Commentary
Towards a Knowledge-Based Ethic for Lethal Control of
Nuisance Wildlife
B. WARBURTON,1 Landcare Research, P.O. Box 40, Lincoln 7640, New Zealand
B. G. NORTON, School of Public Policy, Georgia Institute of Technology, Atlanta, GA, 30332-0345, USA
ABSTRACT Managers of nuisance wildlife have to rely largely on using lethal methods until such time as nonlethal techniques, such as
fertility control, become universally available for a wide range of species. Unfortunately, use of lethal tools has met with opposition from animal
welfare and animal rights proponents. Although research has addressed some of the more tractable welfare concerns (e.g., making traps more
humane), less tractable ethical issues associated with the justification of killing wildlife remain unresolved. Monistic welfare models or rightsbased models have been proposed as ways of addressing these issues, but those that concentrate on the cognitive and conative capabilities of
individual animals fail to resolve the ecological and social complexities involved in management of nuisance wildlife. Solutions need to
recognize and accept the diversity of values (i.e., within a pluralistic strategy) as well as the uncertainty inherent in many of the systems being
managed. Thus, when uncertainty is high in managing wildlife–resource systems, we propose the only ethically defensible action is to apply a
knowledge-based ethic that ensures future actions will be carried out with increased understanding. Such an ethic can be made functional
within an adaptive management framework that has, as its first tenet, the need to learn and reduce uncertainty. Failure to maximize learning in
the presence of uncertainty has the potential to result in increased opposition to even soundly justified operations to manage nuisance wildlife.
(JOURNAL OF WILDLIFE MANAGEMENT 73(1):158–164; 2009)
DOI: 10.2193/2007-313
KEY WORDS adaptive management, animal rights, knowledge-based ethic, nuisance wildlife, uncertainty, vertebrate pest,
wicked problems.
Many vertebrate species, especially invasive species, have
become pests (i.e., nuisance wildlife) because of real or
perceived threats they (both species and populations) pose to
biodiversity values (Clout 2002, Lodge and ShraderFrechette 2003), their impacts on primary production
(Rabiu and Rose 2004, Fleming et al. 2006), or their role
in maintaining disease(s) in animal or human populations
(Dorn and Mertig 2005, Ryan et al. 2006). Management of
nuisance wildlife species can include application of nonlethal
techniques such as fertility control (Rodger 2003), repellents
(Shafer and Bowles 2004), and fencing (Karhu and
Anderson 2006), and although much research is being done
to find new and effective nonlethal methods, as yet such
methods have limited utility. Consequently, management
still relies heavily on using lethal control methods including
poisons (Morgan 1994, Burrows et al. 2003), traps
(Warburton and Orchard 1996, Proulx 1997), or shooting
(Choquenot et al. 1999, Mason et al. 2002). These lethal
control tools, especially traps, have been the focus of
vociferous opposition from welfare and animal rights groups
for many years (Loague 1993, Oogjes 2003). In response,
considerable international effort has been made to improve
the humaneness of the range of tools used (Warburton et al.
2000, Mason and Littin 2003, Shivik et al. 2005). However,
even if control methods are improved to address animal
welfare concerns, ethical issues remain about whether
management of nuisance wildlife is always justified.
For operations that manage nuisance wildlife to be
effective (i.e., to achieve the desired response from the
resource being protected), the abundance of the target
species must be reduced to, or below, levels at which
1
E-mail: warburtonb@landcareresearch.co.nz
158
populations no longer cause unacceptable impacts (Hone
2007). However, to achieve such effective management of
nuisance wildlife is a complex challenge for land managers,
because the relationship between density of the critical
species and resource use is often not linear (Nugent et al.
2001), and if control is carried out in the absence of such
knowledge, control can be both ineffective and wasteful of
control funding. Additionally, wildlife–resource systems
often involve multiple species, and single-species control
can lead to unpredictable and sometimes perverse outcomes
(Norbury et al. 2002, Ramsey and Veltman 2005). If
management programs are implemented with a high degree
of uncertainty and little understanding of the outcomes,
then such programs expose themselves to substantial ethical
challenges.
