Which great ape has the smallest remaining population, with fewer than 300 individuals?

The great ape with the smallest remaining population is the Cross River gorilla, with fewer than 300 individuals estimated to survive. More precisely, it is a critically endangered subspecies of western gorilla, Gorilla gorilla diehli, rather than a completely separate gorilla species.

Cross River gorillas live in fragmented forests and mountainous areas along the Cameroon–Nigeria border. Their groups are scattered across roughly a dozen localities, and the separated populations have limited opportunities to mix. This fragmentation reduces genetic diversity and makes recovery more difficult.

The subspecies was described by zoologist Paul Matschie in 1904, but systematic population surveys did not begin until much later. Researchers estimate that fewer than 250 mature individuals remained in assessments from 2014, while broader surveys often describe the total population as about 300. Hunting, habitat loss, agriculture, and roads remain significant threats. A common mix-up is Mountain gorilla: it is also critically endangered, but its surviving population is substantially larger.