The chimpanzee (Pan troglodytes) is one of the great apes and shares a close evolutionary relationship with humans, making it our nearest living relative alongside the bonobo. These highly intelligent primates are found across a wide, discontinuous range in equatorial Africa, inhabiting diverse environments from tropical rainforests to savanna woodlands. The Common Chimpanzee is not a single, uniform population; it is formally classified into several distinct subspecies based on genetic lineage and geographic separation. These subspecies exhibit important distinctions in their physical appearance, geographic distribution, learned behaviors, and conservation status.
Understanding the Pan Genus
The taxonomic classification of chimpanzees begins at the genus level, Pan, which contains two species. The most familiar is the Common Chimpanzee (Pan troglodytes). The second species is the Bonobo (Pan paniscus), which is physically smaller and possesses a different social structure.
These two species separated geographically and genetically millions of years ago. The massive Congo River acts as a natural barrier, with the Bonobo found exclusively south of the river and the Common Chimpanzee occupying a large range north of it. The significant physical and behavioral differences between them warrant their separate species status, but variations within the Common Chimpanzee species lead to the recognition of multiple distinct subspecies.
The Four Recognized Subspecies
The Common Chimpanzee (Pan troglodytes) is subdivided into four recognized subspecies, each with a unique scientific and common name. These classifications are supported by physical characteristics and genetic data, confirming their long-term evolutionary separation.
- Central Chimpanzee (Pan troglodytes troglodytes): Occupies the central portion of the species’ range.
- Western Chimpanzee (Pan troglodytes verus): Found to the west.
- Eastern Chimpanzee (Pan troglodytes schweinfurthii): Found across the eastern extent of the species’ distribution.
- Nigeria-Cameroon Chimpanzee (Pan troglodytes ellioti): Has the smallest geographic range, located near the border of Nigeria and Cameroon.
Geographic Range and Physical Variation
The distribution of the four subspecies is separated by major geographic features like large rivers and expanses of savanna, which prevent interbreeding and promote genetic isolation.
The Central Chimpanzee (P. t. troglodytes) inhabits the vast forests of Cameroon, Gabon, Equatorial Guinea, and the Republic of the Congo. This subspecies is generally considered the largest and most robust of the four types, with particularly large males.
The Western Chimpanzee (P. t. verus) is found in West Africa, from Senegal to Ghana, though it is extinct in several countries. This subspecies often exhibits a lighter facial coloration and a more pronounced brow ridge than its eastern counterparts. Its range is separated from the Central Chimpanzee by the Sanaga River in Cameroon.
The Eastern Chimpanzee (P. t. schweinfurthii) occupies the forests of the Democratic Republic of Congo, Uganda, Tanzania, and Burundi. This subspecies is generally described as having a smaller overall body size compared to the Central type.
The Nigeria-Cameroon Chimpanzee (P. t. ellioti) is geographically isolated between the Sanaga River and the Niger River. It possesses a unique genetic profile despite having a relatively small population.
Cultural Differences and Conservation Status
Chimpanzee populations display culture, which involves behaviors and traditions learned and passed down socially rather than inherited genetically. This variation is evident in the specific types of tool use seen among the subspecies.
Western Chimpanzees (P. t. verus) are known for using large stones and wooden clubs as hammers and anvils to crack open hard-shelled nuts, a complex technique absent in Eastern chimpanzees. Conversely, Eastern Chimpanzees (P. t. schweinfurthii) use modified stick tools for “fishing” for termites or ants. The complexity of tool use, such as creating a “brush-tip” for honey extraction, is a learned behavior that varies significantly between communities.
The Common Chimpanzee species overall is listed as Endangered by the International Union for Conservation of Nature (IUCN), but conservation status varies dramatically by subspecies. The Western Chimpanzee (P. t. verus) is classified as Critically Endangered due to severe population declines from habitat loss and poaching. The Nigeria-Cameroon Chimpanzee (P. t. ellioti) is also classified as Endangered, facing threats from agricultural expansion and disease. Survival depends on targeted regional conservation efforts addressing threats like illegal wildlife trade and infectious diseases such as Ebola.