Hylochoerus meinertzhageni, Thomas, 1904

Don E. Wilson & Russell A. Mittermeier, 2011, Suidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 248-291 : 278-279

6.

Forest Hog

Hylochoerus meinertzhageni

French: Hylochere / German: Riesenwaldschwein / Spanish: Hilocero

Other common names: Giant Forest Hog ( meinertzhageni )

Taxonomy. Hylochoerus meinertzhageni Thomas, 1904 ,

Kenya, Nandi Forest, near Kaimosi, 2134 m.

The three subspecies provisionally recognized are differentiated on the basis of the dimensions and shape of their skull. The taxonomy of a fourth, the Ethiopian race, is still indefinite.

Subspecies and Distribution.

H. m. meinertzhageniThomas, 1904 — EDRCongo, Rwanda, Burundi, Uganda, Kenya, SSudan, andEthiopia. IthasnotreliablybeenrecordedfromTanzania.

H. m. woriensisBouet & Neuville, 1930 — discontinuouspresenceinGuinea, SierraLeone (?), Liberia, IvoryCoast, andGhana; possiblyalsoinGuineaBissau, andTogo.

H. m. rimator Thomas, 1906 — SE Nigeria, W & SE Cameroon, Central African Republic, Gabon, Equatorial Guinea (extinct?), N Republic of the Congo, and N DR Congo.

Descriptive notes. Head—body 130-210 cm, tail 25-45 cm, shoulder height 75-110 cm; weight 140-275 kg (males) and 100-200 kg (females). Males are significantly larger than females in both weight and dimensions. Although the common name “Giant Forest Hog” is often used, western races ofthis species are not much larger than Bushpigs ( Potamochoerus larvatus ), and only the East African animals are true giants. Their slatey gray skin is densely covered with coarse hair, which gets sparser with age. Adult pelage is coal black, with 15-20 cm long, stout bristles. There is a pale, erectile mane on the neck. The ventral pelage is sparse and grayish to black. The legs are robust, with large and rounded hooves. The long, tasseled tail is slender and flattened at its end, with sparse bristles implanted laterally. The massive head has white to yellowish “whiskers” on the jaw-line callosity. The small, pointed, leaf-shaped ears are fringed with black hairs. In males, the forehead is characterized by a large depression surrounded by five bony, hairless ridges. The species has large, swollen preorbital glands and prominent naked cheeks. The muzzle is flat, with thick tusks flaring outwards and a very broad nasal disc (up to 17 cm in diameter). The skull and facial musculature are adapted to a folivorous rather than an omnivorous diet. Females have four mammae. Dental formulaisl 1/3, Cl1/1,P2/1,M 3/5 (x2) = 30.

Habitat. Like Red River Hogs ( P. porcus ), Forest Hogs are more dependent on forest than the other African pigs. Forest Hogs inhabit a variety offorest types: subalpine areas and bamboo groves, forest—grassland mosaics, montane, lowland, and swamp forests, river galleries, wooded savannas, and thickets. It is an ecotonic species, preferring intermediate habitat zones where the edge effect is maximized and where resources from different vegetation types can be exploited within a limited area. It shows a preference for a convenient and permanent water source, thick understory cover in some parts of its home range, and a diversity of vegetation types. In dense forest areas, Forest Hogs tend to concentrate in isolated hilly, rocky habitats of savanna and forest, around clearings, or in mixed forest patches rather than in monodominant forest. The variety of forest habitats occupied implies a high degree of adaptability to local climatic conditions. Forest Hogslive in cold uplands (where night temperatures may fall to 0°C) as well as hot lowlands, but do not tolerate low humidity or prolonged solar radiation.

Food and Feeding. Forest Hogs are mainly grass-eaters and folivorous. Feeding habits show that they are neither exclusively forest animals nor pure grazers. They display great versatility in food selection, depending on the seasonal content, stage of growth, and quantity of plant resources available. Many species of grasses, sedges, and herbs are cropped. They root much less than other wild pigs and dig only in soft or muddy soils. In a savanna area of the Queen Elizabeth National Park, Uganda, they select more than 100 food plants. In Virunga National Park, however, five major savanna species were selected, on average, over the course of a year; the hogs preferred some grasses during dry seasons and others during rainy seasons, selecting grasses when their nutrient and energetic content is highest. Young piglets are known to feed on grasses well before weaning. In dense forest, both Forest Hogs and Bongos (Tragelaphus eurycerus) use mast seed areas in monodominant stands. Examination of adult hog dung reveals different types of material, including poorly masticated grass seeds, stems, and leaves, fragments of millipedes and shields of ticks, earth nodules, and bristles. They also excavate salty earth with their tusks and lower incisors. These salt licks may be termite mounds, shallow caves, dry river banks, or even the embankment of a deserted road. Occasionally Forest Hogs eat meat and bones ofcarrion, eggs, and larvae. Coprophagy is not common, but piglets are fond of fresh elephant dung.

