Review of existing Red Fox, Feral Cat, Feral Rabbit, Feral Pig and Feral Goat control in Australia. II. Information Gaps

Final report
Ben Reddiex, David M. Forsyth.
Department of the Environment and Heritage, 2004

1. Introduction

The Department of the Environment and Heritage (DEH) commissioned the Arthur Rylah Institute for Environmental Research (Department of Sustainability and Environment, Victoria) to undertake a project to increase understanding of the threats to native species and ecological communities from foxes, wild dogs, feral cats, feral rabbits, feral pigs, and feral goats. The key aims of the project were to investigate; 1) control activities currently undertaken across Australia for from foxes, wild dogs, feral cats, feral rabbits, feral pigs, and feral goats; and 2) pest control that is necessary to secure the recovery of affected native species and ecological communities, especially those listed as threatened (under the Environmental Protection and Biodiversity Conservation Act 1999 (EPBC Act)). The project is being completed in three stages. The first stage, an audit of 1306 existing pest animal control programs in Australia, has been completed (Reddiex et al. 2004). This stage includes identification of gaps in information on control activities and recommendations for filling these gaps. The third and final stage involves development of pest species monitoring protocols, and designing a process to determine priority ranking for control of pest animals in order to minimise threats to native species and ecological communities.

2. Background

Red foxes (Vulpes vulpes), wild dogs (Canis lupus familiaris, Canis lupus dingo, and hybrids), feral cats (Felix catus), feral rabbits (Oryctolagus cuniculus), feral pigs (Sus scrofa), and feral goats (Capra hircus) separately and in various combinations are believed to be responsible for the extinction or decline of a wide range of native species and for adverse changes in ecological communities in Australia. Predation by foxes and feral cats are listed key threatening processes under the EPBC Act, whilst competition with native species and land degradation by feral rabbits, feral pigs and feral goats are also key threatening processes under that Act. Some of these species also have important impacts on agricultural values (through competition for resources and depredation of livestock) and may impact on historic cultural heritage and act as vectors of animal and human diseases (Braysher 1993).

The belief that pest animals have caused these declines in native species (and damaged production values) is reflected in legislation and has led to many attempts to control these pests. Many agencies and organisations including Federal, State and Local governments commit significant resources managing these species. However, there is limited hard evidence that this management has led to a reduction in threats and to a reversal in the decline (e.g., Hone 1994; Dickman 1996). Benefits of pest control are likely to depend on a wide range of factors, including the intensity and frequency of pest control, pest abundance following control, the size of an area controlled, and the ability of impacted species or resources to recover (Hone 1994; Choquenot and Parkes 2000; Coomes et al. 2003).

To our knowledge, this is the first national audit of pest animal control operations by conservation focused organisations in Australia. The distributions and abundances of some pest animals have been reviewed for some states of Australia (West and Saunders 2003), but there have been no detailed reviews of the characteristics of existing pest animal control operations. This review reports on pest animal control information collected in interviews conducted across all states and territories of Australia. Since the key focus of this review was to increase understanding of the threats by pest animals on native species and ecological communities, an emphasis was placed on collecting data from 'conservation' focused rather than 'agricultural' focused control activities. Monitoring of the impact of pest animal control is not absent but less likely to be undertaken by private landholders in the agricultural sector.

3. Objectives

The objectives of this report are to:

  1. Identify gaps in existing information on control activities, especially in relation to the success in reducing/removing pest species, and in subsequent recovery of native species/ecological communities, especially the listed threatened species in the EPBC Act, across Australia.
  2. Identify the native species perceived to be threatened by foxes, feral cats, feral rabbits, feral pigs, and feral goats, for which there is still limited information on results of pest control activities.
  3. Recommend priorities for filling gaps in existing knowledge, by both experimental control and monitoring of existing control activities, to cover as large a range of threatened species as possible, especially those native species perceived to be threatened by foxes, feral cats, feral rabbits, feral pigs, and feral goats.
  4. Design specific control experiments that include varied levels of control and the consequences for a range of native species and ecological communities, in particular, those that are difficult to target through monitoring of existing control activities, and include the cost of conducting these experiments.