How to ethically evaluate operations that target nuisance
wildlife is subject to ongoing debate. Discussions of the
topic in environmental ethics have generally been premised
on an extensionist, nonanthropocentric ethic that attributes
what are usually human moral characteristics to individuals
of other species. Prominent among such approaches are
utilitarian treatments such as those of Singer (1990), who
argues that interests of all sentient beings should be taken
into account equally in deciding all questions affecting
human or nonhuman welfare. Regan (1997), criticizing
Singer’s (1990) utilitarianism, argues that all individuals
have rights to life, rights against assault, etc. Singer’s (1997)
utilitarian approach would seem to allow for experimentation on animals, and perhaps destruction of individual
animals, provided the benefits of the action outweigh the
welfare costs to sentient beings, whereas Regan (1997)
rejects any balancing of welfare costs across individuals.
Besides leading to apparent ethical impasses between
The Journal of Wildlife Management
73(1)
utilitarianism and rights theory, neither of these individualistic ethical approaches seems likely to support actions that
managers of nuisance wildlife might find essential and
unavoidable. Individual-based philosophies have not been
useful when concern extends to situations where populations
of wild animals need to be managed and where such
management often is to protect a nonsentient resource such
as plants (Callicott 1980, Marks 1999). Consequently,
several authors have attempted to define an ethical framework for managing nuisance wildlife (Warburton 1998,
Eggleston et al. 2003, Littin and Mellor 2005). Hickling
(1994) and Marks (1999) highlighted the dilemmas that the
individual-based theories do not allow for consideration of
the value distinction often made between indigenous and
exotic species, do not readily support an action of killing
many exotic animals for the benefit of a few indigenous
ones, and do not allow for consideration of nonsentient
ecosystem components.
ETHICS AND MANAGEMENT OF
NUISANCE WILDLIFE
Over the past several decades animal welfare and animal
rights advocates have focused their concerns on, and
opposition to, many of the lethal tools managers use to
control nuisance wildlife (Gilbert 1991, Hadidian et al.
2002, Oogjes 2003). In response to these concerns there has
been a continuing effort to improve control technologies to
minimize or eliminate welfare impacts (Proulx 1999,
Warburton et al. 2000, Short and Reynolds 2001, O’Connor
2004). However, these improvements have focused on the
welfare of individual animals and little attention has been
paid to whether animals are being subjected to unnecessary
welfare compromise because the operations fail to achieve
their objectives (i.e., many individuals are killed with few if
any benefits). This concern is especially acute when there are
predictable, but difficult to quantify, collateral welfare
impacts causing morbidity and deaths in nontarget species.
Consequently, failure to address this issue has the potential
to result in increased opposition to justified management
operations against nuisance wildlife and may offend any
reasonable ethics of responsibility in the use of wildlife
management tools.
Stone (1987) defined moral monism in environmental
ethics as any view (e.g., utilitarianism or rights theory) that
applies one ethical rule or framework to address all moral
problems. We extend Stone’s (1987) definition to include all
approaches to policy evaluation that apply one approach to
the evaluation of policy options. Hitherto, most attempts to
evaluate wildlife control options have invoked monistic
welfare models or monistic rights-based models, (i.e.,
models that concentrate all attention on the cognitive and
conative capabilities of controlled populations).
In our view, it will be impossible to resolve such complex
issues by paying attention to one aspect, such as the
suffering or comparative suffering of animals as a result of
control activities. As long as values as diverse—and
legitimate—as reduction of unnecessary pain and unnecesWarburton and Norton
An Ethic for Managing Nuisance Wildlife
sary killing and protection of biological diversity, production
values, and hunting resources are in play in these decisions,
no one-dimensional, individually based ethic can adjudicate
among the complex and competing social values involved in
management of nuisance wildlife. We propose to consider
decisions to undertake control activities within a pluralistic
framework of values that considers suffering and death of
sentient creatures but considers other, competing, values as
well.
Control of nuisance wildlife presents a classic example of a
wicked problem (Rittel and Webber 1973, Norton 2005).
Because interest groups with differing values see the
problem so differently, they cannot agree in formulating
the problem, much less in solving problems creatively and
cooperatively (Allen et al. 2001, Robinson and Whitehead
2003, Bronner 2005, Rikoon 2006). Wicked problems,
unlike benign problems that have one definitive answer, defy
right–wrong, either–or answers. Wicked problems cannot be
formulated as problems of optimization and are not
susceptible to computational or algorithmic solutions.
