed can be counted, for example, by spotlight shooting or cyanide baiting; 7.4.3 Mapping • the indices used befor e and after will not Maps can be of various types: simple hand- be affected by the r emoval technique. For drawn charts, topographic maps, land example spotlight counts of foxes after system or land unit maps, aerial spotlight shooting may be biased because photographs, or the sophistication of of changes in behaviour of surviving foxes; interactive computerised geographic information systems (GISs). The choice • the pre-removal index has a constant r ela- depends on r esources, scale of the tr eatment tionship to the initial population size as and the extent of the pr oblem. does the post-r emoval index; ‘Correlations between damage • the period over which animals ar e removed and fox habitat, will help is short; and determine where fox • the changes in indices and the number of management needs to be animals removed is not small. targeted.’ Assuming that little is known about the dis- 7.4 Use of fox impact and tribution and abundance of foxes in the ar ea, density measurements maps are important for deter mining and recording the relationships between variables associated with the distribution of pr ey species 7.4.1 Introduction and features which will need to be identified in planning a fox management pr ogram. As with any pest species, achievement of These will include tracks, trails, fence lines, management objectives is enhanced with lambing paddocks, r efuge habitats for thorough planning (Chapter 8). This is endangered species, property boundaries, facilitated by the r outine recording of natural boundaries, corridors, dens and fox impact assessments, mapping of r elevant refuges (Figure 15). Correlations between information from the designated ar ea, and damage and habitat, wher e they can be allocating action to r ealistic and prioritised identified, will deter mine where fox management units. management needs to be tar geted. A lambing paddock is an obvious example, however 7.4.2 Recording assessments conservation problems are less clear. The refuge habitat for an endanger ed species may Because direct survey of the fox population not necessarily be its pr eferred habitat, and is difficult, and the r elationship between fox the one which will need to be tar geted if density and the level of impact is unknown, the species is to thrive. In these situations assessment of impact is best deter mined by maps can be used to identify the distribution evaluating the status of pr ey populations be of both the r efuge and pr eferred habitats,
70 Managing Vertebrate Pests: Foxes with efforts to remove foxes concentrated all known fox br eeding dens within the in each. Because foxes often depend on Landcare area. This in tur n would allow for rabbits for food, mapping the distribution a coordinated program of fox den fumigation of warrens may also give some indication of during the br eeding season. Other possibili- where to concentrate contr ol effort. ties include the r ecording of all fox poisoning trails/sites during a coordinated baiting Several Landcare groups in Victoria and campaign. Such r ecords depicted on maps elsewhere are now involved in the pr oduction quickly indicate any gaps in the coverage of of customised maps of Landcar e districts and a baiting program. individual farms for a variety of land management issues including pest Computer-based mapping systems also management. In one example, the initial base include the facility for a database r elated to topographic maps (scale 1:25 000) have been the mapped ar eas. This then of fers the means supplied to Landcare groups in digitised for m. to keep highly accurate r ecords of control The groups share a single computer and inputs and outcomes as measur ed by software package which allows for overlays reductions in damage or fox numbers (for of information to be added to the maps. The example spotlight transect counts). On a original topographic map is then printed out broader scale, GISs can be used to deter mine in sections to corr espond with individual correlations which might show, for example, farms or cooperatives. Landholders then assist where foxes potentially have their gr eatest in verifying the maps and adding infor mation impact on endangered species. Wher e fox such as the location of particular weed impact correlates highly with fox population problems or main ar eas of rabbit activity. indices, changes over time in these indices Although foxes have not yet been included can be used to monitor the pr ogress of control in this inventory, it may be practical to map operations.
Lamb paddock Property A Property B Internal tracks D
Home paddocks D 7 Scrub - fox refuge habbit
Property C Property D
Rabbit infestation D
Fences
Boundary
D Fox dens
Figure 15: Example of a simple map of four hypothetical pr operties showing the key factors that landholders should r ecord and use to plan fox management.
Bureau of Resource Sciences 71 7.4.4 Allocating management • type and value of pr ey species. For native units species it is their conservation status and their representativeness in other ar eas; The information collated on maps can be used to identify practical management units. • severity of the damage; Boundaries in the management unit will be • presence of and damage due to other pests evident from natural or artificial barriers or and other threatening processes; apparent changes in the distribution of pr ey species. An important dif ficulty which must • feasibility of reducing damage in time to be considered is the mobility of foxes. This save the pr ey; can negate efforts to manage fox damage • size of the management unit; due to neighbouring foxes moving into vacated territories. This will influence the • availability of appr opriate management size of the management unit which is in techniques; turn influenced by the time-frame of the • availability of funds, time, labour and management program. For example, equipment both for immediate action and protecting a lambing paddock for one for future sustained control; month will be a much smaller operation than ensuring the long-ter m survival of an • the ability to coordinate management endangered species in a natur e reserve. effort; and While the distribution and abundance of • the ability to pr event reinvasion by foxes. foxes in the management ar ea may not be known, the size of management units based 7.5 Control techniques on known figures for density and home range for similar ar eas can be used as a guide (Chapter 2). 7.5.1 Introduction ‘Past fox management A variety of fox contr ol techniques ar e used programs have generally been in Australia. These include hunting by non-strategic and trapping and shooting, poisoning, den uncoordinated.’ destruction, exclusion by fencing, or changes In the past, fox management pr ograms, to farming practices. In the case of agricul- principally poisoning, have mainly been tural protection, the methods used ar e mostly carried out on small management units such determined by the biology of the livestock as an individual pr operty or natur e reserve, being protected rather than the biology of the with little coordination. As the damage fox. As such, a variety of contr ol techniques foxes cause to native fauna has become are employed on a r eactionary basis with little evident, governments have incr eased consideration for sustained r eduction of their inputs into planning and coordination of agricultural impact. This may be the r esult fox management. In many cases it may be of the lack of suf ficient incentive and of cost- necessary to coordinate management of effective techniques. foxes on surrounding agricultural land, say ‘Fox control techniques used in as a buffer zone. The extent to which this Australia include trapping, coordination takes place will also influence shooting, poisoning, den the size of management units. destruction, fencing and changes to farming practices.’ 7.4.5 Establishing priorities For wildlife conservation the issue is much clearer. Fox pr edation is a significant Priority for treatment of management units threatening process to some wildlife species will depend on a number of factors which is alleviated by the management of including:
72 Managing Vertebrate Pests: Foxes foxes. Apart from fencing and poisoned on the small blade of a pocket knife is generally baits, no other method has been tested and accepted as a lethal dose’ (New South Wales shown to be ef fective. Agriculture memo 961). Baits included whole carcasses (although this is not r ecommended 7.5.2 Poisoning by state agencies), of fal, cubes of meat or fat, chicken heads, day-old chicks, butter or dripping. The use of 1080 is much mor e General tightly regulated. Only gover nment or semi- Poisoning foxes using a variety of toxins and government agencies ar e allowed to handle bait types has long been consider ed to be the the poison and pr epare baits. most effective method of fox contr ol. ‘The use of 1080 baits for fox Strychnine was historically the r ecommended control has risen dramatically poison throughout Australia. Following the in recent years.’ introduction of 1080 for rabbit contr ol in the The number of 1080 baits distributed in 1950s, its ef fectiveness against canids was soon New South Wales for fox contr ol has risen realised and it became widely used for fox dramatically from approximately 2000 in control from the late 1960s. 1980 to over 300 000 in 1994 (J. Thompson, The preparation of strychnine baits has Department of Lands, Queensland, pers. usually been the r esponsibility of landholders comm. 1994.). Thompson et al. (1991) often with only general guidance: ‘as much concluded that this incr ease has been due strychnine as will thinly cover half an inch to a combination of factors including r educed hunting pressure resulting from the then high commodity prices for wool and lambs. ‘The use of strychnine for fox control is being phased out in preference to 1080 which is more target-specific and more humane.’ The present requirements for fox poisoning in each state and territory ar e presented in Table 7. Restrictions on application r efer to the laying of baits only, such as r equiring them to be buried, and not on r equirements 7 such as the display of war ning notices. Since the use of strychnine for fox contr ol is being phased out in pr eference to the mor e target- specific, and pr obably more humane 1080, its use is not discussed in detail.
Sodium mono-fluoroacetate (1080) Sodium mono-fluoroacetate or 1080 is the synthetic sodium salt of the naturally occurring mono-fluoroacetic acid. It is odourless, virtually tasteless and highly soluble in water. It is widely used in Australia for vertebrate pest contr ol. Because of its Warning signs are essential to notify people that toxicity and importance to agricultural fox baits have been laid. production and nature conservation, by law Source: Applied Biotechnologies
Bureau of Resource Sciences 73 1080 powder (usually about 96% pur e) can The amount of 1080 r equired to kill a fox only be obtained by gover nment or semi- is about 0.15 milligrams per kilogram body government agencies which in tur n prepare weight (McIlroy and King 1990) via intraperi- bait for use by land managers. toneal injection or stomach intubation routes. As McIlr oy and King acknowledge, Fluoroacetate occurs naturally in a it does not allow for incomplete absorption number of Australian plants of the genera of 1080 fr om the gut when the toxin is Acacia, Gastrolobium and Oxylobium delivered via a bait, nor does it allow for (Oliver et al. 1977) some species of which any loss of toxicity due to leaching or extend from south-west Western Australia, microbial degradation after a bait has been up through the Northern Territory and down laid. into the central highlands of Queensland (Everist 1947). This natural occurr ence Newsome and Coman (1989) r eport a benefits the use of 1080, particularly in weight range for adult foxes of 3.5–7.5 Western Australia where some native fauna kilograms for souther n Australia. Recent have evolved tolerance to the toxin r elative shot samples fr om the wheatbelt of W estern to the introduced fox which is highly Australia (Thomson unpub) r evealed a sensitive (King et al. 1981; McIlr oy 1986; mean weight for males of 5.67 kilograms; King and Kinnear 1991). For example, range 2.7–8.5 kilograms. The sample size brushtail possums from Western Australia was 374 and 8.3% weighed mor e than 7 have an LD 50 of over 100 milligrams per kilograms. Taking into account the heaviest kilogram, whereas possums from near fox sampled (8.5 kilograms) and based on
Canberra had an LD 50 of 0.68 milligrams per a lethal dose of 1080 as 0.15 milligrams per kilogram (King 1990). kilogram, the minimum dose r equired is 1.3 milligrams. For females the statistics wer e: The implication for south-easter n N=351; mean=4.82 kilograms; range 3.0–7.0 Australia, where 1080 tolerance has not kilograms. developed, is that species such as the tiger quoll (Dasyurus maculatus) and other It is dif ficult to determine the absolute carnivorous marsupials, and some r odents minimal dose because the minimum lethal and birds may be at risk fr om fox dose has not been deter mined using meat management programs although this has not baits and, per haps more importantly, been demonstrated experimentally (McIlr oy because of the uncertainties surr ounding 1992; McIlroy and Gifford 1992; Kor n et al. the fate of 1080 in a bait after laying. McIlr oy 1992). Despite these dif ferences in tolerance and King (1990) r ecommend a minimum to 1080 within the Australian fauna, this toxin dose of 2.5 milligrams per bait. This amount remains the best choice thr oughout the should be suf ficient to kill the lar gest fox continent (McIlroy et al. 1986; McIlr oy and sampled (8.5 kilograms), even if 50% of the Gifford 1992). With 1080, there is scope for 1080 were lost due to leaching, micr obial increasing target-specificity even in ar eas degradation or incomplete absorption. The where the fauna has not evolved tolerance. Vertebrate Pests Committee national recommended dose rate is 3 milligrams, and Selectivity of poisoning can be enhanced states are encouraged to adopt this. by: Staples et al. (1995) tested the lethal ef ficacy • using baits highly attractive to foxes; of 3.3 milligram 1080 Foxof f baits (see below) • minimising poison content and maximising after storage (10–39°C) for 0.4, 7 or 11 months bait size to achieve low 1080 concentra- by giving a single bait to each of 6 female and tion in the bait; 8 male foxes (3.3–6.5 kilograms live weight). Efficacy was 100% r egardless of storage time. • placing baits in the best ar eas to encounter Mean time to first visible ef fect was 4.06 hours foxes; and and to death 4.68 hours and appear ed • burying baits. independent of weight or sex.
74 Managing Vertebrate Pests: Foxes Table 7: State and territory legislative r equirements for fox poisoning.
State/ Registered Recommended Bait application territory poison(s) bait(s) restrictions+
WA • 1080 • Meat (110 g) • Distance restrictions* • Strychnine • Manufactured baits (except hobby farms subject to APB approval)
NT • 1080 • Meat • None • Manufactured baits
SA • 1080 • Meat, fish, fowl heads, • Property size restrictions liver, eggs • Distance restrictions* • Manufactured baits • Baits must be buried
QLD • Strychnine • Meat • Distance restrictions* • 1080
NSW • 1080 • Meat (100 g) • Distance restrictions* • Fowl heads • Baits must be buried • Manufactured baits
ACT • 1080 as for NSW as for NSW
VIC • 1080 • Cooked meat • Distance restrictions* (25–500 g) • Baits must be buried • Manufactured baits
Note: Foxes are listed as vermin under the Vermin Destruction Act in Tasmania and so can be destroyed, but no poisons are registered for this use.
+ All states and territories require erection of warning signs in areas where 1080 is used. * In some states there are restrictions on the distance baits may be placed with respect to human habitation, water supply, and property boundaries. 7 A recent trial (D. King, APB, W A, pers. action of cyanide ensur es that the car cass comm. 1993) has shown that meat baits is found close to the bait point for easy containing 2.5 milligrams of 1080 ar e fatal to retrieval of the pelt (Lugton 1987). The foxes weighing up to 4.2 kilograms. Thr ee manufacture and use of cyanide baits in captive foxes (weights 3.0, 4.2, and 4.2 capsule form is simple, inexpensive kilograms), acclimatised to their surr oundings (Appendix B) and poses few hazards if and food, died after consuming a single routine safety precautions are followed. kangaroo meat bait of 120 grams, dried to However, as only 1080 and strychnine approx 50 grams. This supports the above r ec- are registered for fox control in ommendation of 2.5 milligrams, although Australia, the use of cyanide baits is further trials using lar ger foxes ar e needed to illegal and should only be used as a confirm this. research or management tool by government agencies. Cyanide Cyanide capsules are currently being Cyanide has been commonly used to kill evaluated in several studies. A number of foxes for the fur trade in Australia. The rapid different lures and capsule types have been
Bureau of Resource Sciences 75 tested. Tuna and aniseed oils have been incor - still registered in some states, its use is being porated into the wax capsule and a variety of phased out. Cyanide, because of its toxicity blended meat types have been used as and volatility, is only available for scientific attractants to cover the capsule. The best purposes. Potential alter native poisons results have been achieved when using a include anticoagulants such as br odifacoum, naturally white capsule coated with a mixtur e bromadiolone and warfarin. Before these of condensed milk and icing sugar , and a r ed could be r egistered for use against foxes, capsule covered with a lur e of blood and extensive evaluations of toxicity, raw liver blended together into a paste. Red humaneness, non-target effects and bait capsules are made by mixing into the molten delivery systems would be r equired. At this wax a commercial red dye used for imparting stage the expense associated with the colour into candles. evaluations of anticoagulants for fox contr ol (and other alter natives) is not justified. Results have shown foxes display preferences for either capsule type and ‘The only widely recommended therefore a choice is r outinely offered at each poison for fox control is bait station. Bait stations ar e activated at dusk 1080.’ and inspected at dawn. Recent tests designed to assess fox pr eferences for other bait Alternative poisoning techniques materials such as fish and cooked liver , have revealed that fish is less palatable. Cooked One of the pr oblems associated with liver was as ef fective as raw liver . fumigation of fox br eeding dens is the fact that the adult animals ar e often absent fr om Foxes are guided to the stations by a scent the den when the fumigant is applied. One trail created by dragging a car cass from a technique that may possibly over come this vehicle along the track. An incision is made problem is the ‘tarbaby’ poisoning in the abdomen to allow body fluids to trickle technique, developed for rabbit contr ol in out slowly. Tests have shown that artificial the late 1960s (Hale and Myers 1970). This lures, such as meat meal or fish meal, to be technique utilises the gr ooming habit of significantly less effective than carcasses. rabbits by pr esenting the toxic agent in a In Victoria, surface baiting is discouraged sticky grease on the floor of the warr en and not permitted for routine fox contr ol on entrance. Experiments have tested mixtur es the basis of non-tar get risk. The above of lanolin and gr ease containing 1.5–2.5% procedures, developed in Western Australia, 1080 by weight which wer e extruded in a are being modified to suit this r equirement five-track strip. High levels of rabbit contr ol (C. Marks, DCNR, V ictoria, pers. comm. 1994). were achieved in early experiments, but Two types of sodium cyanide ar e under the method was not adopted for r outine evaluation: a cyanide gel and a powder ed use for a number of r easons. The sticking sodium cyanide. Both pr eparations are placed agent contains a very high concentration into specially prepared ‘brittilised’ capsules of 1080 and this was seen to pose a which are made to withstand transport and substantial risk to other wildlife species handling and to impr ove the safety aspects and to people. Also r einvasion of treated of using the poison. These capsules r equire warrens was rapid. more pressure before fracturing than the Applied to the entrances of fox br eeding softer wax ones. However, once the pr essure dens, the tarbaby technique is likely to kill threshold has been exceeded they will both adult foxes and cubs. T iming of the ‘explosively’ shatter. operation would be critical as the den needs to be tr eated while cubs ar e still being fed Other poisons by the parents but old enough to emer ge from the den. The success of the technique The only widely r ecommended poison for would depend upon the animals entering fox control is 1080. Although strychnine is
76 Managing Vertebrate Pests: Foxes 1080 may be injected into fresh meat baits which are highly palatable to foxes and relatively target-specific. Source: R. Knox, APB the den and attempting to r emove the grease Surface application of manufactur ed or from their paws by licking. This appr oach fresh meat baits, which ar e equally or mor e to fox management r equires further inves- attractive than dried meat baits, may put non- tigation. Since foxes ar e highly susceptible targets at risk because they can be r eadily to 1080, it may be that the concentration of ingested. Dried meat is the pr eferred bait 1080 used can be significantly lower ed. material in Western Australia especially for aerial application. In other r egions of Australia Bait materials where native fauna have little tolerance to 1080, it is important that bait consumption by Meat has many desirable pr operties as a bait non-target species is minimised. Wher e man- material. It is very palatable to foxes and is ufactured or fresh meat baits ar e used in con- relatively target-specific, being attractive servation areas they should be buried, alr eady only to a limited number of car nivores and a mandatory requirement in many states. omnivores. Target-specificity can be further enhanced by the manipulation of size and ‘Meat is a good medium for 7 by drying. By making the bait lar ge, and 1080 poison as it is highly thus lowering the overall concentration of palatable to foxes and 1080 within it, smaller non-tar get species relatively target-specific.’ are unable to consume enough bait to The Agriculture Protection Board of receive a lethal dose of 1080. Upon drying, Western Australia procedure for preparing meat initially for ms a crust, and after further dried meat baits is as follows: drying it takes on a biltong consistency. T ests have shown that smaller car nivorous • meat is cut into 120 gram chunks; marsupials and scavenging birds such as • the centre of each chunk is injected with ravens, cannot consume it as it is too tough 2.5–4.5 milligrams of 1080 dissolved in 0.15 and stringy (Calver et al. 1989). However , millilitres of water; and the assumption that dried baits maintain their consistency in the field, and hence their • baits are dried to a weight of 40–50 grams, target-specificity, has not been demonstrated equivalent to about a 60% loss in weight. in the higher rainfall ar eas of south-eastern Baits may be used within a few days or Australia. stored frozen.
