AUSTRALIA'S PEST ANIMALS
New solutions to old problems
AUSTRALIA'S PEST ANIMALS
New solutions to old problems
Penny Olsen
Front Cover: Foxes are widely recognised as one of Australia's most serious agricultural and environmental pests. Source: Owe Marks, D N R E
National Library of Australia Cataloguing-in-Publication data
Olsen, Penny.
Australia's pest animals: new solutions to old problems. Bibliography.
Includes index. ISBN 0 86417 808 5
1. Feral animals - Australia. 2. Pests - C o n t r o l - Australia. I.Australia. Bureau of Resources. II. Title
632.60994
© C o m m o n w e a l t h of Australia 1998
First published in 1998 by Kangaroo Press Pty Ltd An imprint of Simon and Schuster
20 Barcoo Street, East Roseville, NSW2069 A Viacom Company
Sydney Nezv York London Toronto Singapore Printed in Hong Kong
Produced by Phoenix Offset ISBN 0 86417 808 5
Contents
Foreword 9 Preface 10 Introduction 11
1
MORE THAN A N ATTITUDE: PERCEPTIONS OF PESTS
What is a pest? 13
Attitude: origins of a problem 13 Perceptions of pests 18
Attitudes to a n i m a l welfare 22 Attitudes of A b o r i g i n a l peoples 24 Attitudes of governments 26
2 THE CHANGEABLE PEST
The f l u i d nature of pest status 28 Change i n the number of animals 28 Change i n l a n d use 28Pest or resource: the commercial use of pest animals 30 N a t i v e animals as pests 31
Potential pests: exotic animals and translocated natives 32 Criteria for assessing the pest potential of an introduced a n i m a l 34 Pests as disease carriers 36
3 KEYS TO CONTROL: UNDERSTANDING PEST
BIOLOGY A N D PEST DAMAGE
Understanding pests 40
P o p u l a t i o n dynamics: h i g h potential f o r increase 40 A b i l i t y to spread r a p i d l y 45
Favourable habitat changes 46 Few diseases and predators 47
Understanding h o w pests fit into a complex environment 48 Pest damage 52
4 PEST CONTROL TECHNIQUES
C h o o s i n g a control technique 56 K i l l i n g or removal 57Shooting 59 Trapping 60 M u s t e r i n g 61 Exclusion 62
Biological control and anti-fertility agents 65 Habitat manipulation 70
Other management practices 72
INTRODUCING THE STRATEGIC APPROACH
A whole system approach to l a n d management 74 K e y principles of pest management 76Beneficiary-pays 77 The role of legislation 77
M a n a g i n g total g r a z i n g pressure 78
The strategic approach to pest management 79
DEFINING THE PROBLEM
D e f i n i n g the pest p r o b l e m 81Is there a problem? 81
Assessing the scope of the problem 88 W h o has the problem? 89
Where is the problem? 89 M e a s u r i n g the p r o b l e m 90
THE M A N A G E M E N T PLAN: OBJECTIVES A N D OPTIONS
D e v e l o p i n g a management p l a n 94 Setting objectives 94 Management options 95 L o c a l eradication 98 Strategic management 98 Crisis management 100 C o m m e r c i a l management 100 N o management 101Incomplete knowledge: dealing w i t h risk 102 Eradication is rarely possible 104
Criteria for local eradication 104
IMPLEMENTING A N D EVALUATING THE M A N A G E M E N T
PLAN
Putting the p l a n into practice 108
A coordinated group approach to management 109 Formation and maintenance of management groups 110 Successful group approaches 114
CONTENTS
9 C A S E S T U D I E S
Case study 1
Management of feral p i g damage i n the wet tropics of N o r t h Queensland 119
Case study 2
C o n t r o l of fox predation o n rock-wallabies 123
Case study 3
A c o m p a r i s o n of f o u r strategies to control f e r a l p i g damage to l a m b production i n the rangelands 126
Case study 4
Management of feral goats i n a national park and surrounding pastoral land 129
Case study 5
Management of raven damage to an a l m o n d crop 133
Case study 6
A n unsuccessful group approach to rabbit management 136
1 0
PEST MANAGEMENT FOR THE FUTURE
What is the future of pest management? 140 Research: n e w approaches, n e w directions 140 Improved p l a n n i n g 142
Improved communication 144 N e w technology 145
N e w control techniques a n d n e w pests 146 C o n c l u s i o n 147
References 148
List of personal communications 153
A P P E N D I X 1 Selecting a management option 154
A P P E N D I X 2 List of scientific names of species mentioned i n the text 155 Index 157
FEATURED SECTIONS
Kangaroos: f r o m curiosity to resource 18 Rice and M a g p i e Geese 29
F r o m pets to pests 37
Understanding p o p u l a t i o n dynamics 42 The importance of burrows 47
A devastating trio: overgrazing, drought and rabbits 50 Does increased pest control result i n reduced pest damage? 54 Exclusion of pests: the D i n g o fence 65
R C D , a potential biological control agent for rabbits 66 Immunosterility to control foxes, rabbits and house mice 68 Habitat m o d i f i c a t i o n to reduce native rat damage to sugarcane 71 Improved management to control parrot damage to Bluegums 73 Ecologically Sustainable Development 76
Rat damage to H a w a i i a n macadamia nuts: a perceived rather than a real problem 82 Cane Toads: a real or perceived pest problem? 82
European C a r p : problem or scapegoat? 84
Feral p i g damage i n the M a r y River catchment 87 The logic and f u n c t i o n of experiments: an example 91 W h e n is it w o r t h managing a pest population? 97 D e f i n i n g management units 102
Management options for feral p i g impact on lamb production: considering risk 103 Eradication of rabbits on P h i l l i p Island 106
Feral goat management i n south-western Queensland: encouraging participation and ownership 111
The role of extension i n pest animal management 112
Implementing a group management p l a n to protect M a l l e e f o w l 116 Assessing progress: the use of indicators 118
Foreword
Pest animals are those w h i c h threaten the agricultural, environmental and personal resources humans value. European settlement is mostly responsible for the large number of such species i n A u s t r a l i a today.
Beginning last century, m a n y animals were released deliberately for f o o d production, game h u n t i n g , companionship or aesthetic reasons. Other species established accidentally, originating f r o m incidental immigrants or are domestic animals w h i c h escaped to establish w i l d populations. Changes i n l a n d use have also caused some native animals to become pests.
Despite concerted effort to manage pest animals, their populations remain large and widespread and cause considerable damage.
The Bureau of Resource Sciences recently reviewed pest a n i m a l management i n Australia and overseas. State and Territory pest management agencies, C S I R O , Environment A u s t r a l i a and representative c o m m u n i t y groups i n c l u d i n g the N a t i o n a l Farmers' Federation, the A u s t r a l i a n Conservation Foundation and the N a t i o n a l C o n s u l t a t i v e C o m m i t t e e o n A n i m a l Welfare c o l l a b o r a t e d i n the undertaking. The result is a series of national guidelines w h i c h outlines a revised, strategic approach to the management of particular pest animals, i n c l u d i n g feral horses, rabbits, foxes, feral goats, feral pigs and rodents.
The guidelines b u i l d on Australia's sound understanding of the biology of pests, and expertise i n the development and application of pest control techniques. They b r i n g together the experiences of resource managers and researchers across A u s t r a l i a and overseas, challenge o l d assumptions and ask h o w to do it better.
