Three subspecies of forest hog are generally recognized, although some authors propose they may be separate species: H. m. meinertzhageni from east Africa, H. m. rimator from central Africa (Nigeria to Democratic Republic of Congo), and H. m. ivoriensis from west Africa.

Head and body length: 130-210 cm

Shoulder height: 75-110 cm

Tail length: 25-45 cm

Adult weight: 100-275 kg

The forest hog is the largest wild pig species. Males are always larger in size, often weighing 50 kg more than females. Eastern populations also tend to be larger than those from West Africa: male western forest hogs (H. m. ivoriensis) typically weigh no more than 150 kg, while male giant forest hogs (H. m. meinertzhageni) may tip the scales at over 225 kg. Adults of both sexes are black or very dark brown. Long but sparse hair covers the body; down the midline of the back, very long bristles (up to 17 cm) form a mane that is raised when excited. There are no markings. The faces of forest hogs are very distinctive: the nasal disc is exceptionally large (up to 16 cm across), and males develop large naked swellings beneath their eyes. Both sexes have sharp tusk-like canine teeth (those of females are much smaller). In males, the tusks flare outwards with a slight upward curve; the maximum recorded length is 35.9 cm. The ears are not tufted.

Similar species

• Among African pigs, the forest hog is highly distinctive based on its large size and black color. Red river hogs (Potamochoerus porcus) and bushpigs (Potamochoerus larvatus) have long, slender snouts and white facial markings. Warthogs (Phacochoerus spp) have wide faces but are grayish brown, largely hairless, and much smaller.

Gestation period: 151 days.

Litter size: 2-4. There is one isolated report of 11 piglets in a litter.

Weaning: 9 weeks.

Sexual maturity: 18 months.

Life span: Averages 5 years in the wild, but up to 18 years recorded.

Reproduction may take place year-round, but tends to be seasonal; a peak in births usually occurs around the start of the rainy seasons (e.g., in eastern Democratic Republic of Congo, births occur from January-March and July-September). Expectant females isolate themselves and build a large grass-and-branch nest (up to 4 m across and 1.5 m high) in which to give birth. Mother and infants leave the nest and rejoin the group when the piglets are less than a week old. At birth, forest hogs are pale yellowish-brown in color. A pattern of pale stripes along the piglets' sides is faint (most prominent in western populations, and largely absent in eastern populations) and fades quickly: by ten weeks of age, youngsters are entirely dark brown.

A shy and retiring species, the forest hog was not formally described until 1904, and still remains unstudied over large parts of its range. When day-time temperatures are high, or in areas where this species is hunted, most activity occurs between dusk and midnight. Otherwise forest hogs may be active throughout the day, often with a midday rest. Forest hogs create a network of paths and tunnels to connect resting sites, latrines, water sources, mud wallows, salt licks, and foraging areas. Groups occupy home ranges up to 10-20 km² in size; in Kenya, several groups may occupy the same area, but in the Democratic Republic of Congo forest hogs defend a core territory from other groups. Forest hogs travel 8-12 km per day, alternating between foraging and resting. This species is typically found at low population densities (0.4-2.6 individuals per km²), but prime habitat may support over 10 animals per km². In forested environments, forest hogs communicate with quiet grunts to maintain group coherence; a barking call serves to locate individuals at a distance. Males produce a long grunting call. In competing for females, males fight like wild sheep, charging at each other from 20-30 m apart and ramming heads together. This combat may cause skull fractures, although this is often not fatal.

Family group: Families of 6-14 animals, usually with at least one adult male, several adult females, and offspring.

Diet: Primarily grass, but also leaves, fruits, eggs, and animal matter. Forest hogs tend not to root up the soil when feeding.

Main Predators: Spotted hyena, lion, leopard.

Forest hogs inhabit a range of closed canopy forests found in the rainforest belt of Africa, but will use edge habitats and grasslands for foraging. They are found at elevations from sea level to 3,800 m, and need a permanent source of water. The approximate range is depicted in the map below.

IUCN Red List: Least Concern (2016).

CITES Listing: Not listed (2011).

Threats: Habitat destruction (deforestation), hunting for food and as a pest.

The forest hog remains widespread over its native range, which includes numerous protected areas, although the global population is generally decreasing. Habitat fragmentation is of particular concern to the western forest hog.