Bureau of Resource Sciences 77 Volume production can be achieved by fresh meat baits which cannot be kept for forced air drying on racks over four days at later use. 32°C. However this temperatur e is under ° review; a higher temperatur e, 40–45 C, Bait concealment: buried baits would be more satisfactory as it would inhibit microbial growth. As discussed above it may be desirable or necessary to bury baits to r educe the chance Where meat bait is to be used on agricul- of non-target animals taking the bait (Allen tural land, drying befor e application is not et al. 1989). This incr eases the labour costs, always necessary. Once baits ar e prepared by but these extra costs can be of fset to some cutting into the desir ed size they should be extent by using fewer baits and ensuring left to drain on a wir e mesh. This r emoves greater target-specificity. excess fluid which might otherwise leach out the 1080. Baits ar e injected with 1080 solution Baits should be cover ed lightly with litter using an accurately calibrated vaccination gun. or soil to a depth of 5–10 cm to ensur e that the bait is not visible. It has been claimed by some that buried baits ar e more attractive Manufactured baits to foxes than sur face baits (Kor n and With an increasing demand for fox baiting Lugton 1990), although trials have not been programs on agricultural land, the need for conducted with foxes to confir m this. For a more readily available and economic fox wild dogs, Allen et al. (1989) found that bait was identified. This led to the buried baits were equally attractive and development of a manufactur ed bait (Foxof f) palatable compared to surface-laid baits. consisting of a soft meat-like substitute based How long a bait, buried or otherwise, on meat meal and containing animal fat, retains its toxicity is dif ficult to quantify as preservatives, binding agents and some there are many potential variables involved, proprietary flavour enhancers. Ther e are a particularly rainfall. A suite of soil micr obes number of advantages associated with the and others in water have been shown to use of a manufactur ed bait. These include: rapidly degrade 1080 (Eason 1992; King et a prolonged shelf-life, ease of distribution, al. 1991). Staples et al. (1995) assessed packaging incorporating education material degradation of Foxof f baits after two weeks which encourages responsible use, and in loam soil which was either kept dry or factory quality control which allows for the received 56.4 mm of rain. Mean minimum accurate incorporation of 1080. Wher e and maximum temperatur es throughout the necessary a manufactured bait could also two weeks wer e 8°C and 17 °C respectively. include fox attractants, a vaccine for disease Degradation was faster in wet soil with only control and encapsulated 1080 which would 21% of the initial 1080 dose r emaining, potentially reduce non-target uptake. Foxof f whereas baits r emained lethal with 75% of baits are now used extensively thr oughout toxin remaining after two weeks in dry soil. south-eastern Australia wher e they are fully registered by the National Registration Authority. Their use is also supported by Aerial baiting appropriate state gover nment agencies some Western Australia is the only state that uses of which issue instructions specific to Foxof f aircraft to lay baits for fox contr ol. This baiting procedures for fox contr ol. An method is illegal in New South W ales and example is presented in Appendix C issued Victoria. An eight-seater plane such as a by the Land Pr otection Branch of the Britten Norman Islander capable of carrying Queensland Department of Lands up to 6000 baits has per formed well in A disadvantage of manufactur ed bait is Western Australia, although smaller air craft the loss of r egulation over the use of 1080 as could be used. A chute in the floor for a result of prolonged shelf-life compar ed to dispensing baits assists bait laying. A spotter
78 Managing Vertebrate Pests: Foxes with a sound knowledge of the ar ea to be size, dispersal behaviour and rates of baited is r equired to keep the pilot on recolonisation to better quantify the size of course and to advise the bait dispenser areas which can be pr otected and hence when to start and stop baiting. Pr eferred the area over which baiting would need to flying height is appr oximately 200 metres. be conducted. The aircraft follows transect lines, one In Western Australia, small ar ea baiting has kilometre apart, across the site to be baited. been restricted mainly to natur e reserves The air-speed is dependent on wind surrounded by far mland. These have been conditions and drift. Baits ar e dropped at routinely baited once per month. Baits ar e prescribed intervals depending on the laid from a moving vehicle travelling along baiting intensity r equired. Prior to the flight, the perimeter firebreaks by tossing baits under the number of transects and the baiting shrubbery at intervals of 100–200 metr es. Any intensity is calculated in baits per squar e internal tracks ar e baited as well. kilometre. The transect length is then divided by the air -speed to give an even This baiting regime has been used for distribution of baits for the ar ea. ten years at dif ferent sites. In each case, ‘Aerial baiting of foxes is low density populations of marsupials have effective for covering large increased markedly, but it is expensive. areas provided the risk of non- Studies are required to deter mine the target bait take is minimal.’ minimum intensity of baiting r equired to protect native wildlife at risk fr om fox Aerial baiting of foxes is an ef fective way predation. Kinnear et al. (1988) found that of reducing fox populations wher e the risk foxes rapidly invaded 160–300 hectar e of non-target bait take is minimal. T o test its reserves following removal of resident foxes. effectiveness, 11 r esident foxes within a study It was on this infor mation that a monthly area were radio-tagged immediately prior to baiting regime was adopted. a baiting pr ogram. Baits wer e dropped at an ‘Small management areas intensity of six baits per squar e kilometre as require frequent baitings described above. Four days after baiting, eight because they are rapidly radio-tagged foxes wer e confirmed dead and recolonised by foxes.’ two more by 14 days. Assuming that the untagged fox population suf fered the same In a r ecent baiting program, baiting mortality rate, then baiting at an intensity of frequency was r educed to three month six baits per squar e kilometre killed 91% of intervals (four baitings per year) and baits laid the foxes. Further pair ed trials at rates of 5 every 200 metres. Bettongs were released into 7 and 10 baits per squar e kilometre revealed the area in 1980 without fox contr ol but failed bait uptakes typically gr eater than 80%; uptake to thrive. Trapping capture rates wer e near at 5 baits per squar e kilometre was as gr eat zero before baiting and again two years later . as for 10 baits per squar e kilometre (D. Algar, In 1993 the trapping success had incr eased CALM, WA and P. Thomson, APB, WA, to 5%. This is still low, but clearly, bettong unpub.). density is incr easing. Monitoring will continue to see if the population will incr ease and Frequency and intensity of baiting stabilise at this baiting intensity. By way of comparison, a pr evious study showed that A prescription for laying baits for the bettong capture rates reached as high as 30% purpose of fox contr ol will depend on the after five years of baiting at monthly intervals. size of the ar ea to be pr otected. Small ar eas of approximately 10 000 hectar es or less Another factor that wildlife managers need require frequent baitings because they ar e to consider is the desir ed level of incr ease in rapidly recolonised by foxes. However, the target wildlife species. For example, is it more information is r equired on fox territory intended to have the pr ey to increase to the carrying capacity of the habitat, or is some
Bureau of Resource Sciences 79 Manufactured baits have a prolonged shelf-life and ensure accurate and consistent 1080 concentrations. Source: Applied Biotechnologies arbitrary percentage of the carrying capacity trails, and animal pads so that baits can be more desirable? easily relocated. Foxes tend to follow these features when moving about their home Factors such as available r esources for ranges. Trails should be selected during the sustained control, fox density, the rar eness planning procedure. of the prey, amount of cover , prey vulnera- bility and area of habitat will deter mine the ‘Baits are best buried in level of effort required to contr ol foxes. shallow depressions to reduce non-target risk and extend Baiting procedure: agricultural land bait freshness.’ The most common fox poisoning strategy Baits are best buried at r egular intervals involves laying baits at r egular intervals along (100–500 metres), in shallow depr essions a trail. Dragged car casses, offal enclosed in a which reduces non-target risk and extends bag or any matter that leaves a scent trail, can bait freshness. In some states this pr ocedure be used to attract foxes fr om a distance. Scent is mandatory. As a general guide use 50 baits trails can significantly incr ease the initial rate per 400 hectar es. The baiting pr ogram should of uptake which is an advantage wher e time last about 2–3 weeks with baits inspected is limited. However, recent evidence indicates every 2–4 days and r eplaced if taken. It is that foxes will find most baits r egardless of common for lar ge numbers of baits to be scent trails. In many cases the use of scent trails removed at the beginning of a pr ogram, dis- can encourage individual foxes to find and proportionate to the expected number of remove many mor e baits than is necessary, foxes. This could be r elated to the caching particularly during the period after 1080 is first behaviour of foxes wher e they store surplus ingested and before it starts to take ef fect. food without necessarily eating it. Bait should Where scent trails ar e used, they should at least be offered until no mor e is being taken. If be interrupted at r egular intervals to minimise surplus baits ar e cached by foxes and r emain the occurrence of multiple takes. uneaten there is a potential risk to non-tar gets. The trail should be accessible by vehicle The issue of multiple bait take and the ultimate and preferably follow known featur es such fate of all r emoved baits requires further as fence lines, pr operty roads, tracks or stock research.
80 Managing Vertebrate Pests: Foxes ‘The risk to non-target animals time will be quickly r eplaced by sub-adults from cached baits needs during the dispersal period. Conversely, if further investigation.’ poisoning is not carried out prior to the peak predation time, any localised Free feeding with unpoisoned bait is not population reduction may be compensated usual, although how much this might by reinvasion. Maximum effect on foxes by influence the success of the poisoning poisoning for the purposes of agricultural operation is unknown. Wher e there is protection may therefore necessitate two special concern about local non-tar get control programs per year depending on animals such as bandicoots or quolls, fr ee the time of lambing. One of these should feeding in conjunction with sand plots can coincide with the lead-up to peak pr edation be used to assess risk befor e poison baits while the other should take into account the are offered. In some cases, wher e low behaviour of foxes. densities of foxes exist or individual foxes are being targeted, the use of a car cass as a bait station or attraction point has been 7.5.3 Hunting employed. Once foxes have been attracted to the area, poisoned bait can then be placed The hunting of foxes either for their pelts, a nearby. Caution is needed when using bait bounty or mer ely as a sport has long been stations as they may also attract non-tar gets. seen by the agricultural community as a useful and economic way of r egulating fox numbers. The commer cial value of fox pelts Timing of control: agricultural land as determined by export prices saw lar ge Fox control using poisons is usually numbers of animals taken for this purpose. conducted in the month leading up to The majority of these wer e shot with the lambing or kidding to r educe local fox remainder either poisoned or trapped. populations and pr edation rates. This can Hunting of foxes is time consuming and occur from early autumn thr ough to late few landholders carry out this contr ol spring depending on the r egion. The technique. It is mor e common for pr ofessional effectiveness of a poisoning operation may or experienced amateur hunters to be given be improved by taking advantage of the the rights to take foxes fr om individual peak demands for food by foxes (Chapter properties. With the falling value of fox pelts, 2), although this has not been tested and in the absence of bounties, this is now experimentally. For example, br eeding left to the mor e enthusiastic amateurs and a vixens might be most vulnerable during late few remaining professionals. gestation and lactation (spring) when their 7 food demands ar e sufficiently high to increase foraging activity, and hence the Shooting probability of locating bait. Dominant males Shooting is usually done at night fr om a may be mor e exposed to bait during the vehicle and with the aid of spotlights (100 mating season (winter) when they ar e W). Small bor e, high-velocity rifles, for moving over much lar ger areas in search example .222 calibr e, fitted with telescopic of mating opportunities. Late summer sights are preferred. Night spotlight shooting poisoning for autumn lambing is per haps often relies on the ability of the hunter to lur e at a time when fox populations ar e under inquisitive and inexperienced animals into least food pr essure due to an availability of shooting range by rabbit whistle, or to alternative prey and when it is likely to be approach the animal without it r etreating. least effective, although sub-adults fr om the Coman (1988) observed that fewer foxes previous breeding season will be foraging could be taken by this technique as the season for themselves at this time and ar e more progressed due to either rapid r emoval of likely to sample all food types (including young or inexperienced animals or lear ned bait). Similarly, any foxes poisoned at this avoidance of shooters.
Bureau of Resource Sciences 81 In many districts, r ecreational shooters with Traps high-powered rifles are invited onto far ms just prior to or during the lambing season Traps have been used for centuries to and the resultant localised r eduction in fox control predators or for commer cial numbers may give some temporary r espite harvesting, although the captur e of foxes to lamb predation losses. The method is not is relatively difficult compared to other suitable where there is dense cover for foxes. species. Recently there has been much opposition to their use on animal welfar e Newsome et al. (1989) r emoved foxes and grounds (Section 5.3) and considerable cats from Yathong Nature Reserve by shooting effort has been put into development of and observed significant incr eases in rabbits more humane traps (Novak 1987). The use compared to contr ol areas with no fox or cat of steel-jawed traps on agricultural land is shooting. The effort was considerable, one either discouraged or banned in most states week in every two or thr ee. It is not known if and territories. It is also a labour intensive this level of ef fort would have been suf ficient technique which makes it impractical for to allow native pr ey species to incr ease or if large-scale operations. Steel-jawed traps the cost was justified. Replacement of shot have considerable non-tar get catches that foxes was high, particularly during the period are usually fatal or cause serious injury. when young foxes wer e dispersing. ‘Steel-jawed traps are not recommended and are banned Battues or fox drives in some areas.’ Fox drives are still common in some rural In some circumstances, fox damage may communities. Here, groups meet infor mally occur in situations wher e conventional and use unarmed beaters, often with dogs, control techniques ar e not practicable. The to drive foxes into a waiting line of guns. most common example is fox contr ol in Usually it is only small ar eas of prime fox urban or semi-urban ar eas where use of cover that are treated. Significant numbers of poison baits is seen as an unacceptable risk foxes can be taken but the ar ea of land tr eated to domestic cats and dogs. In V ictoria, a is usually very small with human r esource treadle snare trap originally developed for requirements prohibitive. For this r eason, the wild dog control, has been used for the technique provides little long-ter m control capture of foxes in urban ar eas (Coman, of fox damage. The advantage of this method unpublished data). This leg-snar e device is is that it is not selective in ter ms of the type a more humane alter native to the steel-jawed of fox forced to bolt fr om its cover into the trap and has been accepted as a suitable fox range of the hunter, and may help to further control technique by the RSPCA. However , reduce populations already subject to baiting such traps ar e difficult to set, and it is and spotlight shooting and which contain unlikely that they would be suitable for use mostly wary adults. by the general public. ‘Steel-jawed traps may kill or Dogging injure non-target animals.’ Another technique of fox hunting found in The treadle snare consists of a thr ower some parts of Australia is the use of small arm, activated by a conventional trap plate, terrier dogs to flush foxes fr om dens. which draws a cable noose about the Dislodged animals are either killed with animal’s leg. Treadle snares are buried in a shotguns or coursed with lar ge lurcher dogs. manner similar to that of conventional steel- As with fox drives, this technique pr oduces jawed traps and ar e set on runs or used with little more than a temporary and localised lures. A small locking bracket is incorpo - reduction in fox damage and also cannot rated into the snar e cable such that, once be condoned on animal welfar e grounds tightened about the animal’s leg, it cannot (Section 5.3). be loosened.
82 Managing Vertebrate Pests: Foxes The snare cable usually causes minimal natural range wher e hunting has been used injury and, importantly, non-tar get species to reduce predation, to prevent the spread can be r eleased relatively unharmed. The of rabies, or for commer cial harvesting snare plate is set to withstand a certain (Phillips et al. 1972; Hewson and Kolb 1973; weight before triggering which minimises Storm et al. 1976; Harris 1977; Macdonald risk to most smaller animals. If animals ar e 1980; Hewson 1986; Voigt 1987; Wandeler allowed to r emain in these snar es for a 1988). prolonged period, severe tissue damage and ‘Hunting has minimal effect on fractured bones may r esult. Treadle snares fox numbers.’ thus need to be checked at r egular intervals, preferably every 4–8 hours, so that captur ed animals can be humanely r emoved and 7.5.4 Den destruction and destroyed. fumigation Queensland legislation allows the captur e This can be an ef fective technique to r educe of foxes using soft catch traps which wer e fox numbers at the time when cubs ar e born developed in the USA as a humane spring (August/September). The vixen only r emains trap (Section 5.3.5). Unlike the traditional in the den with cubs for the first few weeks steel trap, they have rubber -like padding of life and the dog rar ely inhabits the same on each jaw which cushions the initial impact den. From the commencement of weaning and provides friction thus pr eventing the the adults will lay up away fr om the cubs, captured animal from sliding along or out returning at frequent but short intervals with of the jaws. They have several modifica - food. No fumigants ar e specifically registered tions that are designed to r educe the risk of for foxes. However, phosphine and chlor opi- injury to a captur ed animal. These ar e: off- crin which are recommended fumigants for set jaws that have a gap of 6–8 mm between rabbit warrens are commonly used, but the jaws when closed; r educed spring phosphine is the pr eferred fumigant in ter ms strength; a spring added to the anchor chain; of relative humaneness (Section 5.3.4). and a centrally attached bottom swivel to which the chain is attached. Neither fumigant is humane, although other fumigants such as carbon monoxide Hunting effectiveness could overcome these concer ns (Section 5.3.4). Where the den is accessible it can be The proportion of juvenile to adult foxes destroyed by deep ripping. Den destruction in a population is a good indicator of and fumigation can also af fect non-target hunting intensity pr oviding the population species. Due to pr essure from humane 7 can be sampled with minimal bias towards societies and public opinion, den fumigation any age group. Harris (1977) compar ed a of foxes for rabies contr ol was abandoned fox population with r elatively light contr ol in most Eur opean countries after 1975 measures to other studies with dif fering (Wandeler 1988). The major disadvantage levels of control. He found the ratio of of this strategy is that fox dens, other than juvenile to adult animals varied fr om 1:1 in in urban ar eas, are not easily located. Unless low control areas to as high as 6:1 wher e they have pr eviously been rabbit warr ens, intensive control was carried out. In a fox dens only have a small number of sample collected by Coman (1988) in entrances which ar e usually discretely hidden Victoria between 1982–84 this ratio was under tree roots or r ocky outcrops. Where 1.2:1, suggesting only a low level of fox dens can be located and tr eated, surviving control despite intensive hunting for pelts adults (except those in urban ar eas) will at the time. While hunting may have some rarely reuse them in following years and in effect on overall fox densities, it is generally some cases may change their behaviour to agreed that reductions will be minimal. This avoid new den sites being discover ed. has been observed thr oughout the fox’s
Bureau of Resource Sciences 83 7.5.5 Exclusion fencing ‘Foxes can scale electrified fences.’ A recent review of the ef fectiveness of exclusion fences for foxes (Coman and There is a lar ge range of fence designs, McCutchan 1994) found that although most but generally little detailed infor mation on of these fences pr ovided a barrier to foxes, their effectiveness. However, the review this barrier was not complete. The key to concluded that exclusion fencing r emains success is good fence maintenance, fr equent an important tool in the management of monitoring of the enclosed ar ea for the threatened or endangered species. Exclusion presence of foxes, and quick action to of foxes by fences is dif ficult due to the remove any animals which br each the agility of the animal and the pr ohibitive barrier. Coman and McCutchan concluded expense in large areas such as natur e that not enough consideration was given to reserves or lambing paddocks. Decisions the integration of contr ol and exclusion on whether or not to use pr edator-proof methods available. When a barrier is enclosures cannot be taken in isolation fr om breached by a fox, the damage to enclosed the more general consideration of long-ter m wildlife or domestic stock can be consider - management of the species being pr otected. able. Foxes have been known to raise a litter ‘Little is known about how within an enclosure, and to r outinely scale effective fences are against a formidable electrified fence to hunt and foxes.’ to return with food for their young. The National Consultative Committee on Animal Welfare (Department of Primary Industries and Energy 1992) concluded that exclusion fencing had a limited r ole in vertebrate pest management. Simple wir e- netting fences alone ar e rarely effective regardless of the height. However wher e zoos, private wildlife parks or intensive agriculture is subject to fox pr edation, exclusion fencing, pr eferably incorporating a roof or over hang, has been ef fective. Some success has been achieved using high netting fences with unstrained over hanging tops, for example Warrawong Sanctuary in South Australia. Apparently the floppy nature of the upper fence r esists any attempt by foxes to climb it. Electrified fences may also exclude some foxes pr oviding they are properly designed and maintained. Others have used fences incorporating a combination of wir e-netting and electrified wires, but irr espective of fence type, maintenance costs can be substantial and frequent monitoring of the enclosed ar ea for the pr esence of foxes is still necessary. Fences can have negative ef fects on non- target species through entanglements, accidents or r estrictions on movement. Exclusion fencing for foxes is only viable when protecting native species of high conservation Natural water barriers such as r emote value. Source: R. Knox, APB islands are effective barriers to foxes and,
84 Managing Vertebrate Pests: Foxes indeed, some mammal species for merly may have a similar ef fect, or alter natively, widespread on the mainland ar e only found providing carrion during lambing may r emove on such islands. It is ther efore essential that predation pressure without r educing the fox these island r efuges be kept fox fr ee. population. Neither of these strategies have ‘Fences can interfere with the been tested. movement of non-target ‘Domestic dogs can be trained animals.’ to protect sheep flocks from foxes.’ 7.5.6 Farming practices Newsome (1987) suggested that integrated fox management was essential if levels of Alternative stock management practices may predation were to be r educed. Ad hoc reduce fox predation. Smaller lambing management is not ef fective. A combination paddocks close to homesteads make it easier of adaptive far ming practices (Section 8.3), to monitor the flock and r educes the chance an effective fox management pr ogram, and of young lambs being left unattended by the reductions to their natural food supply to mother. Shed lambing of valuable animals can limit breeding success is r equired. While this also be used. Foxes usually only kill lambs up approach is logical, the optimum to one week of age. Lambing can be r estricted combination of strategies to obtain economic to as short a period as practicable so that relief from lamb predation may be dif ficult susceptible lambs ar e only available over a to identify. limited period. Ideally this should be done in collaboration with neighbouring pr operties. The timing of lambing may also be critical 7.5.7 Fertility control (Section 7.2.3). Fox densities ar e lowest during Reductions to the r eproductive performance early spring, prior to r eproduction and after and hence population densities of pr edators completion of dispersal. Selection of flocks by oral administration of anti-fertility agents for more protective mothers may deter foxes has been attempted in the past with only from approaching lambs. Some pr oducers marginal success (Linhart and Enders 1964; have successfully used trained guard dogs to Linhart et al. 1968; Oleyar and McGinnes protect flocks fr om lamb predation. The 1974; Allen 1982). Diethylstilbestr ol (DES), success of Mediterranean stock guard dog a synthetic oestr ogen, has been commonly breeds in the goat industry is well documented used for this purpose. While DES causes by dog and goat br eeders (E. Scheurmann, temporary sterility, its value is limited by International Wool Secretariat, pers. comm. problems with bait acceptance, the 1994). 7 requirement for precise timing of baiting ‘Foxes usually only kill lambs relative to the animal’s br eeding cycle, and up to one week of age.’ the carcinogenic properties of the drug (Bomford 1990). The density of fox populations depends on the productivity of the envir onment. Lambs ‘Reducing fox fertility is not are a minor component of the fox diet. Catling yet a practical technique for (1988) and Pech et al. (1992) found that the reducing fox numbers.’ size of a fox population in summer was Orally active steroid hormones or dependent on the availability of rabbits over antihormones that induce abortion have the preceding rabbit breeding season. With also been pr oposed as a method for fertility the importance of rabbit in the diet of foxes control (Short 1992). These compounds throughout Australia (Chapter 2), manipula- show a degr ee of species specificity due to tion of this pr ey species may indir ectly reduce variation in the structur e of the uterine the fox population and hence levels of lamb progesterone receptor and could be useful predation. Catling (1987) also suggests that for species with short br eeding seasons such removing carrion such as kangar oo carcasses
Bureau of Resource Sciences 85 as the fox. In pr eliminary baiting trials on ductivity of the tar get population (Caughley wild foxes, an abortifacient was tested at a et al. 1992). combination of urban and rural den sites For the fox, no specific virus has been (C. Marks, DCNR, V ictoria, pers. comm. found that will not also af fect dogs. The 1995). Bait uptake appr oached 90% current approach of the CRC involves the indicating no aversion to tr eated baits. The direct presentation via a bait of a selected resulting observations of cub activity was protein or a r ecombinant virus (T yndale- also markedly reduced at treated dens when Biscoe 1994). The latter has been used very compared to untreated dens. successfully in Eur ope to immunise wild While a range of techniques and foxes against rabies (Artois et al. 1987). substances are now known to r educe the National concerns about the eventual fertility of foxes, r educing fertility will not outcome of this work ar e the possible necessarily lead to a decline in population consequences to human health, domestic density or in damage caused by foxes. Lar ge- stock, companion animals and native fauna. scale field experiments would be needed to International concerns are directed at the determine how practical it is to deliver these risk to foxes in countries wher e the species compounds to wild foxes and to evaluate is indigenous. Close scrutiny is maintained their effectiveness for r educing population on any potential domestic risks, and since size. Delivery of fertility contr ol drugs to the work on the fox is curr ently directed at wild foxes is likely to be expensive and they oral delivery of non-disseminating vectors, may be less ef fective for population contr ol this poses no risk inter nationally (Tyndale- than poisons (Bomford 1990; Bomford and Biscoe 1994). O’Brien 1992). An effective form of biological contr ol Recent understanding of the molecular of foxes appeals as a long-ter m and cost- basis of fertilisation makes it possible to effective method for fox management over develop new strategies to suppr ess repro- large areas. Although the risks involved in duction in free-living animals. Such r esearch developing a suitable technique ar e high, is being undertaken by the Cooperative so are the potential benefits. ANZF AS Research Centre (CRC) for Biological Contr ol strongly supports the development of of Vertebrate Pest Populations established fertility control measures as a mor e humane in 1992 and tar geting initially the rabbit and technique for contr olling pest animals such fox (CSIRO 1992). The theory behind the as foxes. However, while these techniques research is that the genes for pr oteins that have potentially enor mous benefits, it is not are critically involved in fertilisation or yet possible to assess the likely outcome of implantation of eggs can be inserted into a such research. If successful it may still be virus that infects the tar get species. An many years befor e any tangible benefit animal infected with the virus would simul - accrues. In the meantime, and pr obably as taneously raise antibodies to the virus and an adjunct to biological contr ol, con- reproductive protein, resulting in the ventional fox control strategies still need prevention of pregnancy, but at the same to be developed and employed by land time not impair the nor mal endocrine managers. function and reproductive behaviour of treated individuals. Among social species 7.5.8 Habitat modification reproduction by subordinate members of the group may be inhibited by dominant There is some evidence that the wester n ring- members (Mykytowycz 1959), while in other tail possum (Pseudocheirus occidentalis) can species there is active competition among withstand fox pr edation if the for est canopy males for access to br eeding females. In is closed (P. de Tores, CALM, WA, pers. both situations sterilisation of dominant comm. 1993). Protection is needed in open members could theoretically reduce the pro- woodland where possums have to travel
86 Managing Vertebrate Pests: Foxes across open gr ound between trees and also during periods of extr eme temperatures when possums seek heat r efuges on the gr ound. While this might be an isolated example, it illustrates that habitat modification may have a role in pr otecting wildlife from fox predation. Kinnear et al. (1988) concluded that fauna subject to fox pr edation can only survive in sites that act as a r efuge from predators. Removal of pr edators allows prey to utilise less pr otected sites. Conversely, not changing habitat wher e susceptible species are present or recreating necessary habitat may also pr event fox predation. Logging activities and the establishment of r oads through undisturbed habitat for example, may allow foxes to colonise new ar eas which contain endangered or vulnerable species (Mansergh and Marks 1993).
