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BACKGROUND DOCUMENT

for the



Threat abatement plan

for predation by the European red fox

2008

Department of the Environment, Water, Heritage


and the Arts

ISBN 978-0-642-55394-2

© Commonwealth of Australia 2008

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 Commonwealth, available from the Department of the Environment, Water, Heritage and the Arts. Requests and inquiries concerning reproduction and rights should be addressed to:

Assistant Secretary
Biodiversity Conservation Branch
Department of the Environment, Water, Heritage
and the Arts
GPO Box 787
Canberra ACT 2601

This publication and the threat abatement plan are available on the internet at: http://www.environment.gov.au/biodiversity/threatened/tap-approved.html

They are also available by emailing the Department of the Environment, Water, Heritage and the Arts, Community Information Unit, at ciu@environment.gov.au
or freecall 1800 803 772.

This publication should be cited as: Department of the Environment, Water, Heritage and the Arts (DEWHA) (2008). Background document for the threat abatement plan for predation by the European red fox, DEWHA, Canberra.

Front cover photo: Graeme Purdy

Technical editing and production management: Biotext Pty Ltd

Design and artwork: Design Direction

Contents

1 Introduction 1

1.1 Fox distribution 1

1.2 Impact of foxes 2

1.3 Fox biology 3



2 Controlling foxes 4

2.1 Baiting 5

2.2 Biological control 6

2.3 Barriers 6

2.3.1 Fencing 6

2.3.2 Islands as natural barriers 7

2.4 Habitat management 8

2.5 Shooting 8

2.6 Bounties 8

3 Factors affecting fox control 9

3.1 Impacts on non-target species 9

3.2 Effects of wild rabbits, dingoes and feral cats 9

3.3 Animal welfare concerns 10

3.4 Cultural issues 10

4 Developing a national approach to fox management 12

4.1 Planning for nationally coordinated action 12

4.2 Strategies for allocating resources to fox management 12

4.3 Identifying priority areas for action 14



Appendix A: Threat abatement plans and the EPBC Act 16

Glossary 18

Acronyms and abbreviations 20

References 21

1 Introduction

This is the background document to the Threat abatement plan for predation by the European red fox (DEWHA 2008). It provides information on fox characteristics, biology and distribution; impacts on environmental, economic, social and cultural values; and current management practices and measures.

The threat abatement plan (TAP) establishes a national framework to guide and coordinate Australia’s response to the effects of predation by the European red fox on biodiversity. It identifies the research, management and other actions needed to ensure the long-term survival of native species and ecological communities affected by foxes. It replaces the Threat abatement plan for predation by the European red fox published in 1999 (EA 1999).

1.1 Fox distribution

The European red fox (Vulpes vulpes) has a natural distribution across the continents of Europe, Asia and North America. Hereafter in this document, a reference to ‘fox’ means ‘European red fox’ unless specifically indicated otherwise. In the Southern Hemisphere, foxes occur only in Australia, where they were introduced by English settlers in the 19th century (Rolls 1984). The fox is now one of at least 20 exotic mammals that have established a feral population (Strahan 1995). An adaptable and elusive predator and scavenger, the fox is distributed widely across the Australian mainland except for the far north (see Figure 1.1), and is now confirmed to be present in Tasmania (Saunders et al. 2006), although the extent of its distribution there is yet to be determined. Foxes in Tasmania are currently the subject of a major eradication program. The fox is creating environmental and economic impacts in Queensland (Gentle 2006); however, it has not yet colonised the tropical far north and is not established on Kangaroo Island or other offshore islands. In the light of current knowledge of control methods and ecology, the fox must be viewed as a permanent addition to the fauna of the Australian mainland.



Figure 1.1: Occurrence of the European red fox, Vulpes vulpes

Source: IA CRC and NLWRA (2007)



1.2 Impact of foxes

In 2004, foxes were estimated to cost the Australian environment and agricultural industries more than $227 million, of which $190 million was environmental impact (McLeod 2004). This estimate was based on two foxes per square kilometre, and a total of 7.2 million foxes in Australia. Anecdotal, circumstantial and experimental evidence shows that fox predation is a major threat to the survival of native Australian fauna (Saunders et al., in press). Terrestrial mammals at the greatest risk are those that weigh between 35 and 5500 grams (sometimes referred to as critical-weight-range species) and ground-nesting birds, many of which are endangered or vulnerable.

