FINAL REPORT FOR THE AUSTRALIAN GOVERNMENT DEPARTMENT OF THE ENVIRONMENT AND HERITAGE

MAXIMISING THE CONSERVATION BENEFITS OF THE COMMERCIAL GOAT INDUSTRY IN AUSTRALIA Published June 2004 Prepared by: David M. Forsyth¹ and John P. Parkes² ¹ Arthur Rylah Institute for Environmental Research Department of Sustainability and Environment 123 Brown Street Heidelberg Victoria 3084 Australia ² Landcare Research P.O. Box 69 Lincoln 8152 New Zealand © Commonwealth of Australia (2004). Information contained in this publication may be copied or reproduced for study, research, information or educational purposes, subject to inclusion of an acknowledgment of the source. This report should be cited as: Forsyth, D.M. and Parkes, J.P. (2004). Maximising the conservation benefits of the commercial goat industry in Australia. The views and opinions expressed in this publication are those of the authors and do not necessarily reflect those of the Commonwealth Government or the Minister for the Environment and Heritage. This project (ID number: 40499) was funded by the Australian Government Department of the Environment and Heritage through the national threat abatement component of the Natural Heritage Trust.

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Contents Executive Summary..................................................................................................3 1. Introduction ..........................................................................................................7 2. Background ...........................................................................................................7 3. Objectives ..............................................................................................................8 4. Results....................................................................................................................8 4.1 Defining feral and domestic goats...................................................................8 4.2 Evaluating the risks of establishment of new populations of feral goats ......9 4.2.1 Extent of domestic goat farming in Australia...........................................9 4.2.2 Changes in the distribution and density of feral goats in Australia.......10 4.2.3 Conditions for establishment of new populations of feral goats............13 4.2.4 Predicting the future distribution of feral goats.....................................15 4.3 Current legal and regulatory instruments to define and manage goats .....16 4.3.1 Commonwealth legislation.....................................................................19 4.3.2 State and Territory legislation ...............................................................22 4.3.3 Local Government legislation ................................................................27 4.4 Commercial harvesting of feral goats ...........................................................27 4.4.1 History and structure of the feral goat harvest industry........................27 4.4.2 Factors affecting the sustainability of the feral goat harvest industry ..43 4.5 Commercial harvesting of feral pigs ............................................................46 4.5.1 History and structure of the feral pig harvest industry...........................46 4.5.2 Factors affecting the sustainability of the feral pig harvest industry .....54 4.6 Maximising conservation benefits of commercial harvesting of goats.........55 4.6.1 How much can commercial harvesting reduce goat densities? ...............56 4.6.2 Is this enough to provide conservation benefits? .....................................56 4.6.3 Harvesting scenarios................................................................................58 4.6.4 Management options to minimise threats from domestic goat farming ...62 4.7 Key policy issues, information gaps and recommended solutions ................63 4.7.1 Risks of new feral goat populations establishing ......................................63 4.7.2 Lack of information on current management chosen by landholders .......65 4.7.3 Relationships between livestock stocking rates and biodiversity, and how management can achieve the best biodiversity outcomes .....................................66 5. Summary of key recommendations..................................................................69 6. Acknowledgements ............................................................................................70 7. References...........................................................................................................70

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Executive Summary Objectives 1. Review and evaluate methods developed for assessing the risks of new feral goat populations establishing through escapes from new and existing goat enterprises. 2. Describe the different legislative and policy instruments used by jurisdictions in Australia to manage feral and domestic goats, particularly as they affect commercial harvesting, and review their efficacy and utility in limiting the impact of feral goats on the environment and native biodiversity. 3. Describe the nature of the commercial harvesting industries for feral goats and feral pigs and their abilities to deliver sustained benefits to biodiversity values. 4. Consider whether the current or potential legal and policy instruments used to manage goats enhance or hinder the collateral benefits (if any) to the environment and native biodiversity. 5. Recommend changes to legal or policy instruments that might better benefit biodiversity outcomes. 6. Recommend research and other activities required to address gaps in knowledge that are needed to clarify the costs, constraints, and benefits of commercial harvesting as a method, either alone or in combination with others, to manage feral goats. Main findings Background information • The status of goats as feral or domestic animals is clear at the extremes. Domestic goats are those held under some combination of animal husbandry (owned, identified, restrained, managed for population structure and density, and receive welfare). Feral goats are free-living and not subject to livestock husbandry but may be ‘owned’ in the sense that access for harvesting or control is determined by the owner or occupier of the land. However, some goats have one or more of the domestic characteristics but in all other respects are indistinguishable from feral animals with no husbandry. This complicates enforcement of some legislation. • The number of truly domestic goats, mostly held for fibre production, has fallen from about 700 000 in the late 1980s to c. 200 000 at the last survey in 1998/99. The number of feral goats that have been domesticated (to varying extents) appears to be increasing. Feral goats occur over c. 1.2 million km2 of Australia. The distribution of feral goats appears to be stable in the semi-arid rangelands where their distribution is more continuous, but increasing in the western slopes of the main divide in eastern States where their distribution is patchier. • There is only anecdotal information on the causes of establishment of new feral goat populations. This is insufficient to categorise risks and to recommend defensible legislative or management changes to deal with this issue.