7
Bureau of Resource Sciences 87 8. Strategic management performance indicator is a sustained at the local and increase to viable densities of a threatened and vulnerable species when fox regional level management measures are implemented and maintained. For agricultural Summary production, lambing (or kidding) percentages are the obvious indicators. This chapter outlines the process for planning Precautionary management is needed to and implementing the strategic management prevent expansion of the fox’s range either of fox impact at the local and regional level. northwards or to Tasmania and other The components of a strategic management islands. program are problem definition; developing a management plan; implementing the plan; The second step requires the selection of and monitoring progress. the appropriate management options. Generally, the two options most suitable for Defining the problem — With limited (but foxes are strategic, sustained management, important) evidence the authors conclude which is continuing fox control implemented that the fox has a significant impact on on a regular basis, and strategic, targeted Australia’s native wildlife. The difficulty for management, which aims to reduce impact the land manager is that the extent of the at a particular time of the year. With present problem can only be revealed by long-term knowledge, strategic, sustained management evaluations of prey recovery after intensive should be employed where native wildlife is and continuing fox management. In most being protected while targeted management circumstances it has to be assumed that where to coincide with lambing is the best option the distributions of foxes and susceptible, for agricultural systems. Having selected a endangered or vulnerable species overlap, fox management option, the next step is to develop predation occurs. Therefore, fox control may an appropriate management strategy. Poison need to be initiated before the extent of the baiting with 1080 is the only tested and proven option in both conservation and problem can be accurately defined. The agriculture. However, factors still need to be impacts of foxes on agricultural production considered such as methods of application, are not well understood. However, because non-target risks, resources, other pests and the prey — lambs and goat kids — can be supplementary control techniques. intensively monitored, fox impact can more easily be defined. Implementation — Group action is an essential element of the implementation stage. Management plan — The first step in All those who will benefit from fox management planning, setting management management or have a significant stake in objectives and performance indicators, the outcome should be involved in the recognises that the specific conservation coordinated development and implementa- objective for fox management is to promote tion of the management plan. This will help increases in population of endangered fauna foster a strong sense of ownership of the plan, to viable sizes. For agricultural production and successful management which satisfies the objective is to maximise the benefits of fox all relevant players is more likely. control compared to the costs. Objectives for Monitoring and evaluation — Operational particular situations should include interim monitoring ensures that the control operation and long-term goals, a time-frame for is executed in the most cost-effective manner. achieving them and indicators for measuring It includes the recording of what was done, performance. Because of inherent difficul- where and at what cost. Performance ties in determining fox populations, the monitoring assesses the effectiveness of the success or otherwise of fox management must management plan in meeting the conserva- be measured by the response in the prey tion or agricultural objectives for the program. species. For conservation values, the best Both forms of monitoring enable the
88 Managing Vertebrate Pests: Foxes continuing refinement of the management individual landholders did not, and only plan where necessary. implemented the lesser levels of fox contr ol necessary to meet their livestock pr oduction Economic frameworks are needed to assist goals. Such gover nment assistance would in the assessment of the relative value of only be warranted, however , if scientific alternative fox management strategies. Such data verified that implementing fox contr ol frameworks require: definition of the on private land would have conservation economic problem; data on the relative costs benefits for endangered native species. and benefits of fox control; and an under- Another consideration would be whether standing of why the actions of individual or not assisting private landholders to land managers may not lead to optimal levels control foxes was the most cost-ef fective of fox control and how such problems can option for meeting these conservation goals, be addressed by land managers and compared to other options, such as investing governments. more resources in fox contr ol on r eserve Hypothetical examples of the strategic lands. management of foxes at the local and Collecting the economic data r equired regional level for conservation and agri- to assess the economic costs and benefits cultural production scenarios are presented. of fox control to pr otect livestock from fox predation is likely to be easier , although 8.1 Economic frameworks there is still often uncertainty ar ound estimates of fox contributions to lamb Economic frameworks need to be mortality (Section 7.2.3). developed to assist land managers assess the relative value of alter native control strategies. Such frameworks r equire: 8.2 Strategic approach definition of the economic pr oblem; data The components of the strategic appr oach on the r elative costs and benefits; and an to fox management have been described understanding of why the actions of in the Intr oduction. The four steps involved individual land managers may not lead to are defining the pr oblem; developing a optimal levels of fox contr ol and how such management plan; implementing the plan; problems can be addr essed by land and monitoring and evaluation of the managers and gover nments. Land managers program. The challenge for local and can use such economic frameworks to select regional land managers and others with a the most appr opriate fox management major interest in fox management is to use strategy for their cir cumstances. the knowledge described in the pr eceding Such economic frameworks might be chapters, and processes described in this used to deter mine the most cost-ef fective chapter, to develop a strategic management fox management strategies for the plan to address the damage caused by foxes. conservation of biological diversity. First, The process is illustrated for two 8 however, it would be necessary to estimate hypothetical cases, one for a conservation the economic value the community places area and the second for an agricultural on the conservation of native species production area. threatened by foxes, and also the cost and effectiveness of fox contr ol techniques for protecting these species. The pr ocess might 8.3 Problem definition indicate a case for gover nment assistance if for example the community placed a high Section 7.4 sets out the initial steps in value on fox contr ol on private far m land defining the pr oblem of any fox to protect remnant populations of management program, involving the endangered native species, but most measurement of fox impact and density measurements using techniques described
Bureau of Resource Sciences 89 in Sections 7.2 and 7.3. Mapping techniques Agriculture are very valuable in defining the pr oblem, allocating management units, and estab - The impact of foxes on agricultural lishing priority areas for tr eatment (Section production is not well understood. 7.4). However, because the pr ey (lambs or kids) can be intensively monitor ed, the impact can be mor e easily defined and used as a Conservation basis to deter mine the extent of fox contr ol As discussed in Chapter 3, ther e is required, or indeed whether any contr ol is conclusive evidence, albeit geographically necessary (Section 7.2.3). Car e is needed and species limited, that the fox has a in assessing impact, because although fox significant impact on Australia’s native densities may be monitor ed, the cause of wildlife. Some preliminary indications of fox lamb mortalities is less easy to deter mine. impact for a particular site might be ‘An assessment of fox impact available from direct observations of fox should be based on an accurate predation or fr om indirect measures such determination of the cause of as scat analyses. However, the dif ficulty for lamb mortality.’ a land manager is that the extent of the problem can only be r evealed by long-term 8.4 Management plan evaluation of prey recovery after intensive and continuing fox management. W ith present knowledge there are no other useful 8.4.1 Objectives correlates for fox damage. It ther efore The specific conservation objective of fox becomes necessary to make certain management is to pr omote and maintain assumptions about the initial pr oblem. population increases of endanger ed or Foremost is where the distributions of vulnerable fauna to viable densities. This threatened native species and foxes overlap, can be assisted by cr eating more populations the assumption must be made that through introductions and translocations to predation does occur. This means initiating areas or sites wher e the species for merly management without necessarily accurately occurred. Another objective is to pr event defining the problem. Once fox contr ol has future declines in populations of native been initiated, the extent of fox pr edation fauna through fox predation. and other factors which might influence the ‘The conservation objective of desired outcome can be assessed (Section fox management is to promote 7.2.2). viable populations of GIS-based databases such as the endangered fauna.’ Environmental Resources Information For agricultural production the objective Network (ERIN), linked to equivalent state is clear: wher e fox impact has been identified, and territory databases, contain infor mation the level of pr edation must be r educed to an on the habitat, conservation status, acceptable level, pr edetermined by the value threatening processes, and vulnerability of of the enterprise and the cost of contr ol. native plants and animals. These databases can help managers deter mine species most 8.4.2 Management options at risk and help plan a coordinated approach to protecting those species and areas believed to be most at risk fr om fox Flexible management predation. These lists of species most at There are some new appr oaches to threat may be at the r egional, state and managing complex natural systems. One is territory and/or national level. known as adaptive management. As described by Walters and Hollings (1990), Local eradication it is based on the concept that knowledge of such systems is always incomplete. Not Local eradication involves the per manent only is the science incomplete, the system removal of the entir e population of an ar ea. itself is dynamic and evolving because of This option is unr ealistic for foxes except in natural variability, the impacts of special circumstances such as islands wher e management and the pr ogressive expansion there is no potential for r ecolonisation, or of human activities. Hence management possibly on mainland r eserves where long- options must be ones that achieve an term perimeter control of foxes is economi- increasing understanding of the system as cally and technically feasible. For local well as environmental, social and economic eradication to be a viable option, a number goals desired. The management of foxes, of key conditions must be met (Bomford and other vertebrate pests, using ‘best and O’Brien, 1995). These ar e set out in practice’ suggested in these guidelines, AppendixD. embodies many of the concepts of adaptive management, particularly that of ‘lear ning Strategic management by doing’. Strategic management of foxes is an option Given the paucity of infor mation, where local eradication is not feasible. It including scientific infor mation, about many involves integrating fox contr ol operations of the factors that drive natural systems, into overall land management planning to Danckwerts et al. (1992) r ecommend that achieve a specific fox density or fox impact managers need to adopt the adaptive outcome. There are three major types of management approach of ‘lear ning by strategic management: sustained, tar geted doing’. That is, managers lear n from their or one-off. own past successes and mistakes (and those ‘Strategic, sustained of their neighbours), and fr om technical management involves an initial information, and make management campaign to reduce fox decisions based on experience in situations populations to very low levels, where few facts ar e known, but wher e followed by maintenance decisions cannot be postponed. control to prevent population A key to the flexible management recovery.’ approach suggested by Danckwerts et al. is Strategic, sustained management involves the monitoring of thr ee key variables in the an initial widespread and intensive contr ol system — livestock pr oductivity (biological campaign to reduce fox populations to very and economic); vegetation changes; and low levels, followed by maintenance contr ol environmental conditions and management to further r educe or at least pr event responses. These issues ar e further population recovery. This is the only canvassed in Section 8.5. practical option available in most cases for 8 Braysher (1993) discusses management managing fox pr edation on native fauna. It options for managing vertebrate pests and is important to r ealise before embarking on they are summarised below. In selecting this approach that resources must be an option it is important to match it to the allocated to this action for the for eseeable desired objective and to be r ealistic in ter ms future. Managers need to deter mine the of available r esources and technical level of ef fort at which the benefits of feasibility. A useful aid to this selection control at least equates with the costs of process can involve the construction of a control. However for fox populations cost– ‘decision matrix’ to evaluate which option benefit relationships are largely unknown. is most appropriate and a ‘pay of f matrix’ Furthermore, with the most important to determine the benefits (Norton 1988). impact being on endanger ed or vulnerable species, it is dif ficult if not impossible to
Bureau of Resource Sciences 91 place an economic value on the benefits of ‘Recreational fox hunting does wildlife conservation. little to reduce the impact of ‘The cost–benefit relationships foxes on lambs and native of fox control for different animals.’ situations are largely unknown.’ Crisis management One-off management involves a single In some situations it may be envir onmen- action to achieve the long-ter m or per manent tally or economically justified to undertake reduction of fox damage to an acceptable no fox control. This will particularly be the level. Examples might include construction case in a gr eat deal of agricultural land of a permanent fox-proof fence or r elease of where fox predation is not an issue and con- an effective biological contr ol agent. Fencing servation values are judged to be not sig - is likely to be pr ohibitively expensive except nificantly threatened. However, if foxes have in small areas protecting high-value species. intermittent impacts, it may lead to managers Development of an ef fective biological contr ol undertaking crisis management, killing foxes agent is in its infancy. in an unplanned manner as they appear to affect resources. This for m of management ‘Fencing is usually only a cost- is unlikely to pr otect resources. effective option for protecting high-value species in small areas.’ Precautionary management In the case of strategic, tar geted It is important to ensur e that the fox does management, control effort is targeted to not expand its range northwards or on to manage fox damage at a particular time of Tasmania or other islands wher e it is the year. Advantage may be taken of currently absent and wher e native fauna that biological factors of the fox (for example, are vulnerable to fox pr edation exist. This when it disperses or when vixens ar e most will require vigilance in detecting wild foxes food stressed) or when the pr ey is in these regions and public education on vulnerable (during lactation and gestation the risks of keeping or r eleasing foxes. for example). As with strategic, sustained management, cost–benefit relationships for 8.4.3 Management strategy this option are largely unknown. However, should it be found to be economically Having determined the most appr opriate justified, strategic, targeted management is management option the next step is to the most appropriate option for agricultur - choose appropriate management techniques al protection where control effort can (Section 7.5) and to integrate them into a coincide with lambing (Section 7.5). management strategy. Variables which might influence this need to be identified and evaluated. These can include: Commercial harvesting (hunting) • the conservation status of the population This form of management aims at pr oviding of the animals at thr eat; a sustained yield of animals which can be con- tinuously harvested without any long-ter m • the potential for applying strategic contr ol population reductions. With the demise of the to have maximum ef fect on fox populations fox pelt trade, most harvesting ef fort is now at a particular time of the year , for example, by recreational hunters. As outlined in Section through den fumigation at cubbing; 7.5, hunters have little impact on fox pr edation • resources to implement options, for on lambs and native fauna. The only situation example, where funds ar e limited but where this option may be of use is to assist a human resources are abundant, gr ound poisoning program to target surviving foxes. baiting is pr eferable to aerial baiting;
92 Managing Vertebrate Pests: Foxes • nature of the habitat (dense canopy, open An additional per formance indicator, and woodland or range land) and size and often the first positive sign, is an incr ease location of the management unit have in the use of the available habitat — species obvious implications to technique selection, increase and occupy ar eas of the habitat for example, access to management ar ea otherwise denied them. or rates of bait application; ‘The best performance • potential for non-target losses; indicator for fox management in conservation areas is the • presence of other pest species such as feral sustained viability of pigs, rabbits or feral cats; endangered or vulnerable • the potential for r ecolonisation by foxes species.’ from surrounding land and the ef fect this The lack of a significant population will have on management objectives; increase of a pr ey species, despite • the bias in some contr ol techniques apparently adequate fox management, (shooting for example) towards younger would indicate a failur e to achieve the age groups, leaving the br eeding objective. However it may indicate that other population intact; and factors, in addition to fox pr edation, may be affecting production and survival of pr ey, • predator–prey interactions. for example food supply or quality; mortality ‘Animal welfare is an essential due to drought; disease and parasites; or consideration of any control mortality due to other pr edators such as feral program.’ cats, birds of pr ey, reptiles and poachers. For example, in a study of the survival of Mapping may be an important step in translocated malleefowl chicks to Y athong determining and r ecording the relationship Nature Reserve, food was identified as a between variables (Section 7.4.3). limiting factor (Priddel and Wheeler 1990). Consideration of animal welfar e issues This study suggests that, given adequate should be an integral part of any feral animal protection from foxes, the chicks would management plan, including foxes. ANZF AS ultimately starve. Conversely, given considers that the curr ent approach to feral adequate food and no pr otection from foxes, animal management, namely the ad hoc, chicks would be pr eyed upon. opportunistic options based on short-ter m reduction in populations ar e inappropriate. Therefore several factors besides fox They consider that a well planned and predation may limit pr ey response. coordinated strategy, as advocated in these Furthermore, failure of prey populations to guidelines, is likely to be mor e humane in respond to predator control does not the longer ter m. exclude fox predation as a limiting factor . Complex factorial experimental designs, 8.4.4 Performance indicators where feasible, may be necessary to r esolve 8 multiple limiting factors and modelling based on such experimental testing may be Conservation valuable for investigating pr ey population For conservation values, the best dynamics under dif ferent fox management performance indicator for fox management strategies (Pech et al. 1995). Alter natively, is a sustained incr ease in numbers of sequential management of likely limiting endangered or vulnerable species. Likewise, factors might be possible. Per formance may in the case of translocations, the best need to be measur ed over long periods indicator is the successful establishment of before a positive r esponse is evident. For translocated or intr oduced fauna followed example, with malleefowl per haps only by a sustained incr ease of the population. occasional years provide sufficient food for recruitment.