4. Study species

Foxes (Vulpes vulpes)

The red fox was deliberately introduced into Australia in the mid to late 1800's. Foxes are now common throughout most of Australia, except the tropical north and some offshore islands (Figure 4.1). Foxes occupy many habitats, including urban, alpine and arid areas, but are most common in woodland and semi-open habitats (Saunders et al. 1995). Foxes have been shown to eat a wide range of native species (reviewed in Robley et al. 2004) and are thought to have played a major role in the decline of many ground-nesting birds, small to medium sized mammals, and reptiles (see Table 1; Pg 10, for a list of native species for which foxes have been identified as a known or potential threat).

Feral cats (Felis catus)

Cats probably became established in Australia soon after the arrival of the first Europeans. Feral populations now occupy most parts of the mainland, Tasmania and many offshore islands (Figure 4.1). Cats eat a wide range of native wildlife (Dickman 1996; reviewed in Robley et al. 2004), and for this reason are thought to have a major impact on many native species, especially on islands (see Table 1; Pg 10, for a list of native species for which feral cats have been identified as a known or potential threat).

Feral rabbits (Oryctolagus cuniculus)

The rabbit is one of the most widely distributed and abundant mammals in Australia (Williams et al. 1995). Rabbits were first released in 1859 in Geelong, Victoria, and spread rapidly to cover most of Australia, except the far north, by 1910 (Figure 4.1). Feral rabbits occur in many habitats, but are sparsely distributed in the arid north and are most abundant in areas with deep and sandy soils (Myers et al. 1994). They are predominantly grazers and are thought to compete with native wildlife for resources. They may also alter the distribution and abundance of native plant species and physically alter habitats (Williams et al. 1995). Feral rabbits have been implicated in the extinction of a number of small mammals in Australia's arid regions, and may have contributed to the decline in numbers of many native plant and animal species (see Table 1; Pg 10, for a list of native species for which feral rabbits have been identified as a known or potential threat) (Williams et al. 1995).

Feral pigs (Sus scrofa)

Domestic pigs were introduced to Australia by European settlers, and populations of feral pigs were widespread by the 1880s. Feral pigs are now common in the Northern Territory, Queensland, Australian Capital Territory and New South Wales, and less common in western Victoria, Western Australia, and on a few offshore islands (Figure 4.1). Feral pigs are omnivorous habitat generalists, occupying subalpine grasslands, woodlands, tropical forests and, semi-arid and monsoonal floodplains. The primary environmental impacts of feral pigs are habitat degradation and predation of native species. By wallowing and rooting feral pigs modify streamsides, increase erosion, and decrease food resources and habitat for native wildlife (Choquenot et al. 1996). Feral pigs are also thought to compete with native animals for food, eat the eggs of ground-nesting species, spread environmental weeds, and transmit disease. Feral pigs have destroyed breeding sites and degraded key habitats for a number of species (see Table 1; Pg 10; Choquenot et al. 1996).

Feral goats (Capra hircus)

Feral populations of goats established in Australia from the escape, abandonment, or deliberate release of domestic goats (Parkes et al. 1996). Feral goats live in all States and Territories and on many offshore islands, but are most common in areas of western New South Wales, South Australia, Western Australia, and Queensland (Figure 4.1). The diet of feral goats includes grasses, leaves, bark, flowers, fruit, and the roots of many plant species (Parkes et al. 1996). Feral goats are thought to have major effects on native vegetation, and may also compete with native wildlife and stock for food, water and shelter (see Table 1; Pg 10, for a list of native species for which feral goats have been identified as a known or potential threat).

Figure 1. Distribution of foxes, wild dogs, feral cats, rabbits, feral pigs, and feral goats in 2001, in Australia (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001).

Figure 1. Distribution of foxes, wild dogs, feral cats, rabbits, feral pigs, and feral goats in 2001, in Australia (electronic distributions are from subregional or bioregional scale data from the Natural Land and Water Resources Audit, Landscape Health in Australia database, 2001).