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Commercial harvesting • We estimate that about 1 million feral goats were removed annually in 2001–2003 by commercial harvesting. Most of these goats were slaughtered at about 15 Australian abattoirs and exported as either frozen whole carcasses or frozen cuts. The numbers commercially harvested in 2001, 2002 and 2003 were similar to those harvested annually during the early 1990s. • From 2001–2003, between 70 000 and 100 000 goats (mostly feral) have been exported as live animals for slaughter at overseas abattoirs. The future of this industry is less certain than the meat export market. • Goats are either trapped at water in areas where they are forced to drink (the driest and hottest areas) or mustered. This has implications for supply at the abattoirs and potentially affects the profitability of some abattoirs. In Western Australia, most goats are trapped during October-March (when they must drink at stock watering points), and the supply to abattoirs is thus highly seasonal. In the eastern States, a larger proportion of goats appear to be mustered and the supply is more evenly spread through the year. • Landholders have many motives for capturing or mustering feral goats for sale. Some see feral goats as biodiversity pests and/or competitors with livestock and essentially subsidise their control to low densities by selling the animals. Others see feral goats as a profitable resource and either take large but infrequent harvests or regular sustained harvests. Others see feral goats as a means of controlling weeds, and harvest excess animals as a byproduct, resulting in high population densities. However, many landholders do not harvest feral goats despite current high prices for such goats. • The price paid to landholders and the costs of capture appear to be the main factor determining how many feral goats are commercially harvested. However, harvest at a property level is also influenced by many other factors including the purpose of the farming enterprise, the profitability of their main enterprise, range condition and de-stocking needs, occasional peer pressures and governmental regulations, and the need to control weeds. Governments can influence only some of these factors. Governments cannot easily influence market prices, but could improve the profitability of goat harvesting by taxes or subsidies that reduce the costs of capturing goats. Government can sometimes influence where domestic goats are held, where feral goats are controlled, and the timing of destocking via regulatory instruments - ideally based on range condition monitoring systems. − The Commonwealth government can influence the cost structures and profitability of the industry via regulations affecting the quality control chain (i.e., capture welfare, transport, identification rules, and inspection costs). − All governments may directly affect goat control (which may include some component of commercial harvesting) by conservation prioritysetting systems (for particular reserved land or species) and by funding through the Natural Heritage Trust. Some States specifically define the status of domestic and feral goats, indicate management responsibilities, and have the power to spend taxpayers’ money to

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manage them should they choose to do so (WA, SA, Vic and QLD). Other States (NSW, Tasmania and NT) lack one or more of these factors in their legislation. − Local governments appear to have variable ability to spend ratepayers funds to manage goats depending on State legislation. However, few appear to do much, leaving it to landholders or their legal or voluntary organisations (e.g., Pastoral Boards and their equivalents, and Landcare groups). There are no data with which to evaluate whether or not commercial harvesting of feral goats provides any sustainable benefits to the environment or native biodiversity. However, the benefits will likely depend upon the densities to which goats are reduced, the habitat, and the values affected. The benefits are also likely to vary with rainfall and the numbers of other herbivores present. Commercial harvesting can also be used as a first step in any pest control strategy, although this can be compromised if the harvest becomes an end in itself. Commercial harvesting occurs in only part of the feral goat range (the semi-arid rangelands and parts of the rangelands west of the main divide). Not all native species listed as threatened by feral goats benefit from this harvest either because they occur outside the areas harvested or potentially because too many goats remain after harvesting.

Key issues and information gaps Risks of new feral goat populations establishing • Goats that escape from captivity may move into goat-free areas and establish new populations, or may move into areas where feral goats are being controlled. • However, there is no information on the causes and frequency of events that lead to the establishment of new feral goat populations, and therefore on how managers should best deal with these risks. • Stricter goat-fencing standards and restrictions on holding domestic goats are not supported by the majority of landholders and goat meat producers. Lack of information on current management chosen by landholders • Management decisions on commercial harvesting are made at a property level, but there is no information on the proportion of landowners choosing different harvesting strategies. Therefore, the efficacy of any policy or legislation that attempts to change landholders’ behaviour with respect to commercial harvesting is unknown. Relationships between livestock stocking rates and biodiversity, and how management can achieve the best biodiversity outcomes • It is unclear how often feral goats are reduced by commercial harvesting to densities at which conservation benefits are achieved. Harvesting does reduce feral goat densities, but it has been insufficient to halt population increases over large areas where feral goat densities had been reduced by control or drought (e.g., the pastoral rangelands of Western Australia). It is unclear whether the harvesting has provided significant overall benefits for rangeland condition or biodiversity values. • Sustained high prices for goat products relative to sheep products could result in a change from lower densities of feral goats to higher densities of managed goats.

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The best long-term biodiversity outcomes would result from formally linking trends in biodiversity (from monitoring) to required changes in the abundance of livestock (of which goats are one component) and other herbivores. Hence, both managed and unmanaged (i.e., including feral goats) livestock should be included in stocking rates. Stocking rates would thus be determined by trends in biodiversity, and the costs of feral goat control would be borne by the landholder.

Key recommendations 1. The Department of the Environment and Heritage and State conservation agencies should prioritise where they need to actively control goats independent of where commercial harvesting occurs. 2.

States should encourage landowners who are not commercially harvesting feral goats to do so by promoting its financial benefits and noting tax incentives available for investment in infrastructure to capture goats.

3.

