There are only two gorilla species: the western lowland gorilla and the eastern gorilla with a total population about 300.000. Famous mountain gorilla is a subspecies of the eastern gorilla. The Cross River Gorilla evolved from the western gorilla about 18,000 years ago. He has a narrower teeth, palate and shorter skull than the western gorilla. After that, there was still a sporadic genetic exchange between the species, until 400 years ago the Cross-River Gorillas were completely isolated. In this period it should have already come to a drastic decrease of the population. Today, the two species live about 300 km apart.

The Cross River Gorilla also differs from the western lowland gorilla in diet, behavior, and group patterns.

 It lives in an area with more severe climate changes between drought and rain than the lowland gorilla. He prefers to eat ripe fruits, even though they are hard to come by during the 4-5 month dry season. He is familiar with a variety of different types of fruit. Its main food source is leaves, saplings, pith and bark throughout the year. The individual groups differ greatly in their diet. For example, there is less than 50% agreement in main food sources between gorillas in Mone and in Afi. Afi gorillas also travel greater distances when consuming larger amounts of fruit. In contrast, Kagwene gorillas walk shorter distances when fruit is not available. No effect on path length was observed in Mawambi gorillas.