Download Review of fox control measures in Box– Ironbark Conservation

Review of fox control measures in Box–
Ironbark Conservation Management
Networks: Broken Boosey
A. Robley
2010
Arthur Rylah Institute for Environmental Research
Technical Report Series No. 204
Arthur Rylah Institute for Environmental Research Technical Series No. 204
Review of fox control measures in Box–Ironbark
Conservation Management Networks: Broken Boosey
Alan Robley
Arthur Rylah Institute for Environmental Research
123 Brown Street, Heidelberg, Victoria 3084
July 2010
In partnership with:
Broken Boosey Conservation Management Network
and
Biodiversity Policy and Programs Branch, Biodiversity and Ecosystem Services Division,
Department of Sustainability and Environment
Arthur Rylah Institute for Environmental Research
Department of Sustainability and Environment
Heidelberg, Victoria
Report produced by:
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Department of Sustainability and Environment
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Citation: Robley, A. (2010) Review of fox control measures in Box–Ironbark Conservation Management Networks:
Broken Boosey. Arthur Rylah Institute for Environmental Research Technical Report Series No. 204. Department of
Sustainability and Environment, Heidelberg, Victoria
ISSN 1835-3827 (print)
ISSN 1835-3835 (online)
ISBN 978-1-74242-664-8 (print)
ISBN 978-1-74242-665-5 (online)
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that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore
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this publication.
Front cover photo: Fox taking bait (Alan Robley).
Authorised by: Victorian Government, Melbourne
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Contents
List of figures ................................................................................................................................... iv
Acknowledgements............................................................................................................................v
Summary............................................................................................................................................1
General recommendations ........................................................................................................1
Specific recommendations ........................................................................................................1
1
Introduction.................................................................................................................................3
2
Current Broken Boosey CMN fox control program................................................................5
3 Existing monitoring program ....................................................................................................7
3.1 Foxes..........................................................................................................................................7
3.2
Native species ............................................................................................................................7
3.3
Introduced species......................................................................................................................8
4 Areas of possible improvement..................................................................................................9
4.1 General background...................................................................................................................9
4.2
4.3
Implementation ........................................................................................................................10
4.2.1
Fox control areas .....................................................................................................10
4.2.2
Baiting density and placement.................................................................................11
4.2.3
Bait replacement......................................................................................................11
4.2.4
When to undertake fox control ................................................................................12
4.2.5
Where to place baits ................................................................................................14
4.2.6
Non-lethal control techniques..................................................................................14
Monitoring ...............................................................................................................................14
4.3.1
Monitoring foxes .....................................................................................................14
4.3.2
Monitoring native species: change in abundance ....................................................15
4.3.3
Monitoring change in agricultural assets.................................................................16
5 Recommendations for BBCMN fox control program ...........................................................17
General recommendations.................................................................................................................17
Specific recommendations ................................................................................................................17
Fox control..............................................................................................................................17
Native species monitoring.......................................................................................................18
References ........................................................................................................................................19
iii
List of figures
Figure 1. Broken Boosey fox control area, 2005–2007...................................................................... 5
Figure 2. Possible area for concentrated and collaborative fox control in the Nathalia–Picola area
in the Broken Boosey CMN area. .......................................................................................... 11
Figure 3. Fox life cycle and potential baiting times. ........................................................................ 13
iv
Acknowledgements
This review would not have been possible without the invaluable assistance of the former Broken
Boosey Conservation Management Network co-ordinator Jim Castles. Janice Mentiplay-Smith
(DPI) provided information on carpet python monitoring, and Rolf Weber and Stephen Smith
(DSE) provided information on native species monitoring programs in the general area. This
review was funded by the Biodiversity Policy and Programs Branch, Biodiversity and Ecosystem
Services Division, Department of Sustainability and Environment.
v
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Summary
Conservation Management Networks (CMNs) were first formed in Victoria and New South Wales
in the mid-1990s. The purpose of these grass-roots groups is to tackle biodiversity issues in
fragmented landscapes across public and private land. They are both a network of physical sites
with biodiversity values and a network of people who work together to protect and restore these
sites.
The main aim of a CMN is to protect and enhance biodiversity within the network area. CMNs
have an interest in fox baiting to protect biodiversity values, as foxes pose a significant threat to
biodiversity and are a major cause of decline for a wide range of species. CMNs face a significant
challenge in delivering fox control. To be successful, fox control in fragmented landscapes needs
to occur frequently, across a large area (thousands of hectares) and at sufficient intensity to
maintain a reduced fox population, allowing specified biodiversity values to respond positively.