Australia's Pest Animals draws on these guidelines and other sources to give an overview of pest animal problems i n Australia and promote the use of scientifically based strategic management that is humane, cost-effective and integrated w i t h ecologically sustainable l a n d management. The book is written f o r a general audience. It w i l l assist farmers and natural resource managers to deal w i t h their pest animal problems. It represents a useful overview of pest animal management i n A u s t r a l i a f o r p o l i c y - m a k e r s a n d a s o u r c e r e f e r e n c e f o r s t u d e n t s . Conservationists and other interested readers w i l l gain better insight into one of the most significant conservation issues i n Australia. N o t least, the strategic management approach advocated i n Australia's Pest Animals has application to a range of other natural resource management issues.
Peter O ' B r i e n
Executive Director Bureau of Resource Sciences
Preface
W h e n I told a f r i e n d that I was w r i t i n g a book on vertebrate pest management he inquired whether it was about sheep. One thought led to another and it occurred to me that this book is not about pest management at all, but about management of people. It is people w h o decide whether an a n i m a l becomes a pest either b y m o v i n g it physically, b y m o d i f y i n g habitats or l a n d uses or b y altering their o w n perceptions. It is people w h o decide whether an a n i m a l stays a pest either b y managing it or b y softening their perception of it. It is people w h o decide how, w h e n a n d where to manage a pest; and people w h o determine whether a management program w i l l be successful. So, this is a book about people managing themselves and cooperating i n order to better manage their environment, be it f a r m or nature reserve, to m i n i m i s e the damage caused b y pests.
The book is based o n the well-shaped principles, practical approaches and ready-made examples, developed and espoused i n the national guideline series
Managing Vertebrate Pests b y the Bureau of Resource Sciences, w i t h published volumes written b y D a v e Berman, M a r y B o m f o r d , M i k e Braysher, John Burley, Judy Caughley, D a v i d Choquenot, Brian C o m a n , W i l l Dobbie, Robert H e n z e l l , John M c l l r o y , John Griffiths, D a n a Kelly, Jack Kinnear, Terry K o r n , Ian Parer, Bob Parker, John Parkes, Greg Pickles, G l e n Saunders, R o n Sinclair and Kent Williams. The preparation of Australia's Pest Animals w o u l d have been immeasurably harder w i t h o u t the generous contribution, enthusiasm and support of M i k e Braysher. M u c h of the text was drafted b y h i m and his philosophies o n pest management influenced the entire book.
A number of other people were generous w i t h their knowledge and assistance. Quentin H a r t gave valuable guidance at all stages of the preparation of the book and was responsible for general c o m p i l a t i o n of text, figures a n d photos for p u b l i c a t i o n . T h o r o u g h reviews b y John Parkes a n d M a r y B o m f o r d greatly i m p r o v e d the m a n u s c r i p t . R o n S i n c l a i r w a s p a r t i c u l a r l y h e l p f u l w i t h the compilation of the case study o n ravens, D a v i d Choquenot assisted w i t h one o n pigs and Q u e n t i n H a r t prepared the study o n the Sutton Grange project. Steve M c L e o d k i n d l y drafted material on experimental design and population dynamics and Sandy Thomas checked the section on biological control. Information o n immunocontraception and o n mice was k i n d l y p r o v i d e d b y L y n H i n d s and Grant Singleton. G r a h a m G a m e r gave advice on various sections and D a n a B r a d f o r d helped w i t h the boxes o n introduced species. Thanks are also due to the various photographers whose w o r k adds colour, i n f o r m a t i o n and interest, and to Brett C u l l e n for skilled preparation of the illustrations.
I a m also grateful to A n d r e w C o c k b u r n , H e a d of the D i v i s i o n of Botany and Zoology, A u s t r a l i a n N a t i o n a l University, where I a m a Research Fellow, for his unstinting support.
Introduction
Despite ongoing improvements i n established pest control methods and the development of n e w techniques, A u s t r a l i a has basically the same suite of pests n o w as at the turn of the century, and animals that were critical pests then continue to cause concern. Each year hundreds of thousands of foxes, rabbits, kangaroos, goats, pigs, mice, cats, rats and parrots are trapped, poisoned, shot or otherwise destroyed because of the agricultural losses and environmental h a r m they cause. The hope has been that w i t h lots of effort and the support of governments, pests can be all but eliminated. Yet, although several native animals have become rare or extinct because of h u m a n activities, pests continue to thrive. Clearly, it is time to review the past, and to p l a n pest management that is smarter and more successful.
Effective pest management must be sensitive to the ever changing needs of l a n d managers a n d the wishes of the c o m m u n i t y . In recent years several developments have changed the w a y i n w h i c h Australians approach pest animal management i n particular, and l a n d management, i n general. These include: • recognition that l a n d systems s h o u l d be managed as a whole and that pest
animals are o n l y one factor i n f l u e n c i n g sustainable use of the l a n d a n d protection of biodiversity;
• c o n s i s t e n t l y d e c l i n i n g c o m m o d i t y prices—as p r i m a r y p r o d u c e r s are increasingly required to compete o n deregulated w o r l d markets—which place even greater importance o n the need for cost-effective pest a n i m a l control; • better understanding of the range of groups—including community Landcare,
animal welfare and conservation groups, research organisations and financial institutions—interested i n pest animal management and recognition of the need to i n v o l v e them i n the p l a n n i n g and management of pest animals;
• concern over extensive reduction i n native habitat, p a r t i c u l a r l y i n areas converted to broad-scale cropland. This reduction results i n m a n y s m a l l , f r a g m e n t e d h a b i t a t r e m n a n t s w h i c h i s o l a t e n a t i v e p l a n t a n d a n i m a l communities and make them more vulnerable to damage b y pest animals; • recognition that conservation of m u c h of Australia's biodiversity n o w depends
on management of w i l d l i f e outside reserves, often o n private land; and • a decline i n government assistance f o r pest a n i m a l control.
In the light of past experiences and present conditions, the Bureau of Resource Sciences recently reviewed pest a n i m a l management b o t h i n A u s t r a l i a and overseas. State and Territory pest management agencies, C S I R O , Environment Australia and representative community groups i n c l u d i n g the N a t i o n a l Farmers' F e d e r a t i o n , the A u s t r a l i a n C o n s e r v a t i o n F o u n d a t i o n a n d the N a t i o n a l Consultative Committee o n A n i m a l Welfare collaborated i n the undertaking. The
A U S T R A L I A ' S P E S T A N I M A L S
result is a series of national guidelines w h i c h outline an updated and strategic approach to pest management. The guidelines b u i l d onAustralia's knowledge of the biology of pests, a n d expertise i n the development a n d use of pest control techniques. They incorporate the wealth of experience of resource managers and researchers across A u s t r a l i a and overseas, challenge o l d assumptions and ask h o w to control pests better.
Australia's Pest Animals draws on the guidelines to give an o v e r v i e w of pest problems i n A u s t r a l i a , a n d describes the processes of better management i n a clear, thought-provoking way. The n e w approach to pest management is based on a w h o l e l a n d system p l a n , a n d emphasises control of the damage that pests cause rather than simple reduction i n pest numbers. It is built around a central f r a m e w o r k of f i v e interrelated steps that:
• define the p r o b l e m i n terms of pest damage; • determine objectives;
• i d e n t i f y a n d evaluate management options; • implement a management plan; and
• monitor a n d evaluate the outcome.
Pest control is not easy and there is still m u c h to learn. For most pests there is little good information about the type and amount of damage they cause. Without accurate damage assessment, it is not possible to k n o w what benefit to expect f r o m a given level of pest control. There is a need f o r basic research o n these issues and on biological, social and economic pest management systems i n general, but often there is neither the time nor the f u n d s to spend o n long-term research before control begins. A quicker solution is to adapt management so that it functions as a productive ongoing experiment, often i n the hands of the l a n d managers. The outcomes are f e d back into i m p r o v i n g management. This adaptive management, or 'learning b y d o i n g ' , combines observation, experience a n d research to help l a n d managers care for their l a n d i n a more sustainable a n d cost-effective way.
