The western lowland gorilla (Gorilla gorilla gorilla) is one of two subspecies of the western gorilla (Gorilla gorilla) that lives in montane, primary, and secondary forests and lowland swamps in central Africa in Angola, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Equatorial Guinea and Gabon. It is the gorilla usually found in zoos.
Adult male gorillas are prone to cardiomyopathy, a degenerative heart disease. The western lowland gorilla is the smallest subspecies of gorilla but nevertheless still a primate of exceptional size and strength. This species of gorillas participates in sexual dimorphism. They possess no tails and have jet black skin along with coarse black hair that covers their entire body except for the face, ears, hands, and feet.
The hair on the back and rump of males takes on a grey coloration and is also lost as they get progressively older. This coloration is the reason why older males are known as "silverbacks". Their hands are proportionately large with nails on all digits, similar to that of a human's, and very large thumbs. They have short muzzles, a prominent brow ridge, large nostrils, and small eyes and ears.
Other features are large muscles in the jaw region along with broad and strong teeth. A male standing erect can be 5-6 feet (1.5-1.8 m) tall and weigh 300-600 pounds (140-270 kg). According to the Guinness Book of World Records, the average male is 168 kg (370 lb) and stands upright at 163 cm (64 in). Western gorillas frequently stand upright, but walk in a hunched, quadrupedal fashion, with hands curled and knuckles touching the ground.
This style of movement requires long arms, which works for western gorillas because the armspan of gorillas is larger than their standing height. Males in captivity, however, are noted to be capable of reaching weights up to 275 kg. Females stand 5 feet (1.5 m) tall and weigh half as much as males. According to the late John Aspinall, a silverback gorilla in his prime has the physical strength of 7-8 Olympic weight lifters but this claim is unverified.