There are several other programs in Victoria that bait foxes to protect native species, including
Southern Ark, Glenelg Ark and Grampians Ark. This review provides advice, based on current
standards for fox control, for CMNs to help them implement fox control programs and evaluate
their effectiveness. Evaluating the biodiversity outcomes of fox control is fundamentally important
in any fox control program because it identifies ineffective investments of time and resources
which might be more effectively directed elsewhere.
Although this review is focused on the Broken Boosey CMN and aim to help improve the
BBCMN fox control program, the findings and general recommendations may be relevant to other
CMN fox control programs.
There are a number of large-scale government initiatives that aim to improve or recover
biodiversity values through a reduction in predation pressure. Funding for both fox and native
species monitoring is often a core element of these programs, allowing them to implement more
complex monitoring programs. This level of complexity is not possible in CMN projects under the
current funding model.
The following recommendations cover the basic requirements that will enable robust reporting on
the outcome of fox control activities.
General recommendations
• Establish clear statements that describe what success means in both in terms of fox and native
species responses.
• Prioritise actions against foxes. Prioritisation should begin with identifying what impacts foxes
are likely to be having and where these impacts are likely to occur.
• Be concerned for ‘at risk’ or endangered native wildlife in circumstances where cats are present
and foxes are controlled.
Specific recommendations
Fox Control Program
• Consolidate the effort at priority hub(s) of control activity.
• Increase the time that predators are exposed to bait to at least three months twice a year.
• Map the ideal bait station distribution across the area, identifying the minimum number of bait
stations per property and their approximate location.
• Map actual location of bait placement on each property.
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• Record date bait laid, date bait inspected and replaced and numbers of baits taken in a
systematic way, keeping records in centralised electronic database.
• Undertake spotlight counts over three nights (within 10 days) at least once a year to determine
changes in fox populations and help set bait densities.
Native species monitoring
• Increase surveys, for example by increasing effort to engage sufficient landholders to
participate in surveys.
• Use Bush-stone Curlew diaries and nest boxes for gliders to assess changes in occupancy
through time.
• Engage a suitably qualified expert to design fox control and native species monitoring
programs and analyse the resulting data.
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1 Introduction
Conservation Management Networks (CMNs) were first formed in Victoria and New South Wales
in the mid-1990s (Context 2008). The purpose of these grass-roots groups is to tackle biodiversity
issues in fragmented landscapes across public and private land. They are both a network of
physical sites with biodiversity value and a network of people who work together to protect and
restore these sites.
CMN membership is typically a mix of private land owners and managers, public land owners and
managers, local natural resource management agencies and community groups. They aim to
achieve both biodiversity and social objectives across all land tenures. CMNs contribute to the
biodiversity outcomes of the Department of Sustainability and Environment (DSE) through
community engagement, research, planning and on-ground intervention.
DSE directly funds the four CMNs in the Box–Ironbark region: Wedderburn, Broken Boosey,
Whroo and Mid-Loddon. There are also five other CMNs operating in Victoria: Gippsland Plains,
East Gippsland Rainforest, Northern Plains, Longwood Plains and Victorian Volcanic Plains. This
review concentrates on the Broken Boosey CMN and may act as a template for future reviews.
CMNs have an interest in fox baiting to protect biodiversity values, as foxes pose a significant
threat to biodiversity and are a major cause of decline for a wide range of species. The principal
method of controlling foxes is poison baiting, which may be supplemented by shooting. Pairs of
foxes hold territories that can range between three and six hectares in agricultural landscapes in
Australia (Saunders and Mcleod 2007), whereas individual foxes roam, looking to establish pair
bonds and territories of their own. The inherent ability to rapidly establish new territories over
both short and long distances means foxes can easily compensate for any form of population
reduction.
CMNs face a significant challenge in delivering fox control. To be successful, fox control in
fragmented landscapes needs to occur frequently, across a large area (thousands of hectares) and at
sufficient intensity to maintain a reduced fox population, allowing specified biodiversity values to
respond positively. This requires a high degree of continuous landholder support in a landscape in
which there are significant numbers of public and private landholders with diverse interests.
In all their activities, land managers must assess whether their efforts are achieving the desired
outcome. This is particularly so for fox control because of the indirect relationship between the
activity (fox control) and its desired result (change in conservation status of selected native
species), and the difficulty in observing both.
There are several other programs in Victoria that bait foxes to protect native species, including
Southern Ark, Glenelg Ark and Grampians Ark (www.dse.vic.gov.au/Plants and Animals/Pest
Plants and Animals/Initiatives). Monitoring and evaluation is a major component of these
programs.