Some of the answers to past failures and keys to future management can be f o u n d i n the attitudes of people to pests and i n pests' special characteristics; these are discussed i n the early chapters of this book. Later chapters deal w i t h practical management issues, f r o m i d e n t i f y i n g the pest p r o b l e m to choosing control techniques, a n d f o r m u l a t i n g and i m p l e m e n t i n g a management plan. A series of case studies illustrates the application of the five-step approach to a variety of pest a n i m a l problems, and the f i n a l chapter speculates on future developments and directions i n pest management.
I More than an attitude:
perceptions of pests
LEFT The European Red Fox xoas introduced in 1871, or earlier, for hunting with horses and hounds. It adapted well to Australian conditions and by the 1930s had spread over the mainland apart from the tropical north. Although
regarded by many as an attractive animal, it is a major environmental and agricultural pest.
Source: CSIRO
RIGHT The total value of Australia's feral pig meat exports is in the order of $10-20 million annually. Shooters, meat processors and recreational hunters may regard the pig as a resource rather than as a pest.
Source: Peter O'Brien, BRS
What is a pest?
... an animal that causes more harm than good to a valued resource.30'27
The w o r d 'pest' is generally used to describe an animal that conflicts w i t h h u m a n interests. Such a pest may be destructive, a nuisance, smelly, noisy, out of place or s i m p l y not wanted. A more precise and workable definition includes only those animals that cause serious damage to a valued resource. A pest m a y b e an a n i m a l that was originally spread b y humans to new lands—this is particularly the case i n Australia. Or, it might be a native animal such as a kangaroo, p o s s u m or parrot. It is important to note that people decide whether an a n i m a l is a pest. W h a t is a pest to one person m a y be a valuable resource to another.8 6 For example, a feral p i g might be w o r t h $100 at the chiller, where it is processed into game meat for the European gourmet market, and v i e w e d as a valuable resource b y the hunters and meat processors. Others believe that feral pigs are a menace to the environment and agriculture. Such diversity of o p i n i o n is one of the m a i n reasons that past pest control has h a d v a r y i n g success.
Attitude: origins of a problem
WItat it comes down to is a value judgement about whether an animal fits in with your view of the world or not.212
Australians have inherited the consequences of past attitudes, w h i c h have left almost insurmountable pest problems. In the mid-1800s, settlers h a d a v e r y different attitude toward many of the animals n o w regarded as pests. Between
A U S T R A L I A ' S P E S T A N I M A L S
1840 and 1880 alone more than 60 species of vertebrate animals were introduced into A u s t r a l i a .1 4 9 M a n y were brought i n b y E n g l i s h i m m i g r a n t s to b r i n g a semblance of E n g l a n d to the new c o l o n y1 1 8 , 1 9 3 Some, such as the Song Thrush, were considered superior songsters to the A u s t r a l i a n natives and reminded the settlers of home. The members of acclimatisation societies w o r k e d actively and enthusiastically to spread the w o r l d ' s ' u s e f u l and b o u n t i f u l ' species.1 4 9 Rabbits, foxes, trout and deer were released for sport or f o o d and the mongoose imported to control rats i n sugar-cane. Other introductions were accidental: captive stock, such as horses, pigs, goats and camels; and pets and ornamental species, such as the cat and goldfinch, escaped and established feral populations.
Fortunately m a n y introductions failed despite the efforts of acclimatisation societies,1 9 3 but others prospered.2 1 1 A b o u t 96 species of birds have at one time or another been introduced to A u s t r a l i a .1 2 3 O f these, 32 have become established i n the w i l d , a further 12 have probably established and 52 have d i e d out. But o n l y a few of the successful introductions are considered to be serious pests.
Table 1.1 The Australian distribution of some of the introduced species that have established wild populations. Many are pests or have potential to become pests.
Species General distribution in Australia
Fish Rainbow Trout Atlantic Salmon Brown Trout Brook Trout Goldfish European Carp Roach Tench
Topminnow (Mosquito Fish) European Perch (Redfin) Black Mangrove Cichlid Mozambique Tilapia Oriental Weather Loach
south-eastern Australia
south-eastern highlands; southern ocean south-eastern Australia south-eastern Australia south-eastern Australia south-eastern Australia south-eastern Australia south-eastern Australia
southern and eastern Australia; Christmas Island south-eastern Australia
Victoria, Queensland Victoria, Queensland New South Wales; Victoria
Amphibians
Cane Toad north-eastern Australia
Reptiles
House (Barking) Gecko Grass Skink
northern Australia; Cocos (Keeling) Island; Christmas Island
Christmas Island
Birds
Common Pheasant Mallard
Weka (New Zealand Woodhen) Rock Dove (Domestic Pigeon) Senegal Turtledove
Spotted Turtledove Skylark
House Sparrow Eurasian Tree Sparrow Nutmeg Manakin (Spice Finch) Java Sparrow
Rottnest Island, Western Australia; King Island, Tasmania south-eastern Australia; Perth, Western Australia Macquarie Island
cities and towns, coastal eastern, southern and south-westernAustralia
south-western Western Australia
south-western Western Australia; coastal northern Queensland to South Australia
southern and south-eastern Australia
southern and eastern Australia; Norfolk Island south-eastern Australia
pockets of the eastern coast Christmas Island
M O R E T H A N A N A T T I T U D E : P E R C E PTI O N S O F P E S T S
Species General distribution in Australia
In the 1800s, acclimatisation societies actively promoted the destruction of native predators, particularly birds of prey, to protect introduced songbirds. The tide turned and today many introduced animals are regarded as pests, and native birds such as this Australian Hobby are protected.
Source: Nicholas Birks
European Greenfinch European Goldfinch Red-Whiskered Bulbul Common Blackbird Song Thrush Common Starling Common Myna Mammals House Mouse Brown Rat Black Rat Dog Fox Cat Rabbit Brown Hare Horse (Brumby) Donkey Pig One-humped Camel Swamp Buffalo Bali Banteng Goat Sheep Fallow Deer Red Deer Rusa Deer Sambar Deer Chital (Axis Deer) Hog Deer
south-eastern Australia
south-eastern Australia; Albany and Perth, Western Australia; Norfolk Island
Adelaide, South Australia; Sydney, New South Wales; Melbourne, Victoria
south-eastern Australia; Norfolk Island south-eastern Australia; Norfolk Island eastern and south-eastern Australia including Tasmania; Norfolk Island
eastern and south-eastern Australia
Australia-wide
mainly coastal cities of eastern, eastern, south-western mainland; south-western Tasmania
mainly coastal Australia including Tasmania; Christmas Island; Norfolk Island; Cocos (Keeling) Island mainly coastal southern and eastern Australia southern 2/3 of mainland Australia
Australia-wide
southern 2/3 of mainland Australia eastern and south-eastern Australia
throughout Australia; mainly northern and Central north-western, western and central Australia
mainly eastern, northern and south-western Australia Central and mid-western Australia
northern Northern Territory
Cobourg Peninsula, Northern Territory
mainly south-central Queensland; New South Wales; south-eastern South Australia; mid-western Western Australia
isolated, Western Australia; New South Wales scattered, coastal south-eastern Australia south-eastern Queensland; southern Victoria
Sydney area, New South Wales; Melville Island; Prince of Wales Island, Queensland
Gippsland, Victoria, to Australian Capital Territory; Cobourg Peninsula, Northern Territory Maryvale Creek, Queensland
far southern Victoria
Sources: 6; 7; 12; 36; 49; 51; 55; 64; 76; 115; 121; 123; 124; 131; 138; 140; 186; 188; 208; 210; 227.