Bureau of Resource Sciences 93 Agriculture the effectiveness of the contr ol strategy or modify the objectives as necessary. Performance indicators for agricultural production are both straightforwar d and short term. Where fox predation is shown to be a 8.6.1 Operational monitoring limiting factor, lambing percentages, and Operational monitoring aims to assess the hence net income, should immediately efficiency of the contr ol operation, to improve on previous years’ production with determine what was done, wher e and at what effective fox control prior to lambing; and cost. Most states and territories have should continue to impr ove where longer developed, or ar e developing, Pest term or sustained management is Management Information Systems (PMIS) implemented. The only wor d of caution her e which can assist land managers, whether is that allowances may need to be made for government or private, to monitor other factors influencing pr oduction before management operations both for operational and after fox contr ol. These include variation and performance monitoring (For dham 1991). in seasonal conditions. Wher e fox management does not lead to incr eased lambing percentages (criteria for failur e), other 8.6.2 Performance monitoring causes of low lambing per centages should Performance monitoring aims to assess the be considered, such as poor ram fertility. effectiveness of the management plan in Rapid recolonisation by foxes may also be meeting the objectives of the pr ogram. reducing the ef fectiveness of fox contr ol. Performance monitoring begins when it is suspected or assumed that foxes ar e causing 8.5 Implementation significant environmental or agricultural impact. Implementation of fox management is The primary management objective is the described in Chapter 9. The value of the gr oup reduction to an acceptable level of fox damage. approach to pest management has been Therefore, the index monitor ed to assess the discussed in detail in the earlier guidelines effectiveness of the fox contr ol program should for rabbits (Williams et al. 1995). The gr oup be the r esponse of the pr ey species targeted approach requires local community support, for protection (Section 7.2). This may take based on an understanding of the damage several years to achieve, particularly in r elation foxes cause and how it can be addr essed. The to population recovery in native species. group approach fosters a str ong sense of Performance monitoring allows for the ef fec- ownership of the management plan, and tiveness of the pr ogram to be evaluated and successful management which satisfies all modified where required, or to identify the participants. need to set new objectives and per formance indicators. 8.6 Monitoring and Achievement of management objectives evaluation should be qualitatively assessed based on ‘Performance monitoring is performance indicators. Dispersal may soon critical to ensure management negate the benefits of localised fox contr ol thus programs remain focused on necessitating expansion of the management the cost-effective reduction of area. In the case of lamb pr edation, the cost fox damage.’ of fox contr ol needs to be economically justified in ter ms of increased lambing rates. Operational monitoring and per formance Evaluation techniques need to take all of these monitoring (evaluation) are often forgotten factors into account. but essential aspects of implementing a management program. Both pr ovide Where practicable, knowledge of the dis- information which can be used to impr ove tribution and relative abundance of foxes
94 Managing Vertebrate Pests: Foxes helps to plan the management pr ogram within the Grampian Ranges of V ictoria. (Section 8.4). However, estimation of these Throughout the park, containing mostly dry parameters is very dif ficult and a land manager sclerophyll forest, are a number of granite may have to r ely on crude estimates or outcrops which ar e known to harbour the assumptions based on experiences elsewher e. threatened brush-tailed rock-wallaby (Petrogale penicillata). Other important native species In conservation ar eas, performance including the souther n brown bandicoot assessment of the management pr ogram (Isodon obesulus) and spotted-tailed quoll depends on comparisons of census estimates (Dasyurus maculatus) also occur. Foxes and of the pr ey species carried out befor e and feral cats are commonly sighted while rabbits following the implementation of pr edator predominate in more open ar eas. The park is control. In general, if the fox is the primary surrounded by agricultural land consisting of limiting factor, as appears to be the case for grazing, crops and open woodland most of some Western Australian marsupials, the which tends to be rabbit-pr one. methods need not be sophisticated or sensitive because census estimates or indices, befor e Information collected as part of the and after a suitable period of fox contr ol, are preparation of a management plan for the park markedly different. suggested that rock-wallaby populations were significantly smaller than might be expected Irrespective of how management is from historical records. The pr evious wide- evaluated, for example r eductions in fox ranging distribution of the species signified population, increases in distribution and that it might be an adaptable generalist, apart abundance of native pr ey species or incr eased from its preference for rocky terrain, yet its lambing rates, monitoring pr ograms should: numbers had declined drastically thr oughout • consider the use of equivalent non-tr eatment its range with many r ecent population areas to compar e the effectiveness of the extinctions. Studies of similar species indicate management program; that fox pr edation is likely to be a major factor in population decline. • consider changes in the parameter being assessed over time, that is, immediately before and after contr ol and then annually 8.7.2 Defining the problem or more frequently if r equired; In response to these observations, the Parks • use measurement indices and r ecording and Wildlife Service launched a pr eliminary procedures that ar e standardised to enable investigation of all r ock-wallaby populations comparisons over time and between within the park. These censuses pr ovided different habitat types; the following information: • use methods that ar e compatible with the • the populations wer e small and declining; resources and skills available to the land three sites supported less than ten manager; and individuals; 8 • include as many between-site comparisons • the populations were confined to ar eas as resources allow. where the rocks were fragmented for ming break-aways which provided protective 8.7 Hypothetical example of cover from environmental and predation strategic management at stresses while lar ger areas of suitable local and regional level habitat were not being used; — conservation • Brush-tailed rock-wallaby hair was found 8.7.1 Scenario in two fox scats taken fr om the area; • periodic assessments revealed that there This hypothetical case study is set in a 3000 was no population gr owth even though hectare national park such as might be found
Bureau of Resource Sciences 95 most females wer e carrying pouched 8.7.3 Management plan young. Recruitment was low and the age structure consisted of pr edominantly Management objective mature animals; The extent to which fox pr edation affected • there was little or no evidence that the rock-wallaby densities, although not known, wallabies were subject to sever e physi- was considered to be significant. Pr oviding ological stresses. Weight losses wer e they were able to utilise additional habitats minimal and body condition was good in the absence of fox pr edation, it was decided even during a dr ought-declared year; and that a r ealistic objective was to incr ease rock- wallaby density within the park by 400% over • there was no evidence of disease. the ensuing four years. The primary The preliminary survey indicated that the performance indicator would be an incr ease conditions seemed favourable for in the r ock-wallaby population derived fr om population growth, yet there was none. continued rock-wallaby census. The need to Observed was a population of fit and have all adjacent land managers participate in healthy animals unaffected by physiological a parallel rabbit and fox management pr ogram stresses or shortages, pr oducing young and was identified as a supplementary objective. therefore possessing potential for gr owth, but population growth was essentially static. Management options Clearly there was an unknown sour ce of mortality preventing population gr owth. By Strategic, sustained fox management (Section inference it was concluded that foxes wer e 8.4.2) was considered to be the most feasible the greatest threat to rock-wallaby conser- option within the park if r ock-wallabies were vation. Other limiting factors may have to re-establish. Local eradication, while the existed such as the lack of an essential preferred option, was not r ealistic in the habitat requirement. However these could absence of exclusion fencing ar ound the not be revealed unless the thr eat of perimeter of the park. W ith limited resources predation was first r emoved. It was ther efore in surrounding agricultural land, strategic fox decided that a fox management pr ogram and rabbit management in this ar ea was the should be implemented within the park. appropriate choice. Similarly, strategic rabbit The implications of this decision also needed management would be carried out within the to be considered in association with fox park. predation on rabbits and the potential of reinvasion by foxes fr om surrounding agri- Management strategy cultural land. Sustained 1080 baiting pr ograms have proven Removal of foxes could r esult in an to be the most ef fective means of r emoving increase in rabbit densities within the park the impact of fox pr edation in conservation which could in tur n encourage greater areas (Kinnear et al. 1988). The techniques inward dispersal of foxes to r eplace those used to prepare and deliver baits for this removed. Similarly, the contr ol of foxes in purpose can depend on local legislative areas surrounding the park in or der to requirements (Section 6.2). In V ictoria, for establish a low fox density buf fer zone could example, baits must be buried to a depth of see an increase in the alr eady significant at least 8–10 cm. This r equirement is partly agricultural impact by rabbits. The pr oblem to protect non-target species such as the tiger was therefore defined as being not only one quoll which is susceptible to 1080 baits laid of fox management within the park, but indiscriminately. Similarly, wher e agricultural also one of needing to involve adjacent land land is involved, far m dogs need to be managers in parallel rabbit and fox contr ol protected. Baits can be pr ovided as either activities, especially in the buf fer zone of dried meat or pur chased as a manufactur ed 20 kilometres around the park boundary. product. Sustained management of foxes
96 Managing Vertebrate Pests: Foxes requires regular and continuing poisoning ‘Park management should of foxes for the for eseeable future. To what work cooperatively with extent this can be maintained depends on neighbouring landholders to available resources. protect conservation values ‘Sustained 1080 baiting is the and reduce agricultural most effective strategy for impacts.’ reducing fox impact in The entire park is the unit for fox conservation areas.’ management. Mapping of tracks and trails within the park will serve as a useful guide In this example, it was decided that baiting to bait placement and also assist in the frequency should not be less than at thr ee- relocation of baits on a r egular basis so that monthly intervals. This could be supplemented those removed can be r eplaced. The same by den fumigation during the br eeding season applies to neighbouring agricultural land. or by spotlight shooting if time per mitted. Fox Because the latter involves only strategic management on surr ounding agricultural land baiting, mapping and selection of would usually require management ef fort to management units is per haps more be targeted to protect production (for example, important. Previously selected rabbit lambs) at the appr opriate time of the year . management units should be tr eated in order Therefore, it was essential to encourage neigh- of priority. Recolonisation can be minimised bouring graziers to participate in the pr ogram. by treating adjacent management units in From the perspective of pr otecting the park sequence (Williams et al.1995). from reinvasion by foxes, contr ol during the peak fox dispersal period (autumn) would have the gr eatest benefit. 8.7.5 Monitoring and evaluation ‘Rabbit control should be ‘Ineffective baiting programs incorporated into fox may be a result of incorrect management programs.’ baiting techniques, bait- Due to the r eliance of foxes on rabbits, it shyness or fox immigration.’ was decided that the fox management plan The overall ef fectiveness of the pr ogram needed to incorporate a rabbit management will be deter mined by the continuing r ock- strategy. Strategies suitable for rabbit contr ol wallaby census, the desir ed outcome of will be similar for both agricultural and con- which is a significant population incr ease. servation areas. For ar eas of low conservation A factor which might contribute to this is an value, these include r emoval of sur face increase in habitat use by the r ock-wallabies. harbour, destroying warrens by ripping, This should be monitor ed as a per formance followed by r e-ripping or fumigation. The indicator. Failure to ef fectively control foxes use of 1080 poison to contr ol rabbits was could lead to false assumptions being drawn not considered to be an option because of about the ef fect of predation. It would potential non-target effects, particularly therefore be essential to monitor fox density 8 secondary poisoning of tiger quolls fr om within the park (Section 7.3). Possible eating 1080-poisoned rabbits within the park. causes of failur e might include incorr ect baiting technique or bait-shyness by foxes 8.7.4 Implementation and immigration fr om buffer zone. If these problems are identified, management The nature of this pr ogram requires that the techniques will need to be modified. As a park management work cooperatively with useful encouragement to continuing neighbouring landholders. The advantages landholder participation, the impact of fox are twofold: the pr otection of conservation predation on agricultural pr oduction should values and the r eduction of agricultural also be monitor ed (see next case study for impact. an example).
Bureau of Resource Sciences 97 The essential message that has emer ged predators is essential. To take an example, from similar but r eal examples for conser - suppose that food was limiting the density vation agencies and wildlife managers in of an endanger ed mammal that was also particular, is that an exotic pr edator such vulnerable to fox pr edation. If it is assumed as the fox is a major factor in the extinction that food supplements wer e provided there process of many small and medium-sized would be a number of possible outcomes. mammals. Predation keeps population In the absence of pr edator control one may densities precariously low, thus incr easing observe that individuals ar e in a better the risk of extinction fr om other causes. The nutritional state, but with no population fact that a species still persists in an ar ea in increase. Subsequent removal of pr edators the presence of foxes is no guarantee that and the addition of food would r esult in a the species will continue to survive. A population increase. Conversely, predator properly implemented predator removal control alone would not r esult in a program can also r eveal the presence of population increase as food would also be other limiting factors af fecting the limiting. Another example might be that abundance of native species. reduced fox numbers allows an incr ease in rabbit numbers. This could r esult in In Western Australia, predator removal increased competition for food, and by baiting has r esulted in large increases in suppressed population incr ease of a native prey populations. In these instances, threatened mammal. These examples it may be concluded that pr edation is the illustrate how pr edation can confound principal (proximate) factor r esponsible for ecological experiments (and our under - limiting population size, and that the pr ey standing of the factors af fecting wildlife), is existing at levels far below the carrying and conversely, how other limiting factors capacity of the habitat. W ith predation can obscure the potential or actual impact mortality minimised, these Western of predators. Australian populations have incr eased without restraint over a considerable period. Eventually growth will slow and cease when 8.8 Hypothetical example of the carrying capacity of the habitat has been strategic management at reached or as other limiting factors come local and regional level into play. — agriculture Undoubtedly, not every pr edator removal 8.8.1 Scenario program will mirr or the Western Australian response where appreciable increases in This hypothetical case study is based on a prey numbers have been the rule. Given sheep grazing property of about 20 000 that predator control has been adequate, hectares in semi-arid wester n New South there are two possible causes for a less Wales. Paddocks consist of open woodland, spectacular response. It may be due either chenopod scrubland and pastur es of annual to the fact that the species is not vulnerable forbs and grasses. Sheep-carrying capacity to predators, or the carrying capacity of the is 20 per squar e kilometre with the habitat is low due to other limiting factor(s). production of lambs and subsequent sale Priddel and Wheeler (1990) have demon - of surplus stock making up 40% of the strated this in the case of malleefowl (Section landholder’s income. Foxes ar e common as 3.1.2). are kangaroos, feral pigs, feral cats and rabbits. No endangered or vulnerable Clearly, in situations wher e another wildlife species ar e known to occur in the factor(s) is limiting the population gr owth district. A series of good seasons pr oduced of a threatened species, studies will be lamb marking per centages of approximately required to identify the limiting factor(s). 50% on this pr operty which fell below the This may or may not be a simple task but district average of appr oximately 70%. whatever the outcome, the initial contr ol of
98 Managing Vertebrate Pests: Foxes 8.8.2 Defining the problem 8.8.3 Management plan
In an ef fort to identify the possible cause of Management objective reduced lamb production, the landholder compared his operation with neighbouring The available evidence suggested that fox predation may have been causing up to a and more successful properties. Aspects 20% loss in lamb pr oduction. The assessed included stocking rate, pastur e management objective therefore became the condition and timing of lambing, all of which reduction of fox impact thr ough effective can affect a flock’s nutritional status and management using lamb marking hence reproductive performance, as well as percentages as per formance indicators. ram fertility, and blood lines. In all of these Because the landholder was unsur e of the comparisons he could find no dif ferences costs involved in fox contr ol a first year which might be causing his pr oblem. In the objective of a 10% incr ease from the previous season the landholder also previous three-year mean in lamb marking compared wet and dry statistics for one of percentages with effective but low-level fox his larger lambing paddocks with a similar control was set. In the second and thir d paddock on a neighbouring pr operty. In year the objective would be raised to a 20% both cases ar ound 90% of ewes wer e increase with the level of fox contr ol diagnosed as pr egnant; however at lamb adjusted according to the first year r esults. marking the dif ferences were substantial. From this comparison the landholder Management options concluded that lamb loss rather than flock fertility was the primary cause for the lower The only feasible management options wer e number. Few lamb car casses could be found either strategic, sustained or strategic, suggesting that scavenging of dead lambs targeted management (Section 8.4). No fox or predation of live ones was the cause and control or crisis management might also not lack of cover in the lambing paddocks. have been considered. However, because For those carcasses which could be found, the landholder lacked infor mation on the predation was identified as the pr obable cost–benefits of fox contr ol it was decided, cause (Section 7.2.3). as a guide, that some for m of fox management should be undertaken in order The landholder also observed that a small to compare possible increases in net income lambing paddock adjacent to his living ar ea from higher lamb pr oduction. With no prior always produced more lambs per ewe than experience in fox management it was the remainder of the pr operty. This paddock decided that strategic, tar geted management had a constant exposur e to farm dogs and was a more appropriate choice than the humans, and because of attacks on his more resource demanding strategic, domestic poultry, foxes in the immediate sustained management. area were shot on sight. Local shooters had 8 also observed lar ger than normal numbers Management strategy of foxes on the pr operty, particularly in association with sandhills carrying high The local Rural Lands Pr otection Board rabbit densities. With a combination of advised the landholder that poisoning with circumstantial and r eal evidence, the 1080 was the most cost-ef fective fox control landholder discounted feral pigs as a major technique for semi-arid ar eas. Because of factor and concluded that fox pr edation on the difficulty in obtaining fr eshly prepared his property was resulting in a significant baits from the Board office which was impact on lamb pr oduction. Having defined 200kilometres away, the landholder the problem he decided to implement a fox purchased manufactured baits at a cost of management program. $1 per bait.