Effective monitoring and evaluation provides managers with increased capacity to (a) justify
reinvestment of scarce public conservation funds, (b) improve management actions based on
reliable information about the effectiveness of previous management actions, and (c) maintain
community support. Thus monitoring and evaluation is an essential part of management, not an
imposition or adjunct to it.
This review was initiated by the Biodiversity Policy and Programs Branch, Biodiversity and
Ecosystem Services Division, of DSE. It aims to provide advice, based on current standards for
fox control, to help CMNs implement fox control initiatives and evaluate their effectiveness.
Evaluating the biodiversity outcomes of fox control is fundamentally important in any fox control
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program, because it identifies ineffective investments of time and other resources which might be
more effectively directed elsewhere.
Although this review is focused on the Broken Boosey CMN, the findings and general
recommendation maybe relevant to other CMN fox control programs.
The key objectives of this review are to
• confirm the effectiveness of fox control programs, and of monitoring approaches, given
available resources
• identify possible improvements from a scientific perspective (regardless of available funds)
• identify possible improvements within existing resource limits, and the loss of effectiveness if
other ‘more rigorous’ approaches are not pursued.
The primary source of information for this review has been obtained from the Broken Boosey
CMN co-ordinator, public land management agencies and a review of the literature. Information
contained in Saunders and Mcleod (2007) has also been used throughout this report.
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2 Current Broken Boosey CMN fox control program
Information in this section is based largely on interviews with Jim Castles on the future of the
Broken Boosey CMN fox control program, and an unpublished report prepared by him.
The Broken Boosey CMN was established under the Victorian Government’s Box–Ironbark
Program in 2002. The Broken Boosey CMN area covers approximately 3500 km2 and includes
Broken–Boosey State Park and a large number of private properties along 200 km of the Broken
and Boosey Creeks in the Goulburn–Broken Catchment Management Area.
The Broken Boosey CMN area supports a number of fauna species that have been identified as
being at risk from predation by foxes (Robley and Choquenot 2002), including the Bush Stonecurlew (Burhinus grallarius), Squirrel Glider (Petaurus norfolcensis), Brolga (Grus rubicunda)
and Carpet Python (Morelia spilota variegata and M.s. metcalfei).
In 2005 the Broken Boosey CMN commenced a co-ordinated fox control program, using the Bush
Stone-curlew as a focal species to attract and encourage landholder participation. The program
began in the Nathalia district with the aim of undertaking a four-week fox control program each
year to reduce the fox population. It then expanded across the whole CMN area (Figure 1). In
2007, one hundred landowners, with properties covering 80 000 ha (15–20% of the CMN area),
participated in the fox control program (Figure 1). However, in 2008 the participation rate had
dropped to 24 landholders covering 13 052 ha. The reduction in participation rate has been
attributed to the drought and changes in regulations for the distribution and use of 1080 baits (Jim
Castles pers. comm.).
Figure 1. Broken Boosey fox control area, 2005–2007. (Map provided by Jim Castles.)
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The main approach to fox control is through the use of FoxOff® baits, buried in bait stations
spaced at approximately 500-metre intervals on individual private properties. Bait stations tend to
be placed along fencing lines and internal tracks or roads. Baiting is usually undertaken in
February or March each year to coincide with lambing. It is unclear from the information available
whether baits are checked and replaced weekly, fortnightly or at the conclusion of the four-week
program when uneaten baits are removed and destroyed. In some instances, for example in the
initial phase of the CMN, landowners were spending four to five hours per week checking and
replacing baits.
In 2007, bait density was around 0.2/ha (range 0.03–1.3), which translates to approximately
20 baits/km2, although the actual distribution of baits would not be evenly spread across the
landscape.
Supplementary fox control has been conducted by individual landholders when time permitted,
using spotlight shooting. The Sporting Shooting Association has also undertaken fox drives at
various times of the year.
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3 Existing monitoring program
3.1 Foxes
Standard techniques can be applied to determine the success of a fox control program. The most
commonly used methods in agricultural landscapes are spotlight counts and bait take records
(Saunders and Mcleod 2007).
To assess changes in fox populations, annual before-baiting and after-baiting spotlight transects
covering approximately 180 km were undertaken in the Nathalia area from 2005 to 2007 and near
Dookie in 2007. These were undertaken over one night before and after baiting, and the total
number of foxes seen was recorded. This activity ceased in 2007.
Spotlight counts of foxes before and after baiting indicated a decline in fox numbers following the
fox baiting program. For example, in 2005 fifty-five foxes were seen before and sixteen foxes
were seen after baiting, and in 2007 sixteen foxes were seen before and four foxes after baiting. In
2007 in the Carpet Python Project area, spotlight surveys indicated a decrease of 34% of foxes,
and in 2008 an 11% decrease.