A U S T R A L I A ' S P E S T A N I M A L S The main distribution of some of some of the better known animals that have been introduced to Australia and become pests.
Starlings
Northern
Territory
Queensland
Western
Australia
South
Australia
New South
Wales
Victoria
Tasmania
Foxes
Rabbits
Northern
Territory
Queens and
South
Australia
Western
Australia
New South
Wales
Victoria
Northern
Territory
Western
Australia
Queensland
South
Australia
New South
Wales
Victoria
Tasmania
Tasmania
Goats Pigs
Northern
Territory
Northern
Territory
Western
Queensland
Queensland
Western
Australia
Australia
South
South
Australia
Australia
New South
New South
Wales
Wales
Victoria
Victoria^
ft
ft
Tasmania
Tasmania
16M O R E T H A N A N A T T I T U D E : P E R C E PTI O N S O F P E S T S Camels were introduced as beasts
of burden but some escaped and established feral populations that range over Central and mid-western Australia.
Source: David Wurst, CCNT 1
J* J -H6
Nevertheless, the attitudes that l e d to the successful introductions had serious repercussions. Rabbits, foxes and goats are some of the better-known introduced animals that wreak havoc o n the environment, cause great losses to farmers, and endless cost and effort i n ongoing attempts at control. In some Australian habitats, the C o m m o n Starling steals scarce nesting sites i n tree hollows f r o m native birds. House Sparrows, introduced to eat the caterpillars that were ruining the livelihood of m a n y farmers, themselves became m i n o r pests that damage fruit. European Carp, not even regarded as good f i s h for the table, dominate many waterways.
Australia, of course, is not alone i n suffering the consequences of the actions of acclimatisation societies. The societies also introduced m a n y A u s t r a l i a n animals to N e w Zealand, i n c l u d i n g the endearing C o m m o n Brush-tailed Possum. The possum is n o w one of N e w Zealand's most serious pests.1 7 4 It carries tuberculosis, w h i c h is a menace to agriculture, causes extreme damage to native forests and, through predation and habitat changes, threatens populations of native animals.
Table 1.2 A selection of Australian animals that have been introduced successfully to New Zealand, some of which have become pests.
Species Abundance Pest status
Amphibians
Green and Golden Bell Frog Common
Brown Tree Frog Common
Not regarded as a pest Nuisance Birds Sulphur-crested Cockatoo Eastern Rosella Laughing Kookaburra Australian Magpie Rare Common in north Rare Common
Not regarded as a pest Perhaps a pest Unknown Minor pest
Mammals
Common Brush-tailed Possum Tammar Wallaby Parma Wallaby Red-necked Wallaby Brush-tailed Rock-wallaby Swamp Wallaby Abundant Locally common On one small island Locally common On one small island On one small island
Major pest Minor pest
Not regarded as a pest Minor pest
Being eradicated Not regarded as a pest
A U S T R A L I A ' S P E S T A N I M A L S
Australians have also been great transporters of their o w n w i l d l i f e around the country. Platypus, Koalas, C o m m o n Brush-tailed Possums, Tammar Wallabies, Emus, Australian Brush-turkeys, Cape Barren Geese, L a u g h i n g Kookaburras and perhaps A u s t r a l i a n Magpies, are some of the species introduced successfully to Kangaroo Island off SouthAustralia. Recently, the possums were f o u n d to be the m a i n reason f o r the poor breeding success of the endangered Kangaroo Island Glossy Black-Cockatoo, because they eat nestlings,2 3 5 and the Koalas have become so numerous that they have stripped the eucalypts on w h i c h they and other animals depend f o r f o o d a n d shelter.
Perceptions of pests
A t t i t u d e s to animals, whether native or i n t r o d u c e d , change w i t h time a n d circumstance. A n example is the ever changing fortunes of the kangaroo (see below 'Kangaroos: f r o m curiosity to resource'), Australia's National Emblem. Even today it is regarded b y sections of the c o m m u n i t y as being any combination of the f o l l o w i n g : a d a m a g i n g pest to fences and pastures; a cause of road accidents; an animal to hunt; a source of commercial gain; a unique member of the Australian fauna; an attractive a n i m a l w i t h rights; a n d i n need of conservation.
Kangaroos: from curiosity to resource
Kangaroos embodied the earliest European settlers' reactions to the nature of Australia: at once threateningly u n f a m i l i a r and fascinatingly u n i q u e .6 5 They were considered curiosities a n d dangerous to handle, but were also kept as pets a n d put on display. B y First Settlement, i n the late eighteenth century, they were harvested to s u p p l y meat for public consumption. A s the colony became more comfortable, clubs were f o r m e d for the popular sport of hunting kangaroos and Dingoes.Aspecial kangaroo-dog was developed— a cross between a swift greyhound and a mastiff or similar p o w e r f u l l y jawed breed.
Such was the slaughter that even as early as 1822 concerns were expressed about kangaroos' s u r v i v a l i n the Blue Mountains: 'the stockmen hunt them and the cattle and sheep supplant them. In a f e w years, the kangaroo w i l l be as rare as the native burghers ...'9 This was echoed b y the famous evolutionary biologist Charles D a r w i n6 2 w h o , i n the 1830s, after b e i n g taken o n an unsuccessful hunting trip d u r i n g w h i c h no kangaroos were seen, observed that, 'It may not be long before these animals are altogether exterminated.. , '6 5
W h i l e there are no reliable records to substantiate these perceptions of a serious decline i n kangaroo numbers, it is clear that b y the mid-nineteenth century another change i n attitude h a d occurred. The kangaroo h a d come to be regarded as a serious pest that competed w i t h stock for precious pasture. In order to remove large numbers, a h i g h l y successful technique, called a battue, was b o r r o w e d f r o m the A b o r i g i n a l people. This was an organised r o u n d - u p w i t h the objective of heading kangaroos into an ambush, such as a fenced enclosure or pit, where they were either clubbed to death or shot. Slaughter f o r pest control soon developed into a commercial enterprise. A b o u t one m i l l i o n kangaroos per year were destroyed a n d there w a s a
M O R E T H A N A N A T T I T U D E : P E R C E PTI O N S O F P E S T S
lucrative market for kangaroo products such as skins. In 1880, one f i r m i n A m e r i c a received 6000 kangaroo skins weekly. D u r i n g the second half of the nineteenth century, the Melbourne market for skins alone accounted f o r at least 500 000 animals per year.
In the late 1960s, a severe drought reduced kangaroo numbers and there were concerns about the added pressure on populations f r o m harvesting. A n anti-harvesting lobby became influential i n the U n i t e d States (then the major importer of kangaroo products), a n d i n A u s t r a l i a . Both Red a n d Grey Kangaroos were placed o n the U S A threatened f a u n a list a n d an embargo was placed on the import of kangaroo products. W i t h m u c h of the market lost, several commercial harvesters left the industry and for a time the harvest declined dramatically.