Bureau of Resource Sciences 99 A targeted baiting program was aimed at as fence lines, tracks and pr operty protecting lambs at birth. This meant starting boundaries where bait trails will need to fox poisoning operations a week befor e be laid. Mapping will also be an aid to lambing commenced and continuing them monitoring bait uptake. through at weekly intervals until no further bait was taken. The r ecommended procedure 8.8.5 Monitoring and evaluation for baiting (Korn and Lugton 1990) was to bury baits at 100–500 metr e intervals along a With virtually no infor mation on the dragged scent trail. Bait application rate in cost–benefits of fox contr ol for agricultural the vicinity of lambing paddocks was 50 baits protection, the landholder should place a per 400 hectares. high priority on monitoring and evaluation. Fox management is too often implemented The landholder was awar e that foxes r ely without hard evidence about losses due to on rabbits as a year -round food source. He foxes. The cost associated with all aspects had also observed dead foxes after a pr evious of the management pr ogram should be rabbit poisoning pr ogram. As a r esult, a carefully tabulated and compar ed with the supplementary objective was undertaken that perceived increase in pr oduction. Where routine rabbit control using 1080 poisoning performance indicators show that the followed by ripping of warr ens would be management program is unlikely to r each conducted throughout the year commencing the objectives, other causes of lamb loss after the next lambing. He also decided to need to be car efully reconsidered. The modify his farming practices by shortening landholder must also consider that strategic, the lambing period as much as possible. targeted fox management was not ef fective and that mor e intensive control may be 8.8.4 Implementation required. Where practicable, fox management for the reduction of agricultural impact should be undertaken cooperatively with adjacent landholders. Apart from obvious cost- effectiveness through benefits from bulk purchases and sharing equipment, this further reduces the immediate pr oblem of recolonisation particularly when strategic baiting aims to pr otect lambs. The selection of management units on a property will depend partly on available resources. One landholder attempting to protect all lambing paddocks equally would necessarily treat the entir e property as a management unit. Where some lambing paddocks are more susceptible to pr edation than others, smaller management units would be necessary with priority given to those at greatest risk. Because it is dif ficult to pr edict the dis- tribution of foxes, mapping is important to identify the location of lambing paddocks, areas of high rabbit density wher e foxes might be concentrated, and featur es such
100 Managing Vertebrate Pests: Foxes 9. Implementing baits permissible for use (Section 6.2), and management of fox the legal status of the animal as a pest. In fact, the only detailed strategies for fox damage management in Australia ar e those in Western Australia for pr otection of native Summary fauna and the national and state contingency plans for eradication of exotic disease. While governments have endorsed the principle of beneficiary pays, it is not always possible to clearly identify the beneficiary, 9.2 Role of governments especially where foxes are causing damage and landholders to both production and native fauna. Commonwealth, state and territory Landcare and similar community-based governments have endorsed the principle groups can provide a useful mechanism in of beneficiary pays (Braysher 1993). The these cases for developing a common difficulty is in accurately deter mining the approach and for determining appropriate beneficiary. For conservation r eserves, it is input of resources. the community, state or national, and they The Commonwealth, states and territories should pay. For agricultural pr oduction the have a number of programs and other landholder is the beneficiary and should initiatives which can help agencies and bear the bulk of the costs. However , the land managers to add to the knowledge of difficulty arises wher e control over and fox damage, to develop better management above what a landholder may r equire to strategies and to help disseminate relevant protect production is necessary to pr otect information. These include the Endangered native fauna. Similar conflicts can occur Species Program, Feral Pests Program, where private land abuts conservation land Vertebrate Pest Program and the Victorian containing pests. In these cases the various Land for Wildlife initiative. interest groups should coordinate to develop common approaches and to deter mine Effective management of fox damage input of r esources. Landcare and similar requires local community support. The community-based groups provide a useful community needs to be aware of and mechanism for this (Braysher 1993). understand the damage foxes cause and how it can be addressed. Techniques for ‘Most states and territories achieving this include brochures, field days, provide a fox management public addresses and pilot projects to advisory service.’ demonstrate the effective strategies. Most states and territories pr ovide an advisory service for managing foxes and 9.1 Introduction other pests. They can also assist with preparation of poisoned bait, but in many Historically, the management of fox damage parts of Australia this has been poorly in Australia has r elied mainly on sporadic coordinated. Government programs to control of foxes at the local level with little manage fox damage have, in general, been or no infor mation about the associated costs confined to national parks and natur e and benefits. Although widespr ead bounty reserves in order to pr otect native wildlife. 9 schemes have operated in the past ther e has Where fox management is also essential on been no r eal attempt to assess their value. surrounding cropping or pastoral land, Based on overseas experience bounties ar e government usually takes the lead in not an effective method for pr eventing fox organising the control and supply of poison damage (Whitehouse 1977). Existing (see Example 2, Braysher 1993 for the legislation related to fox management Murray Mallee of South Australia). applies largely to the types of poisons and
Bureau of Resource Sciences 101 ‘Government programs to in the past but with the cr eation of the Feral manage fox damage have Pests Program (FPP) in 1992–93, most feral generally been confined to animal projects were transferred to the new national parks and nature program. reserves.’ • Vertebrate Pest Program (Bureau of The Commonwealth Gover nment has a Resource Sciences) (see Introduction). number of programs which can assist in There are also initiatives at the state and managing foxes and other pests. Generally, territory level with r espect to br oader imple- the Commonwealth encourages studies mentation of fox management strategies. In which add to the knowledge of fox damage Victoria, for instance, fox contr ol is being to wildlife and to the development of promoted as an activity for LandCar e groups. suitable control strategies. Those that ar e The Department of Conservation and relevant to fox management ar e: Natural Resources has joined with private • Feral Pests Program (ANCA) — This industry in a ventur e to pr ovide a shelf-stable program aims to develop and implement fox bait for poisoning (Foxof f® — Applied projects in cooperation with other Biotechnologies). Schemes to pr omote the Commonwealth authorities and state and value of private far mland as wildlife habitat territory agencies to r educe the damage such as Land for W ildlife in Victoria may caused by feral animals to native fauna also help implement fox contr ol measures. and/or the natural envir onment, particu- larly in ar eas important for the r ecovery of 9.3 Use of community endangered species. Foxes, feral cats, feral goats and rabbits ar e given priority as these groups are listed as key thr eatening processes In the past, most fox management work under the Commonwealth Endangered has been conducted either by gover nment Species Protection Act 1992. agencies (on public land) or by individual • States Cooperative Assistance Program farmers (private land). Almost all of the (ANCA) — The aim is to develop natur e management has involved either poisoning conservation projects of national or inter - or shooting and, generally speaking, the national significance in cooperation with operation has been a r eaction to perceived the states and territories. Elements of the damage rather than a pr eventative measure program include wetlands conservation, taken in advance. conservation of migratory species and Although community fox drives have control of environmental weeds. been a longstanding tradition in some rural Additionally, the program covers education communities, such initiatives ar e based more and extension for the br oader area of on social and sporting outcomes rather than management and maintenance of biodi- upon a clearly defined aim to r educe fox versity, and as such does not pr eclude numbers for some economic or envir on- investigations of fox pr edation. mental objective. • Endangered Species Program (ANCA) — Given our knowledge of the movement This program aims to ensur e that of foxes and their ability to quickly r ecolonise endangered and vulnerable species and small cleared areas, it is evident that small ecological communities can survive and and sporadic r eactive operations are unlikely flourish, retain their genetic diversity and to give long-ter m respite from damage. Cost- potential for evolutionary development in effective management of fox damage, their natural habitat, and to pr event further especially to pr otect vulnerable wildlife, is species and ecological communities fr om likely to r equire control operations which becoming endangered. Foxes have been cover relatively large areas so that immigration one of the priority ar eas for this pr ogram can be confined to buf fer zones on the
102 Managing Vertebrate Pests: Foxes perimeter of the tr eated area. Implementation sheep on neighbouring pr operties. Here, of such management r equires coordinated there is generally little dispute r egarding the effort across the area to be tr eated. responsibilities of the dog’s owner — they ‘Sporadic and small-scale are expected to either r emove or destroy control operations are unlikely the offending animals. With foxes pr eying to provide long-term respite on lambs, no such clear r esponsibilities exist. from fox damage.’ One farm running cattle, for example, may provide suitable cover for lar ge numbers of The importance of gr oup action for the foxes which then kill lambs on a neigh - effective management of fox damage needs bouring sheep far m with few or no r esident emphasis. Based on experience with the foxes. group approach to rabbit management, Unlike the damage caused by many other groups should be r elatively small, involving pests of agricultur e or the envir onment, that 10–50 landholders. Wher e the nature of the caused by foxes to wildlife may not be fox problem or the land type/land use varies immediately evident. Very often, decline in markedly within a lar ge target area, it is wildlife populations is slow and insidious in advisable to consider the for mation of sub- nature. In a situation wher e the damage has groups such that each smaller gr oup shares been incremental over a very long period of a common approach and a common goal. time and, mor e particularly, wher e it is Most importantly, the impetus for for mation exacerbated by other factors, land managers of a gr oup should come fr om the community can often fail to per ceive the true natur e of itself and not fr om the pest contr ol authority. the problem. Indeed, as pointed out in other It is the function of the latter to encourage sections of this document, the measur ement and facilitate gr oup formation but not to of fox damage can be dif ficult. Even in the impose it such that local landholders will case of fox pr edation on lambs, r ecent have no real sense of ownership of the studies (Section 3.2.1) suggest that simple problem or of the pr oposed solution. examination of lamb car casses may not give ‘Control operations which an accurate measure of total losses to foxes. cover relatively large areas are required to protect vulnerable ‘Fox impact on wildlife affects wildlife.’ the whole community — not just those who actually own or It is important that the damage caused occupy the land.’ by foxes is seen as a community pr oblem — Thus, one of the first r equirements for not a pr oblem to be solved by gover nments successful group action is a general or the next-door neighbour . In this context, knowledge of the local impact or at least it is necessary to pr omote the fact that suspected impact of fox pr edation in the community ownership involves mor e than district. Following this, the gr oup will need just the landholders themselves. Under the some appreciation of the scope and principle of beneficiary pays, fox damage magnitude of the task ahead, particularly the to wildlife, for instance, is a cost to the whole fact that it is likely to r equire a long-ter m community, not just those who actually own commitment to management activities. or occupy the land. Mapping of the ar ea is perhaps the simplest Part of owning the pr oblem can be way to convey this infor mation. As an 9 explained or pr omoted in ter ms of an example, many LandCar e groups put together individual landholder’s responsibility to composite aerial photographs of their territory, neighbours. It is generally accepted that no and by using overlays, deter mine various person has the right to inter fere with a classes of habitat or far ming country at risk. neighbour’s legitimate business. This is Some of these gr oups are now showing easily demonstrated in say, the case of interest in digitised mapping and linking marauding farm dogs which begin killing
Bureau of Resource Sciences 103 into a computerised GIS. This appr oach has fox management. Examples of how a considerable potential for it can community group might coordinate fox accommodate an enormous amount of management would include some or all of useful information. Maps can be pr oduced the following: at any required scale and the particular • surveys designed to identify the location features shown on those maps can be varied and abundance of wildlife species at will (Section 7.4.3). For instance, a fox considered to be in decline and known to management group may require a map be preyed upon by foxes; which combines a particular vegetation type (for example, dense bush or high tussocks • initial survey to deter mine the magnitude which may be favour ed refuge areas for of lamb losses to pr edation in the district; foxes) with cadastral infor mation and • routine spotlight transect counts or other information on the local distribution of measures designed to give some general wildlife species considered to be at risk due index of fox abundance; to fox predation. One of the major benefits of this approach is the ability for individual • planning and execution of a coordinated land managers to supply infor mation to the campaign of bait-laying such that lar ge data bank and to get back fr om the system areas of country ar e treated on a grid basis; detailed maps of individual far ms showing • where applicable, identification of fox den the features required. The landholder, under sites on local maps so that subsequent these types of mapping schemes actually fumigation of dens in the br eeding season becomes the provider as well as the r eceiver can be conducted in the r elevant areas; of the mapping infor mation. and ‘The impact of foxes on wildlife may not be immediately • where applicable, the inclusion into local evident.’ maps of known lay-up points for foxes such as swamps, thickets and bracken One of the major pr oblems associated patches. with the implementation of fox management strategies is deter mining the level of contr ol 9.4 Community awareness activity required to produce some measurable and stable r esponse in the It is clear that the issue of har mful predation chosen indicator wildlife species. In fact, it by both foxes and cats is now r eceiving will require that those implementing fox much more attention in the media and that management gain some skills in measuring community awareness in this particular ar ea the responses of particular pr ey populations. is increasing. Feral and wild pest animals This is likely to be a dif ficult task and one and their impact upon the Australian where assistance fr om expert staff in the environment are now popular school essay wildlife management authority will be topics or school pr ojects and more and required. more media attention is being given to the Landcare and similar community-based problem. groups offer an ef fective mechanism for ‘Community awareness identifying common objectives for programs usually concentrate management and to coor dinate action across on problems rather than a region. Most groups use a catchment- possible cures.’ based philosophy and no longer think in terms of single far ms. Many are now also Nonetheless, current community involved in detailed mapping and the awareness programs often tend to collection of other data such as infor mation concentrate on perceived problems rather on native flora and fauna. These databases than providing a detailed analysis of the are useful for planning and implementing actual problem including identification of
104 Managing Vertebrate Pests: Foxes all major causes. W ildlife management programs should not be pr omoted unless authorities and those concer ned with either good — or at least cir cumstantial — vertebrate pest management need to foster evidence is available to implicate the fox, informed debate on the impacts of or evidence by way of infer ence from other predation, including fox pr edation. This studies strongly suggests the involvement would involve explaining what we know of foxes in some har mful predation. For of predator–prey relationships and such example, the continued existence of a small information as the dietary range of the and remnant colony of r ock-wallabies in the predator and other aspects of its biology Victorian Grampians might r easonably be which have some bearing on management. thought of as being at high risk to fox predation based on the fate of similar Effective management of fox damage in isolated rock-wallaby colonies in Western any area that covers a mix of land uses will Australia, where effective fox contr ol led to require local community support. T o achieve a dramatic rise in population size of the pr ey. this the community needs to be awar e of and understand the damage that foxes cause and how it can be addr essed. Currently in rural communities it can be expected that attitudes toward foxes will range fr om indif- ference to the belief that they ar e the primary cause of lamb loss or wildlife decline. ‘Fox management requires local community support.’ A variety of techniques ar e available to assist information transfer and adoption of appropriate practices. These include brochures, media releases and public addresses which target the r elevant audience. Probably one of the most ef fective education tools is the establishment of small demonstration projects that involve the relevant community in the damage assessment, planning and implementation of the management pr ogram. Braysher (1993) outlines an example of such a pr ogram between the South Australian National Parks and Wildlife Service and the local far ming community to conserve malleefowl in theSouth Australian mallee. First-hand involvement is often a str ong motivating influence to undertake appr opriate action. Finally, in fostering community awar eness of the pr oblems caused by foxes in Australia 9 (particularly in the ar ea of wildlife conser - vation), it is important to discer n between perceived problems and actual pr oblems. Actual wildlife benefits of fox management are known, although only for a limited number of species in a limited range of habitats. Given this, major management
Bureau of Resource Sciences 105 10.Deficiencies in current 10.1 Introduction knowledge and It is clear that mor e information is r equired approaches to determine the significance of fox predation in Australia and, mor e specifical- Summary ly, to define and impr ove techniques for minimising this damage. Until r elatively Apart from the relatively recent studies in recently, the fox has not been a species that Western Australia, quantifiable information has attracted widespread interest in on the damage foxes cause to native fauna Australia. Apart from studies in V ictoria is lacking. While there is good reason to believe (Newsome and Coman 1989) and r ecent that foxes are having similar impact in other work in Western Australia, research on the parts of Australia, control strategies cannot fox has been sporadic. In contrast, it has be planned without reliable data. The iden- been extensively studied in Eur ope and tification of the range of species at risk is an North America because the fox is a major area where reliable information is needed vector of rabies. Since Australia is rabies both in relation to predation by foxes and free, and because for some time the fox was competition between foxes and native wildlife. not perceived to be a conservation pr oblem There is also reason to believe that the or a significant thr eat to primary pr oduction, economic losses due to lamb predation by there was little incentive to study the animal. foxes may be greater than previously thought. Recently this attitude has changed con- Studies are required to quantify the losses. siderably due to the gr owing information about the thr eat foxes present to native fauna. Although a number of techniques can be As a r esult the Commonwealth is supporting used to minimise the harmful impact of foxes, large-scale research programs on biological there has been relatively little scientific control of foxes in Australia (Section 7.5.7). assessment of these techniques. With However this r esearch is long-term and high- poisoning, for instance, much more risk, and even if this biological contr ol information about the required baiting approach is successful, mor e conventional intensity and frequency, the timing of the techniques will still be needed. Considerable poisoning operation, the best toxin to use and work is r equired to improve the efficiency the likely impact on animals is needed. and effectiveness of these techniques. Likewise with den fumigation, there is a need for more humane and effective fumigants. The Commonwealth, through ANCA, is In the case of exclusion fencing, now used also supporting research programs on con- in a number of important recovery programs ventional techniques. A major r esearch program is under way in W estern Australia for endangered species, little scientific work involving the Western Australian has been conducted on the cost-effectiveness Department of Conservation and Land of various designs. Management and the APB of W A with There are a number of deficiencies in non- financial support fr om Alcoa. The r esearch technical aspects of managing fox damage is aimed at deter mining the most appr opriate that can be improved. These include wide baiting regime when 1080 is used for fox variation between states and territories in control over large areas of conservation thestatus and requirements to manage estate. Specific aspects being addr essed are: foxes,poor organisation and coordination • assessing the effectiveness/conservation of management programs, the lack of a value of buf fer zones of 1080-baited agri- community or district approach, and a cultural land abutting conservation estate; general failure to communicate to the general public the scope and nature of the fox problem • determining the level of 1080 bait uptake or potential problem in Australia. in forested areas;
106 Managing Vertebrate Pests: Foxes • estimating fox densities in lar ge areas of Consequences forested conservation estate; and It would enable sensible and ef ficient • assessing the effectiveness of different 1080 allocation of scarce management r esources baiting frequencies when applied to lar ge so that fox management or exclusion is tracts of forested conservation estate. limited to those species or particular habitats where predation is a definite thr eatening 10.2 Specific deficiencies process.
10.2.2 Improvements to baiting 10.2.1 Understanding predator–prey techniques relationships
Developments required Developments required Chief amongst these is the need to deter mine A more thorough understanding of the r ela- the appropriate intensity, frequency and tionship between the fox and its pr ey is timing of baiting in much the same way as needed. In particular, questions regarding has been done for rabbit baiting in Australia. the impact of foxes on vertebrates other than This entails such elements as the number mammals requires investigation. This must of baits per hectar e, the number of baiting include a better understanding of the way episodes needed per year and the most in which other pr ocesses of extinction (the suitable times to carry out such baiting destruction of wildlife habitat for example) exercises. These aspects ar e now being impinge upon pr edation and vice versa. A addressed by the ANCA-funded r esearch in related area is the important question of the Western Australia. role of rabbits in maintaining high fox populations, and the possible incr eased ‘The appropriate intensity, predation pressure on wildlife when rabbit frequency and timing of populations suddenly collapse due to factors baiting needs to be such as myxomatosis or an ef fective rabbit determined.’ poisoning program. The relationship The other important aspects of baiting between fox density and impact on pr ey requiring further r esearch are the pr esenta- populations also needs to be quantified. tion of the bait, the choice of toxin and the Another significant question is whether cats possible non-target effects of the technique, will replace foxes as wildlife pr edators if fox particularly associated with fox caching populations are reduced. These develop- behaviour. With bait pr esentation, some of ments are of fundamental importance, and the factors r equiring work include bait until there is more precise knowledge of the preference trials, particularly to cover possible consequences of fox pr edation, seasonal changes in fox diet, optimum size management of foxes or fox damage will of baits, the value of burying baits, the value always include a lar ge degree of speculation. of lures and, importantly, the biodegradability ‘A greater understanding of the of the bait-toxin combination. relationship between the fox and its prey is needed.’ The issue of multiple bait take and the ultimate fate of all r emoved baits also r equires Wildlife management agencies need further research. It is common at the more information on the benefits to wildlife beginning of a baiting pr ogram to have lar ge of fox contr ol. The adaptive management numbers of baits r emoved, disproportionate approaches used in Western Australia need to the expected number of foxes. If surplus to be trialled in other ar eas and for other baits are cached by foxes and r emain uneaten 10 species. there is a potential risk to non-tar gets.
Bureau of Resource Sciences 107 Choice of toxin is an issue in some ar eas fumigation can be used as part of an where use of 1080 is not advisable. In integrated program to control foxes. The general terms, 1080 must be r egarded as the two fumigants currently being used for most effective toxin currently available for rabbit fumigation in Australia have a the Canidae although cyanide could be number of shortcomings, chief of which is considered more humane. Experiences with the fact that they cannot be demonstrated the use of cyanide baits for r esearch work to cause humane death. One possible in Western Australia suggest that this toxin alternative, which should be consider ed as is both highly ef fective and humane. Further a den fumigant, is carbon monoxide, since studies on the safety to human operators, it is generally believed to be a humane and non-target effects and how best to use this effective fumigant when used corr ectly. toxin are required. Since fox contr ol in urban Allied with the use of den fumigants is and semi-urban areas is a gr owing issue, the possibility of using the tarbaby technique some attention to the development of a safe at entrances to the br eeding dens (Ryan and bait for urban foxes is warranted. In all ar eas Everleigh 1975). This technique is worth of baiting research, the possible non-tar get investigation since it would ensur e that any effects of the technique must be consider ed. fox visiting the den, but not necessarily Further investigation is needed to impr ove living with the cubs, would be exposed to the selectivity of the bait/toxin combina - the mixture of toxin and gr ease. However, tions and their methods of deployment so this technique may have some pr oblems of that other wildlife species and domestic target-specificity. animals are not put at risk.
Other important factors to be consider ed Consequences include: Increased control options for foxes, • the effect of long-term reliance on poisons particularly in ar eas where poisoning is not to suppress fox populations in inducing advisable. May provide a mor e humane neophobia and bait-shyness. Ther e may technique for fox destruction. already be evidence for these develop- ments in dingoes (D. Ber man, CCNT, pers. comm. 1994); 10.2.4 Fox-proof fencing and other barriers • the frequency and intensity of baiting in relation to the size of the ar ea treated; and Developments required • the use of buf fer zones and variations in baiting regimes in dif ferent habitats. With increasing concerns about predator impacts on thr eatened mammals in Australia, emphasis has been placed on the concept Consequences of predator-proof enclosures as a means of Improved efficiency and target-specificity of arresting the decline in some endanger ed fox baiting. More humane control of foxes. species. An example is the easter n barred bandicoot in Victoria. 10.2.3 Improved den fumigants A considerable investment has been made in predator-proof fences, and their ef fec- tiveness has r ecently been reviewed (Coman Developments required and McCutchan 1994) (Section 7.5.5). The Den fumigation, although used widely for main issue concerns its cost-ef fectiveness. fox control in Europe, has rar ely been used It is possible, using existing fence in Australia. With the curr ent interest in technology, to pr oduce designs which ar e community land management initiatives effective against foxes. However the cost of such as Landcare, it may well be that den such fences is usually pr ohibitive, and many of the designs, particularly those employing Examples of how public awar eness of energised wires, suffer from maintenance these problems or potential pr oblems might problems. be raised include the pr ovision of a well- presented textbook on intr oduced predators The evaluation of fencing thus involves in Australia and the inclusion or incr eased a matrix of the following: initial costs, emphasis in school curricula of infor mation maintenance costs, expected life, ease of outlining the har mful impact of foxes. erection, degree of effectiveness, suitability Current community awareness programs for rough terrain, dangers to other wildlife, tend to concentrate on per ceived problems and wildfire hazards. This matrix of factors rather than a detailed analysis of the issue then needs to be assessed in r elation to including identification of all major causes. other methods for pr otecting wildlife from predators, such as the cost-ef fectiveness of controlling predators rather than simply Consequences preventing their access. An example is the An informed public, particularly in rural successful use of fox poisoning by Kinnear areas, will be better able to understand the et al. (1988) in W estern Australia. nature of fox pr edation on livestock and wildlife and to carry out ef ficient and target- Consequences specific control measures. The most suitable and cost-ef fective designs for fox-proof fences can be deter mined for 10.2.6 Ecology various types of terrain and habitat. This will be of considerable importance in the Deficiency management of some vulnerable, endanger ed or locally endanger ed wildlife species. Relatively little is known on the ecology of the fox in Australia (Chapter 2). Ther e is a lack of infor mation in key ar eas such as 10.2.5 Fostering public awareness regional differences in behaviour, reproduc- tive potential, mortality factors, and movement Deficiency and responses to culling. Ther e is also an absence of accurate data on population The damage caused by pest animals in densities, attributable in part to a lack of Australia has r eceived relatively little publicity reliable census techniques. The importance compared with other envir onmental of this pr oblem ranges from the necessity to management issues such as tr ee decline, monitor the presence of very small numbers salinity and the gr eenhouse effect. In part, this of foxes in ar eas where previously they might lack of public understanding of the pr oblem have been absent, to high densities of foxes reflects a dearth of scientific knowledge where the impact on native species needs to regarding the level and severity of pr edation be assessed. and other negative aspects of foxes. Nonetheless, sufficient knowledge of the The potential role of the fox as a competitor potential of fox pr edation to cause significant of native wildlife is poorly understood. This damage, particularly in endanger ed species information is needed to pr otect native species recovery programs, is available to pr omote a that may be at risk thr ough competition with much wider discussion and community foxes (Section 3.1.7). involvement in the pr oblem. There is also, from the European experience, a good idea Consequences of the potential significance of wild foxes as vectors for some strains of the rabies virus. With better ecological infor mation, it will be 10 Both of these negative values of foxes r equire possible to develop mor e specific fox much wider exposur e to the public. management strategies in dif ferent regions
Bureau of Resource Sciences 109 and environments. It will also considerably between the various states and territories benefit the preparation of contingency plans (Section 6.2). Historically, the administrative for fox management in the event of an exotic procedures set in place to deal with fox disease outbreak (Chapter 4). predation arose almost entirely from a con- sideration of the animal as a pr edator of 10.2.7 Organisation of livestock. With a gr owing realisation that fox management programs predation is heavily implicated in the decline of some native species, a r eview of the legal status of the animal is now timely. As far as Deficiency practicable, legislation at state and territory At present, much of the management of fox level should be consistent so that ther e can damage in Australia is r eactive and be a national focus on the pr oblem. The conducted by individual landholders. Ther e Victorian Flora and Fauna Guarantee Act is relatively little emphasis on lar ger-scale 1988 and the Commonwealth Endangered coordinated programs. If any r eal and lasting Species Protection Act 1992 are the exceptions. gains are to be made, it will be because fox In particular, the requirement to pr epare and management is viewed in much the same implement Threat Abatement Plans under the way as rabbit contr ol — viz. the key to Endangered Species Protection Act is a major success being large-scale management advancement in the initiation of strategic fox programs involving groups of landholders management. A concer n with these Acts is or even whole districts. As is the case with that they pr ovide no guidance to the scale and rabbits, recolonisation of small, clear ed areas pattern of management operations which ar e is likely to be rapid. Another important necessary to address a thr eatening process. deficiency in organisation is the lack of Such a scale could range fr om highly localised measurable goals in ter ms of reducing fox to national. Without careful consideration the damage and of benchmark data on which pattern and demand on r esources could to gauge progress towards any such goals. become disproportionate to the distribution Indices or measures of changes in important of key endanger ed species. Guidelines for the indicator species are required. selection of scale and patter n of actions within ‘The best approach is large- Threat Abatement Plans should be pr epared scale fox management by relevant agencies. The pr ocess adopted by programs which coordinate the Department of Conservation in New groups or even whole districts Zealand for Himalayan thar , possums, and of landholders.’ feral goat control is a useful guide (New Zealand Department of Conservation 1993,1994,1995). Consequences Closely allied to the need to r eview Fox management will change fr om being a legislation is the need to ensur e that adequate sporadic and remedial technique carried out attention is given by the r elevant vertebrate by individual land managers to one which pest control authorities to extension and integrates the control process over larger training in the management of pr edator areas and achieves some lasting gains in a damage. This is particularly so for V ictoria cost-effective and measurable manner. and Tasmania, where there are major recent changes in the management of pests. Any 10.2.8 Legislation and move to use exter nal contractors for pest administration control operations when they wer e previously performed by vertebrate pest agencies, must Deficiency ensure that standar ds are maintained and that It is clear that the administrative pr ocedures the availability of trained operators is not and legal status of foxes varies considerably diminished.
