Gorilla

Verified Timeline

Lore & Background

The word gorilla comes from the history of Hanno the Navigator (c. 500 BC), a Carthaginian explorer on an expedition to the west African coast to the area that later became Sierra Leone. Members of the expedition encountered 'savage people, the greater part of whom were women, whose bodies were hairy, and whom our interpreters called Gorillae'. It is unknown whether what the explorers encountered were what we now call gorillas, another species of ape or monkeys, or humans. Skins of gorillai women, brought back by Hanno, are reputed to have been kept at Carthage until Rome destroyed the city 350 years later at the end of the Punic Wars, 146 BC. In 1625 Andrew Battel mentioned the existence of the animal, under the name Pongo. The American physician and missionary Thomas Staughton Savage and naturalist Jeffries Wyman first described the western gorilla in 1847 from specimens obtained in Liberia. They called it Troglodytes gorilla, using the then-current name of the chimpanzee genus. The species name was derived from Ancient Greek Γόριλλαι (gorillai) 'name of a tribe of hairy women', as described by Hanno.

In Their Own Story

The closest relatives of gorillas are the other two Homininae genera, chimpanzees and humans, all of them having diverged from a common ancestor about 7 million years ago. Human gene sequences differ only 1.6% on average from the sequences of corresponding gorilla genes, but there is further difference in how many copies each gene has. Until recently, gorillas were considered to be a single species, with three subspecies: the western lowland gorilla, the eastern lowland gorilla and the mountain gorilla. There is now agreement that there are two species, each with two subspecies. More recently, a third subspecies has been claimed to exist in one of the species. The separate species and subspecies developed from a single type of gorilla during the Ice Age, when their forest habitats shrank and became isolated from each other. The proposed third subspecies of Gorilla beringei, which has not yet received a trinomen, is the Bwindi population of the mountain gorilla, sometimes called the Bwindi gorilla. Population genetics of the lowland gorillas suggest that the western and eastern lowland populations diverged around 261 thousand years ago.

Reader's Guide

Wild male gorillas weigh 136 to 227 kg (300 to 500 lb), while adult females weigh 68–113 kg (150–250 lb). Adult males are 1.4 to 1.8 m (4 ft 7 in to 5 ft 11 in) tall, with an arm span that stretches from 2.3 to 2.6 m (7 ft 7 in to 8 ft 6 in). Female gorillas are shorter at 1.25 to 1.5 m (4 ft 1 in to 4 ft 11 in), with smaller arm spans. Colin Groves (1970) calculated the average weight of 42 wild adult male gorillas at 144 kg, while Smith and Jungers (1997) found the average weight of 19 wild adult male gorillas to be 169 kg. Adult male gorillas are known as silverbacks for the characteristic silver hair on their backs, reaching to the hips. The tallest wild gorilla recorded was a 1.95 m (6 ft 5 in) silverback with an arm span of 2.7 m (8 ft 10 in), a chest of 1.98 m (6 ft 6 in), and a weight of 219 kg (483 lb), shot in Alimbongo, northern Kivu in May 1938. The heaviest wild gorilla recorded was a 1.83 m (6 ft 0 in) silverback shot in Ambam, Cameroon, which weighed 267 kg (589 lb). The tallest gorilla in captivity was Gust, a western lowland gorilla that was captured as a baby in Belgian Congo and spent his life at Antwerp Zoo. He was 2.20 m (7 ft 3 in) tall. Males in captivity can be overweight and reach weights up to 310 kg (683 lb). The eastern gorilla is more darkly coloured than the western gorilla, with the mountain gorilla being the darkest of all. The mountain gorilla also has the thickest hair. The western lowland gorilla can be brown or greyish with a reddish forehead. Gorillas that live in lowland forest are more slender and agile than the more bulky mountain gorillas. The eastern gorilla also has a longer face and broader chest than the western gorilla. Like humans, gorillas have individual fingerprints. Their eye colour is dark brown, framed by a black ring around the iris. Gorilla facial structure is described as mandibular prognathism, that is, the mandible protrudes farther out than the maxilla. Adult males also have a prominent sagittal crest. Gorillas move around by knuckle-walking, although they sometimes walk upright for short distances, typically while carrying food or in defensive situations. A 2018 study investigating the hand posture of 77 mountain gorillas at Bwindi Impenetrable National Park (8% of the population) found that knuckle walking was done only 60% of the time, and they also supported their weight on their fists, the backs of their hands/feet, and on their palms/soles (with the digits flexed). Studies of gorilla handedness have yielded varying results, with some arguing for no preference for either hand, and others right-hand dominance for the general population. Studies have shown gorilla blood is not reactive to anti-A and anti-B monoclonal antibodies, which would, in humans, indicate type O blood. Due to novel sequences, though, it is different enough to not conform with the human ABO blood group system, into which the other great apes fit. A gorilla's lifespan is normally between 35 and 40 years, although zoo gorillas may live for 50 years or more in rare circumstances. At 69 years, 234 days, Fatou is both the oldest living gorilla and oldest living female gorilla. The oldest male gorilla ever was Ozoum, who reached the final age of 61 years, 24 days. The oldest living male gorilla is Guhonda, aged 55 years, 234 days. Gorillas have a patchy distribution. The range of the two species is separated by the Congo River and its tributaries. The western gorilla lives in west central Africa, while the eastern gorilla lives in east central Africa. Between the species, and even within the species, gorillas live in a variety of habitats and elevations. Gorilla habitat ranges from montane forest to swampland. Eastern gorillas inhabit montane and submontane forests between 650 and 4,000 m (2,130 and 13,120 ft) above sea level. Mountain gorillas live in montane forests at the higher end of the elevation range, while eastern lowland gorillas live in submontane forests at the lower end. In addition, eastern lowland gorillas live in montane bamboo forests, as well as lowland forests ranging from 600–3,308 m (1,969–10,853 ft) in elevation. Western gorillas live in both lowland swamp forests and montane forests, at elevations ranging from sea level to 1,600 m (5,200 ft).

Did You Know?

• The word 'gorilla' comes from a Carthaginian explorer's account of 'savage people' called Gorillae around 500 BC.
• Gorilla DNA is 96 to 99% similar to human DNA, depending on what is included.
• The heaviest wild gorilla ever recorded weighed 267 kg (589 lb), shot in Ambam, Cameroon.
• The oldest living gorilla is Fatou, at 69 years, 234 days.
• Gorilla blood does not conform to the human ABO blood group system, unlike other great apes.