Despite persecution a n d exploitation and concerns that numbers were f a l l i n g , most authors believe that, since European settlement, kangaroo numbers have increased substantially i n Australia's rangelands, at least i n the eastern pastoral z o n e .2 0 3 Estimates made i n 1990 showed that the f o u r most c o m m o n species of kangaroo numbered 8.6 m i l l i o n f o r the rangeland areas of N e w South Wales alone.1 3 7
Today, only the larger, more abundant species of kangaroo can be harvested coinmercially and there are three recognised objectives for their management. The p r i m a r y a i m is to ensure the conservation of all harvested species a n d to maintain them over their natural ranges. Secondary aims include reducing the damage they cause to rural production and, where appropriate, ensuring sustainable use of the resource.1 3 7 U n d e r the Commonwealth Wildlife Protection
(Regulation of Exports and Imports) Act 1982, c o m m e r c i a l harvesting of kangaroos for export requires prior C o m m o n w e a l t h approval of a kangaroo management program. U n d e r approved management plans, the 1995 and 1996 national harvest of kangaroos was just over 3 m i l l i o n annually, and the quota f o r 1997 is 4.4 m i l l i o n .2 3 7
J
Even today the pest status of Kangaroos is controversial; are they valued native animals, a harvestable resource or competitors with stock? Source: BRS
A U S T R A L I A ' S P E S T A N I M A L S
In reality, the true status of an animal is often irrelevant—it is h o w the animal is perceived that determines its pest status.1 6 5 A g o o d example of this is the Cane Toad, w h i c h has been branded a pest and has attracted the attention of the public and m e d i a largely because it is unattractive, toxic and h i g h l y visible. Yet there is little reliable i n f o r m a t i o n about the damage it causes to native w i l d l i f e . Indeed, the f e w studies that have been done indicate that Cane Toads have little or no impact. The toad can k i l l f a m i l y pets and native animals b y e x u d i n g a poison w h e n it is eaten or bitten. However, most pets learn to a v o i d the toad, and i n all cases studied, native animals appear to recover to original p o p u l a t i o n levels i n a relatively short time after the toad has i n v a d e d the area7 8 (also see 'Cane Toads: a real or perceived pest problem?', pages 82-84).
U n t i l recently many Australians regarded cats as f a m i l y pets that took the occasional bird or lizard. A public awareness campaign b y C o m m o n w e a l t h and State conservation agencies over the past decade dramatically changed this attitude. Today cats are often presented i n the media as a major threat to native w i l d l i f e ,2 1 2 even though there is little sound research to support this v i e w p o i n t2 8 , 4 0
a b o u t p e t f o o d I \
( f
/ U K
\ 0
0
AUSTRALIAN
ILDLIFE
Source: Environment Australia
Whereas Cane Toads and feral cats are w i d e l y perceived to be serious pests, without good evidence one w a y or the other, some animals elicit more m i x e d reactions. Indeed, at any one time attitudes towards an a n i m a l can v a r y w i d e l y (see Table 1.3). In the Flinders and G a m m o n Ranges i n South A u s t r a l i a , feral goats are pests that threaten the s u r v i v a l of rare plants and animals i n significant national p a r k s .1 5 2 Yet, i n other parts of A u s t r a l i a they are increasingly harvested for their meat and s k i n s .1 7 3 M i x e d feelings also exist f o r f i s h such as introduced trout, w h i c h are p r i z e d b y anglers but are also environmental pests that devour native aquatic l i f e .3 8
Community attitudes can determine the success or failure of a pest control program?0
A l t h o u g h public understanding of pests and pest management is variable, it is generally poor.7 7 Nevertheless, community attitudes can determine the success or failure of a pest control program. Initially, the debate that occurred i n the media about proposed culling of feral horses in the Northern Territory tended to be adverse, and public outcry might have brought an end to the proposed culling program. 20
M O R E T H A N A N A T T I T U D E : P E R C E PTI O N S O F P E S T S Management of popular species
such as horses can be a sensitive issue. This starving herd gathered at a Queensland waterhole during drought vividly illustrates the need for humane control.
Source: Queensland DEH
'.IV
a.
3^.
1
,1-Fortunately, public input had been sought and considered carefully i n the program and the debate matured into one about the damage caused b y feral horses and the need to implement humane control. Most animal welfare organisations n o w accept, albeit reluctantly, that control of feral horses is necessary.6 7-1 5 3
Table 1.3 Some examples of the diversity of opinion about feral rabbits and their control
Legislators 'landholders are compelled by law to suppress rabbit populations'
Rabbit control authorities 'rabbit control is necessary and desirable' Concerned intensive landholders 'control is necessary and desirable'
Unconcerned intensive landholders 'myxomatosis is still doing a good job; I will control my rabbits when my neighbours control theirs; a few good rabbits are good for dog food; the rabbit inspector has not
told me to do anything; the next drought will kill them off
Arid zone, rangeland or extensive 'properties are too large and returns per hectare too small to make control economic' landholders
'properties are too large and returns per hectare too small to make control economic'
Landholders whose land is 'I can't understand why some people cannot control their rabbits' unsuitable for rabbits
Foresters 'control is essential in young plantations'
Hobby farmers 'rabbits? what are they?'
National park authorities 'control or eradication is desirable but insufficient money is available; damage to vegetation from a few rabbits is insignificant'
Conservationists 'the only good rabbit is a dead one'
Commercial harvesters 'CSIRO ruined the industry by introducing myxomatosis' Recreational hunters 'it would be good to see a few more rabbits around'
City people ' i f s nice to see the odd rabbit but there are not as many as there used to be; my father lived on them during the depression'
A U S T R A L I A ' S P E S T A N I M A L S
Attitudes to animal welfare
The Australian and New Zealand Federation of Animal Societies is concerned about the interest of all non-human animals and is amazed at the treatment of these animals once they have been labelled by our community as pests. A lack of public debate enables much of this treatment to persist when reform is possible and well overdue}65
Today it is no longer acceptable to treat animals as objects without rights. There is an increasing expectation i n many sectors of the c o m m u n i t y that a l l animals, including pests, w i l l be treated humanely. A s i d e f r o m the moral obligation, failure to adequately consider animal welfare can cause major problems f o r pest control. It m a y lead to bans on the introduction a n d use of certain techniques. D u r i n g 1992 a n d 1993, the proposal to introduce myxomatosis to N e w Zealand for rabbit control sparked a major, protracted and often bitter debate1 6 5. The importance of animal welfare was also recognised i n the extensive treatment it received i n the recent assessment of the costs and benefits of introducing rabbit calicivirus disease (RCD) into A u s t r a l i a .3 4-1 4 6
Failure to improve the humane treatment of pest animals can also have major implications f o r trade. For example, there has been pressure b y a n i m a l welfare organisations to ban the live export of goats, most of w h i c h are feral.
The N a t i o n a l Consultative Committee on A n i m a l Welfare ( N C C A W ) , w h i c h is composed of both government and c o m m u n i t y representatives concerned w i t h animal welfare, recognises that pest animals cause extensive environmental and agricultural damage a n d that their numbers need to be controlled. N C C A W also understands that a judgement on a pest control program must take a l l factors into account, not just a n i m a l welfare. They further recognise that i n some cases it may not be possible to guarantee the humaneness of control methods f o r each pest a n i m a l although this s h o u l d be the goal.2 3 1
Pest control might be acceptable to the community i n one place but cause great concern i f it is carried out elsewhere, as this quote f r o m the Director of the A u s t r a l i a n and N e w Z e a l a n d Federation of A n i m a l Societies demonstrates: 'Rabbits d u g burrows, f e d i n the open and were more or less contained b y feral cats, some winter f l o o d i n g of burrows (and consequent death of [rabbit] kittens), and the occasional piecemeal control b y land managers. But some cat control and a d r y year recently l e d to the announced need to reduce rabbit numbers to restore the other values of the area. There was a storm of protest f r o m those l i v i n g close to the l a n d . You see the l a n d and the w i l d rabbits were situated i n the m i d d l e of Centennial Park i n Sydney. Right under the noses of members of the public that usually do not even consider what their country cousins are d o i n g to rabbits i n the semi-arid or grazing areas of N e w South W a l e s . '1 6 5
O f t e n it is the pest control method that causes most a n i m a l welfare concerns. N C C A W concluded that people concerned about some pest control methods are not always w e l l i n f o r m e d about them and that better information a n d more open debate might overcome their objections. Strategies for increasing public awareness and the need to consider a n i m a l welfare concerns i n the context of the costs and benefits of control are integral parts of successful pest management.