110 Managing Vertebrate Pests: Foxes Consequences A more rational and mor e uniform set of legislative procedures to deal with the problems caused by fox pr edation. Improvements in the dissemination of information related to fox management strategies.
10
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Bureau of Resource Sciences 121 Rolls, E.C. (1969) They All Ran Wild. Angus Sargeant, A.B. (1978) Red fox pr ey demands and Robertson, Sydney. and implications to prairie duck Rosatte, R.C., Power, M.J. and MacInnes, C.D. production. Journal of Wildlife (1991) Ecology of urban skunks, raccoons Management 42: 520–527. and foxes in metr opolitan Toronto. Pp. Sargeant, A.B., Pfeifer, W.K. and Allen, S.H. 161–167 in: L.W. Adams and D.L. Leedy, (1975) A spring aerial census of r ed foxes eds, Wildlife conservation in metropolitan in north Dakota. Journal of Wildlife environments. National Institute of Urban Management 39: 30–39. Wildlife, Columbia, USA. Saunders, G.R., White, P.C.L., Harris, S. and Roughton, R. and Sweeny, M. (1982) Rayner, J.M. (1993) Urban foxes: food Refinements in scent station methodology acquisition, time and ener gy budgeting for assessing tr ends in carnivore of a generalised pr edator. Symposia of populations. Journal of Wildlife the Zoological Society of London 65: 215– Management 46: 217–229. 243. Rowley, I. (1970) Lamb pr edation in Australia: Schneider, L.G. and Cox, J.H. (1988) incidence, predisposing conditions, and the Eradication of rabies thr ough oral identification of wounds. CSIRO Wildlife vaccination: the German field trial. Pp. Research 15: 79–123. 22–38 in: P.P. Pastoret, B. Brochier, I. RSPCA (1985) Incidence of cruelty to wallabies Thomas and J. Blancou, eds, Vaccination in commercial and non-commercial to control rabies in foxes. Office of the operations in Tasmania. Unpublished report official publications of the Eur opean to the Australian National Parks and W ildlife Communities, Brussels. Service. RSPCA Australia, May 1985. Schneider, L.G., Cox, J.H., Müller , W.W. and Rupprecht, C.E. and Kieny, M.P . (1988) Hohnsbeen, K.P. (1988) Current oral Development of a vaccinia-rabies rabies vaccination in Eur ope: an interim glycoprotein recombinant virus vaccine. balance. Reviews of Infectious Diseases Pp. 335–364 in: J.B. Campbell and K.M. 10: 654–659. Charlton, eds, Rabies. Kluwer Academic Schneider, L.G., Cox, J.H. and Müller , W.W. Publishers, Boston. (1985) Field trials of oral immunisation Ryan, G.E. (1976a) Observations on the of wildlife animals against rabies in the reproduction and age structur e of the fox, Federal Republic of Ger many: a mid Vulpes vulpes L., in New South W ales. course assessment. Revue d’Ecologie la Australian Wildlife Research 3: 11–20. Terre et la Vie 40: 265–266. Ryan, G.E. (1976b) Helminth parasites of the Seawright, A.A. (1989) Animal Health in fox (Vulpes vulpes) in New South W ales. Australia. Vol. 2, Chemical and Plant Australian Veterinary Journal 52: 126–131. Poisons. Bureau of Rural Resour ces, Canberra. Ryan, G.E. and Cr oft, J.D. (1974) Observations on the food of the fox, Vulpes vulpes (L.), in Seebeck, J.H. (1978) Diet of the fox Vulpes Kinchega National Park, Menindee, N.S.W . vulpes in a wester n Victorian forest. Australian Wildlife Research 1: 89–94. Australian Journal of Ecology 3: 105–108. Ryan, G.E. and Everleigh, J.N. (1975) The Sequeira, D.M. (1980) Comparison of the tarbaby technique for poisoning rabbits in diet of the r ed fox (Vulpes vulpes) in Kinchega National Park, Menindee, New Gelderland (Holland), Denmark and South Wales. Technical Bulletin 4, NSW Finnish Lapland. Pp. 35–52 in: E. Zimen, Department of Agriculture, 16pp. ed., The red fox, Biogeographica Vol. 18. Dr W. Junk, The Hague. Sargeant, A.B. (1972) Red fox spatial characteristics in r elation to waterfowl Sexton, M. (1983) Declared Animal Control. predation. Journal of Wildlife Management Trust Publication, Technical Publications 36: 225–236. Trust, Perth, Australia.
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Bureau of Resource Sciences 123 Timm, R.M. (1983) Prevention and Control Tyndale-Biscoe, H. (1994) The CRC for of Wildlife Damage. Great Plains biological control of vertebrate pest Agricultural Council, United States of populations: fertility control of wildlife for America. Open unnumber ed manual. conservation. Pacific Conservation Tinline, R.R. (1988) Persistence of rabies in Biology 1: 160–162. wildlife. Pp. 301–322 in: J.B. Campbell and Vertebrate Biocontrol Centre (1992) Fertility K.M. Charlton, eds, Rabies. Kluwer control of foxes in Australia. VBC Paper Academic Publishers, Boston. No. 2 October 1992. CSIRO Canberra. Toma, B. and Andral, L. (1977) Epidemiology Voigt, D.R. (1987) Red fox. Pp. 379–392 in: of fox rabies. Advances in Virus Research M. Novak, J.A. Baker, M.E. Obbar d, and 21: 1–36. B. Mallock, eds, Wild furbearer Trainer, D.O. and Hale, J.B. (1969) Sar coptic management and conservation in North mange in r ed foxes and coyotes in America. Ministry of Natural Resour ces, Wisconsin. Bulletin Wildlife Diseases Ontario. Association 5: 387–391. Voigt, D.R. and Macdonald, D.W . (1984) Trewhella, W.J. and Harris, S. (1988) A Variation in the spatial and social simulation model of the patter n of behaviour of the r ed fox, Vulpes vulpes. dispersal in urban fox ( Vulpes vulpes) Acta Zoologica Fennica 171: 261–265. populations and its application for rabies Voigt, D.R. and T inline, R.R. (1980) Strategies control. Journal of Applied Ecology 25: for analysing radio tracking data. Pp. 387– 435–450. 404 in: C.J. Amlaner and D.W . Macdonald, Trewhella, W.J., Harris, S. and McAllister , F.E. eds, A handbook on biotelemetry and (1988) Dispersal distance, home-range radio-tracking. Pergamon Press, Oxford. size and population density in the r ed fox von Schantz, T. (1981) Female cooperation, (Vulpes vulpes): a quantitative analysis. male competition and dispersal in the r ed Journal of Applied Ecology 25: 423–434. fox (Vulpes vulpes). Oikos 37: 63–68. Triggs, B. (1984) Mammal tracks and signs Wachendörfer, G., Fr ost, J.W., Gutman, B., — a field-guide for south-eastern Australia. Eskens, U., Schneider, L.G., Dingeldein, Oxford University Press, Melbourne. W. and Hof fman, J. (1985) Pr eliminary Triggs, B., Brunner, H. and Cullen, J.M. results of a field trial in Hesse (FRG) to (1984) The food of fox, dog and cat in control fox rabies by oral immunisation. Croajingalong National Park, south- Revue d’Ecologia la Terre et la Vie 40: 257– eastern Victoria. Australian Wildlife 264. Research 11: 491–499. Wallis, R.L. and Brunner, H. (1987) Changes Tullar, B.F. and Berchielli, L.T. (1982) in mammalian pr ey of foxes over 12 years Comparison of red foxes and gray foxes in a forest park near Melbour ne, Victoria. in central New York with r espect to certain Australian Mammalogy 10: 43–44. features of behaviour, movement and Walters C.J. and Holling C.S. (1990) Lar ge- mortality. New York Fish and Game scale management experiments and Journal 29: 127–133. learning by doing. Ecology 71: 2060–2068. Tullar, B.F., Berchielli, L.T. and Saggese, E.P. Wandeler, A.I. (1980) Epidemiology of fox (1976) Some implications of communal rabies. Pp. 237–249 in: E. Zimen, ed., The denning and pup adoption among r ed red fox: symposium on behaviour and foxes in New York. New York Fish and ecology. Biogeographica Volume 18. Dr Game Journal 23: 92–95. W. Junk, The Hague. Turner, A.J. (1965) A survey of neo-natal Wandeler, A.I. (1988) Contr ol of wildlife lamb losses in a W estern District sheep rabies: Europe. Pp. 365–380 in: J.B. flock. Victorian Veterinary Proceedings Campbell and K.M. Charlton, eds, Rabies. 23: 439–444. Kluwer Academic Publishers, Boston.
124 Managing Vertebrate Pests: Foxes Wandeler, A., Capt, S., Kappeler , A. and Quoted by C. Marks (1991) Management Hauser, R. (1988) Oral immunization of techniques for the common wombat in wildlife against rabies: concept and first eastern Victoria. PhD Thesis, Monash field experiments. Reviews of Infectious University, Clayton, Victoria. Diseases 10: 649–653. Zeuner, F.E. (1963) A History of Domesticated Wandeler, A., Müller, J., Wachendörfer, G., Animals. Hutchinson, London. Schale, W., Förster, U. and Steck, F . (1974) Zimen, E. (1980) The red fox: symposium on Rabies in wild car nivores in central behaviour and ecology. Biogeographica Europe. III. Ecology and biology of the Volume 18. Dr W. Junk, The Hague. fox in relation to contr ol operations. Zimen, E. (1984) Long range movements of Zentralblatt fur Veterinarnarmedizin- the red fox, Vulpes vulpes L. Acta Reihe-B 21: 765–773. Zoologica Fennica 171: 267–270. Whitehouse, S. (1977) Bounty systems in vermin control. Journal of Agriculture of Western Australia 17: 85–89. Wiktor, T.J., MacFarlane, R.I., Reagan, K.J., Dietzschold, B., Curtis, P.J., Wunner, W.H., Kieny, M.P., Lathe, R., Lecocq, J.P., Mackett, M., Moss, B. and Kopr owski, H. (1984) Protection from rabies by a vaccinia virus recombinant containing the rabies virus glycoprotein gene. Proceedings of the National Institute of Sciences of the United States of America 84: 7194–7198. Williams, K., Parer, I., Coman, B., Burley, J. and Braysher, M. (1995) Managing Vertebrate Pests: Rabbits. Bureau of Resource Sciences and CSIRO Division of Wildlife and Ecology, Australian Government Publishing Service, Canberra. Wilson, G.R. (1992) Rabies contingency planning: the wildlife perspective. Pp. 109–116 in: P. O’Brien and G. Berry, eds, Wildlife Rabies Contingency Planning in Australia, Bureau of Rural Resour ces Proceedings No. 11. Australian Government Publishing Service, Canberra. Wilson, G., Dexter, N., O’Brien, P. and Bomford, M. (1992) Pest Animals in Australia: a survey of introduced wild mammals. Bureau of Resour ce Sciences and Kangaroo Press, Sydney. Wood, D.H. (1980) The demography of a rabbit population in an arid r egion of New South Wales. Journal of Animal Ecology 49: 55–79. World Health Organization (undated) Phosphine: occupational health and safety information. WHO, United Nations.
Bureau of Resource Sciences 125 APPENDIX A
Native species believed to be at risk from fox predation The following list, although far fr om comprehensive, gives some indication of species at risk fr om fox predation:
Marsupials Birds Bilby, Macrotis lagotis Bush thick-knee, Burhinus magnirostris Black-footed rock-wallaby, Petrogale Ground parrot, Pezoporus wallicus lateralis Little penguin, Eudyptula minor Brush-tailed bettong, Bettongia penicillata Little tern, Sterna albifrons Brush-tailed rock-wallaby, Petrogale Malleefowl, Leipoa ocellata penicillata Night parrot, Geopsittacus occidentalis Dibbler, Parantechinus apicalis Nullabor quail-thrush, Cinclosoma alisteri Eastern barred bandicoot, Perameles gunnii Kowari, Dasyuroides byrnei Long-footed potoroo, Potorous longipes Mountain pygmy possum, Burramys parvus Mulgara, Dasycercus cristicauda Numbat, Myrmecobius fasciatus Red-tailed phascogale, Phascogale calura Rufous hare-tailed wallaby, Lagorchestes hirsutus Sandhill dunnart, Sminthopsis psammophila Southern brown bandicoot, Isoodon obesulus Spectacled hare-wallaby, Lagorchestes conspicillatus Western ringtail possum, Pseudocheirus occidentalis Western quoll, Dasyurus geoffroii Yellow-footed rock-wallaby, Petrogale xanthopus
Rodents Central rock-rat, Zyzomys pedunculatus Dusky Hopping mouse, Notomys fuscus Heath rat, Pseudomys shortridgei Plains rat, Pseudomys australis
126 Managing Vertebrate Pests: Foxes APPENDIX B Anchoring the capsule pr events the fox from carrying of f an intact capsule. If a fox picks up a capsule with the intention of Technique for the moving off, the capsule ruptur es when it manufacture and use of reaches the end of the tether and cyanide cyanide capsules spills into the fox’s mouth. This arrangement has made the pr ocedure more reliable, and The technique involves laying dry, safer to use as it pr events intact capsules commercial grade sodium cyanide (NaCN) from being carried of f. powder encased in a capsule comprised of a mixture of 90% paraf fin and 10% micr o- ‘Brittilised’ capsules are of the crystalline wax. This combination of waxes conventional gelatine variety which ar e produced a robust yet brittle capsule, with freeze-dried after treatment with acetone a relatively high melting point. The two or formaldehyde. The dehydration pr ocess waxes are melted together and heated to a causes the capsules to become brittle and temperature just below boiling. Stainless the chemical tr eatment causes a cr oss- steel rods are placed in a lubricating agent of linkage in the gelatine which makes it soapy water and then dipped briefly in the resistant to rehydration. The capsules ar e heated wax. The wax capsules ar e then then coated with a mixtur e of paraf fin wax prized off the rods. Each capsule is and animal tallow. Captive trials have approximately 8 mm in diameter and 50 mm shown that foxes will easily ruptur e the in length. Capsules ar e then inverted and left capsules, but the exact field pr esentation to dry at r oom temperature for 48 hours. of the bait is not yet decided (C. Marks, DCNR, Victoria, pers. comm. 1995). The capsules ar e two-thirds filled, approx- imately 1.0 g, with NaCN powder . A cotton Wax capsules can also be pr esented in a wool plug, through which a length of looped buried bait system utilising a capsule wire (hair pin) is inserted, is placed into the deployer. The deployer is an all har dwood capsule at its open end. Melted wax is then construction consisting of two holding used to seal the capsule. Next, cyanide blocks attached to a base plate. The holding capsules are placed in water to wash of f any blocks are a set distance apart to allow the excess cyanide and to ensur e that they ar e placement of half a Foxof f Free Feed correctly sealed. NaCN r eadily absorbs and Econobait. Holes in the holding blocks reacts with moisture causing caking in the allow a wax capsule containing powder ed capsules. Dry, powder ed NaCN is rapidly sodium cyanide to be placed horizontally lethal but caked NaCN can be spat out so above the Foxoff. The capsule is secur ed the animal escapes (Connolly et al. 1986). into position with a locating pin which Because the capsules ar e only partially filled passes through the wire loop embedded in it is possible, by gently shaking the the capsule. Tent pegs hammer ed through completed unit, to see whether the cyanide holes in the base plate ar e used to pr event powder is free-flowing. These capsules ar e removal of the deployer fr om the bait site. then air-dried and securely stored. The capsule deployer of fers a degree of protection to the capsule during excavation Two capsules are used at each bait and it pr events removal of the intact capsule station spaced 200 metr es apart along tracks from the bait site. The fox is for ced to br eak or firebreaks. Each capsule is tether ed to a the capsule befor e it can access the Foxof f buried plate (or other suitable anchors) Econobait (C. Marks, DCNR, V ictoria, pers. using a fishing wir e trace which is attached comm. 1995). to the wir e loop embedded in the capsule. When sited, each capsule is coated with an appropriate lure dispensed from a squeeze bottle.
Bureau of Resour ce Sciences 127 APPENDIX C Unless approved by the r elevant local authority, baits must not be laid on any stock route or reserve for travelling stock. Instructions for the use of ® FOXOFF baits Notification to neighbours Notice must be given of the intention to LAND PROTECTION BRANCH, lay baits at least 24 hours prior to the DEPARTMENT OF LANDS, commencement of the poisoning pr ogram. QUEENSLAND Notice must be served by mail or dir ect (revised 25/10/94) telephone on every r esident and/or occupier of the land adjoining or having Foxoff baits are a meat-based manufactur ed frontage to the holding, or ar ea on which bait for the contr ol of canid pests, particularly poison baits ar e to be laid. foxes. The poison is absorbed into the centr e of the bait and defined by the pr esence of In general, fox contr ol will be mor e red dye. 60 and 35 gram versions ar e effective if action is taken over a wide ar ea. available. READ THESE INSTRUCTIONS Thus it is appr opriate for neighbours to BEFORE USE. cooperate in coordinated campaigns. This reduces the bur den on individual landholders, achieves a gr eater control area, Vertebrate pest species reduces the rate of r einfestation and enables synchronised action and pr ecautions within Baits are to be used for no purpose other an area. than for the destruction of foxes unless otherwise approved by the Dir ector. Warning signs Minimum distances When baits ar e laid and while baits r emain present on the baited ar ea, poison signs All baits must be distributed on the land which are provided with the Foxof f product described in the indemnity for m only. must be placed at all entrances to the Unless otherwise approved by the Regional property and at the extr emities of property Inspector, baits must not be laid: boundaries fronting a public thor oughfare. • WITHIN 1 KILOMETRE of any habitation Poison signs must be r emoved once the (habitation includes any dwelling poisoning campaign is completed. excluding the owner’s), or public amenity, Additional large plastic poison signs ar e or available from Lands Department of ficers. • WITHIN 5 KILOMETRES of a town ar ea, or Bait storage and retrieval • WITHIN 5 METRES of a fenced pr operty boundary, or While the 2–3 week pr ogram is under way and while additional baits ar e required to • WITHIN 50 METRES of the centr e-line of replace those at sites wher e bait take has a road occurred, baits may be stor ed in a dry lockable • On properties smaller than 40 hectar es* area, away from children, pets and foodstuf fs. * With the approval of the Regional Foxoff does not r equire refrigeration. Inspector, baits may be used on smaller All baits which have not been taken, and properties, if cooperation between any baits supplied which have not been used, neighbours allows consolidation of should be collected and destr oyed by incin- landholdings for the purpose of deter mining eration or deep burial at the end of the baiting the minimum property constraints. campaign.