A costed strategy with options for further action should be developed for use by landowners who wish to use commercial harvesting as the initial step to control feral goats as pests.

4.

Future amendments to State ‘national park’ legislation should clarify the unwanted pest status of feral goats on lands in protected tenures, partly to avoid potential contradictory legal definitions of feral goats as actual or potential declared pests and as game animals.

5.

State agencies should consider how to impose legal restrictions on the holding of domestic goats and for standards of management where they are permitted, but these should be commensurate with the risk such enterprises pose to the public good both in situ and on adjacent lands.

6.

Laws to bring feral goats (where goats are permitted) under ‘stocking rate’ rules rather than ‘declared pests’ rules on leased and private land may provide better outcomes, but only if they are enforced and the effects monitored.

7.

Landowners and leaseholders in the pastoral rangelands should be surveyed to ascertain their views on feral goats and their consequent management intentions (e.g., as resources, pests and weed control agents) for goats on their land.

8.

The relationships between feral goat (and other herbivore) densities and biodiversity should be investigated at sites under different management strategies.

9.

The benefits and costs to biodiversity of maintaining high densities of goats to manage exotic weeds should be determined experimentally.

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1. Introduction The Department of the Environment and Heritage (DEH) has published a Threat Abatement Plan for feral goats (Capra hircus) (Environment Australia 1999). That plan aims to “prevent feral goats from occupying new areas in Australia” and “ensure that development of a commercial goat industry does not compromise conservation of native species or ecological communities”. In 2003, DEH commissioned the Arthur Rylah Institute for Environmental Research (Department of Sustainability and Environment, Victoria) to review aspects of the commercial goat industry, and that for feral pigs (Sus scrofa), with respect to maximising its potential benefits for biodiversity conservation in Australia.

2. Background Feral goats are one of five feral vertebrates in Australia listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) as a key threatening process. The others are feral cats (Felis catus), rabbits (Oryctolagus cuniculus), feral pigs (Sus scrofa), and foxes (Vulpes vulpes). However, feral goats also have economic value either exported live or as meat, and large numbers have been commercially harvested. There is no doubt that the size of some of these harvests can reduce feral goat populations and thus potentially reduce the impacts of feral goats on the environment and native biodiversity. The issues about this, from a conservation perspective, are: • Is commercial harvesting undertaken at scales sufficient to provide general benefits? • Where commercial harvesting is undertaken, is the harvest sufficient to reduce goat populations to protect the conservation values being threatened? • Even if it is enough, how frequently should harvesting or control be imposed to sustain the conservation benefits? This is the crux of the matter addressed in this report. If the goats are too valuable, relative to other livestock, it can (a) pay to sustain a regular harvest (a maximum economic yield) from a population that probably exceeds the level at which environmental damage is unacceptable, or (b) to take a large but infrequent harvest, allowing goat numbers to increase to levels that maximise the cost/benefit budget at each harvest but exceed damaging thresholds for part of the time. In theory, the best economic option for a landholder will depend on how goat densities (and so costs of harvesting) and market prices fluctuate. The best conservation outcome will depend on the length of time, timing with respect to rainfall, and the extent to which goat densities exceed levels that cause unacceptable damage to native species and communities or alter the trajectories of these ecosystems. However, landholders have a continuum of attitudes towards feral goats, ranging from ignoring goats as a commercial resource, to managing goats to maximise their profitability, to treating them as a pest. This report reviews the current commercial harvesting of feral goats and feral pigs, and attempts to identify conservation and environmental benefits and costs associated

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with each of the above regimes, particularly in light of legislation that attempts to regulate their management.

3. Objectives 1. Review and evaluate methods developed for assessing the risks of establishing feral goat populations through escapees from new and existing goat enterprises. 2. Describe the different legislative and policy instruments used by jurisdictions in Australia to manage feral and domestic goats, particularly as they affect commercial harvesting, and review their efficacy and utility in limiting the impact of feral goats on the environment and native biodiversity. 3. Describe the nature of the commercial harvesting industries for feral goats and feral pigs and their abilities to deliver sustained benefits to biodiversity values. 4. Consider whether the current or potential legal and policy instruments used to manage goats enhance or hinder the collateral benefits (if any) to the environment and native biodiversity values. 5. Recommend changes to legal or policy instruments that might better benefit biodiversity outcomes. 6. Recommend research and other activities required to address gaps in knowledge that are needed to clarify the costs, constraints, and benefits of commercial harvesting as a method, either alone or in combination with others, to manage feral goats.

4. Results 4.1 Defining feral and domestic goats The biological and legal status of a goat, either as an owned domestic animal subject to livestock husbandry or as a free-living feral animal, is clear at the extremes. However, it is often unclear for animals that are only loosely managed but are owned, often only in the sense that they ‘go with the land’. An animal’s status can also change with circumstance, e.g., when an owned domestic goat escapes and is not recaptured, or when a feral animal is captured and used as livestock. Thus, ownership per se is not a particularly reliable factor to distinguish feral and domestic goats. Livestock husbandry and use are perhaps more reliable discriminators, but again this can be obscure for free-living populations that are infrequently harvested. Lack of certainty about which goats are domestic and which are feral on private and pastoral leasehold land can hamper effective policy and management.