A n y pest a n i m a l management program s h o u l d be appropriately planned a n d coordinated u s i n g the most effective, humane methods a v a i l a b l e .2 2 W h e r e practicable, such programs s h o u l d also a i m to reduce the need for extensive
M O R E T H A N A N A T T I T U D E : P E R C E PTI O N S O F P E S T S
LEFT Animal welfare organisations have done much to promote the use of humane pest management techniques. Traps such as this are discouraged or banned in most States.
Source: Jonathan Lee
RIGHT The signs of myxomatosis begin about a week after infection. The rabbit is listless and a clear watery discharge weeps from the eyes. The eyelids, anal and genital areas swell and lumps form on the body. A virulent strain of myxomatosis kills in less than 13 days.
Source: NSWAF
o n g o i n g treatment.3 0 L a n d managers have several potentially cost-effective methods to reduce pest a n i m a l impact, each w i t h different a n i m a l welfare implications:
• k i l l i n g or removing b y poisoning, shooting, trapping or mustering; • exclusion;
• biological control;
• habitat manipulation; and
• other management practices (these are explained i n Chapter 4).
It is not possible to q u i c k l y develop new, humane techniques to replace those that are questioned on animal welfare grounds. Nevertheless, a n i m a l welfare groups expect pest controllers to be able to show that the a n i m a l welfare costs f r o m control can be justified i n terms of the production and environmental gains. In other words, if techniques are used that cause pest animals to suffer, the resulting reduction i n pest damage must be clear.
Cage traps f o r pigs are considered humane as l o n g as the traps are checked regularly and the trapped animals humanely destroyed. U s i n g dogs to control pests such as feral pigs is considered to be inhumane, not o n l y because of the stress of capture and injuries inflicted o n pigs prior to death, but also because of the risk of i n j u r y to the d o g .4 8
Shooting f r o m helicopters is an effective control technique for several pest species a n d , p a r t l y d u e to the i n f l u e n c e of a n i m a l w e l f a r e g r o u p s , the professionalism of shooters is generally very high. Shooting f r o m helicopters is considered to be acceptable p r o v i d e d that control operations are conducted b y trained marksmen and that there is a follow-up inspection for any injured animals. A l t h o u g h it can be humane, shooting pests f r o m the ground has limited pest control potential for smaller pests, such as rabbits and foxes, because i n most situations it removes o n l y a s m a l l proportion of the p o p u l a t i o n .1 5 3'1 9 8 , 2 2 5
A n o t h e r relatively humane method of controlling pests such as feral horses, donkeys, and goats is mustering, usually for sale for meat. However, the necessary live transport of w i l d animals such as feral horses and goats to abattoirs can cause suffering, especially w h e n they travel l o n g distances.6 7-1 5 3
The humaneness of p o i s o n i n g is variable because of differences i n poisons and variation i n the pest species' response. Some poisons, specifically y e l l o w phosphorus (CSSP) and chloropicrin, used on feral pigs and rabbits, respectively,
A U S T R A L I A ' S P E S T A N I M A L S
are inhumane and s h o u l d be phased out.4 8 , 2 2 5 M o r e humane alternatives are available and include pindone and cholecalciferol.
Concern over the suffering caused b y myxomatosis is one reason that, i n 1993, the N e w Zealand government decided against the introduction of m y x o m a virus to control rabbits. The new rabbit calicivirus disease (RCD) is considered to be m u c h more humane, i n part because it kills more q u i c k l y and the rabbits show no signs of suffering (see ' R C D , a potential biological control agent for rabbits', pages 66-67).
It is important that governments and other organisations responsible f o r pest animal control ensure that animal welfare concerns are appropriately considered, put into perspective and effectively communicated to the community. M o s t States and Territories have comprehensive animal welfare legislation. The relevant State and Territory agencies and national committees, such as N C C A W and the R S P C A , have an important role i n safeguarding the welfare of animals, i n c l u d i n g pests, by developing Codes of Practice f o r the control of animals. Pest management should be consistent w i t h these codes, w h i c h include the Subcommittee on A n i m a l Welfare's ' M o d e l C o d e of Practice f o r the Welfare of A n i m a l s , Feral Livestock A n i m a l s (1991).'
The guidelines expressed i n the ' A u s t r a l i a n C o d e of Practice for the Care and Use of A n i m a l s for Scientific Purposes'1 5 3 apply equally w e l l to pest control: ' P a i n and distress cannot easily be evaluated i n animals, and therefore investigators must assume that animals experience p a i n i n a manner similar to humans. Decisions regarding their welfare i n experiments must be based on this assumption unless there is evidence to the contrary.'
Attitudes of Aboriginal peoples
Feral animals come into the country and settle down. Now they belong here.19*
A b o r i g i n a l peoples are major A u s t r a l i a n landholders w i t h an increasing interest i n returning to or remaining on traditional lands. A m o n g indigenous peoples, attitudes to feral animals are as varied as those h e l d b y n o n - A b o r i g i n a l peoples. Nevertheless, the prevailing v i e w that introduced animals are less valuable than native species is not shared b y m a n y A b o r i g i n a l people.1 9 4 Indeed, feral species are quite often perceived to belong to the l a n d and to have taken the place of the animals that disappeared w h e n Europeans arrived. Some introduced animals have even been incorporated into A b o r i g i n a l l a w and spirituality—for example, cats i n some Central A u s t r a l i a n A b o r i g i n a l c o m m u n i t i e s .1 6 0 1 9 4
Several A b o r i g i n a l communities depend o n feral animals f o r subsistence.2 5 For example, feral pigs are a favoured f o o d of the indigenous communities o n Cape York; rabbits and cats are hunted b y w o m e n i n the Y u e n d u m u - W i l l o w r a region of Central N o r t h e r n Territory; and, after kangaroo, rabbit is the meat most often consumed b y A b o r i g i n a l people on outstations i n the M a r a l i n g a lands of South Australia. Indigenous people are also i n v o l v e d i n commercial exploitation of introduced animals. For example, they are e m p l o y e d to hunt pigs to export as game meat and they harvest buffalo f o r export and to sell to breeders and local abattoirs.5 2
Conservation programs f o r native species such as the Bilby, w h i c h i n v o l v e control of cats, can conflict w i t h A b o r i g i n a l peoples' use of the feral animals for 24
M O R E T H A N A N A T T I T U D E : P E R C E P T I O N S O F P E S T S food. Where feral species have been removed (such as the buffalo w h i c h degraded wetlands i n K a k a d u N a t i o n a l Park) an important resource to the indigenous people m a y also have disappeared. In K a k a d u , to replace the feral b u f f a l o , traditional owners negotiated w i t h the A u s t r a l i a n N a t i o n a l Parks a n d W i l d l i f e Service a n d are allowed to maintain a small herd of buffalo i n the Park f o r their use; they have also increased their harvest of estuarine crocodiles.