In general, bait take on properties involved in the Broken Boosey CMN has not been recorded.
Where bait take data does exist, it was collected by landholders and appears not to be stored in a
systematic manner or in a centralised location. An exception is data collected by Andrew Carter
during field work in the Nathalia district. Details of the results of this monitoring are available in
his PhD thesis (Carter 2010).
Without the systematic collection of bait take or spotlight count data, it is not possible to determine
to what degree the baiting program has been successful at reducing the regional fox population. As
no formal monitoring of any potential prey species has occurred, it is also not possible to
determine if the fox control activities have resulted in positive biodiversity gains.
There are some anecdotal reports of increases in lambing rates, which may or may not be related to
the fox control efforts. Other factors that affect lamb survival may have occurred which could
explain these changes (e.g. changes in farm management practice, weather).
3.2 Native species
CMN projects
The initial focus of the Broken Boosey CMN fox control program was to reduce the fox
population in the area by engaging as many landowners as possible in a coordinated FoxOff®
baiting program. The Bush Stone-curlew was selected as a focal species to encourage landholder
participation.
In 2003, 5000 brochures about Bush Stone-curlews were distributed to landholders, and the
landholders were given the opportunity to record sightings. Eighty sightings were subsequently
mapped across the whole CMN area.
Two fenced areas (0.3 ha and 3 ha) 700 m apart were established in 2003 near the town of St
James, at locations thought to have Bush Stone-curlews present. The fenced areas were monitored
ad hoc by community members, and Bush Stone-curlews were seen inside the 3 ha area. Coordinated fox control was not undertaken in the area before or after the fences were erected.
Related projects
Some native species management programs undertaken by land management agencies within the
Broken Boosey CMN area could benefit from effective reduction in the fox population.
The Carpet Python Project was initiated by the Department of Primary Industries in 2005 with
Goulburn–Murray Water, DSE, and Parks Victoria participating. Broken Boosey CMN provided
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funding for private landholders, who conducted a baiting program as outlined above . The Carpet
Python Project undertook baiting for foxes on public land. Bait takes and spotlight counts were
used to assess the effectiveness of the fox control program. No formal monitoring of Carpet
Pythons has been undertaken for the baiting program.
Nest boxes for Squirrel Gliders (Petaurus norfolcensis) have been erected on both public and
private land (408 boxes at 144 sites) by community members. These have been monitored once,
with planned monitoring each year in autumn. However, it is not clear how this data will be
analysed.
There are also a number of more common species that are likely to benefit from an effective fox
control program but are not subject to any current management or monitoring, e.g. Tree Goanna
(Varanus varius), Brolga (Grus rubicunda) and Brushtail Possum (Trichosurus vulpecula).
3.3 Introduced species
European Rabbits (Oryctolagus cuniculus) are known to respond to a reduction in foxes by
increasing in number. The number of Feral Cats (Felis catus) may also increase after a decline in
the regional fox population, and could replace foxes as the key limiting factor for some native
species. No formal monitoring of these species is currently undertaken.
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4 Areas of possible improvement
4.1 General background
In pest control, the general assumption is that a reduction in the abundance of a pest leads to a
reduction in the damage it causes (Braysher 1993; Hone 1994). A sustained reduction in
abundance is achieved by stopping population growth. However, generally after an initial
reduction in a population more resources are available to the remaining individuals, resulting in an
increased rate of population growth. This growth needs to be stopped after control in order to
maintain reduced levels of abundance (Hone 1999). Management operations to stop subsequent
growth following the initial control aim to keep the rate of increase at a level below which the
population can grow (Hone 1999). In order to maintain the reduced population, strategies to
remove individuals at a rate greater than or equal to the rate at which they can be replaced by
reproduction or immigration need to be implemented.
Strategies used in agricultural protection have been determined mostly by the biology of the
livestock being protected rather than by the biology of the fox. These strategies therefore have
been mostly employed on a reactionary or short-term basis, without due consideration for
sustained reduction. Conservation management strategies focus on alleviating fox predation on
wildlife species by culling foxes from an area using poisoned baits. By necessity, such control
effort must be sustained.
During the 1990s large-scale fox-baiting programs, involving liaison and co-operation between
private and government agencies, were promoted and embraced throughout Australia for both
conservation and agricultural purposes. There are many examples in the conservation literature of
intensive baiting programs conducted over long periods that have significantly reduced the fox
impact on threatened species. However, it is not clear whether agricultural group fox-baiting
programs reduce fox abundance, and (more importantly) whether they reduce the impact of foxes
on lamb production. Gentle (2005) modelled the potential for fox immigration after typical group
baiting campaigns in central New South Wales and found that the spatial coverage and frequency
of baiting was inadequate to prevent fox reinvasion.