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State ‘national park’ legislation is often less than clear about the status of goats as ‘fauna’ or ‘pests’ on the tenures covered by these acts. Goats are often included, by implication, in the definitions of animals, fauna, or mammals and so not specifically distinguished from native and protected species. However, they are simultaneously defined as pests because of their listing as a key threatening process in the EPBC Act. The practical implication of this dichotomy appears to be that goats are often protected from casual or recreational shooting and harvesting but not from official control, presumably under the management planning rules in the acts, on land reserved for conservation purposes. State ‘agricultural’ legislation is often more specific about distinguishing feral from domestic goats, but varies on how to manage these differences. Our working definitions for this report are similar to those used by Freudenberger (1993) and Parkes et al. (1996a): Feral goat: Any free-living goat not subject to livestock husbandry. It may be ‘owned’ in the sense that access to it for harvesting or control is determined by the owner or occupier of the land on which it currently lives. Domestic goat: Any goat owned and subjected to livestock husbandry. Livestock husbandry would include at least one of such things as individual identification via ear tags or brands, provision of health care, constraints on the animals’ movements and location, and management of their sex ratios, breeding and population size to some target.

4.2 Evaluating the risks of establishment of new populations of feral goats There are four ways that new populations of feral goats might be established: • By escape and spread from existing domestic goat herds; • By in situ abandonment of domestic goat herds; • By translocation and release into the wild of domestic or feral goats to new areas they would not reach by natural dispersal; • By natural dispersal from current feral goat populations. Dispersal might be either into areas without goats or into areas where goats are under effective control. The terms of reference of this review are largely concerned with the first three ways of establishment and spread. However, given the uncertain status of many feral goat populations and their current wide distribution, we will also discuss the last case. In this section we summarise information on changes in distribution of feral goats at large and small scales, and speculate on the conditions that promote or inhibit establishment of new herds of goats - both domestic and feral. This information will then be used to give some context to our evaluation of potential methods to assess the risks and potential extent of feral goat range in Australia. 4.2.1 Extent of domestic goat farming in Australia Estimates of the numbers of domestic goats in Australia were collected in the annual agricultural survey conducted by the Australian Bureau of Statistics between 1981/82

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Figure 1. Reported numbers of domestic goats held in Australia, 1981/82 to 1998/99. Source: Livestock and Livestock Products, Australian Bureau of Statistics (ABS) Catalogue No. 7221.0. to 1998/99, but the question has not been included in the survey since 1998/99. The number of domestic goats in Australia peaked at nearly 700 000 in the late 1980s, with most being held in New South Wales (Parkes et al. 1996a). About 200 000 domestic goats were reported in the last survey (Fig. 1). The extent of the apparent changes need to be treated with some caution because the minimum ‘estimated value of the farming operation’ included in the survey has varied greatly: $2500 from 1981/82 – 1985/86, $20 000 from 1986/87 – 1991/92, $22 500 in 1992/93, and $5000 since 1993/94. The peak during the late 1980s is therefore likely to be underestimated because it did not include smaller enterprises. The data are also complicated by the likelihood that respondents reported feral goats as domestic in years when they were worth most. The data for all years do not include the large (but unknown) number of small domestic herds held as pets or for a variety of other purposes. These might total almost as much as the commercial domestic industry. There is no detailed information on where domestic goats are held. 4.2.2 Changes in the distribution and density of feral goats in Australia Feral goats occur over c. 1.2 million km2 (Fig. 2) or 16% of Australia and were estimated to number at least 2.6 million in 1996 (Parkes et al. 1996a).

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Most of the published information on changes in feral goat distribution (and density) is at large scales, often State-wide, and often collected using aerial surveys. As far as the objectives of this report are concerned, changes at such a scale are useful only to record the gross symptoms of the problem or the general results of attempts to solve it. To identify the causes of the problem, there is a need to measure changes in distribution at the much smaller scale of populations, i.e., changes at the edge of current feral and domestic goat distributions. Changes in distributions at State or regional scales Maps of feral goat distribution and sometimes density at a national or State level have been published at various times since the 1970s. Most are based on aerial survey techniques used primarily to count kangaroos (Caughley and Grigg 1981). The method is limited in its ability to detect changes in the distribution and density of feral goats. First, density estimates should be corrected for differences in visibility (Bayliss and Yeomans 1989). Although many earlier surveys were not corrected for differences in visibility, most surveys appear to use correction factors (e.g., see Pople et al. 1996). Second, feral goats at low densities are difficult to detect, meaning that real changes in distribution may go undetected. This problem is likely to be acute at the low survey intensities employed for feral goats (1.3% coverage; see Pople et al.

Area of feral goat commercial harvest Feral goat distribution Dingo Fence

0

900

1800 Kilometers

N

Figure 2. Distribution of feral goats in Australia. Note: This map, supplied by the Department of the Environment and Heritage, ‘smooths’ distributions where feral goats exist in patches (e.g., along the eastern parts of Queensland, New South Wales and Victoria, southern South Australia, southwest Western Australia, and in Tasmania). See Fig. 3 to show the effect of this when distribution is mapped at a finer scale. Note: This figure shows feral goats present in eastern Northern Territory, but our informants suggest none are present.