Given the extent of their impact on biodiversity, predation by the European red fox is listed as a key threatening process under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). Of the threatened species listed under the EPBC Act, foxes are considered a threat to 14 species of birds, 48 mammals, 12 reptiles and 2 amphibians, with the orange-bellied parrot, spotted quail-thrush (from Mt Lofty Ranges), herald petrel, Gilbert’s potoroo and western swamp tortoise listed as critically endangered
(see Appendix A of the current TAP).

For each key threatening process under the EPBC Act, the Minister must decide if a TAP is to be prepared. The Act prescribes the content of a TAP and the mechanisms by which it is to be prepared, approved and published. The relevant sections of the Act are reproduced in Appendix A.

Foxes occur on Commonwealth land such as national parks and Department of Defence properties. On a national scale, however, fox management on Commonwealth land is only a small part of the larger picture of conserving endangered or vulnerable species threatened by fox predation. State and territory wildlife agencies and their counterparts responsible for agricultural pest control have a long history of practical on-ground fox management, and it is largely through their efforts, often supported by Commonwealth programs, that major technical and strategic advances have been made.

1.3 Fox biology

A range of characteristics combine to make the fox an extremely successful invasive animal. It is listed by the World Conservation Union in its 100 worst invasive species in the world (Lowe et al. 2000). Foxes have a wide dietary range, few serious diseases and few natural enemies. They also have a high reproductive rate and a high rate of cub survival, although they only breed once a year.

Movement patterns vary during the year, depending on the breeding cycle. Sub-adult foxes are the most likely to disperse to new areas, particularly from late summer until the start of the breeding season. In one Australian study, some extreme dispersal distances were observed, the longest being a straight-line distance of 300 kilometres (Saunders et al. 2002).

2 Controlling foxes

Eradication of foxes is an attractive prospect because, once achieved, it requires no further commitment of resources; however, eradication is not currently considered a viable proposition for mainland Australia. According to Bomford and O’Brien (1995), to eradicate the fox:

• the mortality rate must be greater than the replacement rate at all population densities

• there must be no immigration

• sufficient foxes must be at risk from the control technique so that mortality from all causes results in a decrease in population

• all foxes must be detectable even at low densities

• a discounted cost–benefit analysis must favour eradication over control, and

• the socio-political environment must be suitable.

Complete removal of foxes from Australia is well beyond the capacity of available techniques and resources because the species is well established across a vast area. However, eradication from an island, or of a localised, newly introduced population, may be feasible provided a sufficiently rapid, well-funded and persistent campaign can be mounted.

Saunders and McLeod (2007) reviewed current knowledge on techniques for suppressing fox populations, including baiting, shooting, trapping, den fumigation or destruction, and exclusion fencing. The review concluded that, with the exception of broadscale baiting, the existing control methods are expensive and labour intensive, require continuing management effort and can be effective in only limited areas.

Fertility control through immunocontraception has been investigated as an alternative or supplementary means of fox control (Bradley et al. 1998), as has chemical fertility control (Marks et al. 1996). Other measures such as the use of guard animals have been promoted (Olsen 1998), but have not yet been fully evaluated in Australia.

Fox predation problems range in scale from individual foxes at a local level, to populations of foxes at the level of a national park or agricultural region (Saunders et al. 1995). The scale of the problem will determine the most appropriate and effective means of control. Large areas could be most appropriately targeted by aerial baiting or fertility control, while individual properties could make use of guard dogs. The cost-effectiveness and efficacy for each control technique, and in combination for integrated control programs, should be measured before deciding the most appropriate strategy.

Control of foxes will also be best achieved where integrated approaches target local or regional circumstances, and use the most appropriate suite of options to reduce and control population numbers and their impacts. Careful attention is needed in the selection and implementation of control methods to minimise any non-target impacts resulting from the control activities.

Control methods discussed here are baiting, biological control, barriers, habitat management, shooting and bounties.



2.1 Baiting

In most situations, poison baiting is the most effective method of reducing fox numbers and impact, although a major drawback is that it may affect native carnivores and scavengers such as dingoes, quolls, goannas and some scavenging birds, and also domestic dogs. The benefits of this control method are confined to the baited area and, unless some barrier prevents re-invasion, last only for as long as baiting is regularly applied.

Bait materials used in Australia include injected eggs, dried meat baits, fresh meat and commercial products such as Foxoff and De-Fox. The Western Australian Department of Environment and Conservation developed and manufactures its own bait, known as Pro-bait.

Aerial baiting of foxes can effectively control foxes in large areas, provided the risk of non-target bait uptake is minimal. In Western Australia — where aerial baiting is the most common form of fox control — baiting programs over areas of up to three million hectares have been shown to dramatically reduce fox numbers, to allow populations of rare species to increase and to have minimal impact on non-target species. This latter point is largely due to the native fauna having a higher resistance to the naturally occurring sodium fluoroacetate (1080) poison found in native plants.

