Chapter 18: Bearded pig Sus barbatus (Müller, 1838)179
Foraging Ecology
Bornean bearded pigs were once glorified for their track-
ing of mast-fruiting events across Borneo’s expansive forests,
although these migrations may have diminished or disappeared
entirely due to habitat loss and fragmentation (Figure 18.3)
(Mackinnon et al. 1996). Masting is an important phenological
phenomenon that occurs in South East Asia every 3–7 years
that causes local forest areas to prolifically fruit at different
times, triggering bearded pigs to move large distances to exploit
the temporary abundance of food (Dove 1993). During mast-
ing, bearded pigs seek the nuts of Dipterocarpaceae tree spe-
cies, whose mass is 50–70 per cent fat (Janzen 1974; Caldecott &
Caldecott 1985). Dipterocarp nuts historically motivated
huge herds of bearded pigs (sometimes > 1000 individuals)
to travel hundreds of kilometres and also provided females
with the resources to raise multiple litters within a year
(Leighton & Leighton 1983; Caldecott & Caldecott 1985).
However, when mast fruiting ended, bearded pig populations
often exceeded their normal carrying capacity, triggering
another round of large group movements, but this time more
desperately in search of food, with individuals often appear-
ing starved (Caldecott & Caldecott 1985; Caldecott 1991).
Descriptions of these large movements usually occurred dur-
ing river crossings, such as Banks’ (1949) account from Baram
River in Malaysian Borneo in October 1935:For five or six weeks, at points sixty to a hundred miles apart,
moves a steady stream of wild pigs, a few solitary, some family par-
ties of seven or eight, many packs from fifteen to thirty or forty,
occasionally convoys estimated at two hundred, sufficiently large
to deter the natives from attack. Every ten minutes or quarter of
an hour pigs pass by, a few large, old individuals, many of medium
size, none in very fat condition.The large bearded pig movements on Borneo were not
normal ‘migrations’ because they occurred at sporadic times
between differing locations. Most accounts of these movements
are anecdotal and often contradictory, with the notable excep-
tion of Caldecott and Caldecott’s (1985) observations from 1983
when groups moved > 1000 km around the Baram headwaters
on the Malaysia–Indonesia border. During non-masting peri-
ods, bearded pigs are usually solitary and only readily observed
when an oak (Quercus), fig (Fagacae), or other large trees are
fruiting. In productive areas (e.g. in ecotones, along riverbanks,
or in alluvial and swamp forests), a few bearded pigs are often
resident and sedentary (Caldecott 1988; Curran & Leighton
2000). In the East Kalimantan province of Indonesian Borneo,
there are reports of some locally migrating populations, with
daily movements from coastal areas to upland Nipa forests and
coconut gardens in the evening in Berau (NIVN 1939). In this
region there are also various smaller group movements, or pos-
sibly annual migrations. For example, near Long Punjungan,
there were
two more or less annual migrations, one in August-September and
one in December–January. The animals came from the basins of the
upper Sesayap, upper Sembaking and Malinau Rivers and moved
en masse to the south. Another route runs more to the west from thesame source area, via the upper Bahau, the upper Kayan, towards
the Iwan River and further south to the Boh River. A third route
ran from Malinau, across the Bahau (between the mouth of the
Punjungan River and the junction of the Kayan and Bahau Rivers)
and then on to the upper Kayan towards the Brem-Brem rapids.
(Meijaard 2000, summarizing Pfeffer & Caldecott 1986)Pfeffer and Caldecott (1986) also reported that these differ-
ent groups of animals crossed the Kayan River at different loca-
tions and times and moved in different directions. Similarly,
Puri (1992) described a number of smaller bearded pig routes
in East Kalimantan along and between headwaters and low-
land rivers. It is also possible that these groups may have over-
lapped with those reported around Baram by Pfeffer (1959),
Banks (1931), or Caldecott and Caldecott (1985). Likewise, in
West Kalimantan, bearded pigs were reported to migrate from
the Kapuas Lakes area in January–March to the highlands
each October–December, coinciding with the start of annual
upland fruiting (Dove 1993). Taken together, the evidence sup-
ports three states for Bornean bearded pigs: (1) large nomadic
groups making movements > 500 km following masts, (2) mul-
titudes of smaller groups making more local and overlapping
nomadic movements or annual migrations, and (3) sedentary
bearded pigs in year-round productive areas.
Sumatra’s ENSO-driven mast-fruiting events are not as dra-
matic as in Borneo and there are shorter distances between asyn-
chronously masting areas (Schaik 1986). Both of these ecological
differences reduce the benefit of massive nomadic migrations like
those occurring in Borneo (Schaik & Noordwijk 1985; Wich &
Schaik 2000). Indeed, in Sumatra, many populations of bearded
pigs are thought to be sedentary or to seasonally migrate within
a few hundred square kilometres (Kawanishi et al. 2006). As in
Borneo, movement routes are not known, but there are reports of
nomadic long-distance movements along the Barisan mountains
in Kerinci Seblat National Park (KSNP), with large groups being
observed crossing the Tapan Valley (Linkie & Sadikin 2003).
There are reports of altitudinal migrations from the coastal areas
in February and April to inland/upland forests on the east and
west coasts, as well as seasonal migrations. For example, during
the local dry season (early May) large groups seasonally crossed
the Gangsal and Tjenako Rivers near Indragiri, Jambi (Balen
1914), and Riau’s bearded pigs are most commonly found in
Bukit Tigapuluh forest in August and December (Bastoni 2008).
It has also been observed that some populations travel to areas
where oak (Quercus) and durian (Durio) species seasonally fruit
(Blouch 1984; Linkie & Sadikin 2003). Sumatra’s bearded pig
movements appear to primarily track seasonal resources and
thus can be called annual ‘migrations’.
Peninsular Malaysia’s extant bearded pigs are restricted to
an annual migration between the eastern province of Pahang
and south-eastern province of Johor, and possibly some resi-
dent pigs within that area. However, historically, pigs moved
from the east to west side of Peninsular Malaysia as described by
Hislop (1949):
Bearded pigs arrived in the Pekan district of Pahang during the
monsoon period from November to April, [and then move to]
southwest Johore [particularly the eastern Kluang and Kahang.020Downloaded from https://www.cambridge.org/core. Faculty of Classics, University of Cambridge, on 04 Dec 2017 at 12:41:45