In this chapter we summarize information on the morphology, genetics, and natural history of the West African gorilla population inhabiting the forests on the Nigeria–Cameroon border at the northern headwaters of the Cross River, a region at the western and northern limits of the species' range. A recent morphological analysis of skeletal specimens from this population has shown that they are sufficiently distinct from other western gorillas to justify being classified as the subspecies Gorilla gorilla diehli, a taxonomic name originally applied to them in the early twentieth century (Sarmiento and Oates, 2000). Just as the distinctiveness of the Cross River gorillas is being appreciated, their continued survival is in jeopardy. Recent surveys suggest that approximately 250 probably remain, concentrated in nine or more isolated hill areas. Because these gorillas are still hunted for their meat and parts of their habitat are under threat, they are one of Africa's most endangered primate taxa. After reviewing data on the status of the Cross River gorillas, our chapter ends by discussing some options for improving their prospects for survival.

In addition to the literature, the information we summarize derives from our own research: Field surveys in Nigeria (by JFO and KLM) and Cameroon (by JLG); an ecological study of a subpopulation inhabiting Afi Mountain Wildlife Sanctuary, Nigeria (by KLM); and the sequencing of mtDNA extracted from hairs of Nigerian gorillas shed into sleeping nests (by RAB and JML in the laboratory of TRD). All our results should be regarded as preliminary.