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Chapter 11: Forest hog Hylochoerus meinertzhageni (Thomas 1904)bushes mixed with savanna in Queen Elizabeth NP, Uganda. They
prefer areas not far from a source of water, with thick vegetation
for cover and containing a diversity of vegetation types (d’Huart
& Kingdon 2013). Despite their preference for forest ecosystems,
the highest abundance of this species may be found in the eco-
tone zones between forest and open or cultivated areas, especially
those covered with dense bushes. In an ecological study carried
out in Virunga NP, DR Congo, d’Huart (1978) found that forest
hog prefer forest galleries, dry forests and bush thickets.
In Kibale NP, Uganda, Reyna-Hurtado (2015) followed two
groups of forest hogs and found that their home ranges were
located in forests that include primary pre-montane forest, riv-
erine forests, forested swamps, Papyrus spp. swamps, and sev-
eral open areas of secondary/regenerating forests that were the
consequence of selective logging 40 years ago (Chapman et al.
2010). These regenerating areas have only a few large trees, but
they are covered with dense thickets of shrubs, mainly composed
of Mimulopsis spp., Acanthus pubescens, and Piper spp. Preferred
habitat types in Kibale NP are dense bushes of herbaceous
plants surrounded by mature or logged forest (87.5 per cent),
but the species occasionally visits swampy areas (6.5 per cent)
and mature forest (4.8 per cent) (Reyna-Hurtado 2015).
In addition to finding food items, forest hog use these dense
bushes as refuge areas by maintaining a network of tunnels
inside that they use to escape from danger in a very secretive
way. They also use these bushes as sleeping sites. In Kibale NP,
Reyna-Hurtado (2015) found 25 sleeping sites of approximately
5 × 5 m under dense cover where the soils have been cleaned of
debris and where the groups have rested several times. Often,
there are also latrines associated to these resting places and situ-
ated 1 or 2 m away from the sleeping sites. In addition, forest hog
often visit salt-licks and bathing points in their territory.
In Budongo, Uganda, Kingdon (1979) mapped a detailed
1600 km^2 block of mixed wooded grasslands, forest, forest/
woodland mosaics and cultivation where he established the
local ecological separation of Hylochoerus, Potamochoerus,
and Phacochoerus. He found that forest hog becomes dominant
only in areas of extensive forest/grassland mosaic. On Mweya
Peninsula in the Queen Elizabeth NP, Uganda, forest hog have
colonized extensive areas that are a mix of grasslands and dense
bushes thickets (Klingel & Klingel 2004).
In one of the few studies of Central Africa, A. Turkalo (in
preparation) has summarized 12 years of observation of giant
forest hog in clearings (bais) surrounded by mature forest in
Dzanga bai, Central Africa Republic, and found that while forest
hogs are observed in the clearings every month of the year, they
visit them in greater frequency during the drier months between
December and April (A. Turkalo, personal observation). In
summary, forest hogs live in a variety of forest environments
ranging from sea level to 3800 m (Rwenzori Mts, Uganda and
DRC) and in humid areas from 800 mm (Masai-Mara, Kenya) to
3200 mm (West Liberia) of rainfall (d’Huart & Kingdon 2013).
Population Dynamics and Mortality
Forest hog densities have been estimated in a few places only,
and most of them in the Eastern part of its distribution. In the
first ecological study of the species, d’Huart (1978) estimated
in DRC an average density of 0.4 ind./km^2 and 2.6 ind./km^2 in
the whole of Garamba and Virunga NP, respectively, but within
their strict forested habitats of Virunga NP, a record density
of 14 ind./km^2 was obtained. Similarly, in the Aberdares NP,
Kenya, Kingdon (1979) estimated 10 ind./km^2 for a 70 km^2 area,
the highest densities obtained in that area. However, the popula-
tion there has since declined due to an influx of lions and leop-
ards into the area.
On Mweya Peninsula of Queen Elizabeth NP, Uganda, a 1998
count of forest hog estimated densities from 9 to 13 ind./km^2 , but
a few years later a 30 per cent decline was reported in the popu-
lation, again due to an increase in carnivore populations (lions,
leopards, and spotted hyenas) as well as competition with other
herbivores, diseases and road kills (Klingel & Klingel 2004). In
Jibat, Ethiopia, an estimated 8.25 ind./km^2 was obtained by
Kebede through the sampling in transects method in a controlled
hunting area (F. Kebede, personal communication in d’Huart &
Kingdon 2013). In Kibale NP, Uganda, Reyna-Hurtado and col-
laborators tracked two groups of forest hog inhabiting forest
clearing surrounded by mature and logged montane forest and
estimated a density of 1.02 ind./km^2 (Reyna-Hurtado et al. 2014).
To our knowledge, there seems to be no study or population
estimates from the central and western parts of the species range
and almost all available estimates are from eastern Africa and
relate to H. m. meinertzhageni. In 1980 an IUCN survey sug-
gested that the species had a restricted distribution in low densi-
ties over most of its range but was locally abundant in Guinea
and Côte d’Ivoire and widespread and in high density in the
lowlands of Republic of Congo. Given the many changes in for-
est hog habitat and heightened threats, this situation needs to be
updated with recent information about local subspecies popula-
tions abundance and condition in central and western African
countries, the range of the H. m. rimator and H. m. ivoriensis.
The main predators on adults are leopards (Panthera par-
dus) and lions (P. l e o), while spotted hyenas (Crocuta crocuta),
python, and eagles prey on young forest hog and the mortality
rate is about 50 per cent (d’Huart 1978; Meijaard et al. 2011).
Infanticide, although difficult to observe, is apparently quite
common in forest hog and usually from unrelated adult males
to male young (Siege 2011; d’Huart & Siege 2012). In Queen
Elizabeth National Park, Klingel et al. (2001) found infanticide
common after a new male joined a new group.Movements and Home Range
Forest hog movements have been poorly studied and home
range has been estimated in only a few places. In Virunga NP,
DR Congo, d’Huart (1978) estimated the home range of several
groups from 2 to 5 km^2. In Queen Elizabeth NP, Uganda, Klingel
and Klingel (2004) found that home range covered several km^2
and that groups overlap on extensive areas. At Yathabara glade
in the Aberdares Mts of Central Kenya, the frequency of visits
and sightings of different groups also implies that their respec-
tive home ranges overlap to different degrees (Kingdon 1979).
Rahm and Christiaensen (1963) estimated home ranges of 7.5
km^2 for Kahuzi-Biega NP in DR Congo. Despite the degree of
overlap showed at these sites, forest hog do defend core areas
when food is scarce, usually during the dry season (d’Huart.01312:33:38