Further, wicked problems resist solutions in terms of
monistic theories of value, because advocates of theories of
value, whether economic or ethical, insist on finding the one
right answer—which leads into useless rhetoric, dogmatism,
and decision-making gridlock. Because wicked problems
involve competing reasonable goals, they have no single,
correct solution.
For the foreseeable future, problems of managing nuisance
wildlife will remain controversial because entrenched
interests (e.g., protection of biodiversity vs. protection of
the lives of individual pest animals) frame the problem
differently, invoking differing values, and every choice made
by managers of nuisance wildlife can be protested from
multiple value and scientific perspectives. For this reason, it
seems unlikely that controversies over managing nuisance
wildlife will be resolved by formulaic applications of
monistic theories such as extending rights to all animals or
by seeking a bottom-line economic, cost–benefit analysis.
Before further addressing these competing normative issues,
we explore some of the complexities and uncertainties of
these highly contested decisions.
WILDIFE MANAGEMENT SCIENCE
Wildlife–resource-system dynamics can be complex and vary
depending on the nature of the interactions between the
wildlife population and associated resources (Parkes 1993a).
For example, some systems may be simple, single-species
systems that have density-dependent processes that can be
easily modeled and their outcomes predicted (Barlow
1991a). In contrast, other systems may have multiple species
and density-independent factors influencing the system.
Consequently, these systems are more difficult to model and
for these it is more difficult to predict likely outcomes from
management intervention (Caughley and Sinclair 1994,
Choquenot and Parkes 2001, Hone 2006).
Management of nuisance wildlife, therefore, often has a
very large component of uncertainty, with outcomes not as
159
expected, either in terms of not achieving the primary goal
(e.g., protection of some conservation value) or in producing
some perverse outcome (e.g., reduction of one species
releases another to cause equivalent or worse impacts;
Billing and Harding 2000, Norbury et al. 2002, Steen et al.
2005, Tomkins and Veltman 2005, Vicente et al. 2007).
For wildlife–resource systems that have clear resource
objectives and known thresholds (e.g., to eliminate a
disease) wildlife managers can often develop control
programs that are effective in achieving the desired goals.
As an example, bovine Tb (Mycobacterium bovis) is the most
important disease of livestock in New Zealand, affecting
dairy, beef, and deer herds (Coleman and Cooke 2001). The
Animal Health Board (AHB; a non–profit-making incorporated society) was formed specifically to manage and
implement the National Pest Management Strategy for
bovine Tb, with the aim of achieving Tb freedom in New
Zealand by 2013 (AHB 2008). Management of the disease
requires reduction of the disease within herds, which is
achieved by a test and slaughter program, movement control
of infected herds, and control of the main wildlife vectors,
the brushtail possum (Trichosurus vulpecula) and ferret
(Mustela furo). The AHB spends approximately $50 million
(New Zealand currency) annually on vector control, over an
area of approximately 9 million ha (AHB 2006). Managers
within land-management agencies (e.g., regional councils)
develop control programs for their regions taking account of
the AHB’s disease reduction targets, stakeholder (i.e.,
farmers, local communities, and interest groups such as
hunters) concerns, and any biological or operational
constraints. Control of possums is mostly contracted out
to private businesses that have the necessary skills for
carrying out aerial control operations using 1080 carrot or
cereal baits (Morgan and Hickling 2000) or ground-based
operations using a range of baits and toxins and traps
(Warburton and Montague 2000). Most control contracts
are performance-based, and require contractors to reduce
possum abundance to below a target level before they are
paid. This performance-based system has been able to be
implemented for 2 reasons: 1) there is a nationally standardized method for assessing possum abundance that
enables managers to determine if contractors have achieved
the desired population reductions (Warburton et al. 2004,
National Possum Control Agencies 2005) and 2) there is
good theoretical (Barlow 1991a, b; 1993; Barlow et al. 1997;
Caley 2006; D. L. Ramsey, Landcare Research, unpublished
report) and empirical (Pfeiffer et al. 1995, Caley et al. 1999,
Ramsey et al. 2002) evidence for the threshold level to
which possums must be reduced to prevent Tb from
persisting in the system.
The possum control program managed by the AHB
satisfies the 4 requirements for achieving effective and what
we believe to be ethically justified nuisance wildlife control:
1) a target threshold for possum population reduction that
needs to be achieved to meet their goal, 2) an objective
methodology for assessing whether the target reductions
have been achieved, 3) effective control tools for achieving
160
those reductions including a performance-based contract
system for service delivery, and 4) necessary legislative
support to ensure compliance.
