Part II: Species Accounts64
likely that diet or seasonal factors would normally influence
inter-birth intervals, litters in the wild may be produced less
frequently. Observation of babirusa in North Sulawesi revealed
adult females accompanied by sub-adult animals as well as juve-
niles (Table 6.2; Patry et al. 1995). It was not clear whether these
youngsters of two different ages represented the progeny of con-
secutive litters from the same adult female. However, it has been
observed in a zoo environment that there can be a close bond
between adult female babirusa and their young that may last
for some time after weaning. It was also noticeable that females
that were normally quite docile in zoological collections became
exceedingly aggressive to their keepers and other babirusa, from
shortly before parturition until about two weeks after the young
were born (Reinhard & Frädrich 1983; Leus et al. 1995). Studies
still remain to be carried out in the wild to establish the precise
nature of the sow’s behaviour at the time of parturition, and the
relationship she has with other adult babirusa during the deliv-
ery and nursing of the young. Experience of small, mixed-sex
groups in some zoological collections suggest that it was not
essential for the survival of the young for the pregnant female to
be on her own. In other zoological collections with similar-sized
groups, cannibalism of newly born animals has been experi-
enced despite considerable attempts at the defence of the neo-
nate by the post-parturient sow.Behaviour
Social Behaviour
Babirusa are social animals (Macdonald et al. 1989; Patry et al.
1995; Clayton & MacDonald 1999). Groups or troops of up
to 13 animals have been observed in the rainforest, especially
around water, communal wallowing areas, and warm salt-licks.
Aggregations as large as 46 individuals, comprising several dis-
tinct groups, have sometimes been observed congregated at a
salt-lick. One of the studies of babirusa in northern Sulawesi
(Patry et al. 1995) enabled the following observations to be
quantified (Tables 6.1 and 6.2).
Most sightings of solitary animals (84 per cent of all solitary
animals) were of adult males. Single adult males were seen
with single adult females, but never with two or more females
unless young animals were present (Table 6.2). Pairs or trios
of males were rarely seen, and bachelor groups of four or more
adult male babirusa have not yet been reported. Adult females
were rarely seen without company; they were sometimes found
together with other adult animals, but most often they were with
young babirusa (Figure 6.2B). Groups containing adult females
and young numbered 84 (of the 226 groups studied), of which
two-thirds (56 groups) had no adult males present.Figure 6.5 (A) Diagramatic representation of the dorsal view of the non-pregnant female reproductive tract of the babirusa, with sectional views of the cervix,
vagina, and vestibule. Modified after Ziehmer et al. (2010). o, ovary; i, infundibulum; t, uterine tube; h, uterine horn; b, body of uterus; c, cervix; u, external urethral
orifice; v, vagina; w, wall of vestibule; g, glans of clitoris; l, lips of vulva. Scale bar = 20 mm. (B) Diagramatic representation of the dorsal view of the male reproductive
tract of the babirusa. Modified after Ziehmer et al. (2013). (C) Diagramatic representation of the left lateral view of the male reproductive tract of the babirusa. The
prostate gland lies between and ventral to the paired vesicular glands, and is partly embedded in the wall of the urethra. Modified after Ziehmer et al. (2013). (B,C) a,
bladder; b, vesicular gland; c, position of the prostate gland; d, bulbourethral gland with Musculus bulboglandularis; e, pelvic urethra; f, Musculus bulbospongiosus;
g, bulb of penis; h, (extended) sigmoid flexure of the penis; i; body of the penis; j, penis spiral; k, glans penis; l, left testis; m, head of epididimis; n, tail of epididymis; o,
ductus deferens. Scale bars = 20 mm.12:34:41