When planning a fox control program there are some important steps that should be considered
(after Braysher 1993, Braysher and Saunders 2002):
What is the trigger to undertake fox management? Is there a community or political pressure for
action on foxes and an expectation that foxes should be controlled? Fox control is unlikely to be
effective unless there is strong local or political will to take action and commit the necessary
resources.
Who is the key group to take responsibility for bringing together those individuals and groups that
have a key interest in dealing with the fox issue?
What is the problem? In the past the fox was seen as the problem, and the solution was to kill as
many as possible. We now know that the situation is more complex. First, determine what the
problem is. It may be reduced lambing percentage, emotional stress from worrying about the next
attack, or reduction in viability of a native species population(s). Several factors affect each of
these problems, and control of foxes is often only part of the solution.
Identify and describe the area of concern. Sometimes it helps to ignore agency and property
boundaries so that the problem can be viewed without the tendency to point blame at individuals,
groups or agencies. Property and agency boundaries can be considered later, once agreement is
reached on the best approach.
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Trying to deal with the complexity of a very large area can be daunting, so it often helps to break
the area into smaller management units for planning. These smaller units may be determined by
water bodies, mountain ranges, fences, vegetation that is unsuitable for foxes, or other suitable
boundaries that managers can work to. Although it is best to work to boundaries that restrict the
movement of foxes, this may not be practicable, and jurisdictional boundaries (e.g. the border of a
Landcare group) may have to be used in combination with physical boundaries. Once the
management units are identified:
• identify, as far as possible, the fox distribution and abundance in each management unit
• estimate, as far as practicable, the damage caused by foxes to agricultural and
conservation values.
Implementing effective and humane pest control programs requires a basic understanding of the
ecology and biology of foxes and (in some cases) those species affected directly (non-targets) or
indirectly (prey) by a control program. It is also essential to understand the impact created by foxes
(i.e. what is the problem?).
There are also some basic requirements for community based fox control programs are that need to
be implemented if there is any chance these programs are to be successful:
baiting must be co-ordinated and synchronised over large area (e.g. 100 km2)
there must be high landholder participation (e.g. 70–80%)
there must be a uniform distribution of baits across the landscape
baiting density must exceed the density of foxes across the landscape
baiting schedule (can depend on species being protected) to include at least two periods of 2–3
months
• baits must be checked regularly (minimum of fortnightly in areas with moderate rainfall, i.e.
50–60 mm) and replaced when taken
• where possible, baiting should be integrated with other control methods, e.g. shooting, den
fumigation.
•
•
•
•
•
The following sections provide information that will be useful in the development and assessment
of a baiting program.
4.2 Implementation
4.2.1
Fox control areas
The Broken Boosey CMN has already recognised that some change in the design of the fox control
program is needed. In his unpublished report, Jim Castles outlined options for altering the baiting
program to focus on a targeted area around Nathalia and Picola. This strategy is supported by this
review. The Murray River forms a natural boundary to fox movement, and using this natural
boundary and Madowla Park, with the existing landholder participation as the basis for a
concentrated effort, would be a sound strategy. If support from Parks Victoria could be obtained
and fox control undertaken in the newly created Barmah National Park, this would increase the
area under fox control significantly (Figure 2).
There are three other potential areas within the Broken Boosey CMN where concentrated fox
control could be undertaken: (1) Winton Wetlands, (2) the consolidated area of current private land
baiting to the west of Wunghu, and (3) the large block of private land baiting to south-west of
Tungamah.
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Figure 2. Possible area for concentrated and collaborative fox control in the Nathalia–Picola
area in the Broken Boosey CMN area.
4.2.2
Baiting density and placement
Spacing between bait stations (500 m or 1 km) is less important than providing sufficient
opportunities for foxes to encounter and take baits. As a general rule, bait density should exceed
the density of foxes. In Central Victoria fox densities can be around 4–6/km2 (Coman et al. 1991),
in similar temperate grazing areas in NSW densities have been reported at 5–7/km2 (Thompson
and Fleming 1994). Hence a baiting density of 10–12 baits/km2 should be sufficient. While broadscale coverage of the landscape would be ideal, this may not be practical in CMN programs. Bait
stations can be placed near features that foxes may prefer, and there should be no significant gaps
(> 2–3 km) in bait coverage across a landscape and between properties.