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1996). Therefore, some reported increases in range might be an artifact of changing goat densities rather than real changes in their distribution. Third, the precision of aerial surveys is low and usually decreases as the density of feral goats declines. Hence, it is difficult to precisely estimate changes in feral goat abundance. Despite these caveats, broadscale surveys have shown some changes in goat densities and distributions over the last few decades (Table 1). Most of these large-scale maps focus on the extensive distributions of goats in the rangelands. Smaller feral goat populations are also patchily distributed outside the rangelands (e.g., along the main eastern dividing range; West and Saunders 2003) (Fig. 3). Patchiness and connectivity between goat populations within the rangeland and elsewhere are critical parameters in deciding which populations of pests might be eradicated and which must be controlled in perpetuity - a point to which we will return. Changes in distributions at local scales There is no information (published or otherwise) on the extent of establishment of new populations of goats, let alone when they are broken down into the four categories of spread described above. However, we can consider the site-specific processes that might increase or decrease the risk of spread and establishment of new herds at local scales.

Figure 3. Distribution map of feral goats in New South Wales. Source: West and Saunders (2003). Note: a similar map is being compiled for Western Australia (A. Woolnough, Department of Agriculture, Western Australia, personal communication).

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Table 1. Summary of information on the changes in distribution and density of feral goats in States and Territories. State/Territory Western Australia

South Australia

Survey years/period 1987; 1990 1990–1999

Queensland Northern Territory

Trend in distribution Stable Perhaps decreased

References

1999–2002

Increased by 64% Decreased under eradication campaign Increase

1978–1994

Stable

Stable

Pople et al. (1996)

No information

No information

Parkes et al. (1996a); Anonymous (2002a)

Down in west Up in east

Stable

Increased Increased Decreased to zero on mainland

Increased Increased Decreased to zero on mainland

Victoria New South Wales

Trend in density

1992 1996; 2002 1982 1992 1999 1970s–2003

Southwell and Pickles (1993) A. Woolnough, personal communication A. Woolnough, unpublished data

Southwell et al. (1993); West and Saunders (2003) Mitchell et al. (1982) Southwell et al. (1993); Thompson et al. (1999) Letts et al. (1979); Wurst and Saalfeld (1994); G. Edwards, personal communication

Tasmania

1995

Down: under control

? down as new herds eradicated

Diwell (1995)

ACT

-

Down to near zero

Down

B. Woodruff, personal communication

4.2.3 Conditions for establishment of new populations of feral goats Whether domestic goats escape and establish new feral goat populations depends upon conditions in both the domestic populations and in the potential new range. Conditions in the domestic populations Establishment of new populations of feral goats obviously requires goats to arrive in new range. We propose three categories of risk: (a) Escape and spread from existing domestic goat herds: The risks of escape under this category will depend on the extent to which the herd is managed, which will depend on the purpose for which they are kept. Valuable goats are more likely to be effectively fenced or recaptured when they escape or stray than goats with lower value. Nevertheless, some escapes are inevitable even from intensively managed lands. Bomford (1991) noted that there are many examples of animals escaping as a result of natural disasters. There are legal requirements setting fencing standards that reduce this risk in some States (see section 4.3.2), but the issue becomes how to deal with the inevitable escapees. We discuss some options for proactive (enforcing fencing standards, and

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banning goats from critical risk areas) or reactive (surveillance and control of escapees) management in section 4.7.1. The purpose for which domestic goats are held is likely to be the main risk factor in determining contribution to establishment of feral populations, both because of the degree of management imposed on the animals and the sort of places they are usually held. Our assessment is that the risks, in increasing order, are: • Fully domestic animals held for milk production. • Pets. • Fully domestic breeds held for meat production. • Fully domestic breeds held for fibre production. • Domesticated feral goats harvested for meat production. • Domesticated feral goats managed for weed control. There is anecdotal evidence that some domestic breeds of goats (e.g., angoras) have smaller home ranges and lower dispersal rates than others (e.g., domesticated ferals). However, we have no data on the actual scale of these risks taken from measurement of the incidences of escape from the various forms of domestication. Data on the proportion of goats with ear tags shot in control operations (if collected) might provide some insight into the prevalence of escapees. (b) In situ abandonment of domestic goats: The economics of keeping goats presumably determines the extent of this problem, although again (apart from anecdotal observations) we have no information yet on the scale of the problem. Proactive requirements to dispose of unwanted domestic goats would seem to be the only solution to this category of problem. (c) Translocation and release: Setting up new domestic goat farms in areas without goats is not generally constrained by law, although the deliberate release of goats into the wild is generally illegal. We have only anecdotal evidence of the latter (e.g., in the Angahook-Lorne State Park in Victoria). It generally appears to be motivated by the desire to establish a hunting resource. Conditions in the potential new range Three factors are likely to affect the ability of goats to establish a population in new range. (a) Habitat suitability: Recent work has shown that species of exotic mammals introduced into Australia (i.e., including feral goats) were more likely to establish a population if they had a larger area of climatically suitable habitat available (Bomford 2003; Forsyth et al. 2004). However, climatic suitability is only one component of habitat suitability, with both biotic and abiotic conditions likely to be important. Goats are hardy animals and can survive in habitats that extend from the sub-antarctic (e.g., on Auckland Island with ≥300 rain-days per year), to areas with no permanent water (e.g., on many islands such as Macauley [Kermadec Group] and Isabela [Galapagos Group]), to deserts. In hot and dry areas, such as the Australian semi-arid rangelands, goats cannot rely on

