Cross River Gorilla

There are two species of gorilla, the western gorilla (Gorilla gorilla) and the eastern gorilla (Gorilla beringei). The western gorilla consists of two recognized subspecies: the Cross River gorilla (Gorilla gorilla diehli) and the western lowland gorilla (Gorilla gorilla gorilla). The Cross River gorilla is classified as Critically Endangered according to the IUCN (2008) Red List (Bergl et al. 2016) meaning that it is considered to be facing an extremely high risk of extinction in the wild.

The range of the Cross River gorilla is restricted to the hilly rainforest region along the Nigeria-Cameroon border (Dunn et al. 2014). Separated from the nearest population of western lowland gorilla to the south by approximately 200 km, the subspecies is scattered across a surface area of approximately 12,000 km² (Dunn et al. 2014). About one-third of Cross River gorilla landscape occurs in three areas of Cross River State, Nigeria (the Afi Mountain Wildlife Sanctuary, the Mbe Mountains, and the Okwangwo Division of Cross River National Park). In Cameroon, there are five key areas for Cross River gorillas, all located within Cameroon’s Southwest Region (Takamanda National Park and adjacent Mowambi Hills, Mone River Forest Reserve, the Mbulu-Oko forest, and Bechati-Fossimondi-Besali forest) except the Kagwene Gorilla Sanctuary which extends a few kilometers into the Northwest Region (Bergl et al. 2012; Dunn et al. 2014).

The total population of Cross River gorillas is estimated at 250-300 individuals (Bergl et al. 2016). Many of the sites where Cross River gorillas are found contain relatively small numbers of animals, commonly 20-30 individuals, and only two sites (Okwangwo and Takamanda) are estimated to contain larger groups up to a maximum of 50-65 individuals. Large areas of unoccupied potential Cross River gorilla habitat remain, and these provide connectivity between many of the subpopulations (Bergl et al. 2012).

References

Bergl, R.A., Dunn, A., Fowler, A., Imong, I., Ndeloh, D., Nicholas, A. & Oates, J.F. (2016). Gorilla gorilla ssp. diehli. The IUCN Red List of Threatened Species 2016. https://www.iucnredlist.org/species/39998/102326240

Bergl, R., Warren, Y., Nicholas, A., Dunn, A., Imong, I., Sunderland-Groves, J. & Oates, J. (2012). Remote sensing analysis reveals habitat, dispersal corridors and expanded distribution for the Critically Endangered Cross River gorilla Gorilla gorilla diehli. Oryx 46: 278–289.

Dunn, A., Bergl, R., Byler, D., Eben-Ebai, S., Etiendem, D., Fotso, R., Ikfuingei, R., Imong, I., Jameson, C., Macfie, E., Morgan, B., Nchanji, A., Nicholas, A., Nkembi, L., Omeni, F., Oates, J.F., Pokempner, A., Sawyer, S. & Williamson, E.A. (2014). Revised Regional Action Plan for the Conservation of the Cross River Gorilla (Gorilla gorilla diehli) 2014–2019. IUCN SSC Primate Specialist Group and Wildlife Conservation Society, NY. https://portals.iucn.org/library/node/44661