Chapter 29: Biological invasion of wild boar and feral pigs in South America317
America, which started much earlier in Argentina. The recent
and ongoing invasions into the northern biomes, such as the
Atlantic forest, did not corroborate this point of view, with no
climate-matching in such regions. Moreover, the expansion
into the northern regions was not expected according to the
deforestation and peccary status (see item below about the inva-
sion into the peccary’s range). Thus, other mechanisms of inva-
sion should be considered to understand this invasion, such as
human-driven dispersal, to set effective strategies to control the
species.
There were also at least two distinct situations aimed at set-
ting priorities to mitigate the wild boar invasion or conserve the
South American ecosystems. As highlighted before (Cuevas et al.
2010; Ballari et al. 2015), it sounds reasonable to make an effort
to control the wild boar invasion in the southern ecosystems
with low or no overlap with peccaries, such as those within the
Temperate Grasslands, Savannas and Shrublands (TGSS) and
Montane Grasslands and Shrublands (MGS) biomes. The eco-
systems in such regions did not coevolve with the native pig-like
peccaries and they will most likely be severely affected by alien
wild pigs (Cuevas et al. 2010; Barrios-Garcia & Ballari 2012).
Nevertheless, the conservation priorities given to invaded
ecosystems within the original peccaries’ range, such as Alto
Paraná Atlantic Forest, need to be balanced between efforts to
reintroduce (native) and control (alien) wild pigs inside and out-
side Protected Areas. The ecosystems in such regions coevolved
with peccaries and somehow support wild pigs without compet-
itive exclusion (Desbiez et al. 2009a; Oliveira-Santos et al. 2011;
Salvador 2012). By contrast, these ecosystems lack wild pigs due
to extinction and there were no Protected Areas large enough to
preserve both peccary species in some regions (Taber et al. 2008).
The reintroduction of peccaries is pointed out in this region as
conservation strategies (IAP 2009; Brocardo & Delgado 2014).Wild Boar Invasion in Protected Areas
There were 459 protected areas within the wild boar’s range, that
is, 13 per cent of the total recorded by the World Database on
Protected Areas in South America’s territory, including differ-
ent designations such as national parks (27), indigenous areas
(60), UNESCO-MAB biosphere reserves (7), etc. (Table 29.1,
Table 29.2). However, few of them have confirmed the presence
of wild boars; 91 (2.6 per cent) protected areas had this confirma-
tion (ECOPAM 2004; Deberdt & Scherer 2007; Marocco 2012;
Hegel & Marini 2013; Nobre et al. 2013; Trovati & Munerato
2013; Kaizer et al. 2014; Ballari et al. 2015; Souza et al. 2015;
GISD 2016; unpublished data).
The difference between the confirmed and potential pres-
ence of wild boars in protected areas was already expected as a
result of a false absence. This aspect has not been evaluated in
most protected areas yet, especially in Brazil, due to the recent
character of the invasion. Either the Brazilian protected areas,
in an effort to report the presence of wild boars, were assessed
before the wave of invasion in Brazil, or the assessment was
biased because only a few of the IUCN’s categories of protected
areas (e.g. I and II) were considered (e.g. Sampaio & Schmidt
2013; Ziller & Dechoum 2013; Guimarães 2015). Sampling
efforts in indigenous areas were rare across South America, forexample. The number of confirmations should then increase
with more samplings.
Based on the confirmations only, Argentina had the protected
area’s system with the highest rate of invasion (12 per cent), as
expected for the oldest and widest invasive process.Wild Boar Invasion in the Peccary Range
The wild boar range overlapped the original distribution of two
out of three peccaries species (Tayassu pecari and Pecari tajacu)
by 6.9 and 5.8 per cent, respectively, especially in Argentina
(34 per cent and 20 per cent), the Humid Pampas (97 per cent
and 100 per cent) and Paraná’s flooded savanna (82 per cent
and 77 per cent) ecosystems (Table 29.1, Table 29.2). The ranges
where they were considered extinct had a lower but still high
percentage of overlap (> 80 per cent).
The expansion of wild boars in ecosystems north of 30°S was
not expected regarding peccaries. Native pigs had a geographic
reduction instead of a growth in those ecosystems as opposed
to the wild boar. The collared peccary, for example, had already
vanished in the 1970s in Uruguay (Mones & Ximenez 1980), but
alien pigs covered almost the entire area of the country.
Further north, the invaded ecosystems of the Tropical and
Subtropical Moist Broadleaf Forests (TSBF-M) and Tropical
and Subtropical Dry Broadleaf Forests (TSBF-D) biomes were
among the Atlantic Forest’s biodiversity hotspots for conserva-
tion priorities (Myers et al. 2000), where peccaries have been
considered either threatened or already extinct in many regions
(Chiarello et al. 2005; Taber et al. 2008; IUCN 2010; Desbiez et al.
2012; Keuroghlian et al. 2012). Protected areas do not ensure
the conservation of those species, as they vanished regardless
of this invasion (Salvador 2012; Brocardo & Delgado 2014) and
S. scrofa has been considered an additional threat by compet-
ing with them in the remnants of the Atlantic Forest nowadays
(Desbiez et al. 2012; Rosa 2015).
On the other hand, biodiversity losses could facilitate the
invasion (Elton 1958; Estes et al. 2011). The lack of competi-
tors was a reason pointed out by Ojeda et al. (2010) to explain
the current S. scrofa’s range expansion in Argentina; a similar
role may have been played by the lack of predation in Brazil
(Deberdt & Scherer 2007). Predation alone may not suffice
to control this invasion (Choquenot et al. 1996; Cavalcanti &
Gese 2010), but competition as a negative reciprocal ecological
interaction may be more effective in buffering the invasion of
the peccaries’ original range. This is a particular feature of the
Neotropic realm in contrast with other continents invaded by
S. scrofa, such as Australia and most parts of North America,
where it is really a pest and where there is a lack of native pig-like
species as a biological barrier to reduce the invasion.
If biodiversity and ecological interactions are significant in
this case, projects to reintroduce or restock the environment
with native competitors should become a conservation pri-
ority as regards wild boar eradication, especially in protected
areas where peccaries were extinct for reasons other than
S. scrofa (Desbiez et al. 2012; Keuroghlian et al. 2012; Salvador
2012). The challenge will be to develop this priority in such
range (seven per cent of the continental area) and in at least
41 Brazilian protected areas (Table 29.1)..031Downloaded from https://www.cambridge.org/core. Faculty of Classics, University of Cambridge, on 04 Dec 2017 at 12:52:31