128 Managing Vertebrate Pests: Foxes In any case, all baits supplied should Following the use of bait, destr oy the be used or destroyed within one month disposable gloves pr ovided and wash of supply. LONG-TERM STORAGE OF hands before eating, drinking or smoking. BAITS IS STRICTLY PROHIBITED. Empty bait trays can be disposed of in a local authority landfill or buried in a deep Safety precautions hole. Regional Inspectors or other authorised The 3 milligram dose of fluor oacetate (1080) persons may determine additional poison used in the Foxof f bait is pr ecisely conditions and r estrictions on use if local controlled to pr ovide a certain lethal dose circumstances pose additional risks. The to the largest fox and is also adequate to supply of baits may be r estricted if local kill most small to medium-sized dogs and risks are considered to be unacceptable. cats which ingest a bait. If in doubt always seek expert advice However, the dose in a single bait is from your local Lands Department generally below that necessary to kill most officer. native animals, bir ds and reptiles due to their higher r esistance to this poison. In case of emer gency the Queensland Approximately 8 baits eaten would pr ovide Poisons Information Centre number is a lethal dose to a sheep and 67 should be (07)253-8233. lethal to a cow. Sheep show no inter est in baits. Cows occasionally investigate sand- Degradation of Foxoff baits marked bait stations. Foxoff baits have been for mulated to remain Extensive research in a variety of stable while in original packaging. However habitats has shown that very few animals once placed in moist soil the baits absorb other than foxes and dogs ar e likely to moisture and this allows the toxin to be dig up and eat Foxof f baits. Thus, ther e is degraded to har mless residues by common a high safety mar gin in r espect of danger soil bacteria and moulds. Ther e is minimal to non-target animals when baits ar e used long-term environmental hazard from the as directed. use of these baits at buried placements. Nevertheless fluoroacetate is toxic to The rate at which the baits degrade will all species including man and there is vary with soil moistur e and temperature. no known antidote. Dogs are highly In controlled tests, baits in dry soil r etained susceptible so it is important to r estrain 75% of their toxin after two weeks wher eas working dogs and pets and advise in wet soil toxin r educed to 21% by two neighbours and guests while baiting weeks. campaigns are under way. Despite this degradation featur e, it is HANDLE BAITS WITH CARE AND recommended that all bait stations ar e CAUTION marked (for example with spray mark on dropper posts, or ribbon tied to a tr ee or It is essential that baits ar e: fence) to facilitate r egular checking and replacement of baits taken and r ecovery of (a) kept away fr om food, pet food and food baits not taken at the end of the pr ogram. preparation areas
(b) kept away from children and pets and Placement of baits working animals Foxoff baits should be buried just beneath (c) disposed of safely by deep burial the surface within a shallow hole (8–10 cm (preferably in wet hold mor e than 50 deep) and cover ed with soil. Foxes ar e cm deep) or by incineration.
Bureau of Resour ce Sciences 129 readily able to find and excavate buried Just one round of bait placement will baits whereas other animals or stock show generally NOT be suf ficient to kill all foxes. little or no inter est. Bait replacement is necessary in most situations. Baits should be placed at intervals of at least 200 metres, usually along inter nal fence lines or vehicle tracks. Placement of baits Bait density close to each other will r esult in several baits This requires local advice but about 50 baits being taken by a single fox. Since only one will be needed per 400 hectar es (1000 bait is needed to kill a fox, the uptake of acres). This allows for a fox density of about several baits by the same fox should be four foxes per squar e kilometre, for some minimised. baits to not be found and for some foxes finding more than one bait. Use of lure trails Replacement should continue until take The use of lur e trails such as car cass drags stops. This often shows that the true fox or other scent markers is NOT necessary. problem is gr eater than anticipated. Fox While the use of lur e trails does r esult in density may exceed eight foxes per squar e more baits being found in the early phase kilometre in some ar eas. of the program, this may be due to some foxes progressing along the trail to find Free feeds several baits. Unpoisoned ‘free-feed’ baits are Lure trails may be used if it is necessary manufactured to allow for the testing of to complete the baiting pr ogram over a non-target risk in sensitive ar eas, prior to short period, but it will usually be necessary placement of poisoned baits. Fr ee-feed to replace baits several times at sites wher e baits are buried and fine damp sand is baits are taken (see below). spread over a one-metr e diameter area around the bait station. Examination and Bait replacement sweeping of the sand every mor ning enables the detection of the tracks of Since the action of fluor oacetate in the fox animals which visit the station and/or take is delayed, the fox r emains active for the bait. approximately four hours after taking a bait. During this time foxes may sear ch for Extensive research has shown that in additional baits and r eturn to lairs or dens most farming areas the risks to non-tar get before succumbing to the toxic ef fects. native animals is so low that the pr e-testing Carcasses are seldom found near to bait with free feeds is not necessary. Seek stations but may be found in gr oups in long advice from your local Lands Department grass or other cover eventually. Officer if there is a special concer n about non-target risk. Fox mark sites of baits by urinating and may leave a pointed scat at the bait station. Other foxes can visit the same station so Fate of carcasses for effective control it is necessary to r eplace The toxin in a fox car cass is destroyed as baits several times at some sites. The extent the carcass putrefies and bacteria degrade to which this is r equired depends upon: the toxin to har mless residues. It is unlikely local fox density; location of the station (for that any animal can r eceive a secondary example, near a major thor oughfare); poisoning from eating a fox car cass. For surrounding habitat (for example, for est, example it is estimated that an eagle would swamp, creek); presence of lambs; and level need to eat appr oximately 13 whole of control undertaken by neighbours. carcasses to receive a lethal dose.
130 Managing Vertebrate Pests: Foxes Carcasses do not need to be r ecovered. Many foxes will r eturn to lairs or dens befor e succumbing to the toxic ef fects of the poison. Such carcasses are not easily found.
The key to responsible and effective use of baits is to plan and implement a thorough program, with bait replacement and proper spacing. Best results are obtained if cooperative campaigns are conducted by neighbours and Landcare groups. Ensure that pets are protected and neighbours are properly notified. Seek advice if any aspect of these instructions is unclear. APPENDIX D discount rates, eradication is unlikely to be cost-effective. Eradication has a lar ge initial outlay but, if it can be achieved, Criteria for eradication there are no continuing costs apart fr om maintaining the outer pr otective boundary. Eradication is the per manent removal of all For cost-effective eradication, each individuals of a species fr om a defined ar ea situation where eradication is technically within a defined time. feasible should be assessed to deter mine There are three essential criteria which whether eradication costs outweigh must be met for eradication to be possible discounted benefits. (Bomford and O’Brien 1995). If all thr ee criteria cannot be met, eradication should not be attempted: • Foxes can be killed at a rate faster than replacement rate at all densities. As the density declines it becomes progressively more difficult and costly to locate and r emove the last few animals. • Immigration can be prevented. This is possible for of fshore islands or small mainland populations which ar e geographically isolated, or wher e completely effective barriers can be erected and maintained, such as well- maintained fox-proof fences. • All reproductive foxes are at risk from the control technique(s) used. If some animals are trap-shy or bait-shy, thr ough either inherited or lear nt behaviour, then this sub-set will not be at risk. There are three additional criteria identified by Bomford and O’Brien (1995) that need to be met for eradication to be preferable to long-ter m fox control: • Foxes can be monitored at very low densities. This can be dif ficult to achieve. • The socio-political environment is suitable. For example, if certain gr oups object strongly to the eradication of foxes they can directly thwart or politically influence the program. • Discounted cost–benefit analysis favours eradication over control. Discount rates are used to estimate the value of futur e benefits against the costs of actions in curr ent dollars. This criterion is difficult to meet because of the high initial cost of eradication and because benefits accrue over a long period. At high
132 Managing Vertebrate Pests: Foxes APPENDIX E 1993), that is, ‘lear ning by doing’ (Section 8.4.5 and Walters and Holling 1990); and incorporate an evaluation strategy to Best practice extension in ensure the pr ogram is flexible and pest management responsive to exter nal changes such as the environment or market (Kelly 1995). Quentin Hart and Dana Kelly Decreasing state government resources Achieving sustainable land management, limit the ability of extension workers to including pest management, can be target individual land managers. Landcar e facilitated by new appr oaches to extension. groups provide a partial solution to this Traditionally, extension has been defined problem in that they allow extension as the dissemination of infor mation. In this workers to target groups rather than definition, it is seen as the link between individuals, and the infor mation diffusion the producers of infor mation (researchers process within these gr oups is relatively and others) and the end-users of the rapid. The gr oup approach offered by information (generally land managers). Landcare can also be used to develop Researchers, public policy makers and regional rather than individual management industry tend to r efer to research transfer, plans for pest management (Chamala and technology transfer or infor mation diffusion. Mortiss 1990). Bennett (1993) emphasises the need for mutual interdependence and cooperative Extension should not dictate solutions but action combining these two appr oaches. If provide the underlying technical extension is to achieve adoption, it must information and decision-making facilitate understanding and involve a framework from which land managers can participatory rather than pr escriptive draw their own conclusions. In this way, approach. both government and land managers will have a greater understanding of the Some characteristics and principles complexity of the pr oblems and the possible inherent in innovative extension pr ograms solutions. Such participatory lear ning are: approaches also pr ovide land managers ownership; with ownership of the pr oblems and solutions, and this facilitates adoption. benchmarking; participatory learning based on principles Involving land managers as co-lear ners of adult lear ning; and co-researchers is being encouraged in demonstration projects currently supported equity and respect for everyone’s views by the Vertebrate Pest Program (VPP) of the (Kelly 1995); Bureau of Resource Sciences. The VPP funds problem definition with stakeholder state and territory gover nment agencies and consensus (Ison 1993); Landcare groups to deter mine best practice pest management for a particular ar ea. The client driven or r esponsive to the needs projects are generally large-scale field trials of clients (McGuckian and McGuckian involving several properties and comparing 1994); several management strategies. Rather than consider the whole pr operty or whole simply providing land for the r esearch, the agribusiness chain (McGuckian and land managers ar e integral parts of the McGuckian 1994); projects and help deter mine management options which ar e practical and incorporate processes to create learning economically sensible for their particular opportunities that lead to locally area. Their involvement also facilitates the meaningful and adaptive changes (Ison dissemination of project findings to other
Bureau of Resour ce Sciences 133 land managers. One of the r oles of extension have to allocate budgets to deal with many is to maintain the momentum of such risks and opportunities and ar e rarely able projects once gover nment funding ceases. to fund pest contr ol at optimal levels. Given limited budgets, the solution is to Relevance of infor mation to the land use cost–benefit analyses, which ar e manager in a framework of whole-pr operty relevant to the local ar ea, to optimise management needs to be consider ed by where, when and how much contr ol is extension workers. Pest damage is a single conducted. As part of this, pest damage and often minor issue amongst a wide range should be quantified and financial of management considerations a land situation of land managers should be taken manager has to contend with. This is into account where data ar e available to particularly true for pests which inflict major do this (see Appendix B); and but infrequent damage — for example, mice. Pest management is peripheral to most ideally, implement local field trials, and land managers’ major activities, and their from these coordinate regional motivation relates to current rather than management strategies to achieve potential damage (Salleras 1995). maximum (and hopefully long-ter m) adoption. Extension workers and r esearch workers ‘must be able to understand the goals and Computer technology may pr ovide a reasons for motivation or otherwise of the partial solution to decr easing resources for various human stakeholders as well as the physical extension. It will enable pest habits and habitat of [the pest animal with] management information to be pr ovided the most effective solutions [being] achieved electronically and r eadily updated. This by examining differences in the human information can be linked to decision dimension rather than concentrating on the support systems to lead landholders step- pest’ (Salleras 1995). by-step through a process of ‘self- assessment’ so that they may deter mine the The above assertions by Salleras, a rural best management options based on their land manager from Queensland, ar e own on-ground observations. probably a good r epresentation of the attitudes of many land managers and The potential value of these systems provide an insight into ef fective extension depends entirely on the extent to which land methodology. Extension should: managers adopt such technology. In the foreseeable future, adoption rates of best offer concise infor mation specific to practice pest management, which ar e regional needs; currently low and vary between localities, offer a framework for making will depend on extension and r esearch management decisions based on generic officers working with land managers to information combined with local determine what best practice is for their observation; situation and becoming actively involved in its implementation. offer a range of options rather than be prescriptive; take account of the availability of pest management tools (for example, Global Positioning Systems and bulldozers for warren ripping) within a r egion so that recommended control techniques ar e appropriate; take a whole-property management approach by recognising that managers
134 Managing Vertebrate Pests: Foxes APPENDIX F outcomes are commodities, such as increasing lambing percentages, this This appendix r efers to feral pigs, but the should be reasonably easy. Where principles apply equally well to fox manage - outcomes are difficult to measur e, such ment. as reduced land degradation, or intangible, such as increased biodiversity, land Economic framework for managers may be obliged to estimate how feral pig management much they consider is an acceptable amount to spend to achieve that outcome. (After Bomford and others 1995) Step 2 — Control options Land managers who wish to deter mine the optimal economic strategy for managing a List all contr ol options and how much they problem caused by feral pigs could use the would cost to implement. Contr ol options stepwise approach outlined in this appendix. can be different techniques or We recognise that managers will have combinations of techniques, or dif ferent incomplete knowledge of the infor mation levels or frequencies of application of necessary to fully complete many of these techniques (Section 7.6). It is important steps. Nonetheless, the exer cise of attempting that the options for contr ol are expressed to complete the pr ocess, and recording the as activities that a manager can select assumptions and best guess estimates that either to do or not to do. are made, may pr ove a useful aid to decision Step 3 — Density-damage making for feral pig management. relationships Step 1 — Desired outcomes Estimate the relationship between pest Identify desired outcomes and estimate a density and damage for each r esource dollar value for each of these. Wher e damaged by the pest (Figur e B1). For
Figure B1: Possible r elationships between pig density and the damage they cause. Line A is the relationship shown in Figur e 9 and line B that shown in Figur e 10. Line C might occur if, for example, only still-bor n lambs are preyed on by feral pigs at low densities, but if pig density increases, they start to kill healthy lambs.
Bureau of Resour ce Sciences 135 example, if pigs ar e reduced by 50%, how of implementing each contr ol option, and much will this incr ease lambing may include costs of monitoring pests and percentages. There may be interactions planning. Benefits will be the value of the between pest density and other far m reduction in damage to the valued management practices which will need to resource caused by implementing contr ol be taken into account. For example the (that is the desir ed outcomes listed under increase in lambing per centage caused by Step 1 above), plus any pr ofits (for reducing pig densities by 50% may vary example, those made fr om selling pigs or with different levels of availability of from allowing hunters on the pr operty). shelter for lambs. Different pest management options will Step 4 — Efficacy generate a variety of cost–benefit Estimate the ef ficacy of each contr ol relationships. Estimates of benefits and option. That is, how much will a given costs can be discounted back to net effort using a particular contr ol option present values (usually using a discount reduce pig density. rate equivalent to the inter est rate the landholder pays on financing the contr ol Step 5 — Cost–benefit relationships operation). This will r educe the value of Use the infor mation from Steps 1–4 to costs and benefits accruing in the distant estimate costs and benefits of future relative to those accruing in the near implementing each control option, future. including options which combine mor e than one technique. Costs will be the cost
Figure B2: Marginal analysis plotting both incr emental changes in the cost of r educing pigs to a given density and incr emental changes in the cost of damage caused by pigs at a given density against level of contr ol activity. Wher e the two lines cr oss is theor etically the optimal level of pest contr ol. At higher levels of contr ol beyond this point, costs will exceed savings in reduced damage. Note: The x-axis units are for control effort (for example, dollars spent on control, hours of shooting or trap nights) not pig densities.
136 Managing Vertebrate Pests: Foxes Step 6 — Marginal analysis. averse, the best options will be those that Plot both the incr emental change in the bring in r easonable returns (benefits in cost of pig contr ol and the incr emental relation to costs) under the widest range change in the cost of damage caused by of conditions (that is, in most seasons and pigs against the level of contr ol activity with a wide range of commodity prices). contemplated (Figure B2). Wher e the two If the manager’s priority is to maximise lines cross is theoretically the optimal level profit, the preferred options will be those of pest contr ol. Further increases in control that are likely to give the highest r eturns activity do not cause commensurate on investment, even though ther e may be reductions in damage, so at higher levels some risk of having no r eturns or even a of control beyond this point, costs will loss if the seasons and prices go badly. exceed savings in r educed damage. An Payoff matrices can also be used by a land example of marginal analysis for shooting manager to compare returns on feral pigs fr om helicopters is pr esented in investment in pest contr ol with returns on Figure 20. using the money for some other purpose, The problem for managers is that, because such as fencing, new stock watering holes they often do not have good infor mation or fertiliser. on the damage-density r elationship, it is Steps 1–7 complete the basic model. The hard to estimate the optimal contr ol point. model can be made mor e accurate by Further, even if they can make a good adding additional features. Incorporation of guess, it is not usually practical with most such additional features will make the model control techniques to simply cut of f control more complex, but including at least some efforts at some pr e-determined pig density. of them may be necessary to make it It is preferable to have a range of contr ol accurate enough to be useful. options ranked along the x-axis, with their associated cost and benefit values for One way of impr oving accuracy may be implementation, so a manager can select to replace single estimates with a range of which option is optimal. For example, possible values, and give associated different frequencies of shooting could be probabilities for each value in the range. put along the x-axis. Managers may also wish to add additional Step 7 — Pay-off matrices features to the model such as: Construct a table listing all the contr ol Social benefits could be included in Step 1, options and their associated costs and such as: benefits (economists call this a pay-of f matrix). For example, Section 8.8.3 — off-site effects and good neighbour compares the costs and benefits of two relations; control strategies — shooting pigs fr om — biodiversity and endangered species helicopters or poisoning with 1080. management in agricultural ar eas; Managers may wish to construct dif ferent — retaining rural communities; and matrices for dif ferent conditions, such as — animal welfare management. different stocking densities, seasonal conditions, or commodity values for wool, Risk management for spr ead of disease by lambs or pigs. Managers will also need to pigs could also be included in Step 1. consider time-scales when constructing Effects of government intervention could these matrixes — what time span is affect value of benefits (in Step 1) or costs covered and how will this af fect costs and (in Step 2). benefits? These matrices can then be used to select Commercial harvest of feral pigs, as an the option(s) which best meet the alternative to contr ol as a pest, could be managers’ goals. If the manager is risk included as a contr ol option in Step 2.
Bureau of Resour ce Sciences 137 Indirect effects of pest contr ol (for example, controlling pigs may lead to an incr ease in rabbit numbers) could be included as interaction effects in Step 3. The form in which benefits come may be significant to a manager (Step 5). For example, cash ‘bonuses’ fr om the sale of feral pigs may be mor e attractive as immediate cash for spending, than futur e money from increased lambing percentages, which may be committed in advance to servicing debts or meeting far m running costs. Much of the infor mation needed to follow the steps outlined in this appendix is not available. Some projects being funded by the Vertebrate Pest Program in BRS aim to collect some of these data.