Aerial baiting has not been implemented to the same extent in eastern Australia due to differences in landscape, land ownership, human habitation and lesser (compared to Western Australia) tolerance of native species to 1080 (Saunders and McLeod 2007), although it is used in Queensland and the Northern Territory (Sharp and Saunders 2004a). Aerial baiting is not legal on private land in New South Wales (Saunders and McLeod 2007), but the New South Wales National Parks and Wildlife Service has a special permit to aerial bait in the Yathong, Nombinnie and Round Hill nature reserves near Cobar to protect endangered mallee fowl. Further information on this program is available from their website.1

An example of a recent fox control program using aerial baiting is the collaboration between the Australian Wildlife Conservancy, the Invasive Animals Cooperative Research Centre and the Western Australian Government to reduce fox and cat numbers at Mt Gibson Wildlife Sanctuary. At the time of writing, sites for monitoring feral predator and prey abundance have been determined, a baseline ‘pre-baiting’ survey has been conducted and more than 70 000 aerial cat baits have been distributed on the property over a period of about six months. Early results suggest the baiting program has had a major impact on cat and fox numbers (IA CRC 2006), with foxes also taking the bait.

Where broadscale baiting is not feasible, and where the risk of bait uptake by non-target species is high, fox suppression at a local scale can be effective. With any small-scale baiting program (less than 1000 hectares), the establishment and maintenance of an effective buffer zone should be considered. Protection of prey species may require developing buffer zones of more than 15 kilometres, where foxes are held at a low density, to decrease the risk of inward migration rapidly replacing the foxes killed (Thompson et al. 2000).

Saunders and McLeod (2007) discuss the use of attractants in fox baits, a practice that has been recommended but not widely taken up. For example, a trial of bait containing synthetic fermented egg product, carried out in the southern highlands of New South Wales, found that the product significantly increased visits to the site from wild dogs and foxes (Hunt et al. 2005). The product is now commercially available, as FeralMone, in an aerosol can. Saunders and McLeod (2007) suggest that the development of this readily available and user-friendly commercial product could mean an increase in the use of attractants. They also note that auditory lures were successful in attracting foxes to bait stations in arid regions of South Australia.

One of the consequences of prolonged baiting is that animals may develop bait shyness or an aversion to the poisons being used. For example, if foxes consume sublethal doses of 1080 due to a combination of bait caching and decay, they may become averse to baits. Saunders and McLeod (2007) suggest that further research is needed to determine whether this situation is important and, if so, how it can be averted.

To be effective, baiting must be intensive and cover a large area (as in the Western Shield program in Western Australia). Therefore, Saunders and McLeod (2007) suggest that research should focus on how baits are deployed rather than on developing the perfect bait.



2.2 Biological control

Some form of pathogen could conceivably affect foxes on a continental scale, but currently none is known to be sufficiently virulent, humane and specific to foxes.

Since foxes only breed once a year over a short period in early winter, fertility control could be applied over a short period of time each year. Targeting fertility may yield an effective long-term approach to reducing fox numbers. However, fertility control will not significantly reduce the danger to prey species until fox numbers have been reduced by natural attrition or by other means. Lethal control (e.g. through baiting) will therefore still be needed to rapidly reduce fox numbers. This could be followed by fertility control, used strategically to keep fox numbers low and thus provide long-term protection for threatened species.

Saunders and McLeod (2007) provide a detailed review of the state of biological control of foxes. Fertility control is still at an experimental stage of development, but the aim is to develop a safe and effective fertility control agent that may be delivered in bait. In practice, fertility control of wild vertebrates has been achieved on only a very limited scale using expensive and labour-intensive methods (Bomford 1990). It has not been successfully applied to a free-ranging population of wild vertebrates over a large area, nor has it been attempted as a method of reducing the impacts of predation on an endangered or vulnerable species.

Methods of fertility control include hormone treatment and the use of abortifacients such as cabergoline. Hormone treatment is not considered a viable option for managing populations of wild foxes as there are no practical methods of ensuring effective treatment of unrestrained animals. Saunders and McLeod (2007) state that preliminary research on the use of cabergoline is equivocal and that the technique, if proven, may be appropriate where active dens can be targeted (e.g. in peri-urban environments), but its suitability in rural settings remains unsubstantiated. The authors also note the need for economic assessment of the use of cabergoline and consideration of ethical concerns.