Baiting density could be established after assessing regional fox density using a series of properly
designed spotlight transects. This would involve spotlight transects operated over three
consecutive nights. Spotlighting would be from the back of a vehicle travelling at 5–10 km/h using
a 100 W spotlight and the same observer(s), recording the angle and distance that each fox was
sighted from the vehicle and the distance from the beginning of the transect. Data required for this
includes the route travelled, the total distance covered, the distance in kilometres from the start of
the transect to the fox sighting, the angle and distance from the vehicle at which the fox was
sighted, the names of people undertaking the survey, the date and time, and weather conditions at
the time of the survey. This assessment need only be carried out once per year to establish baiting
densities, or if funds are limited then once every two years.
4.2.3
Bait replacement
The toxin 1080 (sodium fluoroacetate) is highly soluble and degrades quickly in the environment.
The toxicity of baits can be significantly affected by rainfall, temperature, soil bacteria and fungi.
Staples et al. (1995) found that after moderate rainfall 20% of the 1080 remained in baits after 14
days, whereas in ‘dry’ soils 70% remained. Saunders et al. (2000) found that baits could remain
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toxic for up to 28 days under average rainfall conditions in eastern NSW; they also found that baits
physically degraded after three weeks.
There is a risk that baits that are less than lethal to foxes may still be palatable. This could result in
foxes becoming wary of baits containing 1080 if they consumed a sub-lethal bait. The time when a
bait becomes sub-lethal is likely to be two to three weeks after bait is laid. As there is no way of
monitoring the actual impacts of the environmental conditions on baits, a precautionary approach
is to replace baits after two weeks in areas that have received moderate rainfall and after three
weeks otherwise. All baiting programs need to conform to the appropriate legal and label
conditions for safe use, including safe disposal and handling of baits.
4.2.4
When to undertake fox control
Foxes are susceptible to baiting programs all year round (Figure 3). During the peak of the
breeding season (between July and October) the energy requirements of vixens are highest, and
baiting pregnant and lactating vixens reduces population growth by reducing the next generation.
Following the breeding season (around November) the energy requirements for males and females
rise but the ranging behaviour of juvenile foxes is limited, reducing the potential encounter rate
with baits. Juveniles disperse between about February and April, at which time they will have high
energy demands, so encounter rates with baits may be increased. Baiting around May has the
advantage of giving the greatest proportional reduction in a fox population, as at this time the
population is at its lowest and is stable. However, leading into the breeding season males
concentrate more on defending territories and finding possible mates, so bait-taking may be
reduced.
If limited time is available to conduct baiting operations, targeting periods that have the greatest
impact on reducing the growth of the population would be best. This would be at the beginning of
the breeding season (April–June) and at the time of juvenile dispersal (February–May).
Consideration can then be given to the biology of specific species within the target area. Breeding
time for ground-nesting birds or dispersal time for fossorial mammals are critical phases in their
life history. Consideration of the timing of rabbit eruptions, or at least times when rabbit
populations may increase (potential reactive baiting), may also influence when to undertake
baiting for foxes. Foxes can easily survive and increase if rabbits and blackberries are available.
They need only kill a small number of animals to have a significant impact on the survival of local
populations of native species. Some foxes appear to survive control programs that use buried 1080
baits. Saunders et al. (2006) list kills of between 50% and 97% (mean = 77%) for four operations
using buried baits in New South Wales. From this we might expect a single fox in a baited area to
have perhaps a 23% chance of surviving a single baiting event. It is unclear whether a surviving
fox would be at risk of a second baiting, or whether it would always survive baiting because of
some behavioural trait. If survivors avoided baits by sheer chance (i.e. that individual was not
wary of baits), then a second baiting would reduce its chance of survival to 5% and a third round
to 1%. Saunders et al. (2006) showed that the number of foxes reported by the public from places
within 5 km of a baited area declined over a four-year period. They concluded that repeated baiting
over a year should kill all resident foxes and most foxes that immigrate into the area during the
baiting period, assuming all foxes eat baits.
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Figure 3. Fox life cycle and potential baiting times.
Life cycle of foxes
Jun
Jul
Aug
Sep
Winter
Oct
Nov
Spring
Dec
Jan
Summer
Feb
Mar
Apr
May
Autumn
Jun
Jul
Aug
Winter
Mating Year 1
Gestation 51–63 days
Cubs Born
Peak whelping period
Vixens peak feed demand
Cubs Weaned
Dispersal of young
Cubs sexually mature @ 9 - 10 months
Mating Year 2
Vixens lactating, peak feeding requirements, reduces
recruitment potential.
Breakdown of social groups, dispersal of young,
inexperienced animals, low feed availability, reduces
potential reproduction.
