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Chapter

28

Introduced Wild Pigs in North America: History,

Problems and Management

John J. Mayer

Introduction

As with all members of the mammalian family Suidae, wild
pigs belonging to the species Sus scrofa are not native to North
America. The presence of these animals on this continent is
attributable solely to their introduction by man. Such intro-
ductions have been both accidental (e.g. escaped domestic
swine that have gone wild/feral) and intentional (e.g. Eurasian
wild boar released to provide a new huntable game species)
(Mayer & Brisbin 2008, 2009).
Despite a prolonged presence on the continent, the wild pigs
in North America have undergone a recent dramatic expansion
in both their distribution and numbers. Concurrent with this
increase has been an upsurge in the amount and diversity of
damage being done by these animals to their host environments
(Mayer & Brisbin 2009; West et  al. 2009; Bevins et  al. 2014).
Annual estimates of this damage in the USA alone are in the bil-
lions of dollars (Pimentel 2007).
Because of this recent situation, wild pigs are now typically
considered to be an undesirable invasive species in places where
they are found in North America. Unfortunately, invasive wild
pigs are very difficult to either successfully manage or control.
In response to these circumstances, research is being conducted
to improve control techniques as well as trying to better under-
stand the biology of these animals as it relates to their manage-
ment. However, no viable or consistently successful solution to
this problem has been identified to date.

History of the Introduction

Wild pig populations have had a long history in North America
dating as far back as the European period of exploration and
colonization in the western hemisphere. As such, the introduc-
tions of these animals have been both widespread and varied
over the centuries. Additional new introductions have contin-
ued up through the present.
Taxonomically, all of the free-ranging established popula-
tions of wild pigs found in North America belong to one spe-
cies, Sus scrofa. Two types of S. scrofa, domestic swine and
Eurasian wild boar, were introduced at various times onto the
continent. Because these two types are conspecifics, wherever
both of them have been found together in the wild, interbreed-
ing has occurred (Mayer & Brisbin 2008, 2009). As illustrated
in Figure 28.1, there are at present three general types of wild
S. scrofa found in North America. However, unless otherwise
specified, the term ‘wild boar’ is used within the context of this

chapter only in reference to animals directly descended from

introduced wild boars.

Contrary to the aforementioned European origin, the

apparent presence of swine archaeological remains in prehis-

toric Native American sites has led to at least one theory that

pigs belonging to this species were initially brought into the

western hemisphere from Asia across the Bering land bridge

by the early human emigrants from eastern Asia into North

America (Quinn 1970). However, most palaeozoologists attrib-

ute these purported archaic specimens to the incorporation of

recent material into older archaeological assemblages (Mayer &

Brisbin 2008, 2009).

Historically, the first man-made introduction of pigs into

North America was during the eleventh century with the Norse

settlements in southern Greenland. Domestic pigs had a sub-

stantial presence during the initial settlement period there,

but then declined sharply and disappeared soon thereafter

(Vésteinsson et al. 2002; Nelson et al. 2012). In spite of having

been raised under apparent free-range conditions (Vésteinsson

et al. 2002; Nelson et al. 2012), there is no evidence that the pigs

in Greenland went feral and established themselves in the wild

during their temporary presence there. Based on archaeologi-

cal evidence, no domestic pigs were present further to the south

at the Norse colonies that were established in Newfoundland

(Wallace 2005).

The next important importation of pigs into the western hem-

isphere came with the second voyage of Christopher Columbus

in 1493. His fleet brought eight domestic pigs, acquired on the

island of Gomera in the Canary Islands, over to the Caribbean.

These initial pigs and their descendants were turned loose to

forage for themselves around the newly formed settlements and

outposts on the islands of Cuba, Hispaniola, and Jamaica (Towne

& Wentworth 1950). These free-ranging animals rapidly multi-

plied with enormous success and went wild in the West Indies,

quickly becoming a pest (Sauer 1966; Crosby 1972). An official

proclamation was even issued by the Spanish Crown in 1505 to

reduce the numbers of wild pigs found in the Caribbean colo-

nies at that time (Zadik 2005). In 1506, 13 years after Columbus

first introduced domestic swine to the West Indies, the Spanish

colonists had to begin hunting the feral descendants of the eight

original animals because of the damage that these wild pigs were

causing (Ensminger 1961; Donkin 1985).

When the Spanish explorers provisioned expeditions headed

to the North American mainland, they took pigs from the

Caribbean islands with them (Mayer & Brisbin 2008 2009). From

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