Part II: Species Accounts62
described (Kneepkens et al. 1989; Macdonald & Kneepkens
1995; Kneepkens & Macdonald 2010).
It is clear that babirusa mark territory. Studies in zoologi-
cal collections have shown that adult male babirusa do this in
a variety of ways (Leus et al. 1992, 1995). The side of the face is
rubbed on tree saplings, branches and other uprights, such as
posts or fence rails in the pen. The male will also plough with its
nose in soft sandy soil, apparently depositing secretions from
the face and salivary glands in the substrate. In the forests of
North Sulawesi, adult males have been observed face-rubbing
on the stems of forest saplings, branches and small trees; plough-
ing behaviour in soft substrate has also been described (Patry
et al. 1995). The babirusa male has also been filmed marking the
ground adjacent to wallows, by rubbing the side of his face on
the substrate (Macdonald et al. 1996). Scratches on the canine
teeth of museum skulls had earlier been mistakenly thought
to be due to fighting behaviour (MacKinnon 1981). It has now
been shown that it is ‘scent marking’ face-rubbing behaviour
that causes this very specific pattern of wear of the canine teeth.
Further studies are required to define the chemical nature of
the ‘scent marking’ molecules used by the babirusa (Macdonald
et al. 1996).Activity Patterns
Daily Activity
Babirusa build nests in the wild (Guillemard 1886). These are
constructed from branches or leaves, and provide shelter from
the rain and cold. Sleeping nests tend to have little or no padding
on the ground, and are essentially ‘babirusa-sized depressions’.
Nests built in the forest by sows for farrowing purposes were
up to 3 m long and 25 cm deep, and were layered with branches
torn from trees and bushes (Macdonald 2008). Babirusa make
similar constructions of bedding in zoological collections, pro-
vided they are supplied with suitable plant material (Melisch
1994; Leus et al. 1995). When groups of babirusa have been
penned together and have access to nest-building materials, all
the animals within the pen contributed towards the construc-
tion of a communal nest, which they then shared overnight
(Macdonald 2008). Further studies are required, in the wild, to
discover whether communal nests are constructed by groups
of babirusa. Where no bedding has been provided in zoos, it is
noteworthy that babirusa slept together on the ground in groups
(Macdonald 1991; Leus et al. 1995).
The daily activity profile of the babirusa has not been stud-
ied in the wild. However, some preliminary indication may be
suggested by the distribution of daily behaviour exhibited by
36 babirusa that were housed together as one large group in
Surabaya zoo (Leus et al. 1995). Animals slept at night, which was
consistent with the general lack of activity at night recorded in
North Sulawesi (Patry et al. 1995; Clayton & MacDonald 1999).
About an hour before sunrise, individuals began to wake up
and move about. Voiding of faecal material and urine occurred
at this time, and animals appeared to prefer to defecate under
branches and tree trunks. Foraging extended throughout
the day, but occupied a larger proportion of the time in themorning. This behaviour did not involve rooting if the ground
was dry or compact because the nose of the babirusa lacks a
large rostral bone. In other pigs this structure provides sup-
port for the tough connective tissue plate of the rhinarium. In
its place the babirusa has a thin, partially calcified membrane
instead (Macdonald, unpublished). Food items were looked
for on the ground, under logs and stones, in wet areas and on
bushes and trees (Leus & Vercammen 1996). Animals would
stand with their forelimbs against tree trunks to reach hanging
leaves and fruit. They could even stand free of such support on
their hind limbs to pluck leaves from the trees (Leus et al. 1995;
Macdonald & Leus 1995). From about mid-morning onwards
an increasing proportion of the time was taken up with non-
foraging activity; the animals were either wallowing or lying
down. In the wild, the numbers of animals visiting the salt-lick
were seen to increase from mid-morning onwards (Clayton &
MacDonald 1999). Both in the wild and in zoological collec-
tions, males have generally been observed to wallow more often
than females (Figure 6.2A; Leus et al. 1995).Feeding Ecology
Food Supply and Digestion
Babirusa are omnivorous; in zoos, adult babirusa have been
observed to chase, catch and eat small mammals and birds,
implying that they may show similar behaviour in the wild (Leus
et al. 1995). From observations of both wild and captive indi-
viduals they are known to consume a wide variety of leaf, root,
and fruit material (Leus 1994, 1996; Macdonald & Leus 1995;
Reksowardojo 1995). Studies suggest that fruits in particular
may be an important component of the diet (Leus 1994, 1996;
Leus et al. 2001). Leus compiled an annotated list of species of
trees and palms that grow in Sulawesi and produce fruits that
may contribute to the diet of babirusa (Leus 1996). The dietary
benefits gained by babirusa that ingest wet mud from warm salt-
licks have not been investigated in any detail (Patry et al. 1995;
Clayton & MacDonald 1999; Leus et al. 2001).
Babirusa jaws and teeth are strong enough to crack very
hard nuts with ease (Peters 1985; Leus et al. 1995). Seeds of a
wide variety of fruits, including the canari (Canarium), oaks
(Lithocarpus), figs (Ficus), and chestnuts (Castanopsis), are
available on Sulawesi (Whitmore et al. 1989; Leus 1996). Fruits
are also an important component of the diet of Sulawesi Macaca
spp. The extent to which babirusa feed on the fruit pieces dis-
carded by these primates also awaits study. The babirusa’s appar-
ent requirement for fruit-bearing trees, as a component part of
their environment, has been implied (Whitten et al. 2002); as
soon as mature trees were cleared by forestry operations or lands
converted to food crop production, the babirusa were no longer
to be found in that area. Further detailed studies, of the diet in
the wild and the fruiting patterns of the forest, are required to fill
these gaps in our current knowledge. They would help to explain
how diet availability in wet and dry seasons might influence
babirusa group size, structure and home range.
The anatomical and histological structures of the stom-
ach and digestive organs of the babirusa have been described12:34:41