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obtaining enough water in their food and need periodic access to drinking water. This is especially so in droughts and when the ambient temperatures are over c. 30ºC – they need to drink more than 5 litres per day when temperatures exceed 40°C (Norbury 1993). Thus, feral goat distributions (and densities) are likely to be limited by rainfall and/or the lack of drinking water in parts of Australia. Importantly, because domestic goats are likely to be held in areas where habitat suitability is high, adjacent new range is likely to be highly suitable for the establishment of new populations. (b) Propagule size: The numbers and sex-age classes of goats that arrive in the potential new range, or ‘propagule size’, has a strong theoretical and empirical basis for determining whether a population establishes or not (e.g., Komers and Curman 2000). For a sub-sample of ungulates introduced into New Zealand and Australia for which suitable data were available (not feral goats), there was a strong and positive relationship between the number of individuals introduced and introduction success (Forsyth and Duncan 2001; Forsyth et al. 2004). Although populations of ungulates sometimes established from just a single pair of animals, the probability of establishment increased up to about six individuals, after which nearly all introductions established populations. Since goats have similar life-history characteristics to the ungulates considered in those studies, it is possible that feral goats can establish populations from a pair of escapees. (c) Abundance of wild dogs: Feral goats are now largely absent where dogs are present (e.g., on the northern/western side of the dog fence; Fig. 2), although goats can persist if they have suitable refuge habitat where dogs are present but effectively controlled (Parkes et al. 1996a). We predict that new populations of feral goats are less likely to establish where wild dogs are present, but we do not know of any data with which to test this hypothesis. 4.2.4 Predicting the future distribution of feral goats It would be possible to map the distribution of domestic goats (currently unknown) and feral populations (currently known only at a broad scale; Figs. 2 and 3), and to predict the risks that either will spread or establish new feral goat populations by considering the parameters outlined above. Better information on the distribution of feral goats might become available from current initiatives from the Natural Resource Management Standing Committee’s Monitoring and Evaluation Working Group. This requires development of indicators of how management is reducing regionally significant pests. The data collected will need to be at a scale that would detect the edges of distributions with some precision to be useful in the context of this review. Predicting whether an area would sustain a population of goats should they arrive could be done by developing a model using the ‘constraints’ noted above: climatic suitability (assessed using CLIMATE [Pheloung 1996] or other such software), presence and absence of wild dogs, critical ambient temperatures, and the presence of

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permanent drinking water. We note that Bomford (2003) developed a protocol for assessing the risk of exotic vertebrates establishing in Australia. However, her protocol was developed for species not yet established in the wild in Australia, and we suspect that other models would be more appropriate for predicting the further spread of a single species already widely distributed in Australia. Such models have been developed to predict the spread of weeds (e.g., Weber 2001) in Europe, but they have not been developed for vertebrate pests in Australia and would require a substantial research investment to make them useful. However, P. Fleming and S. McLeod (NSW Agriculture, personal communication) are estimating resource selection functions for feral goats at one site in New South Wales, and these functions could be used in a model predicting the dynamics of feral goats. We also note that a model has been developed for predicting the abundance of introduced brushtail possums (Trichosurus vulpecula) in New Zealand based on the presence/absence of habitat requirements (Fraser et al. 2004). However, given that domestic goats would be held in areas of highly suitable habitat, and that ungulates can establish populations from very small propagules (see above), we believe that domestic goats have a very high risk of establishing new populations in areas where wild dogs are absent. Predicting the rate at which goats might spread given they establish in a new area is more difficult, and probably highly site specific. However, dispersal rates of feral goats, where they have been measured, are low (0.4 km yr-1 in one study in New Zealand; Parkes 1993) compared with those of other ungulates (e.g., Caughley 1963). However, this dispersal rate comes from feral goats with small home ranges (16 kg. In Taiwan, there is little demand for carcasses during February–August, with demand increasing during the festival season; premiums are paid for lean skin-on carcasses weighing 14–20 kg. Middle East buyers preferred 8–12 kg carcasses, with halal slaughter essential. The major market for Western Australian goat meat is Taiwan (Coffey MPW Pty Ltd 1994). About 1800 tonnes of goat meat were exported from that State to Taiwan in 1992, but only 1300 tonnes in 1995/96. Taiwan prefers feral goat meat and Western Australia was apparently unable to supply adequate quantities of goat meat to that market. The Taiwanese market is the highest priced Asian market due to the demand for skin-on product that is widely consumed in a traditional soup dish eaten during the winter months; goats for this market must be lean and young (ca. 14–16 kg). Malaysia is also an important market for Western Australian goat meat. There is a preference for the skin-off product, but that market substitutes goat with mutton and ram carcasses when the price relativities change. Similarly, the Singapore market is pricesensitive and willing to substitute goat for other types of meat (Coffey MPW Pty Ltd 1994).

