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Chapter

27

Modelling Pygmy Hog Habitat to Inform Habitat

Management

Janani Pradhan and Erik Meijaard

Introduction

The pygmy hog (Porcula salvania) is the smallest and most
endangered of the world’s wild pig species (Suidae) (Oliver &
Deb Joy 1993). Historically, it occurred in early successional
tall grasslands along much of the southern Himalayan foothills
from Nepal in the west to eastern India in the east (Hodgson
1847), but it now appears to be extinct in Bhutan and Nepal
and most of its Indian range, and it survives only in three dis-
junct populations in India (Oliver 1980; Narayan et al. 2008).
Until recently it was listed on the IUCN Red List of Threatened
Species as Critically Endangered, with loss and degradation
of grassland habitat due to human settlements, agricultural
encroachments, dry-season burning, livestock grazing, com-
mercial forestry, and flood control schemes being listed as the
primary threats (Narayan et  al. 2008). Assumed to be extinct
in the 1960s, the species was rediscovered in 1971 in Manas
National Park and Barnadi Wildlife Sanctuary, the latter now
having no more pygmy hogs (Oliver 1980). Officially initiated
in 1995, the Pygmy Hog Conservation Programme (PHCP)
was formed under the aegis of an ‘International Cooperative
Management and Research Agreement’ (ICMRA), between the
Ministry of Environment and Forest (Government of India),
the Assam State Forest Department, the Durrell Wildlife
Conservation Trust and the IUCN Wild Pig Specialist group.
The PHCP was started with the primary objective to aid the
implementation of a broad conservation action for the critically
endangered species.
The phylogenetic position of the pygmy hog has been the
subject of debate. It was originally placed in its own genus, then
assigned to the genus Sus based on morphological analyses
(Groves 1981). However, phylogenetic analyses of three mtDNA
loci (control-region, cytochrome b, 16S) shows that Porcula clus-
ters in a separate clade within Suidae (Funk et al. 2007) and is
likely to be a sister lineage to Sus (see Chapter 1 of this book). An
adult pygmy hog measures about 65 cm in length, with a head and
body length of about 55–71 cm, and an adult weight of 6.6–9.7 kg
(Mallinson 1977; Oliver 1980). Pygmy hogs are often mistaken
for the juvenile of a wild boar (Hodgson 1847). As suggested by
their names, pygmy hogs differ from the other members of the
Suidae by the extreme reduction in body size (Oliver et al. 1993).
Additionally, they have relatively small litter sizes: two to six, but
usually three to four (Mallinson 1977; Oliver & Santos 1991)
(Figure 27.1), and female pygmy hogs have three pairs of teats
instead of the six found in Sus scrofa (Lydekker 1907).

Pygmy hogs are now primarily found in tall grasslands,

where their small size and their swift movement make them

difficult to study (Oliver et al. 1993). Limited field observations

indicate that the species prefers undisturbed patches of grass-

lands dominated by early successional riverine communities.

These typically comprise dense, tall (2–3 m) grasses, such as

Narenga porphyrocoma, Saccharum spontaneum, S. bengalen-

sis, Imperata cylindrica, and Themeda villosa, interspersed by

a wide variety of herbs, shrubs, and young trees (Shrestha &

Joshi 1997).

The recent discovery that the genus Porcula was actually

widespread in South and South East Asia (Pickford 2013) during

the Late Pleistocene and not restricted to a small sub-Himalayan

habitat zone sheds a new light on what could be driving popula-

tion declines in Porcula. Pygmy hogs are superbly adapted to

life in tall grasslands. Their small size and bullet shape allows

them to move through dense grasses (Figure 27.2), on which

they also feed and which they use for building their sleeping

and resting ‘nests’ (Oliver et al. 1993). Presumably, Porcula used

such grasslands throughout its range. Did all the Southeast and

East Asian tall grasslands disappear at the end of the Pleistocene,

leaving only the sub-Himalayan habitats, or did other factors

play a role in the major range reduction of Porcula? Is it possi-

ble that habitat alteration or predation by modern humans that

arrived in the region some 60,000–100,000 years ago (Mellars

et al. 2013) played a role? Or did other factors negatively impact

Figure 27.1 A wild boar is about 10–15 times bulkier than a pygmy hog

(source: Oliver 1980).

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