Bongo

Tragelaphus eurycerus

IUCN – Endangered
CITIES – Appendix III, export regulated from Ghana only
USFWS – not listed

Historic and Present Range

Historically, bongo inhabited three regions of Africa: west, central and east. The lowland bongo inhabit the lowland rain forests of West and Central Africa and is considered to be Lower Risk (near threatened). The eastern or mountain bongo, have been isolated to the montane forests of Kenya, namely the Aberdare Forest, Mau Forest and Mount Kenya, since their extirpation in Uganda over eighty years ago (Antelope Specialist Group, 1998).

Today, bongo ranges in all three regions have diminished due to loss of habitat from agriculture and uncontrolled timber cutting, while numbers have also declined from poaching for meat for human consumption. The Mount Kenya population was extirpated within the last decade, limiting the present range of eastern or mountain bongo to the Aberdare and Mau Forests (Antelope Specialist Group, 1998). The Antelope Specialist Group (1998) suggests that the captive bongo population may be equal to or exceed the total number of eastern bongo remaining in the wild.

Habitat

Prime bongo habitat is disturbed forest and forest-savanna ecotone. These areas are fragmented mosaics of pasture, forest and thicket resulting from shifting cultivation, logging or elephant concentration (Kingdon, 1982; Antelope Specialist Group, 1998).

Population Size

The availability of estimates of bongo population density is very limited. For this reason the antelope Specialist Group (1998) made the following assumption: considering average population densities of 0.25 per sq km where bongo are known to be common/abundant and 0.02 per sq km elsewhere, and a total area of occupancy of 327,000 sq km gives a total population estimate of approximately 28,000. Of this population, about 60% are in protected areas. These data suggest that actual numbers of the lowland subspecies, which are unknown, may be in the low tens of thousands. Numbers of bongo in Kenya (eastern or mountain bongo) are unknown, but may not exceed a few hundred animals and are decreasing (Antelope Specialist Group, 1998).

Social Organization and Behavior

Bongo in general are gregarious and non-territorial. Adult males are often solitary, while females have been seen in herds with calves. These female groups seem to be led by senior cows (Hillman, 1986). Females nearing parturition become solitary, but within three months after birth the mothers and calves join nursery herds (Kingdon, 1982). Kingdon (1982) also states that in the Aberdares average group size ranges from 3 to 27 animals. Aggressive interactions and social grooming between cows have been observed, indicating rank order and that individuals associate together for some time (Hillman, 1986).

The behavior of animals within large groups is quite different from that of singletons or pairs. The latter are alert and easily frightened and will move away after a disturbance. Conversely, bongos in nursery herds are more relaxed, avoiding close contact with other large herbivores yet they are relatively fearless, even of predators (Kingdon, 1982).

Ecology

Canopy rain forest has too little vegetation at ground level to be good bongo habitat. This antelope depends on openings in the forest which let the sunlight in and support dense growth of bushes, herbs, creepers and bamboo. These provide both food and cover for the bongo. Accordingly, this species can thrive in areas where the forest is regeneration following logging, cultivation or heavy elephant damage (Hillman, 1986). Bongos are selective browsers of high protein vegetation, feeding on leaves, flowers, thistles, vines, twigs of shrubs and flowering tops of rank succulents. Their long, mobile tongue is used as a feeding tool and the horns are sometimes employed to break high branches (Kingdon, 1982).

In the Aberdares, peak mating periods are in May and November, with very few females in estrus June through July (Kingdon, 1982). In captivity, females cycle every three weeks and remain in estrus for nearly three days. Gestation is nine months. During the lying up periods, calves are vulnerable to pythons, leopards and hyenas (Verchuren, 1958).

Inhabiting dense forest, the bongo emerges into the open or forest clearings during activity peaks around dawn and dusk. This evidence suggests that bongo are mainly mocturnal (Spinage, 1986: Estes, 1991). Bongo tend to rest in thickets and ruminate between the hours of 10:30 am and 4:00 pm (Kingdon, 1982).

Similarity to Other Species' Genes or Family, or its Uniqueness

Similar to other tragelaphine antelopes, the bongo is spiral-horned. However, bongo may be differentiated from other tragelaphines by their lack of inguinal glands (Kingdon, 1982). Kingdon (1982) also points out that tragelaphines are highly visual animals, relying more on sight and sound that most antelopes.

Environmental Factors Affecting the Species

While it is important to gain some insight into the total range and spatial distribution of population units, conservation plans for the species should take account of the bongo's need for appropriate fodder and dense cover. Bongo could eventually be reestablished in many parts of their former range, once their ecological role is fully understood and the habitat managed to their advantage (Kingdon, 1982).