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Figure 10. Destinations of goat meat exported from Australia, 1989/90–2002/03. Data were provided by P. Dumaresq (Meat & Livestock Australia). Note that for clarity the small amounts that went to ‘other countries’ are not shown. (e) Economics of supply It appears that most decisions to harvest feral goats (either by doing it themselves or by contracting the work) are made at a property level by the landholder (e.g., Thompson and Boyd-Law 1995). Thus, the attitudes of the individual landholder towards feral goats are a key variable in the industry. Some landholders see feral goats as competitors with livestock and essentially subsidise their control (or even profit) from sale of the animals. Others see the goats as a resource, either directly as a product for meat, or indirectly as a means of controlling weeds with a harvest of excess animals as a by-product. Some appear never to harvest feral goats when it would clearly be profitable (i.e., they do not see goats as part of their economic enterprise). It might be important to know what motivates landholders to commercially harvest goats if governments wanted to influence their behaviour. One way to explore these attitudes would be by surveying a large sample of individuals. To our knowledge, this has not been done. A second way to explore motivations is to quantify the relationships between measurable outcomes of landholders’ behaviour (e.g., the numbers of feral goats harvested) with variables that might be thought to influence them. Harvesting theory suggests that profit will be the primary determinant of whether or not to harvest (e.g., Choquenot et al. 1998). For feral goats, profitability will depend

37

on the difference between the cost of harvesting the goats and the price paid for the goats (see below). Parkes et al. (1996b) showed that 89% of the variation in the annual commercial harvest of red deer (Cervus elaphus) in New Zealand was explained by price per kg offered by the game buyers. Nevertheless, factors other than price may affect the commercial harvest of goats. First, the efficiency of capture will vary with the methods used or possible and profitability will increase as the number of goats that can be harvested per unit effort increases (sensu Choquenot et al. 1998). Second, managers will be more likely to harvest feral goats when they perceive competition with their livestock (domestic sheep), and/or when rangeland condition is perceived to be poor (A. Dowden, Challa Station, personal communication). Third, farmers may wish not to harvest feral goats when they think there are net benefits in retaining them as weed controllers. We used data collected by G. Pickles and A. Woolnough (Department of Agriculture, Western Australia) to test hypotheses about factors influencing the number of goats received by abattoirs in Western Australia. The data consisted of 180 consecutive monthly records (July 1988 to June 2003, inclusive) for four variables (Fig. 11): • The number of goats received by abattoirs Western Australia. • The average price paid per goat by the abattoirs (adjusted for inflation to 1988 $ using the Consumer Price Index [CPI]). • The average rainfall for the region that the goats were harvested in (mm). • The average price paid per kg of 21 micron wool, the predominant wool grown in the region that the goats were harvested in (adjusted for inflation to 1988 $ using the CPI). Although some domestic goats may be included in these totals, the overwhelming majority of goats were commercially harvested from rangeland pastoral leases and were thus, to all intents and purposes, feral or ‘unmanaged’. From conversations with key players in the Western Australian goat harvesting industry, and from the literature, we generated four hypotheses for testing: • That the number of goats harvested was a function of the average price paid per goat. • That there was a threshold average price paid per goat below which farmers did not harvest goats. • That the number of goats received declined when the wool price increased because it was more profitable for farmers to spend time on wool production activities. • That the number of goats received was a function of monthly rainfall; this was based on the notion that goats were easier to trap in the drier months when they were forced to drink from a small number of available artificial water sources.

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Figure 11. The data used in our analyses. All data were compiled on a monthly basis for July 1988–June 2003, inclusive. (a) Number of goats received by abattoirs in Western Australia. (b) The average price ($) paid per goat by the abattoirs (adjusted for CPI). (c) The mean rainfall (mm) for the area the goats were harvested from. (d) The auction value of 21 micron wool (adjusted for CPI).

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The data show a slight increasing trend in the number of goats received over the period considered, with larger numbers received in recent years compared to earlier years (Fig. 11a). There also appears to be a strong seasonal effect (Fig. 12), characterised by more goats being received in the warmer months and less in the colder months. The ten largest observations occurred in the months of November, December and January while the five smallest observations occurred in the winter months of June and July. The distribution of the number of goats received was skewed to the right; about 50% of the observations in the data set were between c. 6 800 and 21 500, but there were extreme high values (up to 60 400). No goats were received in June 1991 and June 1996. In order to satisfy the assumption that the underlying distribution was normal, a transformation of the response variable was required. The most appropriate transformation was found to be the square root of the number of goats received. The boxplots (Fig. 12) show that the variation in the number of goats received by the abattoir is also considerably larger in the summer months relative to the winter months where numbers remain more stable throughout the observation period. The average price paid per goat was relatively stable during the period August 1990 to December 1993 (Fig. 11b). From January 1994 until August 2003, the price increased. Prices during this latter period also showed a seasonal effect, with higher prices paid in the months at the end of the calendar year. An exception to this occurred in 1999, when the annual maximum price was recorded in August before steadily decreasing for the rest of the year. The rainfall data were the averaged rainfall across the five rainfall districts from which the goats were harvested. Average monthly rainfall was characterised by mostly small values with occasional large values (Fig. 11c). Rainfall followed a seasonal pattern, with the highest values of rainfall observed in February and March, and lowest rainfall during September, October and November.

60000 50000 40000

Number of goats

30000 20000 10000 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Figure 12. Boxplots showing seasonality in the median, lower and upper quartiles, and the lowest and highest numbers of goats received by abattoirs in WA.