A review of the attitudes and perceptions of Central Australian A b o r i g i n a l people to land management issues1 9 4 uncovered a diversity of opinions, i n c l u d i n g that feral animals belong to the country, feral animals are so numerous that they should be used, a n d that there are too many feral animals a n d too f e w native animals. A c o m m o n v i e w p o i n t was that feral animals are a resource rather than an e n v i r o n m e n t a l t h r e a t1 6 0 a n d better use of t h e m is the m o s t d e s i r a b l e management option w h e n they cause environmental damage.2 1 2 A n example is that of feral horses, w h i c h have a commercial value to some desert people w h o believe that, if horses are to be controlled, they should be k i l l e d i n an abattoir and not on the land where the carcass is wasted.1 9 4
W h e n i n t r o d u c e d species are perceived to have a negative impact o n an important w i l d l i f e resource, or to compete for f o o d w i t h cattle o n A b o r i g i n a l pastoral land, m a n y A b o r i g i n a l people support their removal.2 5 Some A b o r i g i n a l peoples also recognise that introduced species can damage sacred sites.
Many of the concerns of non-Aboriginal land managers are not shared by Aboriginal people. Explanations for the nature and condition of land and resources have their root in Aboriginal culture rather than in the western scientific paradigm. This is an issue of great importance when looking at any activities which take place on Aboriginal land}9*
Particularly where the use of introduced species as a subsistence resource conflicts w i t h a need f o r their control to conserve native species or prevent environmental damage, a n d where rare or endangered species are hunted, it is important that the goals and aspirations of a l l concerned are considered i n any management initiatives.2 4 A l t h o u g h the v i e w s of A b o r i g i n a l l a n d managers stem f r o m greatly different cultural roots to those of non-Aboriginal peoples, a common Feral animals have often replaced
native species, such as these wallabies, in the diet of Aboriginal peoples and pest management may cause conflict.
Source: Jon Altman, CAEPR
m
MkV<
mm
A U S T R A L I A ' S P E S T A N I M A L S
commitment to sustainable use of the l a n d m a y help to reconcile the sometimes disparate perspectives. The belief systems of indigenous peoples m a y promote sustainable use of the environment, and the people m a y be sympathetic to pest control i f pests are s h o w n to cause serious damage to v a l u e d resources.2 5 Discussing the issue of pest management objectively, i n terms of the damage pests cause, m a y identify m u t u a l l y acceptable solutions.
Attitudes of governments
With the intention of encouraging fox control in the early 1990s, the
Victorian Government allotted a ticket in Foxlottofor every fox scalp. Foxes continued to thrive and interest in the scheme quickly waned.
In the past, pest a n i m a l control was often heavily subsidised b y government, w h i c h p r o v i d e d bounties and cheap equipment and labour. F o r example, i n 1885 alone, the South A u s t r a l i a n Government spent $2.1 m i l l i o n as bounty o n rabbit scalps.1 5 7 Between 1945 a n d 1959, the Queensland Government p a i d bounties on 240 000 fox scalps at a cost of $1.15 m i l l i o n7 4 and, between 1901 a n d 1907, to prevent the westward movement of rabbits, the Western A u s t r a l i a n Government spent $33 m i l l i o n o n a rabbit-proof fence 1700 kilometres l o n g .1 9 3 A l l of these initiatives failed to control the pests.
M o r e recently, the Victorian Government introduced a bounty called Foxlotto. For each fox scalp, hunters received a ticket i n the Foxlotto p o o l prize. In 1992-93, 15 000 fox scalps were received a n d i n the next year 5600. This h a d no significant effect o n the p o p u l a t i o n a n d the scheme was abandoned the f o l l o w i n g year.1 6 5
Governments generally recognise that traditional bounty schemes are ineffective for controlling vest animals such as pigs.48
It is n o w w e l l accepted that bounties do not w o r k .8 8 , 2 0 6 One reason for this is that, w h e n someone else is p a y i n g for control, there is little incentive to ensure that the money is spent w i s e l y to achieved desired targets. Some scientists have suggested that there m a y be a role for 'smart bounties'. For example, farmers could subsidise commercial feral a n i m a l harvesters to reduce and h o l d the pest
FOXLOTTO
1992 Ticket Number: 36101 Draw Entered: , Name: Postal Address: Phone Number:Shooters Licence Number:
Area Where Fox Taken:
Public L a n d j | Private L a n d j j
I certify thai (he above information is correct and 1 have not broken any Victorian Acts or Regulations during the collection of this skin/scalp.
Signature: Date: Please Circle: Professional Shooting Club Primary Producer
\
FOXLOTTO
1992 Draw Entered: Ticket Number:36101
'•^Conservation & Environment 26M O R E T H A N A N A T T I T U D E : P E R C E P T I O N S O F P E S T S In the past, governments
subsidised rabbit control by paying bounties on scalps, and supplying equipment and labour to build barriers to rabbit movement, but these initiatives proved
unsuccessful. Today governments are more likely to assist by providing advice on management and by funding one-off control strategies such as the release of rabbit calicivirus.
Source: Peter Bird, APCC
a n i m a l population at a level below that w h i c h w o u l d be economic f o r farmers if they were unassisted. However, it is n o w argued that even these forms of payment should not be seen as a bounty, but as part of overall f a r m i n g costs.
G o v e r n m e n t agencies have a major role i n pest a n i m a l management as legislators, representatives of the w i d e r community, and managers of areas such as national parks. It is important that governments do not encourage inappropriate action b y subsidising landholders' management practices, f o r example through bounties. The costs of pest control o n private l a n d s h o u l d be shared equitably between the private goo d (production) and the public good (conservation). If there is no p u b l i c benefit, there is no case for action b y the government. G o o d management can be encouraged through appropriate incentives w h i c h benefit both the l a n d manager and the public, and through research, education and training. If governments w i s h to subsidise the private good it is best done through actions that do not require on-going f u n d i n g . One w a y a government might assist is b y p r o v i d i n g a coordinator to help p l a n and oversee the implementation of a pest management scheme developed b y local private and c r o w n l a n d managers, as n o w occurs under the N a t i o n a l Landcare Program. Another is b y f u n d i n g one-off control strategies such as biological control.
changeable pest
The fluid nature of pest status
The previous chapter outlined h o w the pest status of an a n i m a l can change considerably, d e p e n d i n g o n the w a y the a n i m a l is regarded b y a particular i n d i v i d u a l or group. In other words, humans decide whether an animal is a pest. In this chapter, some of the reasons that the pest status of an a n i m a l can alter are explained i n more detail. For a variety of reasons, an a n i m a l m a y increase i n numbers or distribution and threaten a valued resdurce. Introduced animals, and even pets and native w i l d l i f e , i n the w r o n g place at the w r o n g time, can become pests. A harmless animal can become a pest w h e n l a n d use is changed or because it is f o u n d to carry a disease of concern to humans, stock or w i l d l i f e . Conversely, if a market is created, a harvestable pest can become a v a l u e d resource, and an innovation i n management m a y lessen pest animal damage to such an extent that the animal is no longer regarded as a pest.
Change in the number of animals
The pest status of an animal can v a r y along w i t h its fortunes. A g o o d example of this is the infamous Black or Ship Rat, once feared as the carrier of h u m a n (bubonic) plague, w h i c h spread around the w o r l d w i t h humans to become a major threat to a variety of s m a l l animals. The rat is n o w so scarce i n E n g l a n d , where it was introduced i n pre-Roman times, that it m a y need protection.8 6 A n A u s t r a l i a n example is the L o n g - b i l l e d Corella, w h i c h is regarded as a major pest i n the Victorian grain belt. However, its numbers have declined to the point where it is n o w considered endangered and i n need of management f o r conservation.2 The question of h o w best to manage the corella and the damage it causes is a major d i l e m m a for farmers and conservation agencies.2 4 3
O n the other h a n d , after several years of h i g h b r e e d i n g success, a n i m a l populations m a y reach a size where they begin to be regarded as pests. For example, i n south-east A u s t r a l i a , the H o u s e M o u s e is mostly a relatively benign creature. However, w i t h suitable seasonal conditions (usually every three to five years) a plague occurs and w i t h it a r a p i d rise i n the mouse's pest status.