Much funding has gone into immunocontraception, particularly in the past 10 years. The Cooperative Research Centre for Biological Control of Vertebrate Pest Populations began a major program of research on immunocontraception in 1992 with funding provided through the Australian Government. Saunders and McLeod (2007) suggest that the most likely outcome of research into immunocontraception for foxes would be a bait-delivered, immunocontraceptive vaccine containing zona pellucida antigens, delivered as an oral vaccine through a recombinant canine herpes virus (PAC CRC 2001). However, this research has been discontinued, and the use of an immunocontraceptive vaccine as a control method is unlikely to be trialled.



2.3 Barriers

2.3.1 Fencing

Australia has a long history of fencing to control pest animals, extending over more than a hundred years. The early fences were designed to control rabbits or dingoes. More recently, fences have been proposed as a component in conservation management programs to protect prey species from predators such as foxes and cats.

Various fence designs have been developed to exclude foxes, but their relative effectiveness has not been assessed because of the lack of published information (Long and Robley 2004). A list of fence types for the exclusion of foxes, rabbits and cats, and their estimated cost, is provided in Table 2.1. Moseby and Read (2006) more recently tested fence designs for conservation purposes and found that the most effective against foxes was a 180-centimetre-high wire netting fence with a foot apron and a 60-centimetre-wide external netting overhang, curved in an arc and supported by lengths of heavy gauge wire. Steel posts were more effective than timber, as the foxes targeted the posts. Electric wires were only effective if supplemented with a physical barrier to ensure that animals received a sufficiently severe shock to be repelled.

Table 2.1: Types of fences used for fox, rabbit and feral cat exclusion

Fence type

Characteristics

Estimated cost/kilometre

Floppy top

Floppy top and electric wire to prevent scaling
Mesh apron to deter digging under fence

$10 300
($9700 without electric wire)

Overhang

Overhang to prevent scaling
Wire netting barrier
Mesh apron to deter digging under fence

$9900
($8900 using 30 mm netting at base)

Electric wire overhang

Overhang and electric wire to prevent scaling
Wire netting barrier
Mesh apron to deter digging under fence

$11 400 with two electric wires plus an earth wire in overhang
($9800 with lighter grade posts)

Mesh/electric wire composite


Closely spaced electric wires as a barrier and a deterrent
Wire netting barrier at base
Mesh apron to deter digging under fence

$8000


Capped (New Zealand)


Wire mesh barrier
Wire netting apron to deter digging under fence
Steel roll cap to prevent climbing over
Internal corner angles >120° to prevent jumping or bracing against adjacent fence panels

$50 000


Source: Long and Robley (2004)

Since little is known of the ability of targeted pest species to breach particular fence designs, it is not always possible to determine whether a fence design is going to prove inadequate or over-engineered in a given environment (Long and Robley 2004). Filling such knowledge gaps would allow optimal, cost-effective fence designs to be determined.

Frequent monitoring for the presence of foxes inside the fence is an essential precaution as considerable damage can be caused by a single fox breaching the fence. While fences may restrict movement of foxes, they may also pose a hazard to non-target wildlife, as well as placing limits on the natural ability of native animals to disperse.

The high cost of establishing predator-proof fencing and the ongoing maintenance costs involved mean that it is likely to be useful only for small areas (Aviss and Roberts 1994). However, studies at Shark Bay in Western Australia integrated fencing with baiting and trapping to reduce the frequency of challenge to the fence by incoming predators. The studies combined natural water barriers, fencing and baiting to attempt to create large predator-free reserves on peninsulas (CALM 1994).



2.3.2 Islands as natural barriers

Eradication of predators on islands and subsequent translocation of threatened species has been an important strategy for wildlife conservation. Some of the most successful examples of threatened species conservation have been on such islands or within enclosures from which feral predators are excluded.

Tasmania, Kangaroo Island and a number of small islands off the coasts of South Australia and Western Australia are the primary refuges of mammal species that are extinct or very rare on the mainland (Burbidge 1989). Given the threat that foxes pose to wildlife, it is essential that they continue to be excluded from the significant islands where they do not occur. Now that foxes have been confirmed in Tasmania (Saunders et al. 2006), the Tasmanian Government has announced its commitment to eradicating the fox, working with the Fox-free Taskforce in the state.

Preventing the introduction of foxes to islands of conservation value requires identification of potential routes of invasion, determination of the probability of such an event, and development of procedures to manage and minimise the risk. There must also be the ability to detect incursions before fox populations have a chance to become established, contingency plans that identify the most appropriate control measures and funding sources to implement the required control.




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