In contrast to the possum control program, there are many
examples of nuisance wildlife control operations that fail to
achieve their desired objectives. Failure generally results
from an incomplete understanding of the wildlife–resource
system being managed, including 1) incorrect identification
of the critical threats (Dilks et al. 2003, Berger 2006), 2) no
or incomplete knowledge of the relationship between
wildlife density and resource use (Allen and Sparkes 2001,
Sweetapple et al. 2002), 3) a lack of understanding of the
temporal dynamics of nuisance wildlife and the affected
resources (Cote and Sutherland 1997, Pech et al. 2007), 4) a
lack of understanding of the spatial responses of nuisance
wildlife (Engeman and Campbell 1999, Sullivan et al. 2001,
Byrom 2002), 5) a lack of understanding of how sympatric
species might respond to single-species control (Murphy et
al. 2004, Ruscoe et al. 2006), and 6) ineffective control tools
(Billing and Harding 2000). Additionally, failure often
results from a lack of sustained commitment of funding
because of changes in agency policies and priorities (Parkes
1993a, b).
Given the multiple reasons why such operations may fail
to achieve their objectives and the uncertainty under which
most wildlife managers have to operate, there is a substantial
opportunity to embrace this uncertainty and learn. Unfortunately, few nuisance wildlife management operations
appear to make use of such opportunities.
FAILURE TO LEARN
There are few publications that review how the design of
nuisance wildlife control operations may provide information from which robust inferences can be made (Reddiex
and Forsyth 2006). Personal experience suggests that many
operations are poorly structured in terms of creating
opportunities to learn, and this view is supported by
Reddiex and Forsyth (2006) who reviewed 1,915 vertebrate
pest-control operations in Australia and found most
(67.5%) had only one treatment and did not monitor either
the target species or the biodiversity response. Only 2.4% of
operations had both treatment and non-treatment areas, and
only 0.3% had treatments and non-treatments randomly
assigned. Replication occurred in only 1.0% of operations.
The inability to learn from most control operations
because of lack of experimental discipline, along with
evidence that many operations fail to achieve outcomes,
suggests management is failing on both fronts (i.e., failing to
achieve outcomes and failing to increase knowledge).
Further, aside from the often-criticized welfare effects of
control operations on target and collateral species, there is
an independent—or, perhaps, complementary—argument
against many of these operations: managers 1) do not know
or have an inability to calculate the net impacts of their
actions, and 2) do not act to address this failing.
If nuisance wildlife managers are to address these 2
criticisms their most efficient strategy will be to address the
The Journal of Wildlife Management
73(1)
failing to calculate the net impacts of their actions and do so
by embedding wildlife management within a broader
adaptive management framework in which actions are
evaluated not just for their impacts on welfare (human and
nonhuman), but also for their ability to contribute to
knowledge. This embedding of control operations within
experimental adaptive management is necessary at 2 levels.
First, because the outcome is often uncertain, even when
there is widespread agreement that a given control action
should be undertaken, it is therefore important to monitor
such outcomes (which may include ecological, technical,
animal welfare, or economic factors) so methods and means
can be modified in future programs. Secondly, even
successful killing of nuisance wildlife may not achieve goals
of protecting unquestioned social values, and so the means
to achieve the end result may be questioned, some goals
identified as counterproductive, and some objectives identified as misguided. Adaptive management can thus address
normative goal-setting choices as well as reducing uncertainty, and experimental management can help people to
address uncertainty both about outcomes of treatments and
program objectives (Norton 2005). As new knowledge of
impacts of various treatments is gathered, public discourse
may be widened to include an examination and reexamination of collective ethical responsibilities.
Thus the embedding of control operations within
experimental adaptive management contains the seeds of a
knowledge-based ethic for managing nuisance wildlife,
acknowledging that any actions to control wildlife with
lethal methods will have welfare costs to animals affected
and that, in many cases, positive outcomes carry a risk of
failure. Accordingly, ethical action, even if it fails to achieve
its primary goal of protecting the social value thought to be
at risk, may be justified if it reduces uncertainty, exposes
poorly conceived projects to test, and stimulates discussion
of social values.
