Part III: Conservation and Management332
Because of the aforementioned difficulties in estimating the
impacts of feral pigs, and the sporadic and unpredictable nature
of many impacts, pig control programmes are often conducted
pre-emptively and routinely to protect specific assets, rather
than in response to accumulated damage.
Unlike many parts of Europe, states do not provide compen-
sation for damage caused by pigs. However, local, state, and fed-
eral governments often provide grants or in-kind assistance to
large-scale control programmes that aim to protect important
environmental or agricultural assets across multiple proper-
ties. This support for coordinated control is important, because
pig populations transcend property boundaries so there is little
incentive for individual landholders to invest in controlling feral
pigs if their neighbours do not (Izac & O’Brien 1991). Strategic
allocation of resources for large-scale management or control
programmes could be more effective if it was better prioritized
to protect specific important assets, using economically rational
criteria and robust damage estimation, rather than being based
on grant applications from interested parties (Bengsen et al.
2014a). However, the conflicting costs and values of feral pigs
often make it difficult to establish agreed rational criteria for
implementing or maintaining pig control programmes (Izac &
O’Brien 1991; Meurk 2014).
Wild or feral pig populations have an extraordinary capac-
ity for growth. Sows can have a high lifetime reproductive out-
put because they are long-lived, can begin breeding from about
7–12 months of age, and can produce two litters of up to 10
young every 12–15 months (Choquenot et al. 1996). Effective
reduction of feral pig populations and suppression of recovery
therefore requires repeated removal of a large proportion of the
population. Population growth rates estimated from Australian
feral pig populations indicate that between 55 and 70 per cent of
the population should be removed throughout the year to sup-
press recovery after an initial population reduction (Bengsen
et al. 2014b). However, there is likely to be considerable varia-
tion around these figures, because reproduction in wild pigs is
highly responsive to environmental productivity and other con-
ditions that can vary with climate (Bieber & Ruf 2005). Climatic
conditions experienced by feral pigs in Australia vary consider-
ably among locations ranging from tropical forests to sub-alpine
ranges, and also within locations over time, because Australia’s
climate is highly susceptible to variations in ocean surface tem-
peratures (Nicholls 1991).
In New Zealand, feral pigs are currently listed on the
Regional Pest Management Strategies (RPMS) of 11 of 16 exist-
ing Regional and Unitary Authorities (RUAs) (Ministry for
Primary Industries 2016). Of the RUAs listing pigs on their
RPMS, eight of these state their aims to include a reduction in
the adverse effects of pigs on protected areas or areas of high
conservation value, and 10 of the regions are conducting some
form of pig control. However, New Zealand is lagging far behind
Australia in terms of a national plan for pest management or
a clear national initiative for pig control. In many cases RUAs
are controlling pigs in specified areas while also managing pigs
as a resource for hunters in neighbouring areas. Large areas
of New Zealand Department of Conservation land are man-
aged through a hunting ballot system for feral pigs. This lackof consistency across the country causes confusion and tension
where pigs are regarded as a resource. However, research into
feral pig populations and social and economic issues surround-
ing pig control is also lacking, which makes cohesive decisions
about control/management difficult on a New Zealand scale.Control Methods
The most commonly used methods to reduce feral pig popu-
lation densities are poison baiting, trapping, and shooting
from the air or ground (Reddiex et al. 2006; West & Saunders
2007). Best-practice guidelines recommend that several control
tools or methods should be integrated into management pro-
grammes because some proportion of the population will gen-
erally be insusceptible to any given control method (e.g. Sharp &
Saunders 2014). It is generally best to begin with a non-intrusive
method, such as poison baiting, before moving on to methods
such as shooting, which can disperse pigs from the control area
or change their activity patterns.
Poison baiting is widely used because it can provide a cost-
effective means of reducing pig populations rapidly over a large
area (e.g. Hone 2002, 2012; Twigg et al. 2005, 2006). Baits are not
used to deliver pharmaceuticals as they are in Europe. Several
toxins have been used in the past (e.g. strychnine, arsenic, phos-
phorous, warfarin), but most of these have been withdrawn
because they are unacceptable from an animal welfare per-
spective. Consequently, most baiting programmes now rely on
sodium fluoracetate (1080). A new toxin, sodium nitrite, is also
being developed (Lapidge et al. 2012). This is seen as important
because some organisations have criticised 1080 as being inhu-
mane, whereas symptoms of sodium nitrite poisoning do not
cause major distress to pigs (Cowled et al. 2008b). A paste bait
containing encapsulated sodium nitrite has recently been reg-
istered in New Zealand for controlling feral pigs (Shapiro et al.
2016). This represented the first registration of sodium nitrite
worldwide as a vertebrate toxicant.
Bait media used to deliver toxins include grains, fruit, meat,
and manufactured baits, depending on the types of feed that are
locally available and appealing to pigs in different environments
(Figure 30.7). Poison baiting is not widely used to control pigs
in other parts of the world, except New Zealand, largely because
of concerns over accidental poisoning of non-target native or
domestic animals. However, there are few non-target species
that are susceptible to pig-baiting practices in most parts of
Australia, and risks to those species can usually be managed
through bait medium selection, timing, and the use of physi-
cal barriers to prevent non-target species from accessing bait
(e.g. Cowled et al. 2006b; Twigg et al. 2006; Bengsen et al. 2011b;
Lapidge et al. 2012). Two further limitations of poison baiting
are the requirement for users to be accredited to use 1080, which
is a restricted substance, and a reliance on government sources
for provision of 1080 solution. The recent development of shelf-
stable manufactured pig baits (e.g. Cowled et al. 2006a) should
provide landholders with more flexibility over how and when
they bait in some cases by freeing them of the requirement to
immediately distribute fresh baits.
Live trapping has traditionally been a popular method of
reducing feral pig impacts because it is widely accessible and is.03212:55:46