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The price paid for 21 micron wool declined sharply from July 1988 to about February 1991 (Fig. 11d). Since 1991, the price has fluctuated between 400 and 800 cents. There does not appear to have been a seasonal pattern to these fluctuations, and nor have there been any sudden fluctuations in price. The square root of the number of goats received by the abattoir was serially correlated, with a high (low) value in a particular month tending to be followed by a high (low) value. To overcome the serial correlation, an autoregressive model was fitted to the data. An autoregressive model differs from an ordinary regression model in that it assumes dependence of errors. An autoregressive model is defined in terms of its order, p (i.e., AR(p)), and describes a situation in which each residual from the regression is correlated with the previous p residuals in the time series. The model also contains an independent random error term. An autoregressive model of order 1 (i.e., AR(1)) is usually sufficient to account for the serial correlation present in the residuals of an ordinary regression equation. Variable selection was conducted by first considering the full model containing all explanatory variables of interest and one-byone removing those that made no significant improvements (at the 5% level) to the model (i.e., backward-selection), and by inspection of the percentage of variation in the data explained by the model (i.e., the R2). Fitting the model gives an estimate of the autoregressive parameter and the adjusted coefficients and standard errors of all the included regression variables (Table 8). There was no systematic relationship between the residuals from the best model (Table 8) and the order of the data (i.e., the pattern was random), and the runs test statistic was not statistically significant. We thus concluded that the serial correlation in the error term had been satisfactorily accounted for in this model. The best model explained 72.4% of the variation in the number of goats received by the abattoir. Hence, the important variables were: (i) the number of goats received in the previous month, (ii) the current month, (iii) the average price paid per goat in the current month, (iv) the current month’s average rainfall, and (v) the previous month’s average rainfall. With regard to the hypotheses outlined above, we conclude that: 1. The number of goats received (and hence assumed to have been commercially harvested) was a function of the average price paid per goat in the previous month. A positive relationship existed between the number of goats received by the abattoir and the average price paid per goat in the previous month. The model indicated that, provided all other variables remain constant, a single dollar increase in the average price paid per goat would increase by 2.39 the square root of the number of goats received by the abattoir in the following month. The relationship was non-linear, with a single dollar increase in the price having a decreasing effect on the number of goats harvested in the next month as price in the preceding month increased. For example, if 1000 goats had been harvested in the previous month then a single dollar increase in the average price would lead to a 8% increase in the harvest in the following month. However, if 40 000 goats had been harvested in the previous month then a single dollar increase in the average price would lead to just a 1% increase in the harvest in the next month.

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Table 8. Regression coefficients, standard errors and P-values for the best regression model assuming first-order autocorrelated errors. There were 180 observations in the time series, and the model had an R2 of 72.4%. Variable Month January February March April May June July August September October November December Price paid per goat in the previous month Current month’s rainfall Previous month’s rainfall AR(1) error

Coefficient 155.4 143.9 119.7 84.1 69.2 54.8 70.1 81.3 74.0 71.1 109.9 143.3

Standard error

P-value < 0.001

13.9 13.6 13.4 12.7 12.7 13.1 12.9 12.7 12.9 13.0 13.0 14.0

2.39

0.78

0.002

−0.214 −0.229 0.577

0.070 0.070 0.004

0.002 0.001 < 0.001

2. There was no evidence for a threshold average price paid per goat below which goats are not commercially harvested. The abattoir received goats in all months in which a price was offered. Further analyses (not reported here) showed no evidence of a threshold average price. The data set would probably need to include lower prices if a threshold price was to be estimated (if indeed it exists). 3. There was no evidence that the number of goats received by abattoirs declined when the wool price either increased or decreased. No significant relationship was found between the number of goats received and the average price paid per kg of wool. When this variable was included in the autoregressive model, the coefficient was positive (opposite to that hypothesised) but not statistically significant. 4. The number of goats received decreased with increasing rainfall. Average rainfall in the current month was a significant linear predictor of the number of goats received by the abattoir in the current month. The coefficient for this variable was –0.214, meaning that provided all other variables remained constant, an increase in the average monthly rainfall of 10 mm would decrease by 2.14 the square root of the number of goats received by the abattoir in the same month. There was also a significant lagged relationship between the number of goats received by the abattoir and average rainfall in the previous month. The model coefficient was –0.229, meaning that an increase of 10 mm in the average rainfall of a particular month would decrease by 2.29 the square root of the number of goats received by the abattoir in the following month. Therefore, the number of goats received by the abattoir was a function of both the current and the previous month’s average rainfall. The effects of each of these variables were

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additive. Both coefficients were negative (as hypothesised), thus supporting the hypothesis that feral goats are easier to harvest in the drier months when they must drink from artificial water sources. However, it is also possible that there is a greater incentive for harvesting feral goats in dry months due to perceived competition with sheep. We note that although these data are the best available to test factors influencing the harvest of feral goats, the data were not collected at the level of individual properties, which is where the decisions about commercial harvesting are made. (f) Economics of abattoirs: Ramsay (1994) claimed that most abattoirs processing goats are primarily concerned with slaughtering sheep, with goats purchased ‘opportunistically’. This appears to still be the case, with the majority of goats apparently processed at two abattoirs in 2003 (Geraldton in Western Australia and Charleville in Queensland). Many factors affect abattoir profitability, including animal supply and quality, labour quality and cost, variable skin returns, perishable product, marketing and financing (Holst 1990). Holst (1990) argued that the viability of the export industry depends on ‘exchange rates, cost control and innovation’. Feral goats are transported large distances to abattoirs or exporters in multi-decked truck-trailer units, and distance from the market may be a constraint on the profitability of selling feral goats (Holst 1990). The abattoir loses money on any goat