Breeding. Adult size and sexual maturity are reached by both males and females at 18 months. There are two mating seasons in Virunga National Park, with births occuring at the beginning of the rainy season. Gestation period averages 151 days. Before parturition, the expectant sow leaves the group and retreats under dense thickets in a nest made of grasses and branches where young are born. Litter size is 2-6 (average 2-4) piglets. The mother rejoins her group with her offspring only one week after parturition. Piglets may nurse from any female in the group, and are protected by all. Weaning occurs at 8-10 weeks. The averagelife expectancy is 3-5 years and average life span is five years, with a maximum of 18 years.

Activity patterns. In the grassland-bushland—dry forest mosaic ofVirunga National Park, DR Congo, Forest Hogs spend on average 25% oftheir daily time moving and foraging in savanna, 21% moving, foraging, and wallowing in thickets or forested areas, and 54% resting in a sheltered sleeping site. Activity is most intense in the early morning and late afternoon, with a rest during hottest hours. There is no evidence of true nocturnal activity. Wallowing is a favorite activity, taking up about one hour each day in certain areas. Before sundown, family groupsretire to their sleeping place under dense thickets. Along the trails, the same dung heaps are always used as communal latrines. Males are fierce defenders of their group and sometimes lead the sounders in driving off predators and competitors. When shot at, they will attack humans. Competition between males is violent and may last for half an hour. Males rush at each other from a distance, crashing their foreheads together like rams. Despite their reinforced skulls, deaths among males due to fractures are not uncommon, but most wounds heal. This species is quite vocal, producing a minimum of ten recognizable categories of sounds. The main predators on adults are Leopards (Panthera pardus) and Lions (P. leo). Spotted Hyenas (Crocuta crocuta),, pythons, and eagles prey on young hogs and their mortality rate is about 50%.

Movements, Home range and Social organization. Forest Hogs maintain unmarked and undefended home ranges of 3-10 km? laced with a network of well-worn trails connecting resting sites, latrines, wallows, waterholes, salt licks, and grazing meadows. Daily movements average 8-12 km, most of which takes place on an individual’s own or another animal’s trails. Home ranges may overlap extensively with ranges of other groups. Routine activities in confined territories make Forest Hogs easy targets for poachers. In Virunga National Park, the basic social group is a sounder of 4-20 animals consisting of 1-4 males, 1-9 females, and the offspring of up to three generations. Males can be monogamous or polygamous. Average group size is 10-14 in Virunga and Queen Elizabeth National Parks. Larger groupings of several sounders have been recorded. Groups of bachelor subadults and solitary males are common. In good habitat, population densities are 7-30 ind/km?.

Status and Conservation. Classified as Least Concern on The IUCN Red List as the species is relatively widespread, sometimes locally abundant, has a high reproductive potential, and although itis subject to hunting in many parts ofits range,it is not believed to be declining at a rate that would merit its being listed as Near Threatened or in a threatened category. The speciesis very vulnerable to deforestation and hunting for subsistence and the bushmeat trade. The western race zvoriensis is highly vulnerable to fragmentation of its habitat.

Bibliography. Cerling & Viehl (2004), Estes (1991), Ewer (1970), Fimpel (2002), Grimshaw (1998), d'Huart (1978, 1993), d'Huart & Kingdon (In Press), d'Huart & Klingel (2008), d'Huart & Yohannes (1995), Kingdon (1979), Klingel & Klingel (2004), Kock & Howell (1999), Rahm & Christiaensen (1963), Viehl (2003).

Figures

On following pages 2 Moluccan Babırusa (Babyrousa babyrussa) 3 Tog an Babırusa (Babyrousa rogeanensıs) 4 Common Warthog (Phacochoorus alncanus) 5 Desert Warthog (Phacochoerus aethıopıcus) 6 Forest Hog (Hylochoerus maınenzhagenı) Bushpıg (Pommochoeıus Iarvalusl 8 Red Rıver Hog (Poramochoerus porcas)

Subspecies and Distribution. H. m. meinertzhageniThomas, 1904 — EDRCongo, Rwanda, Burundi, Uganda, Kenya, SSudan, andEthiopia. IthasnotreliablybeenrecordedfromTanzania. H. m. woriensisBouet & Neuville, 1930 — discontinuouspresenceinGuinea, SierraLeone (?), Liberia, IvoryCoast, andGhana; possiblyalsoinGuineaBissau, andTogo. H. m. rimator Thomas, 1906 — SE Nigeria , W & SE Cameroon , Central African Republic , Gabon , Equatorial Guinea (extinct?), N Republic of the Congo , and N DR Congo .