Ecology, Conservation and Management of Wild Pigs and Peccaries

Part III: Conservation and Management

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Many surveys have shown that Australian feral pigs harbour

pathogens such as Brachyspyra spp., Brucella suis, Leptospira

spp., Lawsonia intracellularis, Mycolplasma hypopneumoniae,

and Salmonella spp. (e.g. Mason et al. 1998; Phillips et al. 2009;

Ward et al. 2013; Pearson et al. 2014; Ridoutt et al. 2014). These

pathogens cause important diseases that can reduce livestock

productivity, such as brucellosis, leptospirosis, enteric disease,

and pneumonia. Feral pigs often occur in close proximity to

livestock (Figure 30.6), and they may be important vectors of

livestock diseases in some parts of Australia (e.g. Phillips et al.

2009; Pearson et  al. 2014). Risks of disease transmission may

be most acute where feral pigs are sympatric with free-ranging

domestic herds or in semi-arid regions where feral pigs and

livestock share isolated watering points. There is circumstan-

tial evidence of pigs fulfilling this role in some cases (Elder et al.

1986). However, rates of disease transmission from feral pigs

to livestock have not been estimated and it remains impossible

to estimate the economic impact of lost production from this

source. In New Zealand, feral pigs are a spillover host for bovine

tuberculosis and are often screened by the animal health board

as part of their TB-free New Zealand programme (Parkes 2006).

There has also been great concern about the potential for

feral pigs to amplify and transmit exotic diseases that could

have major economic impacts, such as foot and mouth dis-

ease (Productivity Commission 2002; Doran & Laffan 2005).

Considerable funds and effort have been invested into research

and capacity-building in preparation for such an event over

recent decades, including research to understand the roles of

pigs as potential hosts and how to best control pig populations

to hasten disease eradication (e.g. Saunders & Bryant 1988; Pech

& McIlroy 1990; Dexter 2003; Hampton et  al. 2004; Doran &

Laffan 2005).

Various estimates of gross economic impacts of feral pig

damage on a national Australian scale have been calculated over

recent decades. Tisdell (1982) declined to offer an estimate on

the grounds that doing so would give a misleading impression

of accuracy given the scarcity of useful data, and because the

principles that such an estimate must be based on would not

be acceptable to large parts of the community. Nonetheless,

Choquenot et al. (1996) estimated total costs of feral pig dam-

age to agricultural production to be over 100 million AUD

(over USD 115 million in 2014 terms). Later assessments have

added management and research costs to this estimate to pro-

vide a total of AUD 106.5 million (USD 136 million in 2014)

(Bomford & Hart 2002; McLeod 2004). A more recent estimate

of the lost economic surplus due to feral pig damage to the lamb,

wool and grain industries was AUD 9.2 million (USD 7.2 million

in 2014) (Gong et al. 2009), although this did not include indus-

tries such as sugar production which can be heavily impacted. In

any event, gross estimates such as these can provide only a very

coarse-scale snapshot in time and have limited value for inform-

ing on-ground management.

Despite the apparent diversity and importance of feral pig

impacts on environmental and economic values, it is clear that

very few impacts have actually been well quantified. This is

largely due to the difficulty of estimating impacts that are often

highly variable in space and time, can take long periods to mani-

fest, and are difficult to disentangle from other factors such as cli-

mate, the influence of other pest animals, farming practices, and

commodity prices. A deeper understanding of feral pig impacts

on the environment and agricultural production will require

long-term commitment, considerable survey effort, and innova-

tive survey and analytical methods (Bengsen et al. 2014b).

While it’s difficult to conceive of any substantial positive

values of feral pigs in conservation or agricultural systems, the

commercial harvesting of feral pigs for export as game meat

has provided a small industry in Australia that has helped dis-

tribute wealth into rural communities since 1980. The value of

the industry has been estimated at between 12 and 24 million

USD annually (in 2014 terms) over several years between 1984

and 2006 (Tisdell & O’Brien 1987; Izac & O’Brien 1991; NRIA

2012), but it has been highly volatile due to variation in qual-

ity and quantity for supply and also in demand (Gentle & Pople

2013). Furthermore, commercial harvesting of feral pigs has

Figure 30.6 Feral pigs can harbour

pathogens that cause important

livestock diseases, and may pose

a disease transmission risk where

they share space with cattle, sheep,

or domestic pigs (photo by Jason

Wishart, Invasive Animals Cooperative

Research Centre).

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