ETHICS AND CONTROL OF NUISANCE
WILDLIFE
We are proposing a pluralistic integrated process that
encourages learning through adaptive experimental management. The idea underpinning this approach begins with the
expectation, implied by the judgment that actions to control
nuisance wildlife present wicked problems, and that there
will be considerable conflict over values and goals pursued by
participants in any discussion of policies and actions. By
replacing the monistic approach with a more pluralistic one,
it is possible to accept conflict and to transcend that conflict
by focusing discussion on the shared value of increased
knowledge and understanding.
The one certainty is that public discourse and decisionmaking about choices to be used in controlling nuisance
wildlife will be, for the foreseeable future, carried out amid
uncertainty and conflict. What would be some consequences
of recognizing, even embracing, that uncertainty? Recognition of uncertainty and ignorance would need to be taken
as an opportunity to learn from whatever activities we
Warburton and Norton
An Ethic for Managing Nuisance Wildlife
undertake. This is the first tenet of adaptive experimental
management. Thus, whatever specific and substantive values
are at issue in any dispute about wildlife management, a
knowledge-based ethic will organize any and all control
activities associated with managing nuisance wildlife as
essentially a scientific process.
We need a fresh start. We propose a broad approach to
ethical analysis embedded within an ethic rooted in adaptive
experimental management’s commitment to learning our
way out of difficulties (i.e., learning by doing [Walters and
Holling 1990]). To learn from our doing, however, we must
practice good science, and our ethic necessarily involves a
heavy investment in science (Lee 1993, Gunderson et al.
1995). According to this value approach, we consider each
act of controlling vertebrates in relation to its consequences,
but consequences as they are characterized by all of the
diverse advocates of multiple interests. By affirming pluralism, we attempt not to reduce all social values affected and
interests represented to one measure, but rather to identify
management goals that will protect the broadest balance of
affected social values. Pluralism, although always somewhat
messy, has the advantage that multiple competing values are
made explicit, which in turn may help participants to
reframe issues so as to take more values into account. One
potential process for managing such conflicts is a dialogue
approach, which has been used to find a way forward for
such contentious issues as use of aerial 1080 operations
(Hayes et al. 2004).
What may recommend this knowledge-based ethic for
managing nuisance wildlife is that it can unite individuals
with different perspectives behind the belief that, whatever
one’s interests and value commitments, knowledge has
value. The commitment to increasing knowledge can be
thought of as a meta-value, a value that can be endorsed by
individuals and groups with different substantive values
affected by control activities.
The knowledge-based ethic might be summed up in 2
commitments, which imply strong obligations on the part of
policy-makers in this area: 1) state, or define and agree
upon, what you are doing at the outset (i.e., do not disturb a
system without a hypothesis in mind); 2) When acting in
the face of uncertainty, design experimental actions to
reduce ignorance of the system and impacts on it. These
commitments ensure control actions can be justified
provided the existing knowledge base can identify realistic
goals and prescribe effective treatments. Even here, actions
should be designed with controls and as laboratories to test
hypotheses and experiment with treatments.
In complex and poorly understood systems in which
vertebrate animals are causing undesirable impacts, animals
are often killed without reliable knowledge of the effects of
control and collateral impacts. The knowledge ethic would
require such control programs to be redesigned to include
scientific testing of hypotheses and attempts to learn more
about the impact of current projects on the total range of
affected values. Attempts to deal with such uncertainty have
been made using fuzzy logic that explicitly recognizes the
161
uncertainty of many of the components of the system being
managed (Ramsey and Veltman 2005).
A KNOWLEDGE-BASED SOLUTION
Because most operations targeting nuisance wildlife are
essentially large-scale manipulations of individual animals,
actions of wildlife managers are little different from
researchers who also manipulate animals as part of experiments. However, before a researcher can initiate trials that
include manipulations of animals, they must first (in most
countries) obtain animal ethics committee approval. In
contrast, managers of control operations do not need to
obtain such approvals even if such operations will manipulate considerably higher numbers of animals than would
ever be manipulated within an experiment. Can this
disparity be justified? We think not.
On the basis of the ethical approach we suggest, to
maximize benefits obtained from implementing an operation to manage nuisance wildlife and to minimize the
ethical cost, especially when there is considerable uncertainty, we recommend that all lethal control operations
targeting nuisance wildlife be reviewed (perhaps by an
animal ethics committee) for appropriate experimental
design. We emphasize that it is those operations with high
uncertainty that should be dealt with this way, not
operations that have been proven to achieve desired
outcomes (e.g., the possum–Tb example). Applying an
experimental approach will ensure that learning is maximized even if the operation fails to achieve its operational
objectives. Such adaptive experimental management has
been advocated for addressing uncertainty in ecosystem
management (Walters and Holling 1990, Lee 1993, Walters
and Green 1997, Norton 2005) and such an approach has
been integrated into a Standard Operating Procedure by the
New Zealand Department of Conservation.