138 Managing Vertebrate Pests: Foxes Index Australian and New Zealand Federation of Animal Societies (ANZFAS), 49 attitude to curr ent feral animal 1080 poison, 4, 32, 33, 34, 36, 37, 46, 48, 53, management, 93 73–75 support for fertility contr ol measures, 86 attitude of ANZFAS, 53–54 Australian Capital Territory, ACT Parks and coordinated campaigns in V ictoria, 60 Conservation Service, 59 differences in tolerance, 74 Australian Conservation Foundation, effect on native car nivores, 3 consultation, iii, viii further study r equired, 107 Australian Nature Conservation Agency increased use in NSW, 62 (ANCA) lethal efficacy, 74–75 Endangered Species Program, 102 meat baits, 59–60 Feral Pests Program, 102 recommended dose rate, 74 management of feral animals, 58 use during low fox pelt prices, 54–55 research into impr oved baiting techniques, use in NT, 58 107 use in Qld, 59 role in preparation of the guidelines, iii, viii use in WA, 59 States Cooperative Assistance Pr ogram, 102 research, 106–107 Australian Veterinary Association, viii see also Foxoff AUSVETPLAN Disease Strategy for Rabies, 47 abbreviations see acronyms and abbreviations Aborigines fire regime, 35 baits abundance of foxes, 70–71 achievable rates of population r eduction, 47 see also density aerial baiting, 78–79 acronyms and abbreviations, ix vaccine baiting, 46 advisory service for fox management, 101 bait materials, 77–78 aerial photographs, 69, 103 baiting procedures, 80–81 Agriculture and Related Resources Protection baiting systems, 46, 73–81 Act 1976, 58 buried baits, 78 agriculture chemosterilants, 46 damage from foxes, iii, 1 concealment, 78 assessment, 65–67; free feeding, 81 hypothetical example of strategic frequency & intensity, 79 management, 98–100 improvements to baiting techniques, performance indicators for pr oduction, 93 107–108 amphibians manufactured baits, 78 effect of fox pr edation, 5 meat baits, 59 survey techniques, 64 multiple bait take, 107 Anangu Pitjantjatjara Aboriginal Land Council, neophobia & bait shyness, 108 consultation, iii, viii recolonisation, 79–80 animal welfare, 48, 49–54 RSPCA attitude, 50 fox control/harvesting, iv, 54–55 scent trails, 80 opposition to dogging, 82 surface baits, 77–78 use of steel-jawed traps, 4 use in times of low fox pelt prices, 55 use of strychnine, 54 see also poisoning use of traps, 82 bandicoots, 32, 36, 64 see also humane techniques eastern barred bandicoots, 60 anticoagulant, 76 effect of 1080 baits, 3 definition, x viewing by the public, 40 Australia and New Zealand Envir onment and battues see fox drives Conservation Council, viii best practice, 7–9
Bureau of Resource Sciences 139 Bettongia penicillata see bettongs community-based schemes to contr ol foxes, 3, bettongs, 36 9, 101–104 effect of 1080 baits, 3, 33 community problems, 103 effects of foxes, iii, 31, 32–33 demonstration projects, 105 population recovery, 41, 79 information transfer, 105 predator removal experiments, 31, 32–33 mapping, 103–104 viewing by the public, 40 shooting, 59 biodiversity considerations, 3, 88 see also LandCare biological control agents, 63, 86 see also Landcare see also immunosterility conservation areas biology of the fox, 1, 18–26 agencies need to assess fox damage, 2 birds of prey assessment of pr ogram, 95 fox predation, iii, 15 case study, 90 birds hypothetical example of strategic effects of fox pr edation, 5 management, 95–98 ground parrot, 36 payment problems, 101 ground-nesting birds, 64 conservation performance indicators, 93 little terns, 60 consultation on the guidelines, iii, viii lyrebirds, 60 control techniques, 3, 4, 8, 45, 63, 72–87 survey techniques, 64 coordinated campaigns in V ictoria, 60 bounty schemes, 3, 11, 13, 14, 56–57, 80, 100 fertility control 85–87 see also Foxlotto maintenance control, 91 brittilised capsules, definition, x relationship between fox & rabbit contr ol, see also cyanide 27, 37 buffer zones, 102–03 RSPCA attitude, 50 Bureau of Resource Sciences urban foxes in Qld, 60 role in the guidelines, iii use of traps, 4, 45, 82–83 see also Vertebrate Pest Program water barriers, 84–85 see also individual techniques cadastral information,104 Cooperative Research Centre (CRC) for definition, x Biological Control of Vertebrate Pest Canis lupus, 16 Populations, 86 cannibalism, 24 costs of control, 40, 88–89, 101 carbon monoxide, use as a fumigant, 51 cost-benefit relationships, 91 carrying capacity, 45, 79–80, 98 fencing, 108–109 definition, x fertility control drugs vs poisons, 86 case studies coyotes, 19 agricultural production area, 90 crisis management, 8 conservation area, 90 CSIRO, Division of W ildlife and Ecology, 64 Catchment and Land Protection Act 1994, 60 cyanide, 4, 48, 54, 75–76 cats see feral animals, cats further study r equired, 108 cattle, impact of fox pr edation, iii, 39 technique for the manufactur e & use of chloropicrin, use as a fumigant, 51–52, 83 capsules, 127 chuditch, 36 commercial harvesting of foxes, iv, 8, 27, 38, damage management, iv, 63 41–42, 54–55, 92 deficiencies, 110 price of fox pelts, 27, 41–42 estimation, 64 Commonwealth see governments history, 56 community attitudes, 4 implementation, 100–104 awareness of harmful predation, 104–105, dasyurids, 64 109 definition, x
140 Managing Vertebrate Pests: Foxes effect of 1080 baits, 3 use in fox hunting, 49, 50, 82 Dasyurus geoffroii see chuditch see also dingoes databases, 103 drought, effect on foxes, 2, 15, 21 ERIN, 90 Dryandra State For est lack of benchmark data, 110 ecotourism, 40–41 see also economic data fox control program, 33 deficiencies in knowledge & appr oaches, 1, ducklings, fox pr edation, 40 72, 106–111 dystocia, 40, 65 dens, 83 definition, x den counts, 63, 70 aerial survey techniques, 70 Ecologically Sustainable Development strategy, 7 need for mor e information, 106 ecologically sustainable land management, iv tarbaby technique, 76–77, 108 ecology of foxes, 5 fumigation & destruction, 51, 76, 83, 92 lack of information, 109–110 developments required, 108 economy density of foxes, 3, 15, 16–17, 34, 63, 69 economic & envir onmental impacts, 27–42, 48 hunting effectiveness, 83 economic data, 89 hunting indicator of population density economic frameworks, 89 (HIPD), 69 economic value of wildlife conservation, 92 need for further study, 26, 107 framework for management, 3 population manipulation index, 70 value of fox pelts, 27, 41 scent stations, 69 ecotourism, effect of fox pr edation, 27–28, spotlight counts, 69 40–41 use of measur ements, 70–72 electrified fencing see exclusion fencing see also den counts emu farms, fox pr edation, 40 Dept of Primary Industries and Ener gy, viii Endangered Species Advisory Committee diet of the fox, 2, 15, 24–25, 64 (ESAC) Report, 28–29 diethylstilbestrol (DES), use in fertility contr ol, 85 Endangered Species Pr ogram, 102 dingoes, 15 Endangered Species Protection Act 1992, 58, effect of bounties, 56–57 102, 110 effect of dingo fence, 16, 17 endangered species effect on fox population, 15, 16 definition, x effect on lambs, 39 extinctions, 28–30, 35 poisoning, 22 government assistance, 89 use of soft catch traps, 53 need for Threat Abatement Plan, 58 diseases & parasites, 2, 15, 20–21 predation by foxes, 1 distemper, 2, 15 protection, iv mange, 2, 15, 22 suggested studies, 65 role of foxes in spr ead of exotic diseases, use of exclusion fencing, 84 iii endoparasite, 15, 18, 20 see also rabies definition, x dispersal see distribution environment impact assessment, 64–65 distribution, 12, 15–18 Environmental Impact Statements, 64 dispersal behaviour, 13, 15, 23–24, 94 Environmental Resource Information Network see also geographic infor mation systems (ERIN), 90 dogs environmental damage, iii control of wild dogs, 60 enzootic areas, 2 fox predators, 15 definition, x guard dogs, 85 eradication of foxes, 4 relationships to foxes, 11 criteria, 132 role in rabies, 43–44 local eradication, 91
Bureau of Resource Sciences 141 Eudyptula minor see penguins, little penguin gestation, 15, 19, 81, 92 euro, fox pr edation, 34 definition, x European red fox, 1, 9, 11 glossary, x–xi evaluation see monitoring & evaluation goals, lack of benchmark data, 110 ewes, ultrasound scanning, 2, 39, 67 goats, fox pr edation, 40, 88 exclusion fencing, 58, 84–85 governments electrified fences, 84 assistance for fox contr ol, 89, 101 need for more information, 106 beneficiary pays principle, 101, 103 see also fox-proof fencing Commonwealth management of vertebrate extinctions see endangered species pests, 7, 102 deficiencies in administration pr ocedures, family group, 19, 23, 25, 69 110 definition, x legislation & strategies, 5 farming practices, tool for fox contr ol, 72, 85 need for agency cooperation, 106 fauna see also individual states damage by foxes, 1–2 guidelines for fox management, iii see also native species purpose, 1 see also non-target fauna fencing, 92 habitats see also exclusion fencing modification, 86–87 see also fox-proof fence mosaics caused by fir e regimes, 35 Feral Pests Program, 102 use, 1 1, 15, 17–18, 25 feral animals see also urban foxes ANZFAS attitude to curr ent management, harvesting see commercial harvesting 93 history of foxes in Australia, 1, 11–14 cats home ranges, 15, 22–23 effect of fox contr ol, 34,107 definition, x effect on malleefowl, 33 estimates, 22 effect on numbats, 34 human intervention, ef fect on foxes, 21 effect on rabbits, 2 humane techniques for contr ol of foxes effect on r eintroductions of native cyanide, 54 species, 35 definition, 50 variations in numbers, 20, 21 fumigation, 83 management by ANCA, 58 humane use of snar es, 53 pigs, 39, 64 inhumanity of chlor opicrin, 51 fertility control see reproduction shooting, 48, 50–51 fleas, European rabbit flea, 37 use of 1080, 4, 48 Flora and Fauna Guarantee Act 1988, 60, 110 use of leg-snar e devices & traps, 4, 52, 82 fox drives, 82, 102 humane use of some traps, 52–53 fox-proof fencing, 92, 108–09 use of phosphine gas on rabbits, 52 see also exclusion fencing use of poisons, 4, 48 Foxlotto, 3, 60 view of ANZFAS, 49 Foxoff baits, 59, 78 Hunt Clubs Association of V ictoria, defence of degradation, 78 fox hunting, 50 instructions for use of baits, 128–131 hunting of foxes, iv, 4, 22, 38, 48–49, 82–85, 92 use in Victoria, 60, 102 defence by the Hunt Clubs Association of fumigation of dens, 51 Victoria, 50 effectiveness, 83 geographic information systems (GIS), 63, 70, RSPCA attitude, 50 71, 104 see also commercial harvesting definition, x hydatid parasite in foxes, 2
142 Managing Vertebrate Pests: Foxes immunisation against rabies, 45, 86 SA, 61 immunosterility, definition, x, 4–5 Tas, 62 impact assessment, 64–67 Vic, 60 impact on animals other than mammals, WA, 59 107 time required for hunting, 81
use of impact measur ements, 70–72 LD50, 53, 54, 74 information transfer, 105 definition, x interest groups, attitudes, 1 legislation International Wool Secretariat, viii deficiencies, 110–11 island refuges, 85 legislative provisions for foxes, 58–60, 101 requirements for fox poisoning, 75 jackals, 11, 19 use of soft-catch traps, 83 Leipoa ocellata see malleefowl Lagorchestes hirsutus see wallabies, rufous livestock hare-wallabies commodity prices, 55 lambs fox prey, 1, 2, 38 birth process, 38 assessment, 67 causes of lamb loss, 63, 65–67 Vertebrate Pest Program, 40 cost of fox contr ol, 93 local & community involvement see fox shoots with r educed lamb losses, 49 community-based schemes prey for the fox, 1, 2, 27, 37, 38–39 local or regional approach to management, 4, quantification, 5, 40, 67 88–100 rogue foxes, 39 examples of strategic management, 95–100 use of ultrasound scanning on ewes, 2 macropods & fox management, 5 Land and Water Research and Development definition, x Corporation, viii Macropus eugenii see wallabies, tammar land managers wallaby adaptive management, 91 Macropus robustus see euro assessment of lamb pr edation by foxes, 67 Macrous parma see wallabies, Par ma wallabies awareness of exotic disease risk, 47 maintenance control, 91 case studies, 90 malleefowl, 28, 33 economic frameworks, 89 mammals, survey techniques, 64 holistic approach, 7 management of foxes, iii–iv, 3, 63 information on fox contr ol, 1 advisory service, 101 need for further study, 5, 26 assessment of achieved objectives, 94 primary aim, 7 buffer zones, 102 strategic approach to foxes, 3–4 case studies, 1 use of computerised GIS, 104 coordinated management on public land, 60 LandCare, 102 crisis management, 92 use of maps, 103–104 deficiencies, 1, 71, 106–111 Landcare history, 56 holistic approach, 7 implementation of fox damage involvement in fox contr ol, 1, 5, 71, 101 management, 101–105 regional coordination, 104 integrated management, 85 landholders’ responsibilities, 57–58, 101, 103 legislative provisions, 58 assistance with & use of maps, 70, 104 management programs see individual by state programs ACT, 59 organisation, 110 NSW, 61 past & current management, 56–63 NT, 58 precautionary management, 5, 88, 92 Qld, 59 see also community-based schemes
Bureau of Resource Sciences 143 see also strategic management National Strategy for the Conservation of see also under individual states Australia’s Biological Diversity, 7 management plans, 4, 7–8 native species crisis management, 4 competition by foxes, 36 implementation, 4, 8–9 development of Action Plan, 60–61 local & regional levels, 4, 8, 88 diet studies of the fox, 25 management options, 90–92 display in fox-pr oof enclosures, 40 objectives, 90 effect of foxes on ecotourism, 27–28 performance indicators, 93–94 effects of fox contr ol in WA, iii, 1, 27 see also best practice factors other than foxes causing decline, see also monitoring & evaluation 64–65 management strategy see strategic management government assistance, 101 management units habitat modification outcomes, 87 priorities for treatment, 72 increases in predation pressure, 2, 28–30 use of maps, 72 increasing concern, 22 Managing Vertebrate Pests: Principles and lack of infor mation on the fox as a Strategies, iv, 7 competitor, 109 maps & mapping, 70–71, 93 need for quantification, 5, 25, 29, 64 community use, 103–104 reintroduction attempts, 35 marsupials, predator removal experiments, role of fox & rabbit contr ol, 27, 35 29–33 use in impact assessment of foxes, 64 Meat Research Corporation, viii Nature Conservation Act 1980, 59 mice, chloropicrin fumigation, 51 neophobia, 108 Ministry of Agriculture, Fisheries and Food definition, xi (MAFF) UK, baiting systems, 46 New Zealand, pest contr ol processes, 110 monitoring & evaluation of pr ograms, 4, 9 nocturnal, definition, xi 88–89, 94–95 non-target fauna fox density, 63 aerial baiting, 79 measurement techniques, 63–87 dangers of fr ee feeding, 81 operational monitoring, 4, 94 effect of fences, 84 performance indicators, 93–94 need for further investigation, 80 performance monitoring, 4, 94–95 use of poisons, 58, 73, 77–78, 80 PMIS, 94 use of snar es, 82–83 prey density, 63 use of traps, 82 steps for monitoring pr ograms, 95 Northern Land Council, consultation, iii, viii see also impact assessment Northern Territory, Conservation Commission Murray Darling Basin Commission, viii of the Norther n Territory, 58 Mus domesticus see mice numbats Myrmecobius fasciatus see numbat effects of foxes, iii, 32–33, 34 myxomatosis see rabbits population recovery, 41 numbers of foxes see abundance of foxes National Consultative Committee on Animal Welfare ostrich farms, fox predation, 40 ban on strychnine use, 54 conclusions on exclusion fencing, 84 parasites see diseases & parasites consultation, iii, viii parturition, definition, xi National Farmers’ Federation, consultation, iii, pelts viii anti-fur lobby, 41 National Landcare Program, 7 definition, xi, see also Landcare value of fox pelts, 27, 41 National Parks and Wildlife Act 1970, 62 effect on fox damage, 54
144 Managing Vertebrate Pests: Foxes penguins, 60 Pseudocheirus occidentalis see possums, little penguin, 41 western ringtail possum perceptions of the fox, iii, 48 publicity & public r elations, 105, 109 performance monitoring see monitoring & Puffinus tenuirostris see short-tailed shearwater evaluation purpose of the guidelines, 1 Pest Monitoring Infor mation Systems (PMIS), 94 pest control, quantification of, iii–iv Queensland, Dept of Lands, Land Pr otection pest management Branch, 59–60 New Zealand, 110 quolls training, 110 eastern quoll, 36 Petrogale lateralis see wallabies, rock-wallabies effect of 1080 baits, 3 Petrogale penicillata see wallabies, brush-tailed western quoll, 36 rock-wallaby Petrogale rothschildi, see wallabies, rock- rabbits wallabies effect of feral cats, 2 phosphine gas effect of foxes on numbers, 2, 14, 22, 27, 36 den destruction, 83 effect of numbers on foxes, 2, 3, 13–14, 85 use on rabbits, 52 effect of predators, 20 poisoning of foxes, 1, 4, 22, 40, 53–54, 74–82 effects of chlor opicrin fumigation, 51 arid regions, 35–36 myxomatosis, 2 contract poisoning in WA, 59 need for further study, 107 costs of fox contr ol, 40 need for quantification of fox/rabbit cyanide, 4, 48, 54, 76–77, 108 relationship, 5 home range sizes, 23 role of fox in rabbit contr ol, 2, 27 need for mor e information, 106 use of burr ows by the fox, 19 non-target fauna, 58 rabies, 15, 20, 22, 43–47 regulation by legislation, 58, 76 AUSVETPLAN, 47 RSPCA attitude, 50 control methods, 45 strychnine, 46, 48, 74, 77 dispersal studies, 24 susceptibility to secondary poisoning, 37 immunisation, 45 timing of poison use, 82 population reduction, 47 see also 1080 role of foxes in spr ead of the disease, iii, 2, 44 see also baits simulated outbreaks, 47 see also den fumigation use of HIPD to calculate thr eshold pollution, effect on ecotourism, 41 densities for transmission, 68 population size, 68 vaccination of foxes, 44–47 possums, 64 range expansion consequences, 36
effect of fox contr ol programs, 32 RD50 brushtail possums, 32, 33, 41 definition, xi western ringtail possum, 86–87 measurement after fumigation of mice potoroos, viewing by the public, 40 with chloropicrin, 51 poultry, fox pr edation, 2, 39–40 recolonisation of foxes, 3, 4, 79, 81, 82, 93 predation by foxes, iii recombinant virus, 46, 86 effect of rabbit densities, 36 definition, xi need for further study, 107 recreational hunting see hunting need for quantification, 5 references, 112–25 predator removal experiments, 29–35 reinvasion see recolonisation see also under individual animals relict population, definition, xi predators, 21 reproduction in the fox, 2, 15 , 19–20 Codes of Practice, 50 abortion-inducing hormones, 85 mutilation of lambs, 38 anti-fertility agents, 85–86
Bureau of Resource Sciences 145 gassing of breeding dens, 3 strychnine, 46, 48, 54 litter size, 19 summary, 1–5 sterilisation, 86 survey methods for faunal gr oups, 64–65 reptiles effect of fox pr edation, iii, 5 tarbaby survey techniques, 64 definition, xi road kills, 21 techniques, 76–77, 108 rodents, 64 see also mice Tasmania, Dept of Envir onment and Land RSPCA Australia Management, 62 attitude to hunting, 50 Dept of Primary Industry and Fisheries, 62 attitude to leg-hold snar e trap, 53, 82 Tasmanian devil, 36 Rural Industries Research and Development Territory Parks and Wildlife Conservation Act Corporation, viii 1988, 58 Rural Lands Protection Act 1985, 59 tetanic spasms, definition, xi Threat Abatement Plan, 110 scat, 64, 90, 130 impact of foxes, 58 definition, xi threatened species see endangered species secondary poisoning, 22, 37, 97, 130 Tidbinbilla Nature Reserve definition, xi routine fox management, 59 sheep industry, 18 tortoise species, fox pr edation of eggs, 34 role of the fox, 39 tourist industry see ecotourism shooting of foxes, 3, 21, 48, 49, 50–51, 81–82 training in pest management, 110 community involvement, 59, 81–82 transect, definition, xi short-tailed shearwater, fox predation, 34 translocation, definition, xi snares see traps traps, 3, 4, 21, 45, 52–53, 82–83 social organisation, 25 snares, 82–83 sodium monofluoracetate see 1080 steel-jawed traps, 82 spotlight traverse, 30, 32 Trichosurus vulpecula see possums, brushtail definition, xi possums Standing Committee on Agricultur e and turtles, effect of foxes, 60 Resource Management (SCARM), iii, viii, 7 Sub-committee on Animal Welfare, Codes ultrasound scanning, 67 of Practice, 50 definition, xi States Cooperative Assistance Pr ogram, 102 see also ewes states see landholders’ responsibilities urban foxes, 16 see also individual programs causes of deaths, 21–22 strategic management, iv, 3, 91, 92 further study r equired into baits, 108 attitudes affecting fox management, 48–55 habitats, 17–18 commercial harvesting, 57–58 Queensland, 60 economic frameworks, 89 territories, 22, 23 impact on native fauna of management use of snar es, 53, 81 programs, 34 vaccination of foxes see rabies implementation, 88, 94 vectors, definition, xi key components, 4 Vermin Destruction Act 1950, 62 local and regional level, 88–100 Vertebrate Pest Pr ogram (VPP), iii, 1, 9, 102 hypothetical examples, 95–98 Vertebrate Pests Committee, Strategic management plan, 90–94 Vertebrate Pest Working Group national management, 8 recommended dose rate for 1080, 75 problem definition, 89 role in the guidelines, viii, 1 strategic approach, 89 Victoria, Dept of Conservation and Natural see also monitoring and evaluation Resources (DCNR), 60–61, 102
146 Managing Vertebrate Pests: Foxes vulnerable species definition, xi see also endangered species Vulpes vulpes, 1, 9, 11 wallabies, 64 decline of the brushtailed r ock-wallaby, 28 Parma wallabies, 35 rock-wallabies black-footed rock-wallaby, 1 effects of foxes, iii, 1 predator removal experiments, 29–32 yellow-footed rock-wallabies, 34 rufous hare-wallabies, 35 tammar wallaby, ef fect of fox contr ol program, 32, 33 viewing by the public, 40 Western Australia, Agriculture Protection Board (APB), 58–59 Western Australia, Dept of Conservation and Land Management cooperative research programs, 106–107 fox control programs, 59, 63 whole property planning, 7–8 wildlife conservation, 71 see also native species wolves, relationship to foxes, 11, 16, 19
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