Chapter 6: Sulawesi babirusa Babyrousa celebensis (Deninger, 1909)63
(Leus 1994; Leus et al. 1999, 2004; Agungpriyono et al. 2000;
Macdonald et al. 2008b; Adnyane et al. 2010). The stomach
has an elongated shape and a bulky appearance (Figure 6.4A).
A blind sac with a diverticulum at its extremity is located to
the left of the oesophageal entrance. The total luminal surface
area of the adult stomach is about 3000 cm^2 of which the car-
diac gland area represents the largest portion (>70 per cent).
This region was typically characterised by the ‘honeycomb’ pat-
tern of its luminal surface (Figure 6.4B). The thin-walled tubes,
between 200 and 260 μm in length, that form the ‘honeycomb’
are each sited over the pit of a cardiac gastric gland and are filled
by a stream of its secretion.
Within that secretory mileu was found a complex bacterial
microflora of rods and chains of cocci. The identities of most
of these microorganisms remain unknown. However, the close
association they exhibited with the mucus secreted by the cardiac
glands indicated that this large area of babirusa stomach might
have been structured to form a stable and yet self- refreshing envi-
ronment for the housing and multiplication of what appear to be
autochthonous commensal bacteria. The micro- environment of
the cardiac gland area may be consistent with specialised micro-
bial fermentation of ingesta. Alternatively, it may support micro-
bial modification of glandular secretions. Several experiments
have investigated food digestion by the babirusa (Conklin et al.
1994; Leus 1994, 2000; Leus & Macdonald 1997; Van Wees et al.
2000; Clauss et al. 2008). Much research remains to be done on
this topic, however.
Reproduction and Growth
Babirusa may become sexually mature as early as 10 months of
age, with the age of sexual maturity in the wild being influenced
by a number of factors including the level of nutrition (Ogle &
Macdonald 2008; Ziehmer et al. 2010, 2013). Animals are
unlikely to breed until they are more than one year old. Indeed,
the earliest recorded pregnancies of babirusa in zoological col-
lections occurred in animals aged about 18 months (Chaudhuri
et al. 1990). Oestrus cycle lengths of between 35 and 37 days
have been described by endocrine studies (Chaudhuri et al.
1990; Berger et al. 2006). During the oestrus period, the external
labia of the vulva swell to twice their normal size and slightly
evert, exposing the internal mucous membrane; this is associated
with reddening of the vulvar area and the presence of a fluid
discharge (Leus et al. 1995). Oestrus usually lasts 2–3 days, and
the female is not receptive to males at other times (Macdonald
1993). In zoological collections, females generally re-cycle
within 3 months after the birth of their young.
Studies have been undertaken on the anatomy and histol-
ogy of the female and male reproductive tracts of the babirusa
(Berger et al. 2006; Agungpriyono et al. 2007; Ziehmer et al.
2010, 2013). Their appearance is as illustrated in Figure 6.5.
In the former, the thin-walled infundibulum almost com-
pletely encloses the ovary (Figure 6.5A). The uterus is bicornuate
and relatively short in contrast to the relatively long cervix. The
latter is thick-walled and has a narrow, spirally arranged lumen.
Each testis lies in the scrotum that is located in a sub-anal position
against the caudal surface of the thigh musculature (Figure 6.2A).
The prostate, comprising a corpus and disseminate parts, lies
ventral to the vesicular glands partly embedded in the dorsal wall
of the urethra (Figures 6.5B,C). The ‘corkscrew-like’ twist at the
distal end of the penis corresponds to the shape of the cervix in
the female.
The body weight of the sow increases during gestation
(Chaudhuri et al. 1990). The gestation length is usually 155–158
days, although up to 171 days has been reported (Vercammen
1991). The normal litter size is one or two uniformly brown-
coloured piglets, but a low incidence of triplet births has been
recorded both in zoological collections and in the wild. One
instance of four eggs having been shed from the ovaries of a zoo
animal has been reported (Ziehmer et al. 2013) and this matches
the report of a litter of four fetuses in utero in a wild female (Patry
1990). The babirusa has a diffuse epithelio-chorial placenta
(Macdonald 1994).
Neonatal babirusa are small in size and weigh less than 800 g
at birth. There are usually four functioning mammary glands in
the babirusa, two located inguinally and the second pair on the
abdomen; however, an additional pair of non-functional teats,
slightly cranial to the others, has sometimes been reported (Leus
et al. 1995). Various aspects of nursing behaviour have been
described (Bowles 1986; Patry et al. 1995; Maclaughlin 2000).
The composition of the milk (Chaudhuri et al. 1990) is reported
as: total solids = 23%; fat = 13%; protein = 7.8%; sugars = 2.7%.
Suckling (Figure 6.2B) lasts for about 1–3 minutes.
In zoological collections, sows produce young at all times
of the year, and may produce two litters within a 12-month
period (Chaudhuri et al. 1990; Ogle 2010). However, as it seemsFigure 6.4 (A) Diagramatic representa-
tion of a ventral view of the stomach
of an adult babirusa with the relative
surface areas of the gastric glands and
the cardiac gland mucosa indicated. o,
oesophagus; p, pyloris. Modified after
Leus et al. (2004). (B) Scanning electron
micrograph of the unique honeycomb
appearance on the surface of the cardiac
gland mucosa, with a section to illustrate
the thin-walled tubes above each glan-
dular pit. Modified after Macdonald et al.
(2008b). Scale bar = 0.2 mm.12:34:41