Review of fox control measures in Box–Ironbark Conservation Management Networks: Broken Boosey
In areas where rabbits and foxes co-occur and rabbits are in moderate to high densities, an
integrated approach to fox and rabbit control would be the ideal situation. Even more ideal would
be a program that controls feral cats were they co-occur with foxes and rabbits. However, currently
feral cat control is currently limited to live trapping using cages, making feral cat control very
costly.
4.2.5
Where to place baits
There are two considerations when placing baits in the landscape. One is to provide foxes with the
best opportunity to encounter bait. Encounter rates are dependant on, a) the number of baits in a
given area, and b) attractiveness and palatability; is the bait something the fox will consider worth
investigating and subsequently eating.
Foxes depend strongly on olfactory cues for locating food (Henry 1977) and odorous compounds
have been used for many years in an attempt to draw foxes and other predators into traps and baits.
In Australia there have been a number of studies on attractants. Hunt (2005) reported on the use of
synthetic fermented egg (SFE) for foxes and wild dogs. The application of SFE to bait stations in
the highlands of southern NSW significantly increased the visitation rate of foxes to bait stations.
The commercial version of SFE (FeralMone™) was tested in a large-scale program in Western
Australia, which found no increased rates of visitation by wild dogs (Thomson and Rose 2005).
Given FeralMone™ is easily and widely available; there is an opportunity for local land managers
to use this product if they desire.
Recent work by Andrew Carter (Carter 2010) indicates that foxes have preferred pathways of
movement. Incorporating this knowledge into the placement of fox baits would give more targeted
baiting, reduce the amount of poison in the environment and be more practical. However, where
possible the objective of having a broad, even distribution of baits at a density higher than the
underlying fox density should be the aim.
4.2.6
Non-lethal control techniques
Several techniques can be used to control the impact foxes have on specific and localised values:
aversion conditioning, guard animals, frightening devices, exclusion fencing, manipulating food
supply, and manipulating habitat.1 Most, if not all, of these techniques have to be viewed at this
stage as impractical for any regional application in the Australian environment. Their use would be
limited to small-scale operations where the protection of highly valued wildlife or domestic flocks
was the imperative. However, they should not be discounted, and the verification of the costs and
benefits of suggested changes to management practices would facilitate greater adoption of these
techniques for reducing fox impact.
4.3 Monitoring
4.3.1
Monitoring foxes
Bait take: The numbers of toxic baits taken during the course of a baiting program can be used as
an index of the success of a control operation. Results can be converted into crude density
estimates. Details of bait station location (GPS coordinates) and the dates when baits were laid,
inspected, taken and replaced need to be stored in a centralise database.
The use of free feeding is not recommended unless there is a specific concern about non-target bait
take. In that case free feeding can be used to identify particular areas or bait stations were the nontarget species of concern is taking baits, and those bait stations can be discarded during the toxic
baiting program.
1
For further details on the application of these techniques, see Saunders and McLeod (2007).
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Spotlight counts: Foxes can be difficult to detect because they occur at low densities, so that
spotlight counts are very variable. To overcome this variation it is usual to undertake spotlight
counts over three nights and calculate the mean number of foxes detected. A general rule of thumb
in determining the number of counts needed is for the standard error (SE) of the mean (a measure
of accuracy) to be within 10% of the mean. Increasing the number of counts will decrease the SE.
However, Field et al. (2005) suggested that at least five and as many as nine repeat counts may be
necessary to obtain an accurate index.
Other considerations are to ensure that the route, observers, vehicle type, vehicle speed
(5–10 km/h), spotlight power (100 W) and weather conditions are standardised. Sightings of foxes
should be recorded against the distance travelled from the start of the transect or time since starting
the transect. This allows for an index to be determined, e.g. numbers counted per transect
kilometre or per unit of time. In addition, recording the distance to the fox (or the location the fox
was sighted) and the angle from the vehicle at which the sighting was made can be used to
determine fox density and hence any change in fox numbers, and to guide the density of baits
required.
4.3.2
Monitoring native species: change in abundance
Demonstrating a positive change in the abundance of native species at risk from fox predation is a
key component of success for CMNs. Abundance can be measured in three ways: as the number of
animals in a population, as the number of animals per unit of area (absolute density), and as the
density of one population relative to that of another (relative density) (Caughley 1977).
The majority of ecological problems can be tackled with the help of indices of density. A density
index as used in this sense is any measurable correlative of density. Ideally its trend is linear on
absolute density, but non-linear indices are sometimes sufficient. The number of prints on sand
plots, baits taken per unit of time, faeces per kilometre, and individual animals found per unit time
or unit area are examples of indices that reveal something about a population’s density. A density
index is useful only in comparisons. When one population is compared with another, or the density
of a single population is compared between years, density indices are often sufficient measures of
abundance.
