The Cross River gorilla is a subspecies of the western gorilla, also known as Gorilla gorilla diehli. This species was identified as separate by Paul Matschie in 1904, but its population was not fully studied until 1987. Cross River gorillas are the most endangered gorillas, with a 2014 survey estimating only about 250 mature adults remaining in the wild. Their population is said to have dropped by 59% between 1995 and 2010.
Physical Characteristics
Cross River gorillas have smaller palates, smaller teeth, shorter skulls, and smaller brain cases than other gorillas. They also have a barrel-shaped chest, which makes them some of the largest living primates.
They have shorter hands and feet but a higher opposability index compared to western gorillas. Adult males stand about 165 to 175 cm tall, while females are about 140 cm tall. Males weigh between 140 and 200 kilograms, and females can weigh up to 100 kilograms.
Habitat and Nesting Behavior
Cross River gorillas live in the highlands near the Nigeria-Cameroon border. They build nests differently depending on the season. From April to November, they prefer nests in trees, but after November, they build nests on the ground. Daytime nest building also happens more often in the dry season than in the wet season.
Social Structure and Diet
Groups of Cross River gorillas usually include one dominant silverback, six females, and their offspring, making these groups smaller compared to other gorilla species. They eat plants such as herbs, fruits, bark, leaves, and other vegetation.
Cross River gorillas have been observed using tools, such as throwing grass and branches at researchers. Little is known about their reproduction, but scientists agree their gestation period lasts about eight and a half months.
About Western Gorillas
Western lowland gorillas and Cross River gorillas are both subspecies of the western gorilla. In the 1980s, western gorillas had a population of about 100,000, but by 2007 their numbers had dropped sharply due to poaching, disease, and habitat loss.
Western lowland gorillas have a low birth rate, like other gorilla species, with only 1 to 2 fertile days per month. Female gorillas start having babies between 10 and 12 years old and usually have 4 to 6 offspring in their lifetime. Baby gorillas are as vulnerable as human babies at birth and feed on breast milk for about 3 to 4 years.
Western lowland gorillas mainly eat plants like pulp, celery, tree bark, leaves, shoots, fruits, and stems, sometimes adding ants, termites, and insects to their diet. Adult gorillas can eat up to 18 kilograms of plants each day.
Western gorillas live in home ranges of 8 to 45 kilometers and travel about 3 to 5 kilometers daily. Gorilla groups are led by a dominant silverback who manages the group and has access to all the females, much like the social structure seen among their eastern gorilla relatives in Uganda, Rwanda, and Congo. Interested in seeing them yourself? Explore our gorilla safaris.