Change in land use
A change i n l a n d use often creates a n e w pest. A n obvious example is that of the conversion last century of the rangelands to pastoral land, particularly for lamb production. This soon put the D i n g o , w h i c h had been i n A u s t r a l i a for centuries
T H E C H A N G E A B L E P E S T before Europeans, at odds w i t h the l a n d managers (see 'Exclusion of pests: the D i n g o fence', page 65). Moreover, resultant management of predators a n d the provision of permanent water have made the area more favourable to goats and kangaroos, w h i c h are also often regarded as pests.
Cultivation of Bluegums for paper production is a r a p i d l y developing industry i n south-western Australia. B y the mid-1990s, 40 000 hectares h a d been planted a n d another 60 000 hectares are planned (see 'Improved management to control parrot damage to Bluegums', page 73). U n t i l the gums were cultivated, Australian Ringnecks were considered a c o m m o n a n d attractive part of the local b i r d life. N o w these parrots are regarded as major pests that damage about 20 per cent of the B l u e g u m plantation b y stripping the bark f r o m the branches, n i p p i n g off the lead shoots and causing the trees to g r o w deformed.
In tropical northern A u s t r a l i a , several native birds a n d two species of f l y i n g -fox are considered to be pests of crops.1 1 9 The animals were not regarded as a p r o b l e m u n t i l f r u i t crops such as rambutans were g r o w n i n the area. Recently, some growers have replaced rambutans w i t h crops such as mangoes that are less susceptible to damage.
Rice and Magpie Geese
Magpie Geese were originally blamed b y government and farmer alike for the failure of the ambitious H u m p t y D o o Rice Development Scheme. Traditionally, the geese bred and f e d o n the floodplains of the A d e l a i d e River i n the Top E n d of the N o r t h e r n Territory. The H u m p t y D o o Rice Scheme was i n the m i d d l e of one of the floodplains and the geese f e d o n the rice grain, ate the seedlings, a n d trampled the plants.
Eventually it became evident that the geese were a minor player i n the failure of the Scheme. Rains and floods ruined the first crop i n 1952 and drought thwarted the second attempt. Stem-boring moths, grasshoppers and rats, as w e l l as the M a g p i e Geese, attacked the crops. The next decade was marked b y erratic rainfall, inadequate f u n d i n g , inefficient processing, poor rice yields, and high transport, labour and equipment costs, all of w h i c h contributed to its inevitable failure. The M a g p i e Geese are n o w a major tourist attraction o n Fogg and Harrison dams, both built for the abandoned rice scheme.1 4 1
Wltere they conflict zoith human interests, native birds such as Galahs and Little Corellas can become pests. Large numbers may build up at concentrated food sources like crops and cattle feedlots.
A U S T R A L I A ' S P E S T A N I M A L S
Pest or resource: the commercial use of pest animals
Not surprisingly, the pest status of an animal can change with its commercial worth. The value of feral goats for export, mainly to Asia, has increased significantly i n recent years, to about $15 per head at the farm gate in Queensland. M a n y farmers see harvesting of the goats as an important supplement to their farm income, especially now that the impact of deregulated agricultural markets and other problems have eroded the return f r o m traditional products such as wool, beef and lamb. Worth $29 million i n 1991-92, the feral goat industry is growing rapidly and exporters f i n d it difficult to keep up w i t h demand. If the value of goats was to increase to $25 per animal, farmers w o u l d be tempted to reduce their sheep flocks and r u n more goats. In N e w Zealand, deer were introduced as game animals late last century and seen as a recreational resource u n t i l the 1920s w h e n their damage to native forests and competition w i t h domestic stock led to massive, largely ineffective, government-f u n d e d control campaigns. D u r i n g the 1960s a market government-for venison was developed i n G e r m a n y and, w i t h the advent of helicopters f r o m w h i c h to shoot and collect deer, many hundreds of thousands of animals were killed or, more recently, captured alive to stock deer farms. Today the deer are regarded as a resource b y commercial and recreational harvesters, but are viewed as a pest by conservation groups, and by some farmers concerned that the deer may infect stock w i t h bovine tuberculosis.1 7 3 C o m m e r c i a l harvest of A u s t r a l i a n pest animals, p r i m a r i l y for export, is w o r t h more than $100 m i l l i o n a year.1 8 4 Species taken include feral horses, goats and pigs, and, u n t i l the spread of rabbit calicivirus disease, rabbits. Particularly i n the rangelands, m a n y farmers n o w harvest such pests as a w a y to d i v e r s i f y their production base. This move has been aided by the p r o m o t i o n of game meat as healthy because it is lean, free of chemical residues and l o w i n cholesterol.Some authors suggest that commercial harvesting of pest animals such as feral horses, pigs and goats may help to manage the damage they cause.4 8'6 7'1 7 3 However, further studies are needed to determine whether this is the case. For other pests, such as rabbits a n d foxes, harvesting seems to be of little value. The density of rabbits at w h i c h shooters w i l l stop commercial harvest is thought to be w e l l above Before the introduction of
myxomatosis, rabbits were abundant in south-eastern Australia. Government bounties and strong markets for meat and fur made rabbit trapping profitable.
Source: NSWAF (duplicated from print, circa 1948, Coiora)
1
T H E C H A N G E A B L E P E S T that necessary to prevent significant damage.2 2 5 Similarly, harvest of foxes for fur, even at its peak w h e n A u s t r a l i a was exporting 350 000 pelts per year, h a d little apparent effect o n their density.1 9 8 Moreover, hunters removed animals where it was easiest, not necessarily where control was most needed.
Native animals as pests
L i k e exotics, native animals m a y also be seen as pests i f they conflict w i t h h u m a n interests. N a t i v e animals rarely cause environmental problems unless they have been transplanted to a place where they do not occur naturally, or where the environment has been altered first b y other agents of change, such as vegetation clearing or the p r o v i s i o n of water.
N a t i v e animals such as kangaroos, wallabies, wombats, parrots and f r u i t bats can cause damage to crops, pasture and natural ecosystems. E v e n some rare species, such as the Southern Hairy-nosed Wombat, and threatened species, such as the Long-billed Corella, can be pests. This was acknowledged b y Australia's p r i m a r y nature conservation body, the Australian and N e w Zealand Environment and Conservation Council ( A N Z E C C ) i n its recognition of three aims for managing kangaroos:
• conservation of kangaroo species;
• reduction of the damage kangaroos cause; and
• where possible, management of kangaroos as a renewable resource.
The damage control and harvesting aims are permitted p r o v i d e d that they do not compromise the p r i m a r y a i m of conserving kangaroos.
N a t i v e animals that have been m o v e d to new habitats can also become pests. Two Western A u s t r a l i a n examples are L a u g h i n g K o o k a b u r r a s , w h i c h were introduced as snake-killers, and Sulphur-crested Cockatoos, originally brought to the west as pets. Both have spread and compete w i t h local species for scarce nest h o l l o w s i n trees, and the cockatoo is also an agricultural pest. A s a result, Western A u s t r a l i a has strict legislation to control the import of potential pests, i n c l u d i n g m a n y native animals, f r o m east of the Nullarbor.
Whereas the approach to managing native pests is similar to that for introduced animals, it is usually more complex because of p u b l i c concern about the balance between conservation and control of native w i l d l i f e . The preferred strategy for n a t i v e pests is to attempt to m a n a g e the d a m a g e they cause b y habitat manipulation or other non-lethal techniques.1 8 9
Native animals, such as the Emu, can become pests through changed land use or increased numbers.
Source: Noel Preece & Penny van Oosterzee