The use of the proportion of a monitoring area that is occupied (referred to as site occupancy) can
be used to assess changes in species at risk from fox predation. The phrase ‘occupancy’ is used
here to mean the proportion of a sampling unit (e.g. property, nest boxes) that contain the target
species at a given point in time.
Occupancy surveys involve searches of sample units for evidence of species presence (sightings,
calls, nests, scats). It is possible to use animal sign (e.g., tracks, faeces or hair) as an indicator of
presence, and detecting such signs will frequently be easier than observing or capturing animals.
Tools used to determine the presence of an animal can include heat and motion activated digital
cameras, call backs and hair collection devices.
Site occupancy may well change over years or between seasons as populations change. When sites
are surveyed between these periods of change, over a number of years, the approach described
here can be combined with robust analytical methods. For example, sampling is repeated each year
and continued for several years, and that the same sites are surveyed each year. This approach
could be used to estimate the occupancy rate. The change in occupancy rates over years could then
be modelled as functions of site colonisation and extinction rates, analogous with the birth and
death rates in a population study. Comparisons of changes in these rates between treated (fox
control) and non-treated (no fox control) sites or between years on treated sites could be used to
evaluate trends associated with the fox control program.
Arthur Rylah Institute for Environmental Research Technical Report No. 204
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On individual properties, the of use Bush Stone-curlew diaries at the same time of year to collect
and collate sighting data, and the inspection of nest boxes for Brush-tailed Phascogales or gliders
undertaken by community members, are examples of how this approach may be incorporated into
the Broken Boosey CMN monitoring program.
If this approach were to be adopted, further work would be required to properly develop the
monitoring, analysis and reporting framework.
4.3.3
Monitoring change in agricultural assets
Lambing rates could be used to assess the effectiveness of fox control programs. Detailed
information on pregnancy and birth rates as well as survival rates of lambs, along with some
indication of the cause of death, would be required to unequivocally determine the impact of fox
control on lambing rates.
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5 Recommendations for BBCMN fox control program
The following recommendations aim to help improve the BBCMN fox control program and maybe
applicable to other CMN fox control programs.
One of the stated objectives of the review was to provide recommendations improving fox control
and native species response monitoring without regard to cost, but based around the best science.
There are a number of large-scale government initiatives that aim to improve or recover
biodiversity values through a reduction in predation pressure. Funding for both fox and native
species monitoring is often core to these programs, allowing them to implement more complex
monitoring programs. This level of complexity is not possible in CMN projects under the current
funding model.
The recommendations below are the basic requirements to enable robust reporting on the outcome
of fox control activities. There is scope within the specific recommendations for flexibility in their
application. However, if a recommendation cannot be implemented in a form that provides the
necessary information, the ability of managers to confidently determine whether fox control has
had a positive impact will be diminished.
General recommendations
•
Management needs to establish clear statements that describe what success means in terms
of these programs, both in terms of foxes and native species responses.
•
Given the many competing demands for resources, greater emphasis on prioritising actions
taken against foxes is required. Prioritisation should begin with identifying what impacts
foxes are likely to be having and where these impacts are likely to occur.
•
There is a need to be concerned for ‘at risk’ or endangered native wildlife in circumstances
where cats are present and foxes are controlled. This particularly applies where rabbits cooccur and where resources are limited in time by drought. The relationship between cats
and foxes and the implications of mesopredator release requires further research. If
conclusive evidence is available that cats will become a significant problem following the
control of foxes, strategies that address the simultaneous control of both species must be
considered.
Specific recommendations
Fox control
•
•
•
•
•
•
Consolidate the effort at priority hub(s) of control activity, for example by increase effort
to obtain participation from more landholders in the hub(s).
Increase the time that predators are exposed to bait (currently greater participation in
autumn than spring) to at least 3 months twice a year, targeting the life cycles of foxes,
native species or both.
Map ideal bait station distribution across the area, identifying the minimum number of bait
stations per property and their approximate location.
Map actual location of bait placement on each property. The result could be a hand-drawn
map of approximate locations to enable the spatial distribution of bait stations in the
landscape to be determined.
Record in a systematic way the date that the bait was laid, the date it was inspected and
replaced, and numbers of baits taken, and keep records in a centralised electronic database.
Undertake spotlight counts over three nights (within a 10 day period) at least once per year
to determine changes in foxes and help set bait densities.
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Native species monitoring
18
•
Increase surveys, for example by increasing effort to engage sufficient landholders to
participate in surveys.
•
Use Bush Stone-curlew diaries and nest boxes for gliders to assess changes in occupancy
through time.
•
Engage a suitably qualified expert to design fox control and native species monitoring
programs and analyse the resulting data.
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