Because large-scale (operation-based) experiments will
have higher costs resulting from increased monitoring and
implementation (Walters and Green 1997), we acknowledge
that the cheaper option of just killing nuisance wildlife will
often be the favored choice of action. Land-management
agencies will resist allocating funds to such experimentation
because of higher direct costs, risks, and opportunity costs,
unless there is a clear net increase in economic benefit.
Walters and Green (1997) proposed using an accounting
framework based on comparison of expected values or
utilities (Raiffa 1968) to objectively determine the net
present value of competing hypotheses or treatments. That
is, the value of knowledge gained from experimentation is
accounted for in terms of expected future management
performance (Walters and Green 1997). We note, however,
that management of nuisance wildlife will often provide
multiple nonmonetary benefits (e.g., biodiversity protection,
individual species protection, ecosystem services, carbon
storage, and animal welfare) and, therefore, to assume all
values can be accounted for within an economic framework
may not be appropriate for such systems (Jensen and
Sorensen 1998). Walters and Green (1997) recognized some
162
benefits would be nonmonetary and provided a 5-step
process for objectively integrating nonmonetary benefits into
the valuation process. Walters and Green (1997) also warn
of possible risks posed to the valuation process if nonmonetary values are set unrealistically high.
Our discussion of uncertainty, questionable objectives, and
ignorance of the true impacts of managing nuisance wildlife
suggest the usefulness of a knowledge-based ethic for
managing nuisance wildlife. The essential elements of such
an ethic are 1) when nuisance-wildlife control programs are
proposed with incomplete knowledge of the overall effects,
including animal welfare, the program must be reconstituted
as a management experiment and administered as an
element of an adaptive management system; 2) when facing
uncertainty about the effects of controlling nuisance wildlife,
act to identify key factors underpinning this uncertainty and
explore options for testing these factors to increase knowledge; 3) use new knowledge to update understanding of the
system being managed (ecological and social) and to
decrease uncertainties; and 4) continue to seek improvements in managing nuisance wildlife that maximize benefits
(social, environmental, economic) and minimize costs.
MANAGEMENT IMPLICATIONS
Management of nuisance wildlife that relies on manipulation of sentient animals will continue to be scrutinized by
opponents of lethal control and those concerned about
animal welfare. If management of nuisance wildlife is to be
justified, it is essential that animals are not killed wantonly
and that when they are killed this action is part of wildlife
management programs that have clearly defined objectives
and monitoring and audit procedures.
There will be some immediate implications of imposing
ethical rigor onto nuisance-wildlife management programs
as well as more long-term implications. In the short-term,
management agencies will need to develop a process for
evaluating their nuisance-wildlife management plans (as
animal ethics committees do for research proposals) and this
process, along with compliance with any requirements to
structure management as adaptive management experiments, will have additional costs. The process followed in
implementing such requirements could initially be voluntary
with agencies having in-house standard operating procedures to guide managers in how plans should be developed
and reviewed. If the recommended process was to be given
more legal weight then the process would have to comply
with relevant federal and state legislation, and the details of
such regulatory process will varying depending on the
country and state.
In the longer term, management should become smarter
(i.e., based on increased knowledge) because of more rapid
learning, and as a consequence management actions should
become more defendable because of the higher probability
of achieving successful management outcomes and doing so
with reduced ethical costs. For such a process to be
successful those involved in managing nuisance wildlife will
need to acknowledge and accept that there will be a cost, at
The Journal of Wildlife Management
73(1)
least in the short-term. To reduce uncertainty and increase
knowledge, management operations should become more
effective and efficient, and funds wasted on ineffective
management should decline.
ACKNOWLEDGMENTS
B. Warburton was funded by Landcare Research capability
funding, and B. Norton was partially funded by The Human
Social Dynamics program of the National Science Foundation grant no. 0433165. We thank P. Cowan, A. Byrom,
and W. Allen for review comments and C. Bezar for editing
a final draft.
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The Journal of Wildlife Management
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