A flagship species for the region the Cross River gorilla Gorilla gorilla diehli is classified as critically endangered and is the most threatened ape in Africa. Hunted almost to extinction fewer than 300 Cross River gorillas survive in a small mountainous area at the headwaters of the River Cross straddling the border between Nigeria and Cameroon. Although levels of hunting have reduced in recent years hunting still poses a serious threat to such a small fragmented population, today habitat loss and isolation probably represent the greatest threat to their long-term survival.
In Nigeria Cross River gorillas are known from three areas of Cross River State: Afi Mountain Wildlife Sanctuary, the Mbe Mountains and the Okwangwo Division of Cross River National Park. Most gorillas are found in rugged areas of lowland and submontane forest at elevations from 400 to 2,000 m where human disturbance and hunting pressure is reduced.
Despite the small size and fragmented nature of the population the genetic variability of this population is still relatively high and there is evidence to suggest that gorillas do occasionally move between sites using corridors of suitable habitat. Furthermore many of the known gorilla strongholds are still surrounded by large areas of unoccupied forest and there is strong hope that the existing gorilla population could expand in the future if such areas can be protected from hunting.