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Chapter

30

Feral Pigs in Australia and New Zealand:

Range, Trend, Management, and Impacts of

an Invasive Species

Andrew J. Bengsen, Peter West, and Cheryl R. Krull

Introduction

Feral pigs (Sus scrofa L.) are widely regarded as one of
Australasia’s most destructive pest animals. They inhabit a large
proportion of both Australia and neighbouring New Zealand.
They can cause severe damage to a wide range of agricultural,
biodiversity, and environmental resources. Private landholders,
government agencies, and other authorities carry out many feral
pig control programmes each year. However, pigs are also highly
valued by some sections of the community for hunting or com-
mercial exploitation.
Although wild or feral pigs are widely distributed across
the globe (Long 2003), the Australian situation is in many ways
unique. There has been a long history of active feral pig man-
agement in Australia and, in contrast to New Zealand, Europe,
and the Americas, wild-living pigs are consistently recognized
and treated as a pest in all onshore jurisdictions. Conversely, the
most widely used methods and tools for controlling feral pigs in
Australia are uncommon elsewhere.
This chapter will review the origin and distribution of
feral pigs across Australia and New Zealand, their destructive
impacts, useful values, and their management and control. It
will highlight current and future challenges to the effective miti-
gation of pig impacts, and propose possible solutions. At a fine
scale, some of these challenges may be peculiar to the region,
but the broader trends and pressures from which they emerge
are common to many regions of the globe where wild-living pig
populations conflict with human values.

Trends in Abundance and Distribution

Notwithstanding speculation of a pre-colonial origin for wild-
living pigs in some parts of north-eastern Australia (Baldwin
1983), the first known introduction of pigs onto the Australian
continent occurred with the arrival of at least 48 animals with
the first European settlers in 1788. While other livestock failed to
thrive, free-roaming pigs increased rapidly and soon became such
a pest to the fledgling colony’s food supply that orders for their
control were issued within seven years of settlement (Robertson
1932). The subsequent declaration of a series of increasingly dire
control orders suggests that the first attempts at regulation to
manage damage caused by pigs were not very effective.
The introduction of pigs to other parts of the Australian con-
tinent in the early nineteenth century appears to have followed
patterns of European settlement or visitation (Pullar 1953).
Domestic pigs from Asia were released in northern Australia

after the abandonment of a settlement on the Northern

Territory’s Cobourg Peninsula (Letts 1962). Sealers and other

mariners also deliberately released pigs on islands, nota-

bly Kangaroo and Flinders Islands, during the same period.

Elsewhere, feral populations became established from domestic

herds that commonly roamed in a semi-feral state prior to the

establishment of well-defined property boundaries in the 1860s

(Pullar 1953). Pigs also appear to have naturally dispersed along

watercourses into semi-arid regions of central-eastern Australia

during a period of above average rainfall between 1913 and 1921

(McKnight 1976).

Maps compiled from surveys of land and natural resource

managers since 1947 suggest that feral pig populations have

further expanded through Australia during the last 70 years

(Figure 30.1). It is difficult to draw precise conclusions about

patterns of range expansion and changes in abundance because

of the different methods used to compile the maps. However, the

apparent increase in range between 1947 and 1982 is consist-

ent with reports of further natural dispersal in eastern Australia

during a series of wet years in the 1950s (McKnight 1976). New

populations also became established from escaped domestic

pigs and deliberately translocated feral pigs during this time

(Tisdell 1982; Hone & Stone 1989; Choquenot et al. 1996).

Surveys conducted between 1988 and 2008 suggest further

range expansion and increasing densities in many areas over

recent decades (Figure 30.1). Today, feral pigs are thought to

occur across at least 45 per cent of the Australian continent;

nearly 3.5 million square kilometres (West 2008). This equates

to more than a third of the landmass of Europe or the USA. In

many parts of Australia, further expansion of feral pig distri-

bution will probably be contained by unfavourable bioclimatic

conditions in the arid interior, although these limitations can

be diminished by the provision of watering points for livestock

(Figure 30.2). Future changes in distribution and abundance

throughout large areas of Queensland and New South Wales will

likely be driven by cycles of above- and below-average rainfall

that influence water availability and vegetation dynamics, and

are characteristic of the Australian climate. However, habitat

suitability modelling suggests that pig populations could con-

tinue expanding in parts of north-western Australia (Cowled

et  al. 2009). Habitat and climatic conditions also suggest that

there is substantial capacity for range expansion across large

parts of the south-west and south-east of the continent, includ-

ing much of the island state of Tasmania, where a small number

of isolated populations are currently contained (West 2008).

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